Method and device for supplying inert gas for an additive manufacturing chamber

Abstract

A supplemental system for sensing oxygen concentration in a chamber of an additive manufacturing system and providing additional inerting gas. The supplemental system may be independently controlled from an OEM / primary system and is preferably capable of accurately sensing oxygen concentrations as low as 100ppm. The supplemental system may use a sampling circuit, a sampling pump, and an oxygen sensor external to the chamber to measure oxygen concentration. Conduits for the sampling circuit and inerting gas in the supplemental system may use existing openings in the chamber.

Description

METHOD AND DEVICE FOR SUPPLYING INERT GAS FOR AN ADDITIVE MANUFACTURING CHAMBERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Application 63 / 748,111 filed on January 22, 2025, which is incorporated by reference herein.BACKGROUND OF THE INVENTION

[0002] Additive manufacturing, also referred to as 3D printing, is a technique for rapid manufacturing and prototyping of parts. In general, additive manufacturing entails the layer-by-layer deposition of material by computer control to form a three-dimensional object. Many early additive manufacturing techniques utilized polymeric or plastic materials as raw materials, as such materials are easily handled and melt at low temperatures. Additive manufacturing of metal parts, particularly for complex structures, has become more widely used.

[0003] Some additive manufacturing processes, such as powder bed fusion additive manufacturing, are conducted entirely within an enclosed chamber at positive pressure. An inert gas such as argon is utilized to purge the chamber prior to the manufacturing process. Typically, an oxygen sensor is positioned within the chamber to measure the oxygen content within the chamber. During the initial purge, inert gas is fed into the chamber until a desired oxygen level is detected, typically below 1000 ppm. Once the desired oxygen level is achieved, the controller allows the printing process to begin. In some implementations, a constant inert gas flow is maintained during the printing process. In existing systems, oxygen is not monitored or controlled once the printing process begins. Another drawback to current additive manufacturing systems is the potential for the in-situ oxygen sensor to produce inaccurate readings due to its location within the additive manufacturing chamber. If the in-situ oxygen sensor is located near a sidewall or a corner of the additive manufacturing chamber where it takes longer for fresh gas flow to be detected, the oxygen sensor may produce lagged oxygen measurement readings. Another drawback to current additive manufacturing systems and processes is the effect that impurities within the additive manufacturing chamber have on the performance of the in-situ oxygen sensors, especiallywhen oxygen concentration is below 1000 ppm. For example, if hydrogen is present in the chamber, the in-situ oxygen sensor may falsely indicate a lower concentration of oxygen than what is actually present.

[0004] Due to the limitations of current additive manufacturing systems, it can be difficult to use additive manufacturing systems to fabricate parts from oxygen-sensitive materials that are highly reactive to oxygen, such as nickel alloys, stainless steel, and titanium alloys. Therefore, there is a need for an improved additive manufacturing process having the ability to monitor and maintain lower oxygen concentration in the additive manufacturing chamber throughout the printing process.SUMMARY OF THE INVENTION

[0005] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0006] Embodiments of the invention provide an integrated solution to improve additive manufacturing systems and processes by increasing oxygen sensitivity by introducing additional monitoring and control capabilities. An additive manufacturing system adapted to operate at positive pressure includes a chamber having an interior volume and comprising an inert gas inlet and a gas outlet. A primary oxygen sensor is located within the interior volume of the chamber and is adapted to measure oxygen levels within the chamber. A primary inert gas source is in fluid communication with the interior volume of the chamber. A primary controller is operably connected to each of the primary oxygen sensor and the primary inert gas source. A secondary inert gas source is in fluid communication with a secondary inert gas flow controller, and the secondary inert gas flow controller is in fluid communication with the interior volume of the chamber. A sampling pump is in fluid communication with the gas outlet. A secondary oxygen sensor is located exterior to the chamber and is adapted to measure oxygen content of a gas stream from the sampling pump. A supplemental controller is operably connected to the secondary oxygen sensor and the secondary inert gas flow controller.

[0007] Several aspects of the systems and methods are outlined below.

