Volumetric plasma gas flow measurement and control system for wire plasma arc additive manufacturing applications

Abstract

Systems and methods for regulating mass flow and monitoring volume flow, regulating volume flow and monitoring mass flow, and regulating mass and volume flow of gases to a plasma torch for a wire-plasma arc additive manufacturing process are provided, as well as methods for manufacturing metal objects by additive manufacturing using one or more systems.

Description

[0001] Cross-citation to related applications

[0002] This patent application claims priority to U.S. provisional patent application serial number 62 / 948,148, filed on December 13, 2019, entitled “VOLUMETRIC PLASMA GAS FLOW MEASUREMENT AND CONTROL SYSTEM FOR METAL-BASED WIRE-PLASMA ARC ADDITIVE MANUFACTURING APPLICATIONS,” and U.S. application serial number 17 / 116,092, filed on December 9, 2020, similarly entitled “VOLUMETRIC PLASMA GAS FLOW MEASUREMENT AND CONTROL SYSTEM FOR METAL-BASED WIRE-PLASMA ARC ADDITIVE MANUFACTURING APPLICATIONS,” both of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention generally relates to systems and methods for controlling and consistently delivering gas flow to a melt tool of an additive manufacturing process to produce consistent melt pool force as gas density varies due to mechanical and environmental factors. Background Art

[0004] Structural metal parts made of titanium or titanium alloys are typically produced by casting, forging, or machining from billets. These techniques have numerous drawbacks, such as high material usage due to the expensive titanium metal and long lead times for manufacturing metal objects. Casting, while typically used to produce objects close to net shape, often reduces material quality due to a lack of control over solidification and cooling rates. Tooling costs and the inability to produce complex shapes are additional drawbacks of these traditional methods.

[0005] Fully dense physical objects can be created through additive manufacturing, a manufacturing technique also known as rapid prototyping, rapid manufacturing, freeform manufacturing, and layered manufacturing. Additive manufacturing creates a near-net-shape product by successively layering material one layer at a time to produce a three-dimensional object. This contrasts with subtractive manufacturing, in which a blank or block is machined by removing material to produce the final product.

[0006] Some additive manufacturing processes use wire and arc welding. This is often referred to as wire and arc additive manufacturing (WAAM). WAAM encompasses three distinct processes. Gas metal arc welding (GMAW) uses an arc formed between a consumable wire electrode (usually coaxial with the torch) and the workpiece metal. Gas tungsten arc welding (GTWA) and plasma arc welding (PAW) differ from GMAW in that they can use a non-consumable tungsten electrode and an inert gas to generate an ionized plasma to heat and melt metallic materials, such as wire, to form a three-dimensional preform or workpiece. In GTWA and PAW, ionization can occur between a non-consumable cathode (tungsten) and the workpiece as a direct transferred arc, either alone or in combination with a pilot arc between a non-consumable cathode (tungsten) and an anode, where the preform or substrate can serve as the anode. The torch configuration and its position and placement relative to the workpiece can cause the plasma column to strike the molten pool.

[0007] In plasma arc welding applications for additive manufacturing, the number of gas molecules per time and the volume of gas per time are critical, as both factors influence the thermal characteristics of the plasma arc. Specifically, the gas mass flow rate (the number of gas molecules per unit time) influences the degree of ionization of the plasma arc (i.e., the number of ionized gas atoms relative to the total number of available gas atoms), while the gas volume flow rate (the volume of gas per unit time) influences the kinetic energy of the plasma arc flow and the resulting pressure on the melt pool. The pressure exerted by the plasma column on the workpiece during the forming process has a significant impact on layer uniformity and process repeatability. The pressure of the plasma column can be influenced by controlling the inert gas supply to the torch. Current gas flow control technology for wire plasma arc additive manufacturing processes measures and controls the mass flow rate—i.e., the number of gas molecules per unit time—supposedly assuming standard conditions of supply gas pressure and temperature. However, the gas density supplied to the torch can vary significantly due to environmental changes, either alone or in combination with machine-to-machine variability.

[0008] Therefore, the actual volume flow of gas supplied at the torch and the pressure exerted by the plasma column on the workpiece can vary significantly during manufacturing. These variations can lead to inconsistent products produced by the wire plasma arc additive manufacturing process.

[0009] Therefore, there is a need in the art for an improved method of controlling the flow of an inert gas to a plasma torch for ionization into a plasma for use in a metal additive manufacturing process. Summary of the Invention

[0010] Thus, embodiments described herein are directed to systems and methods for controlling the flow of inert gas to a plasma torch that can determine the actual volumetric flow rate and can allow for adjustment of the plasma arc pressure and melt pool dynamics for use in a wire plasma arc additive manufacturing process. Systems are provided for regulating the mass flow rate and monitoring the volumetric flow rate of gas to a plasma torch. Systems are provided for regulating the volumetric flow rate and monitoring the mass flow rate of gas to a plasma torch. Systems are provided for regulating both the mass flow rate and the volumetric flow rate of gas to a plasma torch. The systems and methods can include a volumetric flow control element that can be located within a production chamber at or near a gas inlet of a plasma torch for receiving gas to be ionized into a plasma by the plasma torch to enable measurement and / or control of any gas density changes due to arc radiation interference, such as temperature changes in a gas hose or piping. The volumetric flow control element at or near the gas inlet of the plasma torch can also allow for detection of any mass flow reduction, such as due to a leak, and can act as a second opinion sensor for the mass flow rate.

[0011] The embodiments described herein are directed to providing a consistent force on the molten pool during an in-line plasma arc additive manufacturing process, even when the gas density varies due to mechanical or environmental disturbances, or both. In embodiments, consistent force can be achieved by controlling the volumetric flow rate of gas at a plasma torch where the ionized gas or plasma is formed. In some embodiments, control of the volumetric flow rate of gas at the plasma torch can be achieved by adjusting the mass flow rate of the gas to be ionized from the gas supply, or by adjusting the density of the gas to be ionized at the plasma torch by varying the temperature or pressure of the gas, or a combination thereof, or by adjusting the temperature and / or pressure of the gas to be ionized at or near the gas inlet of the plasma torch to thereby adjust the mass flow rate of the gas to be ionized at the gas supply and the volumetric flow rate of the gas to be ionized by the plasma torch.

[0012] The embodiments described herein aim to improve the melt pool dynamics, thereby improving the geometry and mechanical properties of preforms produced by a wire plasma arc additive manufacturing process, thereby improving consistency and quality.

[0013] Another object of the embodiments provided herein is to produce a consistent plasma arc pressure (i.e., arc force per unit area of ​​the molten pool) on the molten pool across various density levels of the inert gas supplied to the plasma torch by maintaining the gas discharge velocity of the plasma arc from the nozzle of the plasma torch at a target discharge velocity.

[0014] A system and method for controlling the flow of an inert gas ionized into a plasma to a plasma torch of an additive manufacturing apparatus is provided. The system can allow for adjustment of the plasma arc pressure applied to the melt pool, thereby allowing for modification of the melt pool dynamics during the fabrication of an object using a wire plasma arc additive manufacturing process.

[0015] A system for controlling gas flow to a plasma torch of an additive manufacturing apparatus is provided. The system may include: an inert gas source; a supply manifold in fluid communication with the inert gas source; a plasma torch including a gas inlet for receiving inert gas from an inert gas line connected to the supply manifold; and a gas ionizer electromagnetic field for ionizing the inert gas into a plasma. The system may include a sensing package that may include a temperature measurement unit, a pressure measurement unit, and a mass flow measurement unit. Each unit may communicate with one or more sensing connectors connected to a location in the inert gas line between the supply manifold and the gas ionizer electromagnetic field. The system may also include a control valve in fluid communication with the gas supply manifold for regulating the flow of inert gas from the gas supply manifold.

[0016] The system may include a process master controller in communication with the sensing kit. The system may include a part program that provides a mass flow setpoint, a volume flow setpoint, or both to the process master controller. The system may include a calculation function running on the process master controller that calculates an actual volume flow rate. The system may include a mass flow control function running on the process master controller, wherein the mass flow control function may compare the mass flow setpoint from the part program with an actual mass flow value from the sensing kit mass flow measurement cell and may adjust a control valve, a density control element, or both to increase or decrease the mass flow of the inert gas to reduce a difference between the mass flow setpoint and the actual mass flow value.

[0017] The system may include a volumetric flow control function running on the process master controller, wherein the volumetric flow control function may compare a volumetric flow setpoint from a part program with a calculated volumetric flow value from the calculation function and adjust a control valve or a density control element or both the control valve and the density control element to increase or decrease the volumetric flow of the inert gas to reduce a difference between the volumetric flow setpoint and the calculated volumetric flow value.

[0018] The system may include a mass flow control function and a volume flow control function running on a process master controller, wherein the mass flow control function may compare a mass flow setpoint from a part program with an actual mass flow value from a mass flow measurement unit of a sensing kit, and the volume flow control function may compare a volume flow setpoint from the part program with a calculated volume flow value from a calculation function, and may adjust a control valve and a density control element to regulate the mass flow rate and volume flow rate of the inert gas delivered to a gas ionizer electromagnetic field of a plasma torch.

[0019] The system may include a combined mass flow and volume flow control function operating on a process master controller, wherein the mass flow and volume flow control function compares a mass flow setpoint from a part program with an actual mass flow value from a mass flow measurement unit of a sensing kit, and compares a volume flow setpoint from the part program with a calculated volume flow value from a calculation function, and adjusts a control valve and a density control element to regulate the mass flow and volume flow of the inert gas delivered to a gas ionizer electromagnetic field of a plasma torch.

[0020] In the system provided herein, a mass flow control function can compare a mass flow set value from a part program with an actual mass flow value from a mass flow measurement unit of a sensing kit, and can adjust a control valve to increase or decrease the mass flow rate of the inert gas to reduce the difference between the mass flow set value and the actual mass flow value, thereby reducing the mass flow rate of the inert gas delivered to the gas ionizer electromagnetic field of the plasma torch; and a volume flow control function can compare a volume flow set value from a part program with a calculated volume flow value from a calculation function, and can adjust a density control element to control the volume flow rate of the inert gas delivered to the gas ionizer electromagnetic field of the plasma torch.

[0021] In the provided system, the process master controller can further communicate with a) a mass flow controller processor on which a mass flow control function is executed; or b) a volume flow controller processor on which a volume flow control function is executed; or c) a calculation processor on which a calculation function is executed; or d) any combination of a), b), and c). Any one or a combination of the process master controller, the calculation processor, the volume control processor, and the mass flow control processor can further communicate with a data server, and mass flow and volume flow data can be sent to the data server.

[0022] In the systems provided herein, the sensing connectors for each of the temperature measurement unit, pressure measurement unit, and mass flow measurement unit of the sensing assembly can be connected anywhere between the gas manifold or any other type of gas distribution system and the gas ionizer electromagnetic field of the plasma torch. In some configurations, the sensing connectors for each of the temperature measurement unit, pressure measurement unit, and mass flow measurement unit of the sensing assembly can be connected near the plasma torch gas inlet. In some configurations, the sensing connectors for each of the temperature measurement unit and pressure measurement unit of the sensing assembly are located within the plasma torch.

[0023] The system provided herein may include a density control element that controls the temperature and / or pressure of the inert gas delivered to the inlet of the plasma torch. In some configurations, the gas density regulator may include a) a temperature regulator and a temperature sensor; or b) a pressure regulator and a pressure sensor; or c) a temperature regulator, a temperature sensor, a pressure regulator, and a pressure sensor; or d) any combination of a), b), and c). In the configuration where the gas density regulator includes a temperature regulator, the temperature regulator may include a heater. The heater may include or be an induction heater, a resistive heater, a piezoelectric ceramic heating element, or a combination thereof. In some configurations, the temperature regulator may also include a cooling device. The cooling device may include: a) a pipeline connected to a refrigeration fluid reservoir and a pump to form a closed-loop cooling path to supply cooling fluid to the temperature regulator; or b) a pipe passing through the temperature regulator and a fan connected to the pipe to force cooling gas through the temperature regulator; or c) a combination of a) and b).

[0024] In a system configured to include a pressure regulator, the pressure regulator can include a movable plenum chamber capable of increasing the volume of the pressure regulator, thereby reducing the pressure of the inert gas leaving the pressure regulator, or decreasing the volume of the pressure regulator, thereby increasing the pressure of the inert gas leaving the pressure regulator. In the systems provided herein, the control element can be configured to control the velocity of the inert gas to the plasma torch.

[0025] In the system provided herein, the temperature measurement unit of the sensing kit may include a temperature sensor. In the system provided herein, the pressure measurement unit of the sensing kit may include a pressure sensor. In the system provided herein, the mass flow measurement unit of the sensing kit may include a mass flow sensor. In some configurations, the sensing connector may be located within the production chamber of the additive manufacturing system and at the plasma torch gas inlet to measure radiated interference from the plasma torch and / or the workpiece. The system provided herein may include a mass flow meter located upstream of the control valve and in communication with a process master controller, the mass flow meter being capable of detecting a decrease in the mass flow of the inert gas from the manifold, and the process master controller sending a signal to a data monitoring system to indicate a leak.

[0026] The system provided herein may include: an inert gas source; a supply manifold in fluid communication with the inert gas source; a plasma torch including a gas inlet for receiving the inert gas; a control valve in fluid communication with the gas supply manifold and regulating the flow of the inert gas from the gas supply manifold; a sensing kit including a temperature measuring unit, a pressure measuring unit, and a mass flow measuring unit, wherein each unit is in communication with a sensing connector connected anywhere between the gas manifold or any other type of gas distribution system and the gas ionizer electromagnetic field of the plasma torch; a processor group connected to the sensing kit and in communication with the control valve, wherein the processor group includes: a process master controller in communication with the sensing units; a computing processor in communication with the sensing kit and the process master controller, the computing processor calculating the actual volume flow rate; and a) a flowmeter in communication with the process master controller. a mass flow controller; or b) a volume flow controller in communication with a process master controller; or c) a mass flow controller and a volume flow controller in communication with the process master controller; and a part program that provides a mass flow setpoint or a volume flow setpoint or both a mass flow setpoint and a volume flow setpoint to the process master controller, wherein: the mass flow control function compares the mass flow setpoint from the part program with an actual mass flow value from the sensing assembly and adjusts the control valve to increase or decrease the mass flow of the inert gas to reduce the difference between the mass flow setpoint and the actual mass flow value; or the volume flow controller compares the volume flow setpoint from the part program with a calculated volume flow value from a computing processor and adjusts the control valve to increase or decrease the flow of the inert gas to reduce the difference between the volume flow setpoint and the calculated volume flow value. The sensing connector can be connected to or near the plasma torch gas inlet.

[0027] The sensor kit components can be separated, and elements can be embedded in different parts of the inert gas line. For example, the mass flow measurement unit of the sensor kit can be positioned anywhere along the inert gas line. Additionally, the temperature and pressure measurement units can be located along the gas line or inside the plasma torch. Multiple sensor connectors can be positioned along the inert gas line.

[0028] In the system, the processor group may include a mass flow controller, and the mass flow controller may further communicate with the control valve and adjust the control valve to increase or decrease the flow rate of the inert gas to reduce the difference between the mass flow setpoint and the actual mass flow rate. In the system, the processor group may include a volume flow controller, and the volume flow controller may further communicate with the control valve and adjust the control valve to increase or decrease the flow rate of the inert gas to reduce the difference between the volume flow setpoint and the calculated volume flow rate. The processor group may be a group of processors that perform different tasks in parallel, or may be a master processor, such as a process master controller, that performs a group of tasks in parallel to support various functions.