[0008] Aspect 1 : A method for modifying an additive manufacturing system for forming a manufactured object from an additive material, the additive manufacturing system comprising a chamber, a first controller, a first oxygen sensor in fluid flow communication withthe chamber and electrically connected to the first controller, a first source of inert gas in fluid flow communication with the chamber, a first valve to control flow of inert gas from the first source of inert gas into the chamber, the first controller being adapted to receive signals from the first oxygen sensor, control the first valve, and to prevent an additive manufacturing process from being initiated in the chamber unless the first oxygen sensor senses an oxygen concentration that is less than a first maximum oxygen concentration, the method comprising:(a) providing a second source of inert gas in fluid flow communication with the chamber;(b) providing a second valve adapted to control a flow rate of inert gas from the second source of inert gas to the chamber;(c) providing a sampling circuit including an inlet in fluid flow communication with the chamber and outlet in fluid flow communication with the chamber, a sampling pump, and at least one gas sensor, the at least one gas sensor including a second oxygen sensor;(d) providing a second controller in electrical communication with the at least one gas sensor and the second valve;(e) measuring a sampling oxygen concentration of gas flowing through the sampling circuit using the second oxygen sensor;(f) reducing and maintaining the sampling oxygen concentration below a second maximum oxygen concentration by controlling the flow rate of inert gas into the chamber from the second inert gas source using the second controller;wherein the first maximum oxygen concentration is greater than the second maximum oxygen concentration.

[0009] Aspect 2: The method of Aspect 1, wherein the first maximum oxygen concentration is greater than 1000 ppm and the second maximum oxygen concentration is less than 1000 ppm.

[0010] Aspect 3: The method of Aspect 1, wherein the first maximum oxygen concentration is greater than 1000 ppm and the second maximum oxygen concentration is less than 500 ppm.

[0011] Aspect 4: The method of Aspect 1 , wherein the additive manufacturing system comprises a powder bed fusion system.

[0012] Aspect 5: The method of Aspect 1, wherein the additive material is a titanium alloy.

[0013] Aspect 6: The method of Aspect 1 , wherein the additive manufacturing system is adapted to carry out the additive manufacturing process at a positive pressure.

[0014] Aspect 7: The method of Aspect 1, wherein steps (e) and (f) are performed both before and after initiating the additive manufacturing process.

[0015] Aspect 8: The method of Aspect 1, wherein performing steps (e) and (f) are performed during an entire duration of the additive manufacturing process.

[0016] Aspect 9: The method of Aspect 1, wherein the second oxygen sensor is an optical oxygen sensor.

[0017] Aspect 10: The method of Aspect 1 , further comprising:(g) providing an indicator generated by the second controller when the sampling oxygen concentration is less than the second maximum oxygen concentration.

[0018] Aspect 11: The method of Aspect 1, wherein the first controller is in electrical communication with the sampling pump, the at least one gas sensor, and the second valve of the sampling circuit.

[0019] Aspect 12: A method for forming a manufactured object from an additive material using an additive manufacturing process, the method comprising:(a) forming the manufactured object in a chamber;(b) prior to performing step (a), reducing an oxygen concentration in the chamber below a maximum oxygen concentration using first and second inert gas purging subsystems;(c) maintaining the oxygen concentration in the chamber below the maximum oxygen concentration using the first and second inert gas purging subsystems during the performance of step (a);wherein the first inert gas purging subsystem comprises a first controller, a first oxygen sensor, and a first source of inert gas;wherein the second gas purging subsystem comprises a second controller, a sampling circuit including an inlet in fluid flow communication with the chamber and outlet in fluid flow communication with the chamber, a sampling pump, a second oxygen sensor located between the inlet and outlet, and a second source of inert gas;wherein the first inert gas purging subsystem operates independently of the second inert gas purging subsystem and there is no electrical connection between the first and second controllers.

[0020] Aspect 13: The method of Aspect 12, wherein the additive material is a titanium alloy.

[0021] Aspect 14: A method for modifying an additive manufacturing system for forming a manufactured object from an additive material, the additive manufacturing system comprising a chamber, a first controller, a first oxygen sensor in fluid flow communication withthe chamber and electrically connected to the first controller, a first source of inert gas in fluid flow communication with the chamber, a first valve to control flow of inert gas from the first source of inert gas into the chamber, the method comprising:(a) providing a second source of inert gas in fluid flow communication with the chamber;(b) providing a second valve adapted to control a flow rate of inert gas from the second source of inert gas to the chamber;(c) providing a sampling circuit including an inlet in fluid flow communication with the chamber and outlet in fluid flow communication with the chamber, a sampling pump, and at least one gas sensor, the at least one gas sensor including a second oxygen sensor;(d) measuring a sampling oxygen concentration of gas flowing through the sampling circuit using the second oxygen sensor;(e) reducing and maintaining the sampling oxygen concentration below a second maximum oxygen concentration by controlling the flow rate of inert gas into the chamber from the second inert gas source using the first controller;wherein the first maximum oxygen concentration is greater than the second maximum oxygen concentration;wherein the first controller is in electrical communication the first oxygen sensor, the first valve, the at least one gas sensor, and the second valve and is adapted to prevent an additive manufacturing process from being initiated in the chamber unless the second oxygen sensor senses an oxygen concentration that is less than a second maximum oxygen concentration.