[0029] A method for delivering a target volume flow rate of an inert gas to be ionized into a plasma to a plasma torch is also provided. The method includes: providing an inert gas from a gas supply manifold to an inlet of the plasma torch via a control valve attached to the inert gas supply manifold; measuring the temperature, mass flow rate, and pressure of the inert gas at or near the inlet; calculating an actual volume flow rate of the inert gas at or near the inlet; and comparing the actual volume flow rate to the target volume flow rate to generate a difference. Based on the difference, the control valve can be adjusted to increase or decrease the mass flow rate of the inert gas through the control valve to the inlet of the plasma torch; or the density of the inert gas can be adjusted by increasing or decreasing the pressure and / or temperature of the inert gas to produce a modified inert gas, and the modified inert gas can be directed to the inlet of the plasma torch.

[0030] In the method, adjusting the control valve may include: generating an adjustment signal based on the difference; and sending the adjustment signal to an actuator attached to the control valve, the actuator increasing or decreasing an opening of the control valve based on the adjustment signal. In the method, adjusting the density of the inert gas may include a) measuring the temperature of the inert gas and increasing or decreasing the temperature of the inert gas in response to the difference; or b) measuring the pressure of the inert gas and increasing or decreasing the pressure of the inert gas in response to the difference; or c) both a) and b).

[0031] In the method, increasing the temperature of the inert gas may include directing the inert gas to a temperature regulator including a heater and activating the heater. The heater may include an induction heater, a resistance heater, a piezoelectric ceramic heating element, or a combination thereof. In the method, reducing the temperature of the inert gas may include directing the inert gas to a temperature regulator including a cooling device and activating the cooling device. The cooling device may include: a pipeline connected to a refrigeration fluid reservoir and a pump to form a closed-loop cooling path to supply cooling fluid to the temperature regulator; or a pipe passing through the temperature regulator and a fan connected to the pipe to force cooling gas through the temperature regulator; and a pipeline connected to a refrigeration fluid reservoir and a pump to form a closed-loop cooling path to supply cooling fluid to the temperature regulator; or a pipe passing through the temperature regulator and a fan connected to the pipe to force cooling gas through the temperature regulator.

[0032] In the method, increasing or decreasing the pressure of the inert gas delivered to the plasma torch may include directing the inert gas to a pressure regulator. The pressure regulator may include a movable plenum chamber capable of increasing the volume of the pressure regulator to reduce the pressure of the inert gas exiting the pressure regulator, or decreasing the volume of the pressure regulator to increase the pressure of the inert gas exiting the pressure regulator. In the method, the inert gas may be argon.

[0033] Also provided is a method of delivering a target volume flow of an inert gas to be ionized into a plasma to a plasma torch, the method comprising attaching a system provided herein to a source of inert gas; and activating the system.

[0034] Additional features and advantages of the embodiments described herein will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the exemplary embodiments will be realized and attained by the structure particularly pointed out in the written description and claims as well as the accompanying drawings.

[0035] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention.

[0037] In the attached figure:

[0038] Figure 1is a simplified diagram illustrating an exemplary embodiment of an inert gas flow to be ionized by a plasma torch, flowing from a gas supply manifold through a flow control system provided herein, and through a plasma torch to generate a plasma arc, the pressure of which can be controlled.

[0039] Figure 2 is a simplified diagram illustrating an exemplary embodiment of an inert gas flow to be ionized from a gas supply manifold, passing through a flow control system as provided herein, and through a plasma torch including a temperature sensor and a pressure sensor within the plasma torch, the gas passing through a region of an ionized EM field to generate a plasma arc, the pressure of which can be controlled.

[0040] Figure 3A The present invention is a flow chart illustrating, in block diagram form, an exemplary embodiment of a system for regulating mass flow and monitoring volumetric flow of a gas to be ionized into plasma through a plasma torch of an additive manufacturing system. In the illustrated embodiment, the processor complex includes a separate computational processor, a master process controller, and a mass flow controller, wherein the mass flow controller communicates with a control valve.

[0041] Figure 3B A flow chart illustrating, in block diagram form, an exemplary system for regulating the mass flow of a gas to be ionized into a plasma by a plasma torch of an additive manufacturing system. In the illustrated embodiment, a single process master controller is provided, wherein the control tasks of the computational processor and the mass flow controller are integrated software code or functions running on the process master controller, wherein the process master controller communicates with a density control element and a control valve and transmits mass flow control commands to the control valve and / or the density control element.

[0042] Figure 4A The present invention is a flow chart illustrating, in block diagram form, an exemplary embodiment of a system for regulating the volumetric flow and monitoring the mass flow of a gas to be ionized into plasma through a plasma torch of an additive manufacturing system. In the illustrated embodiment, the processor complex includes a separate computational processor, a master process controller, and a volumetric flow controller in communication with a control valve and a density control element.

[0043] Figure 4B The present invention is a flow chart illustrating, in block diagram form, an exemplary system for regulating both the mass flow rate and the volumetric flow rate of a gas to be ionized into a plasma through a plasma torch of an additive manufacturing system. In the illustrated embodiment, a single process master controller and a volumetric flow controller that compute the control tasks of a processor are software codes or functions running in an integrated manner on the process master controller, wherein the process master controller communicates with a density control element and a control valve and transmits volumetric flow control commands to the control valve and / or the density control element.

[0044] Figure 5 is a simplified diagram illustrating an exemplary embodiment of a density control element that can control the pressure of an inert gas by changing the temperature of the gas.

[0045] Figure 6 is a simplified diagram illustrating an exemplary embodiment of a density control element including a plenum chamber in which the volume of an inert gas can be adjusted to control the pressure of the inert gas.

[0046] Figure 7A A flow chart illustrating, in block diagram form, an exemplary system for regulating both the mass flow rate and the volume flow rate of a gas to be ionized into a plasma through a plasma torch of an additive manufacturing system. In the illustrated embodiment, the processor complex includes a separate computational processor, a master process controller, a volumetric flow controller, and a mass flow controller, wherein the volumetric flow controller communicates with a density control element, and the mass flow controller communicates with a control valve.

[0047] Figure 7B The present invention is a flow chart illustrating, in block diagram form, an exemplary system for regulating both the mass flow rate and the volume flow rate of a gas to be ionized into a plasma through a plasma torch of an additive manufacturing system. In the illustrated embodiment, a single process master controller, a mass flow controller, and a volume flow controller that compute the control tasks of a processor are software codes or functions that run in an integrated manner on the process master controller, wherein the process master controller communicates with a density control element and a control valve and transmits a volume flow control command to the density control element and a mass flow control command to the control valve.

[0048] Figure 7C The present invention is a flow chart illustrating, in block diagram form, an exemplary system for regulating both the mass flow rate and the volume flow rate of a gas to be ionized into a plasma through a plasma torch of an additive manufacturing system. In the illustrated embodiment, a single process master controller that computes the control tasks of a processor and a combination of a mass flow controller and a volume flow controller are software codes or functions running in an integrated manner on the process master controller, wherein the process master controller communicates with and transmits mass and volume flow control commands to a density control element and a control valve.

[0049] Figure 8AThe present invention is a flow chart illustrating, in block diagram form, an exemplary single-input, single-output (SISO) controller that can be used in a system for regulating both the mass flow rate and the volume flow rate of a gas to be ionized into a plasma through a plasma torch of an additive manufacturing system. In the illustrated configuration, a mass flow error from a sensing kit unit is directed to a SISO mass flow controller function, which, in response, sends a commanded valve position to a control valve in communication with the mass flow controller function. A volume flow error from the sensing kit unit is directed to a SISO volume flow controller function, which, in response, sends a density control command to a density control element in communication with the volume flow controller function. Two parallel SISO controllers can negate any coupling between mass flow error and volume flow error.

[0050] Figure 8B The present invention is a flow chart illustrating, in block diagram form, an exemplary multiple-input multiple-output (MIMO) controller that can be used in a system for regulating both the mass flow rate and the volume flow rate of a gas to be ionized into a plasma by a plasma torch of an additive manufacturing system. The configuration illustrates a multivariable MIMO controller having two inputs: one for a mass flow error and one for a volume flow error received from a sensing kit unit. The MIMO controller is configured to include a control algorithm that can account for any coupled dynamics between the mass flow rate and the volume flow rate. The MIMO controller has two outputs, a command valve position signal and a command action signal to a density control element, which are directed to a control valve and a density control element, respectively. This configuration can allow the system to individually stabilize individual mass flow and volume flow values, as well as account for or compensate for any disturbances of one variable on the other, thereby stabilizing the entire system. DETAILED DESCRIPTION

[0051] Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[0052] A. Definition

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Unless otherwise indicated, all patents, patent applications, published applications and publications, websites, and other published materials mentioned throughout this disclosure are incorporated by reference in their entirety. If there are multiple definitions of terms herein, the definitions in this section shall prevail.

[0054] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0055] As used herein, ranges and amounts may be expressed as "about" a particular value or range. "About" also includes an exact amount. Thus, "about 5%" means "about 5%" and "5%." "About" means within the range of experimental error for typical applications or intended purposes.

[0056] As used herein, "optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event or circumstance occurs and instances where the event or circumstance does not occur. For example, an optional component in a system means that the component may or may not be present in the system.

[0057] As used herein, "combination" refers to any association between two or more items. The association can be spatial or refer to the use of two or more items for a common purpose.

[0058] As used herein, the terms "comprising," "containing," and "including" are synonymous and are inclusive or open-ended. Each term indicates that additional, unrecited elements or method steps may optionally be included.

[0059] As used herein, "and / or" means "either or both" of the elements so combined, i.e., elements that are present in combination in some cases and separately in other cases. Multiple elements listed with "and / or" should be interpreted in the same manner, i.e., "one or more" of the elements so combined. In addition to the elements specifically identified by the "and / or" clause, other elements may optionally be present, whether related or unrelated to the specifically identified elements. Thus, as a non-limiting example, when used in conjunction with open language such as "comprising," a reference to "A and / or B" may, in one embodiment, refer only to A (optionally including elements other than B); in another embodiment, to only B (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); and so on.

[0060] As used herein, "additive manufacturing" or "AM," also referred to as "additive manufacturing process" and "additive layer manufacturing," refers to an additive process that builds an object layer by layer. The process can employ 3D model data, a metal source (e.g., wire or powder), a melting tool containing an energy source (e.g., plasma arc, laser, or electron beam) for melting the metal source, or a combination thereof.

[0061] As used herein, an "additive manufacturing system" refers to a machine used for additive manufacturing.

[0062] As used herein, "directed energy deposition" or "DED" refers to an additive manufacturing process in which a heat source is used to melt material, particularly metal, by melting it as it is deposited.

[0063] As used herein, the term "metal material" refers to any known or conceivable metal or metal alloy that can be used in an additive manufacturing process to form a three-dimensional object. Examples of suitable materials include, but are not limited to, titanium and titanium alloys, such as Ti-6Al-4V alloy.

[0064] As used herein, "plasma gas" refers to an inert gas that is converted into plasma under the action of a plasma torch. The inert gas to be ionized into plasma is typically argon, or a combination of argon and helium.

[0065] As used herein, a "plasma torch" refers to any torch that can be used for plasma arc welding.

[0066] As used herein, a "plasma arc welding torch" or "PAW torch" refers to a welding torch that can be used for plasma arc welding. The torch is designed so that the gas can be heated to a high temperature to form a plasma and become conductive, and the plasma then transfers an arc to the workpiece, and the intense heat of the arc can melt the metal and / or fuse two pieces of metal together. The PAW torch can include a nozzle for constricting the arc, thereby increasing the power density of the arc. The inert gas to be ionized into plasma is typically argon. The PAW torch also typically has an external nozzle for providing a shielding gas. The shielding gas can be argon, helium, or a combination thereof, and the shielding gas helps to minimize oxidation of the molten metal. PAW torches include plasma transferred arc torches.

[0067] The terms "plasma transferred arc torch" or "PTA torch," as used interchangeably herein, refer to any device capable of heating an inert gas stream and energizing it into a plasma using an electric field, then transferring the plasma stream, including the arc, through a nozzle to form a contracting plume that extends out of the nozzle and transfers the intense heat of the plasma to a target area. The electrodes and target area are electrically connected to a power source, such as a DC power source, such that the electrodes of the PTA torch can serve as the cathode and the target area can serve as the anode. This ensures that the plasma plume, including the arc, can deliver a highly concentrated heat flux to a small surface area of ​​the target area, and provides good control over the areal extension and magnitude of the heat flux provided by the PTA torch. The plasma transferred arc can have the advantages of providing a stable, consistent arc with little drift and good tolerance to length deviations between the cathode and anode. Therefore, the PTA torch is suitable for both forming a molten pool in a substrate and heating and melting a metal wire feed. The PTA torch can advantageously have electrodes made of tungsten and a nozzle made of copper, and various parts of the PTA torch can be water-cooled. However, the present invention is independent of any particular choice or type of PTA torch or any particular configuration thereof.Any known or conceivable device capable of functioning as a PTA torch may be used.

[0068] As used herein, "near the gas inlet of a plasma torch" refers to a location at or near the gas inlet of a plasma torch where electromagnetic radiation from the plasma arc or workpiece, or temperature changes caused by such electromagnetic radiation, can be measured. The location where the inert gas sample is collected to measure gas flow and density can be several millimeters, centimeters, or meters away from the torch inlet.

[0069] As used herein, the term "substrate" refers to the target material from the heat of the melting tool, onto which the molten pool forms. This will be the support substrate when the first layer of metallic material is deposited. Once one or more layers of metallic material have been deposited onto the support substrate, the substrate will be the upper layer of the deposited metallic material, onto which new layers of metallic material will be deposited.

[0070] As used herein, the term "workpiece" refers to a metal body produced using solid freeform fabrication.

[0071] As used herein, a "preform" is a workpiece produced by an additive manufacturing process and is an intermediate or semi-finished product of the final finished product. The preform has a near-net shape close to the final finished product, but requires at least some (if minimal) further processing, such as final finishing to a high-tolerance configuration, in order to produce the final finished product.

[0072] As used herein, a "melting tool" refers to a device that includes a heat source for melting a metal material, a portion of a workpiece surface, or both during an additive manufacturing process. Examples include a PTA torch that generates a plasma arc as a heat source, a laser device that generates a laser beam as a heat source, and an electron beam device that generates an electron beam as a heat source.

[0073] As used herein, "gas exhaust velocity from the nozzle" refers to how fast the gas moves out of the nozzle of a plasma torch per unit time.

[0074] As used interchangeably herein, the terms "design model" or "computer-aided design model" or "CAD model" refer to any known or conceivable virtual vectorized layered three-dimensional representation of an object to be formed by an additive manufacturing process. For example, the model can be obtained by forming a virtual vectorized layered model of a three-dimensional object by first dividing the object into a set of virtual parallel layers, and then dividing each parallel layer into a set of virtual quasi-one-dimensional pieces that can be used by a controller of an additive manufacturing system to form the object via metal layers deposited or melted according to the virtual parallel layers.

[0075] As used herein, "controller" refers to any logic circuitry and / or processing element involved in communicating with and / or controlling one or more components of an additive manufacturing system, as well as associated software or programming for the additive manufacturing system components. The controller may include a computer and / or computer memory.

[0076] As used herein, a "computer" may include, but is not limited to, hardware and / or software that can capture and / or store data, and any program that can be programmed to communicate with and / or control one or more electronic devices or software that controls mechanical devices. A computer may include non-transitory computer-readable media, which may include, but is not limited to, a CD-ROM, a removable flash memory card, a hard drive, or magnetic tape.

[0077] As used herein, "computer memory" refers to a configurable storage element capable of storing digital data or information that can be retrieved by a computer.

[0078] As used herein, an "inert atmosphere" refers to any known or conceivable gas or gas mixture that can cover or surround an object to isolate the object from ambient air. An inert atmosphere can protect the object from exposure to oxygen or from oxidation or other unwanted chemical effects of ambient atmospheric components. Exemplary inert atmospheres include one or more inert gases.

[0079] As used herein, "melt pool" refers to the volume of molten metal formed during additive manufacturing.

[0080] As used herein, "electromagnetic force" refers to the Lorentz force generated by the electromagnetic field used to ionize a gas to create a plasma.

[0081] As used herein, "electromagnetic axial pressure" refers to the electromagnetic force per unit melt pool area.

[0082] As used herein, "plasma fluid dynamics" refers to the mechanical disturbance caused by the momentum of the plasma as a fluid flowing toward the molten pool.

[0083] As used herein, "plasma flow axial pressure" refers to the plasma flow force per unit melting pool area.

[0084] As used herein, "plasma arc pressure" or "total arc pressure" refers to the arc force per unit melt pool area.

[0085] As used herein, "total arc pressure" is equal to the sum of the electromagnetic axial pressure and the plasma flow axial pressure.

[0086] As used herein, "arc force" refers to the electromagnetic force (ie, the Lorentz force) generated by the electromagnetic field used to ionize the gas to create the plasma, plus the mechanical disturbance created by the mass of the plasma flowing as a fluid toward the melt pool.

[0087] As used herein, "mass flow rate" refers to the number of gas molecules supplied to a plasma torch per unit time.

[0088] As used herein, "volumetric flow rate" refers to the volume of gas supplied to the plasma torch per unit time.

[0089] As used herein, "stagnation pressure" or "Pitot tube pressure" interchangeably refer to the static pressure at a stagnation point in a fluid flow. At a stagnation point, the fluid velocity is zero and all kinetic energy has been converted to pressure energy.

[0090] As used herein, "melt pool temperature" refers to the temperature that characterizes the melt pool, which can be the melt pool volume average temperature, the melt pool time average temperature, the melt pool surface temperature, or the melt pool peak temperature (the highest temperature reached by any surface or area within the melt pool).

[0091] For any range described herein, unless expressly stated otherwise, the range includes all values ​​therein and all subranges therein. For example, if a range of 1 to 10 is listed, the range includes 1 and 10 and all values ​​between 1 and 10, such as 1.1, 2.5, 3.333, 6.26, 7.9989, etc., and includes all subranges therebetween, such as 1 to 3.5, 2.75 to 9.33, 1.5 to 9.999, etc.

[0092] B. Gas flow control system

[0093] Direct energy deposition techniques may use a localized heat source, such as a plasma arc, to heat and melt a metal feedstock, which may be provided to a plasma torch in the form of a metal wire. Figure 1 An exemplary plasma transferred arc (PTA) configuration using a PTA torch is shown in FIG. The figure shows a plasma torch 600 generating a plasma arc 625 positioned above a workpiece 650. Not shown is the metal wire melted by the plasma arc 625, which melts the metal wire causing droplets of molten metal to be deposited layer by layer onto the workpiece 650 to form a three-dimensional object through an additive manufacturing process. Although Figure 1 A single plasma torch 600 is depicted, but other configurations are contemplated and may include two or more plasma torches, or two or more wire feeders, or multiple wires, or a wire feeder with a head that can handle multiple wires, and may be included in the systems provided herein. Figure 1The gas supply manifold 120 is shown connected to a gas volume and mass flow control system 800 via a gas hose 160. The control system 800 is connected to the plasma torch via a gas hose 196.

[0094] In an exemplary embodiment, the workpiece can be included in the circuit.By connecting a power source (eg, inverted terminals) to the torch and the workpiece, a plasma is formed between the workpiece and the plasma torch due to the ionization effect of the electromagnetic field generated between the torch and the workpiece.

[0095] An inert gas (such as argon) can be the gas to be ionized by the plasma torch, for example, by using an arc electrode, although alternative inert gases, ions, molecules, or atoms can be used in conjunction with the plasma torch in place of argon. These alternative mediators of plasma energy can include positive and / or negative ions, or electrons alone or in combination with ions. In addition, reactive elements can be combined with the inert gas (such as argon) to optimize the performance of the torch. The plasma generation process can excite the argon gas to a relatively high gas temperature, for example, between 5,000 K and 30,000 K. Thus, only a small amount of excited argon gas is required to melt the metal feedstock wire into molten metal for deposition on the workpiece. The plasma torch can include one or more nozzles. For example, nozzles of different apertures can be used to provide specific geometries and / or plasma collimation for manufacturing different parts. The plasma torch can include one or more apertures. Exemplary apertures include straight-beam nozzle apertures and fan-shaped apertures. These apertures can also be used to impart a desired geometry and / or plasma collimation to the plasma column.

[0096] The plasma stream exiting the plasma torch, whether directed toward a metal feedstock wire, a workpiece, or a combination thereof, can impinge on or near the surface of a melt pool. Thus, the volumetric flow rate of the plasma column can affect melt pool dynamics, such as the pressure exerted by the plasma column on the melt pool. The systems and methods provided herein can allow for adjustment of the plasma arc pressure and, therefore, can allow for modification of melt pool dynamics during the fabrication of an object using a wire plasma arc additive manufacturing process.

[0097] Plasma torches can be designed so that the gas can be heated to a high temperature to form a plasma and become conductive. The plasma can then transfer the arc to the workpiece. The intense heat of the arc can melt metal and / or fuse two pieces of metal together. The plasma torch can be a "plasma transferred arc torch" or "PTA torch", which can heat an inert gas stream and excite it into plasma through an arc discharge, and then transfer the plasma stream including the arc through a hole (such as a nozzle) to form a contracting plume that extends out of the hole and transfers the intense heat of the arc to a target area, such as a metal wire or a workpiece or both. The plasma can be fed along an electrode and ionized and accelerated near the cathode. The arc can be directed toward the workpiece and is more stable than a free-burning arc (such as in a TIG torch). The current is typically up to about 500A DC (direct current) and the voltage is typically in the range of about 10-70V. By adjusting the flow rate of the inert gas, such as mass flow rate and / or inlet pressure and volume flow rate, and / or by adjusting the plasma power (e.g., by adjusting the plasma voltage and current), a range of plasma arc configurations can be generated for a given plasma torch or plasma head geometry.

[0098] The pressure and temperature distribution of the plasma arc can also be affected by factors such as the relative position of the plasma torch and the workpiece, as well as the transfer voltage between the workpiece and the plasma head. Generally speaking, the energy of a plasma-transferred arc can be more direct than that of a non-plasma-transferred arc, resulting in a more concentrated transfer of heat energy to the material deposited on the workpiece. During manufacturing, the total arc pressure applied by the plasma arc to the melt pool can be a function of plasma power, gas density and temperature, and gas flow rate (velocity). For example, it has been observed that any X% change in the inert gas flow rate at the torch inlet can result in a change of up to 2X% or more in the plasma arc's melt penetration area. For example, in certain configurations, increasing the inert gas flow rate to the plasma torch from 2.5 L / min to 2.75 L / min resulted in an approximately 10% increase in the plasma arc's melt penetration area, while all other process variables remained constant. This is the effect of increasing the kinetic energy of the plasma flow.

[0099] The plasma arc pressure on the molten pool can be one of the most critical factors defining the molten pool dynamics. The plasma arc pressure can affect the geometry or mechanical properties of the deposited metal layer, or both, which can impact the consistency and quality of the additive manufacturing process. The systems and methods provided herein can be used to generate consistent plasma arc pressure on the molten pool across various densities of the ionized gas supplied to the plasma torch by regulating and maintaining the gas discharge rate from the plasma torch at a desired level.

[0100] Current gas flow control technology for wire plasma arc additive manufacturing processes measures and controls the welding gas mass flow rate supplied to the plasma torch, i.e., the number of gas molecules per unit time, by "assuming" standard conditions of pressure and temperature for the supply gas. Typical plasma welding gas control systems regulate the standard volume flow rate in units of NL / min, where N stands for normal. The standard volume flow rate assumes a gas temperature of, for example, 0°C (273.15K, although other temperatures such as 20°C or 25°C have also been used in the art) and a gas pressure of 1 atmosphere (atm or 1.013 bar). These reference conditions can be referred to as normal temperature and pressure, or NTP conditions. Therefore, the actual volume flow rate (in units of L / min) varies depending on the temperature and pressure of the gas. Under non-standard conditions compared to standard conditions, such as during an additive manufacturing process, the change in volume flow rate can be obtained by the following formula:

[0101]

[0102] in is the actual volume flow rate under non-standard conditions, is the volume flow rate under non-standard conditions, P std is the pressure under non-standard conditions, is the actual pressure under non-standard conditions, T act is the actual temperature under non-standard conditions, T std is the temperature under nonstandard conditions. This method eliminates the need to use gas density values ​​under standard and practical conditions. This equation assumes that the cross-section of the hose is constant throughout the system. Generally, as temperature increases, the gas expands, and the average distance between gas molecules increases. Because the distance between gas molecules increases, the mass of gas in a given volume decreases. If the mass flow rate remains constant, then as the temperature increases, the volume flow rate increases so that the same number of gas molecules (mass) are supplied to the plasma torch per unit time over a given cross-section. This increase in volume flow increases the pressure that the plasma arc can exert on the workpiece melt pool.

[0103] Conventional measurements are performed at the gas source, without taking into account possible variations in the cross-sections of hoses and connectors throughout the system, nor environmental factors near the plasma torch. At distances away from the gas source, the density of the gas supplied to the torch can vary significantly due to environmental variations, alone or in combination with mechanical tolerances (e.g., variations in the diameters of hoses, pipes, and connectors). As a result, the actual volumetric flow rate of gas supplied to the plasma torch is subject to significant variations, regardless of the conditions that may exist at the gas source.

[0104] The actual volume flow rate is an important factor in defining the plasma arc pressure on the melt pool, which has a crucial impact on the driving force of the melt pool and the melt pool dynamics. Volume flow rate measures the volume occupied by a gas as it flows through a pipe (such as a hose or plasma torch) and can therefore be considered a measurement of the space occupied by gas molecules. In contrast, mass flow rate measures the number of molecules flowing through the pipe. By using the systems and methods provided herein to generate a consistent volume flow rate for the supply gas at the plasma torch, the robustness of the manufacturing process can be improved, resulting in consistent final product quality of workpieces produced using the additive manufacturing deposition process, regardless of different environmental and / or mechanical variations.

[0105] By controlling the effect of the actual plasma volume flow rate on the melt pool dynamics, the systems and methods provided herein can be used to improve the robustness of the additive manufacturing process. Control can be achieved by adjusting and controlling the volume flow rate, alone or in combination with simultaneous mass flow control. By controlling the gas volume flow rate, alone or in combination with the mass flow rate, the effects of environmental disturbances, mechanical variations, or a combination thereof on the melt pool and the manufactured workpiece can be mitigated. For example, when the deposition process is performed using the same machine, changes in gas density due to environmental disturbances can be controlled so that the environmental disturbances do not affect the dynamic behavior of the melt pool or have a negligible effect on the dynamic behavior of the melt pool. When the deposition process is performed in "different" machines, whether of the same, similar, or different designs or configurations, environmental variations and variations between mechanical machines can be mitigated so that the melt pool dynamic behavior does not affect or has a negligible effect on the dynamic behavior of the melt pool.

[0106] In the wire-plasma arc additive manufacturing process, the flow rate of the gas to be ionized into plasma is one of the key process parameters. The gas to be ionized by the plasma torch is supplied to the plasma torch through a supply line, pipe or hose. At the plasma torch, the gas is ionized and can be accelerated in an electromagnetic field generated by a power supply (such as an inverter) and form a plasma arc, which is the heat source for the additive manufacturing process. This arc can then be used to heat / melt metal feedstock, such as titanium wire and substrate, which is the basis of metal-based additive manufacturing, where the goal is to create a three-dimensional shape by adding layer after layer of solidified material to produce the desired workpiece geometry.

[0107] When discussing the flow rate of gas to be ionized by a plasma torch, the flow rate can be expressed as mass flow rate (number of gas molecules provided to the plasma torch per unit time) or volume flow rate (volume of gas provided to the plasma torch per unit time).

[0108] For wire plasma arc additive manufacturing applications, conventional gas flow control techniques rely on mass flow measurement and control. Consequently, while the number of gas molecules supplied to the plasma torch to form the plasma arc remains at a desired level, variations in gas density (i.e., gas pressure and temperature) affect the average distance between gas molecules. The system can deliver varying gas volumetric flow rates to the torch to maintain a constant mass flow rate. In other words, the control system adjusts the gas velocity to compensate for variations in gas density.

[0109] One of the most important drivers of melt pool dynamics can be the total plasma arc pressure, which is the sum of the electromagnetic axial pressure and the plasma flow axial pressure. In some additive manufacturing processes, the electromagnetic axial pressure can be controlled by the arc current for a given arc length. The arc current is generated by a power supply, the negative terminal of which is connected to the consumable electrode in the plasma torch and the positive terminal to the workpiece. The strength of the generated electric field is then controlled by ionizing a certain number of gas atoms to support the desired level of primary current.

[0110] In the additive manufacturing process, in order to achieve accurate total arc pressure under various conditions, it is necessary to accurately control the axial pressure of the plasma flow. The total arc pressure can be described in the form of "stagnation pressure" or pitot tube pressure as a function of gas density and gas flow rate (velocity). Therefore, changes in gas density (which can be affected by temperature and pressure) will lead to changes in the axial pressure of the plasma flow, thereby leading to changes in the dynamic behavior of the molten pool. Therefore, the systems and methods provided herein can control the volume flow rate by the plasma torch alone or in combination with the mass flow of the gas to be ionized into plasma, so as to obtain a consistent force on the molten pool by the plasma arc, even if the gas density of the gas to be ionized into plasma changes due to mechanical disturbances, or environmental factors or disturbances, or a combination thereof.

[0111] In some configurations of the systems and methods provided herein, a plasma torch can be provided that includes a pressure sensor that can measure the pressure of the inert gas within the plasma torch. In some configurations, a plasma torch can be provided that includes a temperature sensor that can measure the temperature of the inert gas within the plasma torch. In some embodiments, a plasma torch can be used that includes both a pressure sensor and a temperature sensor. By including a pressure sensor and / or a temperature sensor in the plasma torch, the system can determine the pressure and / or temperature, respectively, within the plasma torch before the inert gas is ionized into plasma. The system can use this data to adjust the mass flow rate and / or volume flow rate of the inert gas to the plasma torch.

[0112] Figure 2is a simplified diagram showing an exemplary embodiment of an inert gas flow ionized from a gas supply manifold, passing through a flow control system as provided herein, and through a plasma torch including a temperature sensor and a pressure sensor within the plasma torch, the inert gas passing through a region of ionized EM field to generate a plasma arc, the pressure of which can be controlled. Figure 2 In the illustrated embodiment, inert gas from a gas supply 100 flows to a gas supply manifold 120 to a control valve 130, which regulates the flow of inert gas to the plasma torch 600. The inert gas flows through a flow meter 265 located at or near the torch inlet 605, allowing for measurement of the mass flow of the inert gas under the conditions experienced in the area of ​​the torch inlet 605. The inert gas flows through the torch inlet 605 through the plasma torch 600, which includes a pressure sensor 245 that measures the pressure of the inert gas within the plasma torch 600. The inert gas also flows through a temperature sensor 225 that measures the temperature of the inert gas within the plasma torch 600. The inert gas flows through a tungsten electrode 610 and into a region of an ionizing electromagnetic field (EM), where the inert gas is ionized into a plasma and exits the plasma torch 600 as a plasma arc 625.

[0113] The gas volume and mass flow control system 800 may be used to control or modify the mass flow rate or the volume flow rate or both. The gas volume and mass flow control system 800 may be the system 1000, an exemplary embodiment of which is described in Figure 3A and Figure 3B , which regulates the mass flow and monitors the volume flow of the gas to be ionized by the plasma torch. The gas volume and mass flow control system 800 may be the system 2000, an exemplary embodiment of which is shown in FIG. Figure 4A and Figure 4B , which regulates the volume flow and monitors the mass flow of the gas to be ionized by the plasma torch. The gas volume and mass flow control system 800 may be the system 3000, an exemplary embodiment of which is shown in FIG. Figure 7A 、 Figure 7B and Figure 7C It is shown in , which regulates the mass flow and volume flow of the gas to be ionized by the plasma torch. Figure 3A 、 Figure 3B 、 Figure 4A 、 Figure 4B and Figure 7A 、 Figure 7B and Figure 7C In the diagram shown, dashed lines represent data connection paths; solid lines represent fluid connection paths, such as pipes and hoses through which fluid can pass; and dotted lines enclose different groups of components, such as sensor kits or processor groups.