[0022] Aspect 15: The method of Aspect 12, wherein the additive material is a titanium alloy.BRIEF DESCRIPTION OF DRAWINGS

[0023] The present invention will hereinafter be described in conjunction with the appended drawing figures wherein like numerals denote like elements.

[0024] FIG. 1 is a schematic flow diagram depicting an exemplary additive manufacturing system including inert gas purging subsystem according to the prior art.

[0025] FIG. 2 is a schematic flow diagram depicting an exemplary implementation of an additive manufacturing system including a supplemental inert gas purging subsystem.DETAILED DESCRIPTION OF THE INVENTION

[0026] The ensuing detailed description provides preferred exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the ensuing detailed description of the preferred exemplary embodiments will provide those skilled in the art with an enabling description for implementing the preferred exemplary embodiments of the invention. It being understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the invention.

[0027] In order to aid in describing the invention, directional terms may be used in the specification and claims to describe portions of the present invention (e.g., upper, lower, left, right, etc.). These directional terms are merely intended to assist in describing and claiming the invention and are not intended to limit the invention in any way. In addition, reference numerals that are introduced in the specification in association with a drawing figure may be repeated in one or more subsequent figures without additional description in the specification in order to provide context for other features.

[0028] Unless otherwise indicated, the articles “a” and “an” as used herein mean one or more when applied to any feature in embodiments of the present invention described in the specification and claims. The use of “a” and “an” does not limit the meaning to a single feature unless such a limit is specifically stated. The article “the” preceding singular or plural nouns or noun phrases denotes a particular specified feature or particular specified features and may have a singular or plural connotation depending upon the context in which it is used.

[0029] As used in the specification and claims, the terms “flow communication” or “fluid communication” or “fluid flow communication” are intended to mean that two or more elements are connected (either directly or indirectly) in a manner that enables fluids to flow between the elements, including connections that may contain valves, gates, tees, or other devices that may selectively restrict, merge, or separate fluid flow.

[0030] As used in the specification and claims, The term “operably connected” refers to a relationship between two or more components within a system or device, indicating that they are arranged or linked in a manner that allows them to work together to perform a function or achieve a purpose. As used herein, the term "operably connected" may imply any form of functional connection, which may be physical, electrical, communicative, or through intermediary components.

[0031] Unless otherwise stated herein, any and all percentages identified in the specification, drawings, and claims should be understood to be on a mole percentage basis.Unless otherwise stated herein, any and all pressures identified in the specification, drawings, and claims should be understood to mean gauge pressure.

[0032] Unless otherwise stated herein, introducing a stream at a location is intended to mean introducing substantially all of the said stream at the location. All streams discussed in the specification and shown in the drawings (typically represented by a line with an arrow showing the overall direction of fluid flow during normal operation) should be understood to be contained within a corresponding conduit. Each conduit should be understood to have at least one inlet and at least one outlet. Further, each piece of equipment should be understood to have at least one inlet and at least one outlet.

[0033] In the claims, letters are used to identify claimed steps (e.g. (a), (b), and (c)). These letters are used to aid in referring to the method steps and are not intended to indicate the order in which claimed steps are performed, unless and only to the extent that such order is specifically recited in the claims.

[0034] As used in the specification and claims, the term “positive pressure” refers to an enclosed or partially enclosed system in which the pressure within the system, chamber, or space is greater than the surrounding or ambient pressure. As used herein, the term “positive pressure” may also refer to an enclosed or partially enclosed system having a pressure greater than zero, such that the system operates at neither an absolute vacuum nor a relative vacuum.

[0035] As used in the specification and claims, the term “inert gas” means a gas that are chemically inert or non-reactive under normal conditions. Inert gases include helium, neon, argon, krypton, xenon, radon and nitrogen.

[0036] As used in the specification and claims, the term “additive manufacturing” (also referred to as additive layer manufacturing and 3D printing) means a computer-controlled process that creates a three-dimensional objects by depositing materials, usually in layers. Examples of additive manufacturing processes include direct energy deposition, binder jetting, material extrusion, powder bed fusion, sheet lamination, and vat polymerization.