[0114] In a conventional system, a source of gas to be ionized can be connected to a manifold that can direct the gas to more than one end use, such as multiple plasma torches to be ionized into plasma, or to be used as a shielding gas, or to maintain an inert environment, such as within a chassis, and the manifold can provide gas to meet these needs simultaneously. In some configurations, the system can include a facility inert gas supply line that can supply inert gas to various components of the system directly or via a manifold. Exemplary inert gases are rare gases. In some embodiments, the inert gas is selected from helium, neon, argon, krypton, xenon, and combinations thereof. In some embodiments, the inert gas is argon. For example, the facility inert gas supply line can be an argon supply that can be in fluid communication with the manifold. For example, the density of the argon supplied to the manifold can be controlled in the gas supply line by using pressure control elements such as a pressure regulator and temperature control elements such as a heater and a temperature sensor. The inert gas from a gas manifold or any other type of gas distribution system can be directed to a mass flow unit that can measure and regulate the flow of the inert gas under standard conditions to provide the inert gas to the plasma torch of the additive manufacturing machine.

[0115] However, because conventional systems rely on standard conditions, the density of the inert gas supplied via the gas supply manifold can vary significantly due to several factors. One factor may be the varying lengths and cross-sections of the tubing supplying the inert gas to different areas of the AM system component. Another factor may be the variability in inert consumption at different stages of the AM process and between different AM system components and machines. Yet another factor influencing the density of the supplied inert gas may be the significant variations in temperature and pressure across different components in the AM process system. For example, the gas hoses and tubing supplying the inert gas to the plasma torch are subject to a wide spectrum of electromagnetic radiation from the plasma arc and workpiece, which can vary from part to part and also vary during the deposition process depending on workpiece thickness or mass. As a result, the temperature of these hoses and tubing can vary, affecting the temperature of the inert gas being ionized by the plasma torch and, consequently, the pressure at which the plasma torch directs the generated plasma toward the melt pool.

[0116] While maintaining mass flow rate, changes in plasma density can affect the volumetric flow of plasma at the plasma torch, which in turn affects the arc pressure on the molten pool. To address this issue, a system is provided herein that can monitor, regulate, or both regulate mass flow, volume flow, or both. The provided system includes a sensing suite comprising a temperature measurement cell, a pressure measurement cell, and a mass flow measurement cell. The sensing suite includes sensors located near the gas inlet of the plasma torch so that the sensing suite can measure changes in temperature, pressure, and mass flow due to environmental or machine changes.

[0117] The system may also include a processor group or controller group that can monitor, modify and maintain the gas volume flow rate / speed at a desired and consistent level, regardless of any changes in gas density due to any of the above reasons. The controller group may include a controller for calculating the actual volume flow rate based on the above mathematical formula. The controller group may include a mass flow controller and / or a volume flow controller to monitor, adjust and maintain mass flow and volume flow, respectively. In such a configuration, the system may include a separate or independent central processor unit to perform the functions of a calculation processor, a mass flow controller, a volume flow controller and a process master controller. The process master controller may communicate with each of the separate calculation processors, volume flow controllers and mass flow controllers. This configuration may allow the process master controller to control the functions of each separate processor that controls the calculation processor, mass flow controller and volume flow controller. Each of the calculation processor, mass flow controller and volume flow controller may also be configured as a separate microcontroller that communicates with the process master controller. Figure 3A 、 Figure 3B 、 Figure 4A 、 Figure 4B and Figure 7A 、 Figure 7B 、 Figure 7C An exemplary configuration of a system including a processor group as provided herein is shown in FIG. Although a single processor or CPU (e.g., a microcontroller) can be used for the computational processor, mass flow controller, and volume flow controller to embed control tasks onto several CPUs, system functionality does not require a processor group. The controller does not necessarily need to be in the form of a single CPU.

[0118] The system may also include a process master controller, rather than a set of separate processors, wherein the computational processor, mass flow controller, and / or volume flow controller are not separate processors or separate central processing units, but rather are functions or software codes that run (e.g., in an integrated manner) on the process master controller. The functionality of the mass flow controller and the volume flow controller may be integrated into a unified controller, such as the process master controller. In this configuration, the process master controller may communicate with the control valve and the density control element, and using data generated by the mass flow controller and the volume flow controller, the mass flow rate and / or volume flow rate of the inert gas to be ionized by the plasma torch may be modified and controlled, thereby regulating the plasma arc pressure applied to the molten pool. Figures 8A to 8B An exemplary embodiment illustrating a system in which a computing processor, mass flow controller, and / or volumetric flow controller are functions or software code running on a process master controller is depicted in FIG.

[0119] Systems for regulating mass flow and monitoring volume flow

[0120] An exemplary embodiment of a system 1000 for regulating mass flow and monitoring volume flow is described in Figure 3A Shown in. Figure 3A The embodiment shown in FIG includes a processor complex 300 comprising a separate computing processor 320, a process master controller 340, and a mass flow controller 380. The process master controller communicates with the computing processor 320 and the mass flow controller. The process master controller 340 also communicates with a part program 400, a sensing package 200, and a data monitoring system 500. The mass flow controller further communicates with a control valve, resulting in a controlled mass flow of inert gas to the plasma torch.

[0121] An alternative embodiment of the system 1000 for regulating mass flow and monitoring volume flow is Figure 3B As shown in Figure 3B In the exemplary system shown, a single process master controller 340 includes the control tasks of the computational processor and the mass flow controller, which are software codes or functions running in an integrated manner on the process master controller. The process master controller communicates with the density control element and the control valve and transmits mass flow control commands to the control valve and / or density control element to generate a controlled mass flow of inert gas to the plasma torch.

[0122] These configurations can be used to troubleshoot the system. For example, these configurations can be used to detect leaks in the system. In the depicted configuration, mass flow and gas density are measured directly at or near the plasma torch inlet. This allows all leaks in pipes, hoses, or connections that may have a reduced mass flow rate between the gas supply 100 and the sensing connector 195 to be detected and compensated for by the action of the control valve. In addition, density measurement using any of these configurations can allow density changes due to environmental factors, mechanical tolerances, and absorbed heat due to arc radiation to be taken into account when adjusting the inert gas flow.

[0123] exist Figure 3A and Figure 3B In the exemplary embodiment shown, the gas supply 100 is connected to a gas supply manifold 120 via a hose 110. The inert gas of the gas supply 100 can be a rare gas. In some embodiments, the gas supply 100 provides a gas selected from the group consisting of helium, neon, argon, krypton, xenon, and combinations thereof. In some embodiments, the gas supply 100 provides argon to the system. The gas supply manifold 120 can provide gas to several different components of the additive manufacturing machine, or to different additive manufacturing machines, as well as or in addition to providing gas to maintain a desired environment near the plasma arc or workpiece. For example, the gas supply manifold 120 can provide gas to a chamber that houses the additive manufacturing machine. For clarity, Figure 3A and Figure 3B Only the gas line 125 connecting the gas supply manifold 120 to the control valve 130 is shown. The control valve 130 can be operated to increase or decrease the opening in the valve to increase or decrease the amount of gas flowing through the control valve 130.

[0124] exist Figure 3A In the configuration shown, inert gas can flow from the control valve 130 through the hose 185 to the plasma torch 600, which ionizes the gas to form a plasma arc 625, which can be used to melt the metal wire source to deposit molten metal from the molten metal wire source onto the workpiece 650. Figure 3B In the configuration shown, inert gas can flow from the control valve 130 through the hose 135 to the density control element 140, and then through the hose 190 to the plasma torch 600, which ionizes the gas to form a plasma arc 625, which can be used to melt the metal wire source to deposit molten metal from the molten metal wire source onto the workpiece 650.

[0125] Figure 3A and Figure 3BThe sensing package 200 in the embodiment includes a sensing connector 195 to the gas line 185 to allow measurement of the temperature, pressure, and flow of the gas to the plasma torch. The sensing package may include a temperature measurement unit 220, a pressure measurement unit 240, and a mass flow measurement unit 260. The temperature measurement unit 220 may include a temperature sensor 225 (not shown). The pressure measurement unit 240 may include a pressure sensor 245 (not shown). The mass flow measurement unit 260 may include a flow meter 265 (not shown) for measuring mass flow under standard conditions. Other environmental measurement devices may be included.

[0126] The sensing connector 195 of the sensing kit 200, which can be a gas sampling hose or tube, can be connected to any portion of the inert gas delivery line located anywhere between (i) a gas manifold or any other type of gas distribution system and (ii) the gas ionizer electromagnetic field. Due to the various configurations of different deposition machines, placement can be selected to accommodate any spatial limitations of placing system hardware (e.g., the sensing kit). As the placement of the sensing connector 195 becomes farther from the ionization field, some external disturbances to the controlled gas flow, such as changes in gas temperature due to gas leaks or radiation from the plasma arc and workpiece, may not be detected and, therefore, may not be compensated for by the gas flow controller. When physical limitations permit, it may be advantageous to place the sensing connector 195 as close to the torch as possible to detect external disturbances, such as leaks in the hose, reduce mass flow or radiation absorption by the hose, and increase gas flow temperature. In some embodiments, the sensing connector 195 can be located 10 mm to 15 cm, or 2 cm to 2 m, or more, from the plasma torch gas inlet. Although depicted as a single element 195 for clarity, each component of the sensing connector, such as the temperature sensor, pressure sensor, and / or flow meter, may be placed in a separate physical location and provide data from different locations to the sensing suite.

[0127] exist Figure 3A and Figure 3B In the exemplary embodiment shown, the sensing connector 195 can be connected directly to the torch inlet. An advantage of this configuration is that all external disturbances to the controlled gas flow, such as gas leaks or changes in gas temperature due to radiation from the arc and the workpiece, until the torch inlet will be detected and compensated by the gas flow controller. Using this configuration, the gas flow controller will not capture and compensate for external disturbances to the gas flow introduced inside the torch assembly, such as pressure changes due to mechanical tolerances of the torch, or temperature changes due to a cooling circuit malfunction. In an exemplary embodiment, the sensing connector 195 can be connected to the gas delivery line inside the production chamber only at the gas input of the plasma torch or near the plasma torch gas inlet.

[0128] In an exemplary embodiment, the pressure sensor and / or the temperature sensor of the sensing assembly may be located inside the torch. Figure 2 An exemplary embodiment of a plasma torch that includes both a pressure sensor and a temperature sensor is shown. An advantage of this configuration is that all external disturbances to the gas flow, including the effects of mechanical tolerances of the torch, radiation and leakage from the plasma arc, will be measured and compensated by the gas flow controller, which will control the radiation and leakage from the plasma arc. Placing the pressure and temperature sensors in the sensor kit inside the torch allows for the most precise control of the inert gas flow, which will be delivered to the ionizing electromagnetic field inside the torch. Disadvantages of modifying the torch to include the pressure and temperature sensors of the sensor kit may include limitations on introducing the hardware for the pressure and temperature sensors of the sensor kit into the torch, such as space limitations. Another disadvantage may be the increased cost of this torch configuration.

[0129] In some embodiments, multiple sensing connectors 195 can be used, each sensing connector connected at a different location. Exemplary multiple locations can include any combination of (a) in the inert gas feed line between the gas manifold and the torch inlet, (b) at the torch inlet, and (c) inside the torch. Multiple sampling by multiple sensing connectors 195 can allow the sensing kit 200 to more accurately measure and control gas density changes in the entire system. The sensors of each individual component of the sensing kit can each be separated and independently placed in a different location. For example, the mass flow measurement 260 of the sensing kit 200 can be positioned along multiple portions of the inert gas line 175 or 185. Separate temperature sensors and / or pressure sensors can be positioned along the inert gas line 175 or 185, or even into the plasma torch 600.

[0130] Figure 3A 、 Figure 3B 、 Figure 4A 、 Figure 4B and Figure 7A 、 Figure 7B 、 Figure 7C The sensor assembly 200 shown in FIG can be separated and each element can be embedded in a different part of the inert gas line (125 and 185). Specifically, the grouping of sensors 220, 240 and 260 is only for Figure 3A 、 Figure 3B 、 Figure 4A 、 Figure 4B and Figure 7A 、 Figure 7B 、 Figure 7C This is shown for clarity of presentation in FIG. 1 and is not intended to limit the generality of the control scheme since, as mentioned above, the sensors may be separated from one another anywhere between the gas manifold and the gas ionizer electromagnetic field.

[0131] By using information generated by the elements of the sensing suite 200 (e.g., Figure 3A The processor group 300 may be a group of processors that perform different tasks in parallel, or a single processor that performs a group of tasks in parallel to support various functions. The processor group 300 represents the parallel computation of a logical process that may be embedded on different physical processors ( Figure 3A ), or can be integrated into a process master controller in the form of a logic function ( Figure 3B ), which depends on the computing power of the processor. Specifically, the processes 320, 360 and 380 can be implemented in the form of different functions on a physical processor, which can be 340, such as Figure 3B As shown, or similarly can be done in parallel on different processors, as Figure 3A shown.

[0132] The part program 400 can be communicated with the process master controller. The part program 400 includes the data required by the additive manufacturing system to produce a given preform, including the trajectory of the plasma torch that forms layer after layer of molten metal to form the preform, as well as gas flow and gas setpoint signals. The process master controller can then provide the mass flow setpoint obtained from the part program 400 and the actual mass flow rate value obtained from the sensing kit 200 to the mass flow controller 380. The mass flow controller 380 can compare the mass flow setpoint with the actual mass flow rate and send a signal to the control valve 130 to gradually open the control valve 130 to increase the mass flow rate of gas to the plasma torch. The mass flow controller 380 can also send a signal to the control valve 130 to gradually close the control valve 130 to reduce the mass flow rate of gas to the plasma torch. The process master controller 340's action of regulating the gas mass flow from the gas supply manifold 120 to the plasma torch 600 based on the data received from the sensing kit 200 via the sensing connector 195 allows a controlled gas mass flow rate to be delivered to the plasma torch. This can allow a controlled number of gas molecules to be supplied to the plasma torch per unit time (i.e., a controlled mass flow rate). The system can also monitor the volumetric flow rate of the inert gas. The calculated volumetric flow rate data received by the process master controller 340 from the computational processor 320 can be sent to the data monitoring system 500 for operator review. By monitoring the actual volumetric flow rate data, the operator or the system can determine the plasma arc pressure and make any necessary adjustments to the inert gas mass flow rate to adjust the plasma arc pressure. In this configuration, the volumetric flow rate data can be used for position process analysis, machine status analysis, and leak detection and elimination (or compensation).

[0133] Data generated by any one or a combination of the sensing suite, computing processor, mass and volumetric flow controllers, control valves, and density control elements can be logged to a data server or other form of data monitoring system and / or presented to a user in real time or as a data file. This can allow the system or user to evaluate the data for system operation, quality control, diagnostics, or problem detection and / or correction. In some instances, previously recorded data can be used to update a part program to adjust flow setpoints. In some instances, real-time data can be monitored during manufacturing to allow adjustments to flow rates to provide controlled flow parameters consistent with the flow setpoints used for workpiece production.

[0134] In some instances, daily operational data can be compared to determine the inert gas requirements needed for the manufacture of a given workpiece, thereby allowing for allocation of resources. In some instances, the data can be compared with information from quality control analysis of finished workpieces to determine whether flow parameters need to be adjusted or flow setpoints need to be reset to achieve similar quality control results in subsequent workpieces. The collected data, such as a combination of mass flow control and volumetric flow control, can be used to generate flow setpoints that achieve desired performance in the final workpiece by controlling the plasma arc pressure on the melt pool during workpiece manufacture. The collected data can also be compared with archived data to minimize production variations from day to day or across different manufacturing machines or systems. Any one or a combination of the process master controller, the computation processor, the volumetric control processor, and the mass flow control processor can be in communication with a data server, and the mass flow and volumetric flow data can be sent to the data server.

[0135] The control valve 130 can be operated by an actuator in response to a setpoint signal that can be generated by a process master controller 340. The setpoint can correspond to a desired mass flow rate of the inert gas. The process master controller 340 can receive the mass flow setpoint from the part program 400, and the process master controller 340 can be connected to the actuator connected to the control valve 130 directly or via a mass flow controller 380. The process master controller 340 can compare the actual mass flow value with the mass flow setpoint to generate an adjustment signal that can be transmitted to the actuator of the control valve 130 to adjust the opening of the control valve 130 to cause a change in the flow rate of the inert gas through the control valve 130, thereby reducing any difference between the set mass flow value and the measured actual mass flow value.

[0136] The mass flow controller 380 may include a sensor attached to the control valve 130 that may detect the open position of the valve, and the sensor may transmit the valve position to the mass flow controller 380 in communication with the process master controller 340 to adjust the valve position based on valve position feedback received from the sensor.

[0137] The signal transmitted from the mass flow controller 380 or the control valve 130 to the process master controller 340 can be a digital signal, such as a high voltage, a low voltage, or a zero voltage, indicating that the measured value is above, below, or at a preferred level. Similarly, any output transmitted by the process master controller 340 directly or via the mass flow controller 380 to the control valve 130 can be an open, closed, or neutral signal. Alternatively, the signal can transmit an analog value.

[0138] The process master controller 340 can be configured to output the valve control signal to the control valve 130 or mass flow controller 380 as a high, low, or zero voltage, and may also include an option for outputting an error signal. If the valve control signal is a high signal or a low signal, the control valve 130 can gradually close or open, respectively, until a zero signal is reached. If the valve control signal is zero, the valve will not change position. If the valve control signal is an error, the valve can be completely closed or the error output can be interpreted as a zero output, depending on the type of error. For example, if the flow rate is too low to support the desired flow rate, the control valve 130 can be fully opened to maximize the flow rate. Alternatively, if the sensor detects insufficient or no inert gas flow, the error signal can be interpreted as closing the valve and sending an alarm signal to the data monitoring system 500.

[0139] Due to changes in pipe length and / or diameter, or changes in inert gas consumption and changes in the demands placed on the gas supply manifold 120 by different components of the additive manufacturing machine or related system, coupled with the influence of environmental factors such as production ambient temperature (deposition chamber temperature or production hall temperature), the density of the gas supplied from the gas supply manifold 120 varies significantly (in terms of temperature and pressure). The embodiments of the system provided herein are configured as follows Figure 2 The system 1000 shown in FIG. 1 allows for a controlled inert gas mass flow to be provided to a plasma torch despite various requirements on the gas supply manifold 120 .

[0140] Gas flow measurement and control systems in conventional additive manufacturing systems are typically located within a control cabinet, which may be located far from the torch due to space limitations in the production room of the additive manufacturing machine. This means that the regulated flow in the control cabinet is subject to disturbances that increase with the distance between the control cabinet and the torch. However, by positioning the flow sampling hose of the sensing kit at or near the torch inlet, all disturbances to the mass flow (e.g., due to leaks in the pipes, fittings, or hoses) and volume flow (e.g., due to mechanical tolerances in pipe and hose diameters, and temperature variations due to the gas hose absorbing radiant heat from the arc and workpiece or temperature variations in the production cell) can be detected. Positioning the sensing connector 195 near or near the gas inlet of the plasma torch 600 allows for the detection of any reduction in the mass flow of the gas delivered to the plasma torch, such as a reduction in plasma flow due to leaks, so that the sensing kit 200 can serve as a second opinion sensor for the plasma mass flow from the gas manifold 120 to the plasma torch 600.

[0141] The temperature measurement unit 220 of the sensing kit 200 may include a temperature sensor to measure the temperature of the inert gas. The temperature sensor of the temperature measurement unit 220 is not limited. Exemplary temperature sensors include thermocouples, thermistors, resistance temperature devices, infrared detectors, bimetallic devices, liquid expansion devices, and any combination thereof.

[0142] The pressure measurement unit 240 of the sensing assembly 200 may include a pressure sensor to measure the pressure of the inert gas. The pressure sensor of the pressure measurement unit 240 is not limited. Exemplary pressure sensors include piezoelectric strain gauges, capacitive sensors, strain gauges, resistive pressure sensors, piezoresistive strain gauges, metal thin film sensors, titanium alloy sensing elements, ceramic thick film sensors, optical sensors, accelerometers, micro-electromechanical system sensors, and combinations thereof.

[0143] The mass flow measurement unit 260 of the sensing assembly 200 may include a flow meter to measure mass flow. The mass flow meter can be of any configuration. For example, a mass flow meter can measure the mass of a substance passing through the mass flow meter in a given time, regardless of the space occupied by the molecules of the substance. Based on this information, the mass flow rate can be calculated. Exemplary mass flow meters include thermal mass flow meters and Coriolis mass flow meters. Such instruments are known in the art (e.g., see U.S. Patent Nos. 4,542,650 (Renken et al., 1985); 4,934,196 (Romano, 1990); 5,497,665 (Cage et al., 1996); 7,032,462 (Barger et al., 2006); 7,181,982 (Christian et al., 2007); 7,905,139 (Lull, 2011); 8,356,623 (Isobe et al., 2013); and 8,504,318 (Mendelson et al., 2013)).

[0144] Systems for regulating volume flow and monitoring mass flow

[0145] In the system provided herein, the gas flow to the plasma torch can be calibrated and controlled by selecting between mass flow control as described above and volume flow control based on the requirements and advantages and disadvantages of the process. In an exemplary embodiment, the volume flow of the gas is controlled by comparing the set value and the actual value of the volume flow to adjust the gas volume per unit time (i.e., compensate for density changes). The data generated by the sensing kit of the system provided herein can be used to adjust the gas flow to the plasma torch. The mass flow rate of the plasma column can be adjusted to achieve the actual volume flow rate at the target level across the gas density changes, thereby achieving the target plasma discharge rate at the plasma torch.

[0146] An exemplary configuration is shown as Figure 4A and Figure 4B System 2000 in. Figure 4A The embodiment shown in includes a processor group including a separate computing processor, a process master controller, and a volumetric flow controller, wherein the volumetric flow controller communicates with a control valve and a density control element. Figure 4B In the embodiment shown, a single process master controller controls the tasks of the computational processor and the volumetric flow controller, which are software codes or functions running in an integrated manner on the process master controller. The process master controller communicates with the density control element and the control valve and transmits volumetric flow control commands to the control valve and / or density control element. Figure 4A and Figure 4B In the system 2000, the fluid flow path of the inert gas from the gas supply 100 to the plasma torch 600 is similar to Figure 3A 1000. The difference is that there is a density control element 140 between the control valve 130 and the sensing connector 195. The density control element 140 can modify or control the temperature and / or pressure of the inert gas. The density control element 140 can include a temperature regulator 150 (not shown) or a pressure regulator 160 (not shown) or both the temperature regulator 150 and the pressure regulator 160. The density control element 140 can be used in a controlled manner to change or modify the temperature or pressure, or both the temperature and pressure of the gas in order to control the gas volume flow / gas velocity to the plasma torch to achieve and maintain a target plasma emission level from the plasma torch. Figure 4A In the configuration shown in FIG, the density control element 140 communicates with the volumetric flow controller 360 of the processor group 300. The volumetric flow controller 360 also communicates with the control valve 130. Figure 4B In the configuration shown in , the density control element 140 is in communication with the process master controller 340 , which is also in communication with the control valve 130 .

[0147] Adjusting the temperature and / or pressure can control the inert gas density to maintain the average distance between inert gas molecules constant despite environmental and mechanical disturbances that may affect this distance, thereby achieving a target volumetric flow rate for the plasma. A gas density regulator can help adjust all parameters that define the volumetric flow rate, which can result in consistent application of the plasma arc to the melt pool even as external conditions or disturbances change. The density control element can include a temperature regulator, a pressure regulator, or both.

[0148] The density control element 140 may include a temperature regulator. There is no limitation on the type of temperature regulator that may be included in the density control element. The temperature control regulator may include an element capable of increasing the temperature of the gas passing through the density control element. The temperature control regulator may include an element capable of decreasing the temperature of the gas passing through the density control element. The temperature control regulator may include a first element capable of increasing the temperature of the gas passing through the density control element and a second element capable of increasing the temperature of the gas passing through the density control element.

[0149] The temperature regulator may include a heater. The heater may increase the temperature of the inert gas within the density control element 140, which may increase the volume occupied by the same number of gas molecules. The heater may include an induction heater, a resistive heater, a piezoelectric ceramic heating element, or a combination thereof.

[0150] The temperature regulator may include a cooling device. The cooling device may reduce the temperature of the inert gas within the density control element 140, which may reduce the volume occupied by the same number of gas molecules. The cooling device may include piping connected to a refrigeration fluid reservoir and a pump to form a closed-loop cooling path to supply cooling fluid to the temperature regulator within the density control element 140. The cooling device may include a closed duct passing through the temperature regulator and a fan connected to the closed duct to pass cooling gas through the temperature regulator within the density control element 140. A combination of a closed-loop refrigeration cooling path and piping for passing cooling gas through the temperature regulator may be used. The density control element 140 may include a closed-loop cooling path to supply coolant to the temperature regulator within the density control element 140, as well as a heater to increase the temperature of the gas flowing through the density control element, allowing the temperature to be independently regulated using either device alone.

[0151] Figure 5 An exemplary density control element 140 for controlling the pressure of the inert gas to the plasma torch inlet and thus controlling the average distance between gas molecules is shown in FIG. Figure 5 In the exemplary embodiment shown in , the density control element 140 adjusts the pressure of the inert gas by changing the temperature of the inert gas. For a given volume of gas, by increasing the temperature, the pressure can be increased, and conversely, by decreasing the temperature, the pressure can be decreased. Figure 5In the exemplary embodiment shown in FIG, the density control element 140 includes a temperature regulator 150, which includes a liquid temperature regulator 151. The liquid temperature regulator 151 can increase or decrease the temperature of the fluid. The liquid temperature regulator 151 is in fluid communication with a heat exchanger 154 within the density control element 140 via a conduit 153 connected to an outlet 152 of the liquid temperature regulator 151. The heat exchanger 154 is positioned in thermal communication with the inert gas flowing through the density control element 140. When the temperature of the liquid from the liquid temperature regulator 151 flowing through the heat exchanger 154 is lower than the temperature of the inert gas flowing through the density control element 140, the liquid can absorb thermal energy from the inert gas, thereby reducing the temperature of the inert gas as it passes through the heat exchanger 154 toward the plasma torch inlet. When the temperature of the liquid from the liquid temperature regulator 151 flowing through the heat exchanger 154 is higher than the temperature of the inert gas flowing through the density control element 140 , the liquid can provide thermal energy to the inert gas, thereby raising the temperature of the inert gas as it passes through the heat exchanger 154 toward the plasma torch inlet.

[0152] exist Figure 5 In the embodiment shown in , the liquid temperature regulator 151 includes an outlet 152 connected to a pipe 153, which is connected to a heat exchanger 154 to allow fluid to flow from the liquid temperature regulator 151 to the heat exchanger 154. In the embodiment shown, the temperature regulator 150 includes a pump 170 that can pump liquid from the heat exchanger 154 through a pipe 155, which is connected to an inlet 176 of the pump 170 and returns to the inlet 158 ​​of the liquid temperature regulator 151 through the outlet 174 of the pump 170 through the pipe 156 to complete the fluid flow circuit. Pipes 153, 155 and 156 can be hoses or pipes. The pump 170 is shown as being connected between the heat exchanger 154 and the liquid temperature regulator 151 after the heat exchanger 154. The pump 170 can also be connected between the liquid temperature regulator 151 and the heat exchanger 154 before the heat exchanger 154. The pump 170 may allow the liquid of the liquid temperature regulator 151 to circulate through the fluid flow loop and return to the liquid temperature regulator 151 .

[0153] To allow for faster temperature changes, the pump can be configured to include a drain 178 to allow liquid received from the heat exchanger 154 to be drained from the fluid flow circuit rather than being recirculated back to the liquid temperature regulator 151. The pump 170 can also include an inlet 172 to allow replacement fluid from an external liquid source 175 to be introduced into the fluid flow circuit for channeling to the liquid temperature regulator 151 for temperature regulation of the liquid.

[0154] The density control element 140 may include a pressure regulator. The pressure regulator may include any mechanical pressure regulator. For example, the pressure regulator may include a movable plenum chamber that can increase the volume of the pressure regulator, thereby reducing the pressure of the plasma column exiting the pressure regulator, or reduce the volume of the pressure regulator, thereby increasing the pressure of the plasma column exiting the pressure regulator.

[0155] exist Figure 6 An exemplary embodiment of a density control element 140 including a pressure regulator is shown in FIG. In the illustrated embodiment, the pressure regulator 160 includes a plenum chamber 162, the volume of which can be adjusted by adjusting the position of a sealing element 164 via a position adjuster 166. The position adjuster 166 can raise at least a portion of the sealing element 164, thereby increasing the volume of the plenum chamber 162, or can lower at least a portion of the sealing element 164, thereby decreasing the volume of the plenum chamber 162. By increasing the volume of the plenum chamber 162, the effective volume within the pressure regulator 160 increases, and thus the distance between the inert gas molecules decreases. By decreasing the volume of the plenum chamber 162, the effective volume within the pressure regulator 160 decreases, and thus the distance between the inert gas molecules increases. The sealing element 164 can be a solid disk that can be raised or lowered to increase or decrease the volume of the plenum chamber 162. The sealing element 164 may be a flexible or elastic diaphragm secured to the wall of the plenum 162, and the position adjuster 166 may push the center of the sealing element 164 toward the airflow tube to reduce the volume of the plenum 162, or the position adjuster 166 may pull the center of the sealing element 164 away from the airflow tube to increase the volume of the plenum 162. Although the illustrated embodiment shows a single plenum, the pressure regulator 160 may include two or more plenums.

[0156] exist Figure 4A and Figure 4B In the exemplary embodiment of the system shown in , a volumetric flow controller 380 is included that communicates with the control valve 130 and the density control element 140. In system 2000, a gas supply 100 is connected to a gas supply manifold 120 via a hose 110. The inert gas of the gas supply 100 can be a rare gas. In some embodiments, the gas supply 100 provides a gas selected from the group consisting of helium, neon, argon, krypton, xenon, and combinations thereof. In some embodiments, the gas supply 100 provides argon to the system. The gas supply manifold can provide gas to several different components of the additive manufacturing machine, or to different additive manufacturing machines, in addition to or in addition to providing gas to maintain a desired environment near the plasma arc or workpiece. Figure 4A and Figure 4BOnly the gas line 125 connecting the gas supply manifold 120 to the control valve 130 is shown. The control valve 130 can be operated to increase or decrease the opening in the valve to increase or decrease the amount of gas flowing through the control valve 130. From the control valve 130, the gas can flow through the hose 135 to the density control element 140, and then through the hose 190 to the plasma torch 600, which ionizes the gas to form a plasma arc 625, which can be used to melt a metal wire source to deposit molten metal from the molten metal wire source onto a workpiece 650.