[0037] As used in the specification and claims, the term “oxygen-sensitive additive material” means a material that is used in additive manufacturing that is reactive to oxygen. Examples of oxygen-sensitive additive materials include Inconel 718, Ti-6AI-4V, and other titanium alloys. While aspects of the present invention are intended to address challenges faced when using oxygen-sensitive additive materials in additive manufacturing processes, the present invention is not limited to use with any particular additive material.

[0038] Referring to FIG. 1 , a schematic flow diagram depicting a conventional additivemanufacturing system 100 is shown. The system 100 is adapted to carry out an additive manufacturing process at a positive pressure. The system 100 comprises a powder fusion system 112 contained within a chamber 110. The powder fusion system 112 includes a powder fusion bed 114 in which a manufactured object 120 is formed. Powder is maintained at a desired level in the powder fusion bed 114 using a powder roller 124 that pushes additional powder into the powder fusion bed 114 from an adjacent powder stock bed 122. A powder delivery piston 126 is used to manage the level of powder in the powder stock bed 122. A build platform 116 supports the manufactured object 120 and the powder fusion bed 114 and moves downward as each layer of the manufactured object 120 is formed. Each layer of the manufactured object 120 is formed by a laser 118 that fuses the powder.

[0039] The system 100 includes a conventional inert gas purging subsystem 144 which comprises a controller 128, an oxygen sensor 132, and a source of inert gas 136 having a conduit 138 in fluid flow communication with the chamber 110. The purpose of the conventional inert gas purging subsystem 144 is to reduce the oxygen concentration in the chamber 110 to a predetermined concentration prior to commencement of the building of a manufactured object 120 with an oxygen-reactive material using the powder fusion system 112. This is accomplished by flowing inert gas through the conduit 138 until the controller 128 determines (using signals received from the oxygen sensor 132) that the oxygen concentration in the chamber 110 is less than the predetermined concentration. An outlet conduit 140 enables gas to exit the chamber 110 and may be stored in a tank 142 or vented. In some implementations, the gas exiting the chamber 110 may be routed to a waste gas treatment unit before being vented. The gas exiting the chamber 110 may also be routed to a gas recovery system, after which recovered inert gas is routed back into the chamber 110 (not shown). In some implementations, the controller 128 will prevent the user from activating the powder fusion system 112 until and unless the oxygen concentration in the chamber 110 is less than the predetermined oxygen concentration. In some implementations, the predetermined oxygen concentration is 1000 ppm or greater. In some implementations, the controller 128 will continue the flow of inert gas from the inert gas source 136 during the process of building of a manufactured object 120.

[0040] The conventional inert gas purging subsystem 144 is capable of reliably maintaining an oxygen concentration in the chamber 110 that is below 1000ppm, but is not capable of measuring or maintaining a significantly lower oxygen concentration, which is desirable for fabrication using oxygen-sensitive additive materials. The oxygen sensor 132 is typically a zirconia oxygen sensor, which is not capable of reliably measuring oxygenconcentrations below 1000ppm in the additive manufacturing process because of effects from other gaseous impurities, i.e., hydrogen and hydrocarbons. In addition, in most implementations, the inert gas source 136 is sized to provide a flow rate (often about one liter per minute) that is insufficient to reliably maintain an oxygen concentration in the chamber substantially lower than lOOOppm.

[0041] Referring to FIG. 2, a schematic flow diagram depicting a modified additive manufacturing system 200 having a supplemental inert gas purging subsystem 248 is shown. Elements included in system 200 that are also present in system 100 are labeled with reference numerals increased by 100. For example, the chamber 210 of the system 100 corresponds to the chamber 110 of the system 100. If an element is not separately discussed with respect to the system 200, it may be assumed that the element has the same structure and function as described with respect to the system 100.