[0157] The sensing package 200 includes a sensing connector 195 to the gas line 190 to allow measurement of the temperature, pressure, and flow of the gas to the plasma torch. The sensing package can include a temperature measurement unit 220, a pressure measurement unit 240, and a mass flow measurement unit 260. The temperature measurement unit 220 can include a temperature sensor. The pressure measurement unit 240 can include a pressure sensor. The mass flow measurement unit 260 can include a flow meter for measuring mass flow under standard conditions. Other environmental measurement devices can be included in the sensing package 200.

[0158] The sensing connector 195 of the sensing assembly 200 can be located within the production chamber directly at or near the plasma torch gas inlet. This positioning can allow the sensing assembly 200 to measure and control changes in gas density due to any arc radiation interference, such as temperature changes caused directly by the action of the plasma column, or heat contributions from the workpiece, such as radiant heat from the melt pool, or a combination thereof. This positioning can also allow a mass flow meter to detect changes in flow rate that can be attributed to leaks in the gas line between the gas supply and the plasma torch. In some embodiments, the sensing connector 195 can be located 10 mm to 15 cm from the plasma torch gas inlet.

[0159] By using information generated by the elements of the sensing suite 200 (e.g., Figure 4A and Figure 4B temperature, pressure, and mass flow in the embodiment shown), the processor group 300 ( Figure 4A ) or process master controller 340 ( Figure 4B ) can calculate the actual volume flow of the gas to be ionized. Figure 4A The processor group 300 may include a calculation processor 320 for calculating an actual volumetric flow rate, and a volumetric flow controller 360 that may operate the control valve 130 based on data received from a process master controller 340. For example, the process master controller 340 may receive the calculated volumetric flow rate from the calculation processor 320 and the measured gas mass flow rate from the sensing kit 200. Figure 4BThe process master controller 340 may include software functionality that performs the tasks of a computational processor to calculate the actual volumetric flow rate, and software functionality that performs the functions of the volumetric flow controller 340. The process master controller 340 may operate the control valve 130 based on data generated by the software functionality that calculates the actual volumetric flow rate and the functions of the volumetric flow controller.

[0160] The part program 400 can be communicated to the process master controller. The part program 400 includes the data required by the additive manufacturing system to prepare a given preform, including the trajectory of the plasma torch that forms layer after layer of molten metal to form the preform, as well as the gas flow and gas setpoint signals. The process master controller can then provide the volume flow setpoint obtained from the part program 400 and the actual volume flow calculated and obtained from the calculation processor 320 to the volume flow controller 360 ( Figure 4A ) or software functions provided to perform the functions of the volumetric flow controller 340 ( Figure 4B ). The volume flow controller 360, whether configured as a separate processor or as a software function, can compare the volume flow setpoint to the volume flow calculated value. Figure 4A In the configuration shown in , when the calculated volume flow value is lower than the volume flow setpoint, the processor comprising the volume flow controller 360 sends a signal to the control valve 130 to gradually open the control valve 130 to increase the gas mass flow to the plasma torch. Figure 4B In the configuration shown in , the process master controller receives data from the volumetric flow controller 360 software function, and when the calculated volumetric flow value is higher than the volumetric flow setpoint, the process master controller 340 can send a signal to the control valve 130 to gradually close the control valve 130 to reduce the gas mass flow to the plasma torch.

[0161] The process master controller 340 regulates the volumetric flow of gas from the gas supply manifold 120 to the plasma torch 600 based on data received from the sensing kit 200 directly via the sensing connector 195 or via a separate volumetric flow controller, allowing a controlled volumetric flow of gas to be delivered to the plasma torch. This can allow a controlled volume of gas molecules (i.e., a controlled volumetric flow) to be supplied to the plasma torch per unit time. The system can also monitor the mass flow rate of the inert gas. The mass flow data received by the process master controller 340 from the mass flow measurement unit 260 of the sensing kit 200 can be sent to the data monitoring system 500 for operator or system inspection. In this configuration, the mass flow data can be used for deposition process analysis, control system calibration, and leak detection and elimination (or compensation).

[0162] The control valve 130 may be operated by a driver in response to a set point signal, which may be supplied by a volumetric flow controller 360 ( Figure 4A ) or the process master controller 340 ( Figure 4B ) is generated. The set point may correspond to a desired volumetric flow rate of the inert gas. The process master controller 340 may receive the volumetric flow rate set value from the part program 400, and the process master controller 340 may be connected to the actuator connected to the control valve 130 directly or via the volumetric flow controller 360. The process master controller 340 may compare the actual calculated volumetric flow rate value with the volumetric flow rate set value to generate an adjustment signal that may be transmitted to the actuator of the control valve 130 to adjust the opening of the control valve 130 to cause a change in the flow rate of the inert gas through the control valve 130, thereby reducing any difference between the set volumetric flow rate value and the calculated actual volumetric flow rate value.

[0163] Whether configured as a separate processor or as a software function running on the process master controller, the volumetric flow controller 360 can include a sensor attached to the control valve 130 that can detect the open position of the valve, and the sensor can transmit the valve position to the volumetric flow controller 360 in communication with the process master controller 340 so that the valve position can be adjusted based on the valve position feedback received from the sensor.

[0164] The signal transmitted from the volumetric flow controller 360 or the control valve 130 to the process master controller 340 can be a digital signal, such as a high voltage, a low voltage, or a zero voltage, indicating that the measured value is above, below, or at a preferred level. Similarly, any output transmitted by the process master controller 340 directly or via the volumetric flow controller 360 to the control valve 130 can be an open, closed, or neutral signal. Alternatively, the signal can transmit an analog value.

[0165] The process master controller 340 can be configured to output the valve control signal as a high, low, or zero voltage to the control valve 130 or volumetric flow controller 360, and may also include an option for outputting an error signal. If the valve control signal is a high signal or a low signal, the control valve 130 can gradually close or open, respectively, until a zero signal is reached. If the valve control signal is zero, the valve will not change position. If the valve control signal is an error, the valve can be completely closed or the error output can be interpreted as a zero output, depending on the type of error. For example, if the pressure is too low to support the desired flow, the control valve 130 can be fully opened to maximize the flow. Alternatively, if the sensor detects insufficient or no inert gas flow, the error signal can be interpreted as closing the valve and sending an alarm signal to the data monitoring system 500.

[0166] The density of the gas supplied from the gas supply manifold 120 is subject to large variations (in terms of temperature and pressure) due to variations in line length, or variations in inert gas consumption and demands placed on the gas supply manifold 120 by different components of the additive manufacturing machine or related system, as well as temperature disturbances due to radiant heat from the arc, production chamber variations, and ambient temperature disturbances. The embodiments of the system provided herein are configured as Figure 4A and Figure 4B The system 2000 shown in FIG. 1 allows a controlled volumetric flow of inert gas to be provided to a plasma torch, despite various requirements on the gas supply manifold 120 .

[0167] Systems for regulating volume and mass flows

[0168] In another embodiment of the system provided herein, the flow rate of the inert gas delivered to the plasma torch can be controlled based on the number of gas molecules over time and the volume of gas over time. Figure 7A 、 Figure 7B and Figure 7C An exemplary configuration of a system 3000 that regulates both mass flow and volume flow is shown in The system 3000 can maintain the gas volume flow rate / velocity at a desired and relatively consistent level regardless of any changes in the inert gas density. Figure 7A The illustrated embodiment includes a processor complex comprising a separate computational processor, a process master controller, a volumetric flow controller in communication with a density control element, and a mass flow controller in communication with a control valve.

[0169] Instead of using separate processors, the system provided herein can include a single process master controller, wherein the control tasks of the computational processor, the mass flow controller, and the volumetric flow controller are software codes or functions running in an integrated manner on the process master controller. For example, the mass control function and the volumetric flow control function can be two single-input single-output (SISO) controllers operating in parallel. Figure 8A An exemplary configuration is shown in Figure 1. In this configuration, the mass flow error from the sensing kit unit is directed to a SISO mass flow controller function, which in response sends a commanded valve position to the control valve. The volumetric flow error from the sensing kit unit is directed to a SISO volumetric flow controller function, which in response sends a density control command to the density control element. Using parallel SISO controllers can simplify control design. The two parallel SISO controllers ignore any coupling between the mass flow error and the volumetric flow error.

[0170] Figure 7BThe exemplary embodiment shown in FIG shows a single process master controller, wherein the control tasks of the computing processor, the mass flow controller, and the volume flow controller are software codes or functions that run separately on the process master controller in an integrated manner, wherein the process master controller communicates with the density control element and the control valve and transmits the volume flow control command to the density control element and the mass flow control command to the control valve. In this configuration, SISO controllers operating in parallel can be used.

[0171] Alternatively, the mass and volume control functions can be implemented using a multivariable controller (multiple-input, multiple-output, MIMO). A multivariable controller can have two inputs (mass flow error and volume flow error) and two outputs (commanded valve position and commanded action on the density control element). A MIMO controller can account for any coupled dynamics between or among the variables. This consideration of multiple variables can be incorporated into the control algorithm. For example, variable X can be regulated to a certain setpoint, variable Y to some other setpoint, and the two variables can be checked to see if they are stable when operating independently. When the coupling between variables X and Y in a dynamic system is relatively weak, the effect of variable X on variable Y may not perturb the overall system. However, when the coupling between variables X and Y in a dynamic system is strong, the mutual effect of variable X on variable Y can perturb the overall system, and in very strong coupling cases, the effect of variable X on variable Y can lead to system instability (i.e., variables X and Y "interfere" with each other). Under these conditions, a MIMO controller can outperform a single SISO controller operating in parallel because it can account for the "coupled dynamics" of the different variables. Using MIMO controllers can maximize the stability of interconnected systems with coupled variables. A unified MIMO controller can take into account the coupling terms between variables and adjust the system accordingly.

[0172] exist Figure 8B An exemplary configuration of the MIMO controller of the system provided herein is shown in FIG. Figure 8B As shown in Figure 1, a multivariable MIMO controller has two inputs (the mass flow error and volume flow error received from the sensing unit, and a control algorithm that can account for any coupled dynamics of the two variables) and has two outputs (the commanded valve position and the commanded action of the density control element), directed to the control valve and density control element, respectively. This configuration allows the system to stabilize to a single value, as well as to account for or compensate for any disturbances in one variable on another, thereby stabilizing the entire system.

[0173] Figure 7CThe exemplary embodiment shown in shows a single process master controller using a MIMO controller, which is shown as a combined mass flow and volume flow controller. The control tasks of the computational processor and the combined mass flow and volume flow controller are software codes or functions running in an integrated manner on the process master controller, where the process master controller communicates with the density control element and the control valve and transmits mass and volume flow control commands to the density control element and the control valve. Figure 7B and Figure 7C In the configuration shown in , a controlled mass flow of inert gas is delivered from the control valve 130 to the density control element 140, and the density control element delivers a controlled mass and volume flow of the inert gas to the plasma torch.

[0174] In such Figure 7A 、 Figure 7B and Figure 7C In the embodiment shown in the system 3000 in FIG, the mass flow rate and volume flow rate of the inert gas to the plasma torch can be measured and regulated. For example, the mass flow rate data can be converted to a volume flow rate by assuming standard conditions (e.g., 0°C temperature and 1 atmosphere pressure), which may be different from the actual volume flow rate of the inert gas due to density variations. In an exemplary embodiment, by measuring the mass flow rate of the gas and calculating the volume flow rate of the gas, the data generated by the sensing kit 200 of the system 3000 can be used to regulate the gas flow to the plasma torch, and by comparing the set values ​​and actual values ​​of the mass flow rate and volume flow rate, the final volume flow rate of the inert gas can be adjusted to compensate for any density variations. The mass flow rate of the inert gas and the temperature and / or pressure of the inert gas can be adjusted to achieve a target level of actual volume flow rate across gas density variations, thereby achieving a target plasma column discharge velocity at the plasma torch.

[0175] The fluid flow path of the gas from the gas supply 100 to the plasma torch 600 in the system 3000 is similar to Figure 4A and Figure 4B The fluid flow path of the system 2000 is shown in FIG. The difference is the presence of the mass flow controller 380, which is Figure 7A 1 is shown in communication with the process master controller 340 and the control valve 130. The density control element 140 can modify or control the temperature and / or pressure of the inert gas. The density control element 140 can include a temperature regulator or a pressure regulator, or both a temperature regulator and a pressure regulator. The density control element 140 can be used in a controlled manner to modify the temperature or pressure, or both the temperature and pressure, of the gas in order to control the gas volume flow / gas velocity to the plasma torch to achieve and maintain a target plasma emission level from the plasma torch. Figure 7AIn the embodiment shown, the density control element 140 communicates with the volumetric flow controller 360 of the processor complex 300, and the control valve 130 communicates with the mass flow controller 380. Figure 7B and Figure 7C In the illustrated embodiment, the density control element 140 and the control valve 130 are in communication with a master process controller 340 .

[0176] Adjusting the temperature and / or pressure controls the inert gas density so that the average distance between inert gas molecules remains constant despite environmental and mechanical disturbances that may affect this distance, thereby achieving a target volumetric flow rate of inert gas to the plasma torch. A gas density regulator can help regulate all parameters that define the volumetric flow rate, which results in consistent application of the plasma arc to the melt pool, even as external conditions or disturbances change.

[0177] The density control element 140 may include a temperature regulator. The temperature regulator may include a heater. The heater may increase the temperature of the inert gas within the density control element 140, which may increase the volume occupied by the same number of gas molecules. The heater may include an induction heater, a resistive heater, a piezoelectric ceramic heating element, or a combination thereof.

[0178] The temperature regulator may include a cooling device. The cooling device may reduce the temperature of the inert gas within the density control element 140, which may reduce the volume occupied by the same number of gas molecules. The cooling device may include piping connected to a refrigeration fluid reservoir and a pump to form a closed-loop cooling path to supply cooling fluid to the temperature regulator within the density control element 140. The cooling device may include a closed pipe passing through the temperature regulator and a fan connected to the closed pipe to pass cooling gas through the temperature regulator within the density control element 140. A combination of a closed-loop refrigeration cooling path and piping for passing cooling gas through the temperature regulator may be used.

[0179] The density control element 140 may include a pressure regulator. The pressure regulator may include a movable plenum chamber that can increase the volume of the pressure regulator, thereby reducing the pressure of the inert gas leaving the pressure regulator, or reduce the volume of the pressure regulator, thereby increasing the pressure of the inert gas leaving the pressure regulator.

[0180] exist Figure 7A 、 Figure 7B and Figure 7CIn the exemplary embodiment shown, a gas supply 100 is connected to a gas supply manifold 120 via a hose 110. The inert gas of the gas supply 100 can be a noble gas. In some embodiments, the gas supply 100 provides a gas selected from the group consisting of helium, neon, argon, krypton, xenon, and combinations thereof. In some embodiments, the gas supply 100 provides argon gas to the system. The gas supply manifold can provide gas to several different components of an additive manufacturing machine, or to different additive manufacturing machines, in addition to or in addition to providing gas to maintain a desired environment near the plasma arc or workpiece. 7A to 7C Only the gas line 125 connecting the gas supply manifold 120 to the control valve 130 is shown. The control valve 130 is shown connected to the density control element 140 via a hose 135. The control valve 130 can be operated to increase or decrease the opening in the valve to increase or decrease the amount of gas flowing through the control valve 130 to the density control element 140. The gas can flow from the control valve 130 through the hose 135 to the density control element 140, and then through the hose 190 to the plasma torch 600, which ionizes the gas to form a plasma arc 625, which can be used to melt the metal wire source to deposit molten metal from the molten metal wire source onto the workpiece 650.

[0181] The sensing package 200 includes a sensing connector 195 to the gas line 190 to allow measurement of the temperature, pressure, and flow of the gas to the plasma torch. The sensing package can include a temperature measurement unit 220, a pressure measurement unit 240, and a mass flow measurement unit 260. The temperature measurement unit 220 can include a temperature sensor. The pressure measurement unit 240 can include a pressure sensor. The mass flow measurement unit 260 can include a flow meter for measuring mass flow or volume flow under standard conditions. Other environmental measurement devices can be included in the sensing package 200.