[0042] The supplemental inert gas purging subsystem 248 includes a supplemental controller 250, a source of inert gas 252, and an oxygen sensor 260 located on a sampling conduit 264. The sampling conduit 264 extracts gas from the chamber 210 at a sampling outlet 272 and returns it to the chamber at a sampling inlet 274. A sampling pump 266 drives gas flow through the sampling conduit 264. The oxygen sensor 260 is located along the sampling circuit 268. In this implementation, the oxygen sensor 260 is an optical sensor. Alternatively, the oxygen sensor 260 could be a different type of sensor that is capable of reliably measuring oxygen concentrations below OOppm and preferably as low as 100ppm. In some applications, an oxygen sensor may be used that is capable of reliably measuring oxygen concentrations lower than 100ppm. Optionally, additional sensors may also be provided in the sampling circuit 268. Examples of other sensor types include a moisture sensor, a hydrocarbon sensor, a carbon dioxide sensor, a carbon monoxide sensor, and a hydrogen sensor. Inert gas from the source of inert gas 252 can be supplied to the chamber 210 through a conduit 256 and flow may be controlled using a flow controller 254. In order to maintain oxygen concentrations around 100ppm, the flow controller 254 may maintain an inert gas flow from the source of inert gas 252 between three and five air changes per hour (ACPH). As used herein, ACPH is defined as the hourly volumetric flow rate of inert gas from the source of inert gas 252 divided by the volume of the chamber 210. Higher ACPH values correspond to more ventilation and lower oxygen concentrations.

[0043] The supplemental controller 250 is preferably programmed to control flow of inert gas from the source of inert gas 252 (using the flow controller 254) in order to reduce and maintain the oxygen concentration in the chamber 210 (as measured by the oxygensensor 260) to a predetermined oxygen concentration that is lower than the predetermined maximum oxygen concentration set by the controller 228. In this implementation, the predetermined oxygen concentration of the supplemental controller 250 is 100ppm. In other implementations, the predetermined oxygen concentration of the supplemental controller 250 could be any oxygen concentration that is lower than the predetermined concentration of the controller 228 - for example, 300ppm or 500ppm.

[0044] The supplemental inert gas purging subsystem 248 is intended to enable the oxygen concentration in the chamber 210 to be reduced and maintained at or below 100ppm during the entire fabrication process without making any structural or electrical modifications to the conventional inert gas purging subsystem 244 or the chamber 210. Accordingly, all of the components of the supplemental inert gas purging subsystem 248 are preferably controlled by the supplemental controller 250. The supplemental controller 250 preferably does not have any data, electrical, or control connection to the controller 228. In other words, the supplemental inert gas purging subsystem 248 may operate independently of the conventional inert gas purging subsystem 244. All of the components of the supplemental inert gas purging subsystem 248 (other than the sampling outlet 272 and the sampling inlet 274) are located outside of the chamber 210. The sampling outlet 272 and the sampling inlet 274 penetrate the wall of the chamber 210 using existing openings in the chamber 210.

[0045] In the system 200, prior to initiating fabrication, the conventional inert gas purging subsystem 144 is activated as described above in relation to the system 100. Once the oxygen concentration is reduced below 1000ppm, the controller 228 will enable the user to initiate fabrication. The supplemental inert gas purging subsystem 248 may be manually activated by a user and may be activated at the same time as the conventional inert gas purging subsystem 144 or after the controller 228 determines that the oxygen concentration is below WOOppm. In some implementations, the supplemental inert gas purging subsystem 248 measures a sampling oxygen concentration and reduces and maintains the sampling oxygen concentration below the predetermined oxygen concentration of the supplemental controller 250 both before and after initiating the additive manufacturing process. In some implementations, the supplemental inert gas purging subsystem 248 measures a sampling oxygen concentration and reduces and maintains the sampling oxygen concentration below the predetermined oxygen concentration of the supplemental controller 250 during the entire duration of the additive manufacturing process. Preferably, the supplemental controller 250 is adapted to generate or provide an indication to a user that the oxygen concentration (as measured by the oxygen sensor 260) is below the predetermined concentration set by thesupplemental controller 250. For example, this could take the form of a readout of the oxygen concentration, an indicator light, and / or an audible noise.

[0046] As such, an invention has been disclosed in terms of preferred embodiments and alternate embodiments thereof. Of course, various changes, modifications, and alterations from the teachings of the present invention may be contemplated by those skilled in the art without departing from the intended spirit and scope thereof. It is intended that the present invention only be limited by the terms of the appended claims.

Claims

CLAIMS1. A method for modifying an additive manufacturing system for forming a manufactured object from an additive material, the additive manufacturing system comprising a chamber, a first controller, a first oxygen sensor in fluid flow communication with the chamber and electrically connected to the first controller, a first source of inert gas in fluid flow communication with the chamber, a first valve to control flow of inert gas from the first source of inert gas into the chamber, the first controller being adapted to receive signals from the first oxygen sensor, control the first valve, and to prevent an additive manufacturing process from being initiated in the chamber unless the first oxygen sensor senses an oxygen concentration that is less than a first maximum oxygen concentration, the method comprising:(a) providing a second source of inert gas in fluid flow communication with the chamber;(b) providing a second valve adapted to control a flow rate of inert gas from the second source of inert gas to the chamber;(c) providing a sampling circuit including an inlet in fluid flow communication with the chamber and outlet in fluid flow communication with the chamber, a sampling pump, and at least one gas sensor, the at least one gas sensor including a second oxygen sensor;(d) providing a second controller in electrical communication with the at least one gas sensor and the second valve;(e) measuring a sampling oxygen concentration of gas flowing through the sampling circuit using the second oxygen sensor; and(f) reducing and maintaining the sampling oxygen concentration below a second maximum oxygen concentration by controlling the flow rate of inert gas into the chamber from the second inert gas source using the second controller;wherein the first maximum oxygen concentration is greater than the second maximum oxygen concentration.

2. The method of claim 1, wherein the first maximum oxygen concentration is greater than 1000 ppm and the second maximum oxygen concentration is less than 1000 ppm.

3. The method of claim 1, wherein the first maximum oxygen concentration is greater than 1000 ppm and the second maximum oxygen concentration is less than 500 ppm.

4. The method of claim 1, wherein the additive manufacturing system comprises a powder bed fusion system.

5. The method of claim 1, wherein the additive material is a titanium alloy.

6. The method of claim 1 , wherein the additive manufacturing system is adapted to carry out the additive manufacturing process at a positive pressure.

7. The method of claim 1, wherein steps (e) and (f) are performed both before and after initiating the additive manufacturing process.

8. The method of claim 1, wherein performing steps (e) and (f) are performed during an entire duration of the additive manufacturing process.

9. The method of claim 1 , wherein the second oxygen sensor is an optical oxygen sensor.

10. The method of claim 1 , further comprising:(g) providing an indicator generated by the second controller when the sampling oxygen concentration is less than the second maximum oxygen concentration.

11. The method of claim 1, wherein the first controller is in electrical communication with the sampling pump, the at least one gas sensor, and the second valve of the sampling circuit.

12. A method for forming a manufactured object from an additive material using an additive manufacturing process, the method comprising:(a) forming the manufactured object in a chamber;(b) prior to performing step (a), reducing an oxygen concentration in the chamber below a maximum oxygen concentration using first and second inert gas purging subsystems; and(c) maintaining the oxygen concentration in the chamber below the maximum oxygen concentration using the first and second inert gas purging subsystems during the performance of step (a);wherein the first inert gas purging subsystem comprises a first controller, a first oxygen sensor, and a first source of inert gas;wherein the second gas purging subsystem comprises a second controller, a sampling circuit including an inlet in fluid flow communication with the chamber and outlet in fluid flow communication with the chamber, a sampling pump, a second oxygen sensor located between the inlet and outlet, and a second source of inert gas; andwherein the first inert gas purging subsystem operates independently of the second inert gas purging subsystem and there is no electrical connection between the first and second controllers.

13. The method of claim 12, wherein the additive material is a titanium alloy.

14. A method for modifying an additive manufacturing system for forming a manufactured object from an additive material, the additive manufacturing system comprising a chamber, a first controller, a first oxygen sensor in fluid flow communication with the chamber and electrically connected to the first controller, a first source of inert gas in fluid flow communication with the chamber, a first valve to control flow of inert gas from the first source of inert gas into the chamber, the method comprising:(a) providing a second source of inert gas in fluid flow communication with the chamber;(b) providing a second valve adapted to control a flow rate of inert gas from the second source of inert gas to the chamber;(c) providing a sampling circuit including an inlet in fluid flow communication with the chamber and outlet in fluid flow communication with the chamber, a sampling pump, and at least one gas sensor, the at least one gas sensor including a second oxygen sensor;(d) measuring a sampling oxygen concentration of gas flowing through the sampling circuit using the second oxygen sensor; and(e) reducing and maintaining the sampling oxygen concentration below a second maximum oxygen concentration by controlling the flow rate of inert gas into the chamber from the second inert gas source using the first controller;wherein the first maximum oxygen concentration is greater than the second maximum oxygen concentration; andwherein the first controller is in electrical communication the first oxygen sensor, the first valve, the at least one gas sensor, and the second valve and is adapted to prevent an additive manufacturing process from being initiated in the chamber unless the second oxygen sensor senses an oxygen concentration that is less than a second maximum oxygenconcentration.

15. The method of claim 14, wherein the additive material is a titanium alloy.

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