[0182] The sensing connector 195 of the sensing assembly 200 can be located in the production chamber directly at the gas input of the plasma torch, or near the plasma torch gas inlet. This positioning can allow the sensing assembly 200 to measure and control changes in gas density due to any arc radiation interference, such as temperature changes caused directly by the action of the plasma column, or heat contributions from the workpiece, such as radiant heat from the melt pool, or a combination thereof. This positioning can also allow a mass flow meter to detect changes in flow rate, which can be attributed to leaks in the gas line between the gas supply and the plasma torch. In some embodiments, the sensing connector 195 can be located 10 mm to 15 cm, or 2 cm to 2 m from the plasma torch gas inlet.

[0183] By using information generated by the elements of the sensing suite 200 (e.g., 7A to 7CIn the embodiment shown), the computing processor 320 ( Figure 7A ) or software functions that perform the functions of the computational processor 320 running on the process master controller processor ( Figure 7B and Figure 7C ) can calculate the actual volume flow of the gas to be ionized. Figure 7A In the exemplary configuration shown, the processor group 300 may include a calculation processor 320 for calculating an actual volumetric flow rate, a volumetric flow controller 360 that communicates with and can operate the density control element 140, and a mass flow controller 380 that communicates with the control valve 130 and can operate the control valve 130 based on data received from the process master controller 340. For example, the process master controller 340 may receive measured gas mass flow data from the sensing kit 200, a calculated volumetric flow rate from the calculation processor 320, and a flow setpoint from the part program 400.

[0184] exist Figure 7B In the exemplary configuration shown, the calculation processor 320 for calculating the actual volumetric flow rate, the volumetric flow controller 360, and the mass flow controller 380 are each software functions running on the process master controller 340. The process master controller 340 communicates with and can operate the control valve 130 and the density control element 140. The process master controller 340 can receive measured gas mass flow data from the sensing package 200 and use the calculated volumetric flow rate from the calculation processor 320 software function and the flow setpoint from the part program 400 to determine the difference between the set volumetric flow rate value and the calculated actual flow rate value, as well as the difference between the set mass flow rate value and the actual mass flow rate value from the mass flow measurement 260 of the sensing package 200. Based on the mass flow rate difference value, the process master controller 340 communicates with the control valve 130 to increase or decrease the mass flow rate of the inert gas so that the mass flow rate difference value approaches or becomes zero, thereby generating a controlled mass flow rate from the control valve 130 to the density control element 140. Based on the volumetric flow rate difference, the process master controller 340 communicates with the density control element 140 to increase or decrease the temperature and / or pressure of the inert gas so that the volumetric flow rate difference approaches or becomes zero, thereby generating a controlled volumetric flow rate and a controlled mass flow rate from the density control element 140 to the plasma torch 600.

[0185] Figure 7C The exemplary configuration shown in Figure 7C The configuration shown in FIG. 1 differs in that the process master controller 340 includes a software function 385 running on the process master controller 340, wherein the software function 385 performs Figure 7BThe functions of the mass flow controller and the volume flow controller of the process master controller 340 are shown. Figure 7C The mass and volumetric flow controller 385 of the configuration shown in FIG. 1 utilizes the calculated actual volumetric flow rate from the software function executing the functions of the computational processor 320 to determine the difference between the volumetric flow setpoint from the part program 400 and the calculated value of the volumetric flow rate, and this difference is communicated to the process master controller 340. The process master controller also compares the set mass flow rate value from the part program 400 with the actual mass flow rate value from the mass flow measurement 260 of the sensing assembly 200 to determine the difference between the mass flow setpoint and the actual mass flow rate value. Based on the mass flow rate difference, the process master controller 340 communicates with the control valve 130 to increase or decrease the mass flow rate of the inert gas so that the mass flow rate difference approaches or becomes zero, thereby generating a controlled mass flow rate from the control valve 130 to the density control element 140. Based on the volumetric flow rate difference, the process master controller 340 communicates with the density control element 140 to increase or decrease the temperature and / or pressure of the inert gas so that the volumetric flow rate difference approaches or becomes zero, thereby generating a controlled volumetric flow rate and a controlled mass flow rate from the density control element 140 to the plasma torch 600.

[0186] Part program 400 can be communicated to the process master controller. Part program 400 includes the data required by the additive manufacturing system to produce a given preform, including the trajectory of the plasma torch that forms layer after layer of molten metal to form the preform, as well as gas flow and gas setpoint signals. The process master controller 340 can provide the mass flow setpoint and the actual measured gas mass flow rate to the mass flow controller 380. The process master controller 340 can also provide the volume flow setpoint obtained from part program 400 and the actual volume flow rate calculated and obtained from the computation processor 320 to the volume flow controller 360.

[0187] Without loss of generality, the mass flow controller can be a separate processor, such as a controller, or can be a software function running on a process master controller processor. The mass flow controller 380 can compare the gas mass flow setpoint with the actual mass flow value and, when the measured mass flow value is lower than the mass flow setpoint, send a signal to the control valve 130 to gradually open the control valve 130 to increase the gas mass flow to the density control element 140. When the measured mass flow value is higher than the mass flow setpoint, the mass flow controller 380 can send a signal to the control valve 130 to gradually close the control valve 130 to reduce the gas mass flow to the density control element 140.

[0188] The volumetric flow controller 360 can compare the volumetric flow setpoint with the calculated volumetric flow rate and, when the calculated volumetric flow rate is below the volumetric flow setpoint, send a signal to the density control element 140 to gradually increase the temperature to increase the volume of the gas, or to reduce the pressure to increase the volume. When the calculated volumetric flow rate is above the volumetric flow setpoint, the volumetric flow controller 360 can send a signal to the control valve 130 to gradually decrease the temperature to decrease the volume of the gas, or to increase the pressure to decrease the volume of the gas. The process master controller 340 regulates the volumetric flow of gas from the gas supply manifold 120 through the density control element 140 to the plasma torch 600 based on data received from the sensor kit 200 via the sensor connector 195. This allows a controlled volumetric flow rate and regulated mass flow rate of the inert gas to be delivered to the plasma torch 600. This allows for a controlled volume and number of gas molecules to be supplied to the plasma torch. The system can also monitor the mass flow rate of the inert gas. The mass flow rate data and volumetric flow rate data received by the process master controller 340 can be transmitted to the data monitoring system 500 for operator or system review. Mass flow and actual volume flow data can be used, for example, for deposition process analysis and development, leak detection and elimination (or compensation), and gas control system calibration.

[0189] The control valve 130 can be operated by an actuator in response to a mass setpoint signal, which can be generated by the process master controller 340 and sent to the mass flow controller 380. The process master controller 340 can receive the mass flow setpoint from the part program 400, and the mass flow controller 380 can be connected to the actuator connected to the control valve 130. The process master controller 340 can compare the actual calculated volume flow value with the volume flow setpoint to generate an adjustment signal that can be transmitted to the mass flow controller 380 to be transmitted to the actuator of the control valve 130 to adjust the opening of the control valve 130 to cause a change in the flow rate of the inert gas through the control valve 130, thereby reducing any difference between the set mass flow value and the measured actual mass flow value. The mass flow adjusted gas can then be sent to the density control element 140 via the hose 135.

[0190] The process master controller 340 may also receive a volumetric flow setpoint from the part program 400, and the process master controller 340 may be connected to the density control element 140 directly or via a volumetric flow controller 360. Without loss of generality, the volumetric flow controller may be a separate processor, such as a controller, or may be a software function running on the process master controller processor. The process master controller 340 may compare the actual calculated volumetric flow value with the volumetric flow setpoint to generate an adjustment signal that may be transmitted to the density control element 140 to adjust the volume of the gas by modifying the temperature and / or pressure to cause a change in the volumetric flow of the inert gas therethrough, thereby reducing any difference between the set volumetric flow value and the calculated actual volumetric flow value.

[0191] The mass flow controller 380 may include a sensor attached to the control valve 130 that may detect the open position of the valve, and the sensor may transmit the valve position to the mass flow controller 380 in communication with the process master controller 340 to adjust the valve position based on valve position feedback received from the sensor.

[0192] The signal transmitted from the mass flow controller 380 or the sensor of the control valve 130 to the process master controller 340 can be a digital signal, such as a high voltage, a low voltage, or a zero voltage, indicating that the measured value is above, below, or at a preferred level. Similarly, any output transmitted by the process master controller 340 directly or via the mass flow controller 380 to the control valve 130 can be an open, closed, or neutral signal. Alternatively, the signal can transmit an analog value.

[0193] The process master controller 340 can be configured to output the valve control signal to the control valve 130 or mass flow controller 380 as a high, low, or zero voltage, and may also include an option for outputting an error signal. If the valve control signal is a high signal or a low signal, the control valve 130 can gradually close or open, respectively, until a zero signal is reached. If the valve control signal is zero, the valve will not change position. If the valve control signal is an error, the valve can be completely closed or the error output can be interpreted as a zero output, depending on the type of error. For example, if the pressure is too low to support the desired flow, the control valve 130 can be fully opened to maximize the flow. Alternatively, if the sensor detects insufficient or no inert gas flow, the error signal can be interpreted as closing the valve and sending an alarm signal to the data monitoring system 500.

[0194] The density of the gas supplied from the gas supply manifold 120 varies significantly (in terms of temperature and pressure) due to variations in line length and / or diameter, and / or mechanical tolerances of the lines and hoses, and / or variations in inert gas consumption and demands placed on the gas supply manifold 120 by different components of the additive manufacturing machine or related system, as well as variations in gas temperature due to tolerances on the manifold gas temperature and pressure controllers, thermal disturbances, such as radiant heat absorbed by the gas hoses from the arc and workpiece, and ambient temperature disturbances, such as variations in production hall and production room temperatures. Embodiments of the system provided herein are configured as follows. Figure 7A 、 Figure 7B and Figure 7C The system 3000 shown in FIG. 1 allows for a controlled inert gas mass flow and volume flow to be provided to the plasma torch despite various requirements on the gas supply manifold 120 , or gas leaks in the system between the gas supply 100 and the plasma torch 600 , or gas temperature variations due to radiation from the plasma arc and the workpiece.

[0195] Any wire-based additive manufacturing system can be modified for use with any of the inert gas flow control systems provided herein.

[0196] C. Flow Control Method

[0197] Also provided is a method for controlling the flow of inert gas to a plasma torch to be ionized into plasma for producing a workpiece via an additive manufacturing process. The method provided herein can deliver a target inert gas mass flow rate or volume flow rate, or a mass flow rate and a volume flow rate, to a plasma torch. The method can include integrating one of the systems provided herein into a DED manufacturing system and using the system to regulate and control the inert gas flowing to the plasma torch. The plasma arc pressure on the molten pool can be one of the most critical factors in defining the molten pool dynamics, thereby determining the geometry and mechanical properties of the beads, which can characterize the consistency and quality of the additive manufacturing process. The method provided herein can generate a consistent plasma arc pressure (i.e., arc force per unit molten pool area) on the molten pool by maintaining the gas discharge rate from the plasma torch at a desired level, across various density levels of the inert gas supplied to the plasma torch. The method provided herein can calculate the actual volume flow rate, which has a crucial impact on the driving force of the molten pool (i.e., molten pool dynamics). Because these methods can provide a consistent volumetric flow of inert gas to the plasma torch, a better, more robust deposition process can be achieved across different environmental and mechanical variations that may affect gas density.

[0198] In certain embodiments, the method for depositing the plasma torch can be controlled by the method for controlling the actual volume flow of inert gas to the plasma torch, because the variation of gas density (for example, due to environmental disturbance, the dynamic behavior of the molten pool will not be affected), the deposition process is more consistent. When performing deposition process on different machines, the variation between the mechanical machines due to environmental variation and mechanical parts tolerance will not affect the dynamic behavior of the molten pool, also can cause forming more consistent preforms on different machines. The sensing connector can be a gas sampling hose / tube, can be connected to the inert gas flow line, it is located anywhere between the gas manifold and the gas ionizer electromagnetic field. In certain embodiments, the sensing connector can be directly attached to the torch inlet or near the torch inlet. In certain embodiments, the temperature and pressure sensor of the sensing connector can be incorporated into the torch inside. In certain embodiments, actual volume flow control element can be located in the production chamber, just in time at the input of inert gas to the plasma torch, so that the gas density changes caused by the arc radiation interference or the heat radiation interference caused by the workpiece can be measured and controlled.

[0199] The method may include adding a mass flow measurement element to the plasma torch at the inlet of the inert gas, which is capable of detecting any mass flow reduction, such as due to a leak, and can act as a second opinion sensor for the mass flow of the inert gas. The method may include using a temperature sensor and / or pressure sensor included inside the plasma torch to measure the temperature and / or pressure of the inert gas.

[0200] The methods provided herein can allow for realistic volumetric flow rates across variations in gas density to achieve a target gas discharge rate at the plasma torch. The methods and systems provided herein can also allow for the inert gas flow to be delivered to the plasma torch in terms of both the number of gas molecules over time and the volume of gas over time. The volumetric control of the inert gas can be achieved by varying the temperature and / or pressure of the inert gas, which can control the gas density to maintain a constant average distance between gas molecules, which can be affected by environmental and mechanical disturbances.

[0201] The method may include: transmitting a target inert gas mass flow rate or volume flow rate, or both, to a process master controller; measuring the mass flow rate of the inert gas; determining a calculated volume flow rate based on the mass flow rate of the inert gas; comparing the calculated volume flow rate to the target volume flow rate; calculating a difference between the calculated volume flow rate and the target volume flow rate; and adjusting the inert gas flow rate to the plasma torch by a) adjusting a mass flow control valve to increase or decrease the mass flow rate of the inert gas to the plasma torch, or b) adjusting the gas density of the inert gas by adjusting the temperature and / or pressure of the inert gas delivered to the plasma torch.

[0202] The method may also include positioning a gas density regulator in an inert gas flow line of the additive manufacturing system and measuring and regulating changes in gas density in the inert gas due to radiated interference from the plasma torch, the formed workpiece, or a combination thereof. The gas density regulator may be located inside the production chamber. The gas density regulator may be located outside the production chamber. The gas density regulator may be in communication with a sensing kit that is in communication with a location at or near a gas inlet of the plasma torch, a location within the plasma torch, or connected anywhere between the gas manifold and the electromagnetic field of the gas ionizer. The sensing kit may be in communication with a plurality of flow meters, temperature sensors, pressure sensors, or any combination thereof. The sensing kit may detect external interference that affects the flow of inert gas to the plasma torch. Adjusting the gas density may include increasing or decreasing the gas temperature. Adjusting the gas density may include increasing or decreasing the gas pressure. Adjusting the gas density may include varying both the gas temperature and the gas pressure.

[0203] In a method for adjusting the flow of an inert gas to be ionized in a plasma torch via a control valve, the method may include adjusting the control valve by generating an adjustment signal based on a difference value representing a difference between a set value and an actual value; and sending the adjustment signal to an actuator attached to the flow control valve, the actuator increasing or decreasing an opening of the control valve based on the adjustment signal. In some methods, the inert gas may be directed to a gas density regulator that can adjust the density of the inert gas. Adjusting the density of the inert gas may include a) measuring the temperature of the inert gas and increasing or decreasing the temperature of the inert gas in response to the difference; or b) measuring the pressure of the inert gas and increasing or decreasing the pressure of the inert gas in response to the difference; or c) both a) and b). Increasing the temperature of the inert gas may include directing the inert gas to a temperature regulator including a heater and activating the heater. Decreasing the temperature of the inert gas may include directing the inert gas to a temperature regulator including a cooling device and activating the cooling device. Increasing or decreasing the pressure of the inert gas delivered to the plasma torch may include directing the inert gas to a pressure regulator.

[0204] An exemplary method of delivering a target volumetric flow rate and a target mass flow rate of an inert gas to be ionized into a plasma to a plasma torch comprises: providing an inert gas from a gas supply manifold to an inlet of the plasma torch through a control valve attached to the inert gas supply manifold via an inert gas line; a) measuring the temperature, mass flow rate, and pressure of the inert gas between the inert gas supply manifold and an electromagnetic field of a gas ionizer of the plasma torch; or b) measuring the temperature, mass flow rate, and pressure of the inert gas at or near the gas inlet of the plasma torch; or c) measuring the temperature and pressure of the inert gas inside the plasma torch and the mass flow rate at or near the gas inlet of the plasma torch; or d) any combination of a), b), and c); calculating the actual volumetric flow rate of the inert gas to the plasma torch: i) at or near the plasma torch inlet; or ii) at the plasma torch inlet. or iii) at a location in the inert gas supply line between the gas manifold and the plasma torch gas inlet; comparing the actual volume flow rate with the target volume flow rate to generate a volume flow difference; comparing the actual mass flow rate with the target mass flow rate to generate a mass flow difference; based on the mass flow difference and the volume flow difference: a) adjusting the control valve to increase or decrease the mass flow rate of the inert gas through the control valve to the plasma torch gas inlet; or b) adjusting the density of the inert gas by increasing or decreasing the pressure and / or temperature of the inert gas to produce an improved inert gas volume flow rate and directing the improved inert gas to the inlet of the plasma torch; or c) adjusting the control valve and the density of the inert gas by increasing or decreasing the pressure and / or temperature of the inert gas to control the mass flow rate and volume flow rate of the inert gas to the ionizing electromagnetic field of the plasma torch.

[0205] In the method, adjusting the control valve may include: generating an adjustment signal based on the mass flow rate difference and / or the volume flow rate difference; and sending the adjustment signal to an actuator attached to the control valve, the actuator increasing or decreasing an opening of the control valve based on the adjustment signal. In the method, adjusting the density of the inert gas may include a) measuring the temperature of the inert gas and increasing or decreasing the temperature of the inert gas in response to the volume flow rate difference; or b) measuring the pressure of the inert gas and increasing or decreasing the pressure of the inert gas in response to the volume flow rate difference; or c) both a) and b).

[0206] Increasing the temperature of the inert gas includes directing the inert gas to a temperature regulator including a heater and activating the heater. Any heater may be used as long as it can increase the temperature of the inert gas. Exemplary heaters include induction heaters, resistance heaters, piezoelectric ceramic heating elements, and any combination thereof.

[0207] Lowering the temperature of the inert gas may include directing the inert gas to a temperature regulator including a cooling device and activating the cooling device. Any cooling device may be used as long as it is capable of lowering the temperature of the inert gas. The cooling device may include a refrigeration system or a heat exchanger that can lower the temperature of the inert gas. The cooling device may include a refrigeration fluid that can remove heat energy from the inert gas. In some methods, the cooling device may include: a) a pipeline connected to a refrigeration fluid reservoir and a pump to form a closed-loop cooling path to supply cooling fluid to the temperature regulator; or b) a pipe passing through the temperature regulator and a fan connected to the pipe to force the cooling gas through the temperature regulator; or c) a combination of a) and b).

[0208] In the methods provided herein, increasing or decreasing the pressure of the inert gas comprises directing the inert gas to a pressure regulator. Any pressure regulator may be used, as long as it is capable of increasing or decreasing the pressure of the inert gas. For example, the pressure regulator may include a movable plenum chamber that is capable of increasing the volume of the pressure regulator, thereby decreasing the pressure of the inert gas leaving the pressure regulator; or decreasing the volume of the pressure regulator, thereby increasing the pressure of the inert gas leaving the pressure regulator. In the methods provided herein, the inert gas may be argon.

[0209] It will be apparent to those skilled in the art that various modifications and variations may be made to the present invention without departing from the scope or spirit of the present invention. Therefore, the present invention is intended to encompass modifications and variations of the present invention as long as they fall within the scope of the appended claims and their equivalents.

[0210] Reference Symbol List

[0211] The following is a list of reference numbers used in the description and drawings.

[0212] 100 Gas Supply

[0213] 110 Hoses or pipes between the gas supply and the gas supply manifold

[0214] 120 Gas supply manifold

[0215] 125 Hoses or pipes between the gas supply manifold and the control valves

[0216] 130 Control Valve

[0217] 135 Hose or pipe between control valve and density control element

[0218] 140 Density Control Element

[0219] 150 Temperature Regulator

[0220] 151 Liquid Temperature Regulator

[0221] 152 Exit

[0222] 153 Pipeline

[0223] 154 heat exchanger

[0224] 155 Pipeline

[0225] 156 Pipeline

[0226] 158 Entrance

[0227] 160 Pressure Regulator

[0228] 162 Booster Room

[0229] 164 Sealing element

[0230] 166 Position Regulator

[0231] 170 pumps

[0232] 172 Entrance

[0233] 174 Exit

[0234] 175 External Liquid Source

[0235] 176 Entrance

[0236] 178 emissions

[0237] 181 Hoses or pipes between the gas supply manifold and the gas volume / mass flow control system

[0238] 185 Hose or pipe between control valve and plasma torch

[0239] 190 Hose or pipe between density control element and plasma torch

[0240] 195 Sensing connector between gas supply line and sensing kit

[0241] 196 Between hoses or pipes

[0242] 200 Sensor Kit

[0243] 220 Temperature measurement unit

[0244] 225 Temperature Sensor

[0245] 240 Pressure Measuring Cell

[0246] 245 Pressure Sensor

[0247] 260 Mass Flow Measurement

[0248] 265 Mass Flow Meter

[0249] 300 Processor (Controller) Group

[0250] 320 Calculation processor for calculating actual volume flow

[0251] 340 Process Master Controller

[0252] 360 Volume Flow Controller

[0253] 385 Mass and Volume Flow Controller

[0254] 400 Part Programs

[0255] 500 Data Monitoring System

[0256] 600 Plasma Torch

[0257] 605 Plasma Torch Inert Gas Inlet

[0258] 610 tungsten electrode

[0259] 615 Regions of ionized electromagnetic fields

[0260] 625 Plasma Arc (Ionized Gas)

[0261] 650 artifacts.

Claims

1. A system for controlling gas flow to a plasma torch of an additive manufacturing apparatus, comprising: Inert gas source; a supply manifold in fluid communication with the inert gas source; a plasma torch comprising a gas inlet for receiving an inert gas from an inert gas line connected to said supply manifold, and a gas ionizer electromagnetic field for ionizing said inert gas into a plasma; a sensing package comprising a temperature measurement unit, a pressure measurement unit, and a mass flow measurement unit, wherein each unit is in communication with one or more sensing connectors connected to a location of the inert gas line between the supply manifold and the gas ionizer electromagnetic field; a control valve in fluid communication with a gas supply manifold and regulating a flow of the inert gas from the gas supply manifold to the plasma torch; a process master controller in communication with the sensing suite; a part program that provides a mass flow setpoint and a volume flow setpoint to the process master controller; a calculation function, executed on the process master controller, to calculate the actual volume flow rate; and a) a mass flow control function and a volume flow control function, running on said process master controller; or b) a combined mass flow and volume flow control function, operating on said process master controller; And among them, The system also includes a density control element that controls the temperature and / or pressure of the inert gas delivered to the inlet of the plasma torch.

2. The system according to claim 1, wherein: The mass flow control function is adapted to compare the mass flow setpoint from the part program with an actual mass flow value from the mass flow measurement unit of the sensing kit and adjust the control valve or density control element, or both, to increase or decrease the mass flow rate of the inert gas to reduce a difference between the mass flow setpoint and the actual mass flow value.

3. The system according to claim 1, wherein: The volumetric flow control function compares the volumetric flow setpoint from the part program with the calculated volumetric flow value from the calculation function and adjusts the control valve or density control element, or both, to increase or decrease the volumetric flow of the inert gas to reduce the difference between the volumetric flow setpoint and the calculated volumetric flow value.

4. The system according to claim 1, wherein: The mass flow control function and the volume flow control function are run on the process master controller, wherein: The mass flow control function is adapted to compare the mass flow setpoint from the part program with an actual mass flow value from the mass flow measurement unit of the sensing kit, and the volume flow control function is adapted to compare the volume flow setpoint from the part program with a calculated volume flow value from the calculation function, and to adjust the control valve and density control element to regulate both the mass flow rate and the volume flow rate of the inert gas delivered to the gas ionizer electromagnetic field of the plasma torch.

5. The system according to claim 1, wherein The combined mass flow and volume flow control function is adapted to compare the mass flow setpoint from the part program with an actual mass flow value from the mass flow measurement cell of the sensing kit, and to compare the volume flow setpoint from the part program with a calculated volume flow value from the calculation function, and to adjust the control valve and density control element to regulate both the mass flow rate and the volume flow rate of the inert gas delivered to the gas ionizer electromagnetic field of the plasma torch.

6. The system of claim 1 , wherein: the mass flow control function being adapted to compare the mass flow setpoint from the part program with an actual mass flow value from the mass flow measurement cell of the sensing assembly and to adjust the control valve to increase or decrease the mass flow rate of the inert gas to reduce a difference between the mass flow setpoint and the actual mass flow value, thereby reducing the mass flow rate of the inert gas delivered to the gas ionizer electromagnetic field of the plasma torch; and The volumetric flow control function is adapted to compare the volumetric flow setpoint from the part program with the calculated volumetric flow value from the calculation function and adjust a density control element to control the volumetric flow of the inert gas delivered to the gas ionizer electromagnetic field of the plasma torch.

7. The system according to any one of claims 1 to 6, wherein: The sensing connector of each of the temperature measuring unit, the pressure measuring unit, and the mass flow measuring unit of the sensing kit is connected near the gas inlet of the plasma torch, and wherein the sensing connector of each of the temperature measuring unit and the pressure measuring unit of the sensing kit is located inside the plasma torch.

8. The system according to claim 1, wherein: The density control element comprises: a) a temperature regulator and a temperature sensor; or b) pressure regulators and pressure sensors; or c) temperature regulators, temperature sensors, pressure regulators and pressure sensors; or d) Any combination of a), b) and c).

9. The system of claim 8, wherein: The density control element includes the temperature regulator, and the temperature regulator includes a heater, The heater comprises an induction heater, a resistance heater, a piezoelectric ceramic heating element or a combination thereof, and The temperature regulator also includes a cooling device.

10. The system according to claim 9, wherein: The cooling device comprises: a) piping connected to a refrigeration fluid reservoir and a pump for forming a closed-loop cooling path to supply cooling fluid to the temperature regulator; or b) a duct passing through the temperature regulator and a fan connected to the duct for passing cooling gas through the temperature regulator; or c) A combination of a) and b).

11. The system of claim 8, comprising the pressure regulator, wherein: The pressure regulator includes a movable pumping chamber capable of: increasing the volume of the pressure regulator, thereby reducing the pressure of the inert gas leaving the pressure regulator; or The volume of the pressure regulator is reduced, thereby increasing the pressure of the inert gas exiting the pressure regulator.

12. The system according to claim 8, wherein: The density control element is configured to control a velocity of the inert gas to the plasma torch.

13. The system of claim 1, wherein: The sensing connector is located inside a production chamber of an additive manufacturing system and at the gas inlet of the plasma torch to measure radiated interference from the plasma torch and / or a workpiece.

14. The system of claim 1 further comprising a mass flow meter located upstream of the control valve and in communication with the process master controller, the mass flow meter being capable of detecting a decrease in mass flow of the inert gas from the manifold and the process master controller sending a signal to a data monitoring system to indicate a leak.

15. The system of claim 1, wherein: The sensing connector is connected to the gas inlet or is connected near the gas inlet; And wherein the system further comprises a processor group connected to the sensing kit and in communication with the control valve, wherein the processor group comprises: the process master controller in communication with the sensing suite; a computing processor in communication with the sensing suite and the process master controller, the computing processor calculating actual volume flow; and a mass flow controller and a volumetric flow controller in communication with the process master controller; and The part program provides a mass flow setpoint or a volume flow setpoint, or both, to the process master controller.

16. A method of delivering a target volume flow rate and a target mass flow rate of an inert gas to be ionized into a plasma to a plasma torch, comprising: providing an inert gas from a gas supply manifold to an inlet of the plasma torch through a control valve attached to the inert gas supply manifold via an inert gas line; a) measuring the temperature, mass flow and pressure of the inert gas between the inert gas supply manifold and the electromagnetic field of the gas ionizer of the plasma torch; or b) measuring the temperature, mass flow rate and pressure of the inert gas at or near the gas inlet of the plasma torch; or c) measuring the temperature and pressure of the inert gas inside the plasma torch, and the mass flow rate at or near the gas inlet of the plasma torch; or d) any combination of a), b) and c); The actual volumetric flow rate of the inert gas to the plasma torch is calculated at: i) at or near the inlet of the plasma torch; or ii) the interior of the plasma torch; or iii) at the location of the inert gas supply line between the gas manifold and the gas inlet of the plasma torch; comparing the actual volumetric flow rate to a target volumetric flow rate to generate a volumetric flow difference value; comparing the actual mass flow rate to the target mass flow rate to generate a mass flow difference value; Based on the mass flow difference and the volume flow difference: x) adjusting the control valve to increase or decrease the mass flow of the inert gas through the control valve to the gas inlet of the plasma torch; or y) adjusting the density of the inert gas by increasing or decreasing the pressure and / or temperature of the inert gas to produce a modified inert gas volume flow, and directing the modified inert gas to the inlet of the plasma torch; or z) regulating the control valve and adjusting the density of the inert gas by increasing or decreasing the pressure and / or temperature of the inert gas to control the mass flow and volume flow of the inert gas to the ionizing electromagnetic field of the plasma torch.

17. The method according to claim 16, wherein: Adjusting the control valve includes: generating a regulating signal based on the mass flow difference and / or the volume flow difference; and The adjustment signal is sent to a driver attached to the control valve, and the driver increases or decreases the opening of the control valve based on the adjustment signal.

18. The method according to claim 16 or 17, wherein Adjusting the density of the inert gas comprises: a) measuring the temperature of the inert gas and increasing or decreasing the temperature of the inert gas in response to the volume flow rate difference; or b) measuring the pressure of the inert gas and increasing or decreasing the pressure of the inert gas in response to the volume flow rate difference; or c) Both a) and b).

19. The method according to claim 18, wherein Increasing the temperature of the inert gas includes directing the inert gas to a temperature regulator including a heater, and activating the heater.

20. The method according to claim 19, wherein The heater includes an induction heater, a resistance heater, a piezoelectric ceramic heating element, or a combination thereof.

21. The method according to claim 18, wherein Reducing the temperature of the inert gas includes directing the inert gas to a temperature regulator including a cooling device, and activating the cooling device.

22. The method according to claim 21, wherein The cooling device comprises: a) piping connected to a refrigeration fluid reservoir and a pump for forming a closed-loop cooling path to supply cooling fluid to the temperature regulator; or b) a duct passing through the temperature regulator and a fan connected to the duct for passing cooling gas through the temperature regulator; or c) A combination of a) and b).

23. The method according to claim 20, wherein Increasing or decreasing the pressure of the inert gas includes directing the inert gas to a pressure regulator.

24. The method according to claim 23, wherein The pressure regulator includes a movable boost chamber that is capable of: increasing the volume of the pressure regulator, thereby reducing the pressure of the inert gas leaving the pressure regulator; or reducing the volume of the pressure regulator, thereby increasing the pressure of the inert gas leaving the pressure regulator.

25. The method according to claim 16, wherein The inert gas is argon.

26. The method according to claim 16, wherein The target volume flow rate and the target mass flow rate are provided by a part program.

27. A method of delivering a target volume flow of an inert gas to be ionized into plasma to a plasma torch, comprising: attaching the system according to any one of claims 1 to 15 to a source of inert gas; and Activate the system.

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