Plasma arc fuse additive manufacturing device and method

Abstract

The invention discloses a plasma arc fuse additive manufacturing device and method. The temperature value is converted into an electrical signal through a monitoring process and fed back to a control system in real time. The control system compares the set temperature with the real-time temperature. When the real-time temperature is lower than the workpiece adjustment target value, the plasma arc moves to a low-temperature area for heating, which can effectively reduce the deformation and cracking problems of printed parts caused by uneven temperature distribution during the temperature printing process of large components. The method of the invention has high equipment utilization rate and strong flexibility, and reduces the setting of auxiliary components. The method is simple in process operation and strong in feasibility. Metal wire is used as raw material, and a heat source melts the metal wire to continuously form a molten pool, which solidifies to form a deposition surface. This is repeated and finally completed by melting and solidifying layer by layer. The manufacturing process has lower raw material cost than powder, an open processing environment and fast deposition efficiency, and is more suitable for the processing and manufacturing of large structural parts.

Description

Technical Field

[0001] The present invention relates to the field of metal welding and additive manufacturing, and in particular to a plasma arc fuse additive manufacturing device and method. Background Art

[0002] Additive manufacturing technology is widely used in mold manufacturing, industrial design and other fields, and is now gradually being used for the direct manufacturing of some products, especially some high-value applications (such as hip joints or teeth and some aircraft parts). The main methods for additive manufacturing of metal parts include laser selective melting (SLM), laser coaxial powder feeding direct manufacturing, electron beam fuse forming (EBAM), electron beam selective melting forming (EBM) and other methods. These methods all have limitations to varying degrees. For example, laser selective melting and electron beam selective melting forming technologies can only manufacture some small-scale parts due to the high cost of raw material powder and the limitation of the size of the forming chamber. Electron beam / laser fuse additive forming technology is also difficult to be widely used due to the limitations of technical barriers and equipment costs. Therefore, arc fuse additive forming technology has received great attention in recent years due to its mature and commercialized heat source equipment, low technical barriers, unlimited product size, and high forming efficiency. It has become a breakthrough in the manufacture of low-cost, large-scale components. Among them, the plasma arc has a high energy density due to its own compression arc advantage, and can melt and manufacture various refractory metal materials. It has broad application space in the manufacturing of aerospace and atomic energy parts.

[0003] Although plasma arc fuse forming technology has advantages over other methods in terms of fast forming speed and simple process, the plasma arc fuse manufacturing process uses heat source to melt the wire point by point, and the temperature near the melting point is high and the temperature far from the melting point is low, which leads to uneven temperature distribution of the component, resulting in large differences in expansion and contraction deformation at various locations. When welding or additive manufacturing is performed, the huge stress generated by the above reasons will cause the component to deform or even crack.

[0004] In order to avoid the extremely uneven temperature problem mentioned above, the method commonly used in engineering applications is preheating before welding and slow cooling after welding. That is, a heating device is added to the bottom of the workpiece to make up for the problem of unwelded melting points or too low temperature at the location far away from the melting point after welding. This method can reduce the problem of uneven temperature distribution, but the heating device is usually limited in size and lacks flexibility, which is not suitable for the manufacture of large components. With metal wire as the raw material, the heat source melts the metal wire to continuously form a molten pool, and the molten pool solidifies to form a deposition surface. This is repeated and finally completed by melting and solidifying layer by layer. This manufacturing process has lower raw material costs than powder, an open processing environment and fast deposition efficiency, and is more suitable for the processing and manufacturing of large structural parts. Summary of the invention

[0005] The purpose of the present invention is to provide a plasma arc fuse additive manufacturing device and method to overcome the shortcomings of the prior art. The present invention has high utilization rate and strong flexibility, reduces the setting of auxiliary components, and further improves the automation level and process control accuracy of plasma arc fuse additive manufacturing technology.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A plasma arc fuse additive manufacturing device comprises a control system and a motion actuator, a temperature measuring device, a welding gun, a wire feeding mechanism, a working platform and a plasma arc generator connected to the control system; the welding gun is fixed to the end of the motion actuator, the temperature measuring device is fixed to one side of a to-be-formed area of ​​the working platform, the welding gun is connected to the plasma arc generator, the wire feeding mechanism is mounted on the motion actuator, the wire outlet nozzle of the wire feeding mechanism is located at the lower end of a heat source of the welding gun, and the control system is used to control the plasma arc generator to provide current and voltage for welding and to control the motion path of the motion actuator.

[0008] Furthermore, the motion actuator adopts a robotic arm or a machine tool, which is used to carry the wire feeding mechanism and the welding gun to move according to the set planned path.

[0009] Furthermore, the wire feeding mechanism includes a wire feeding disc, a wire feeding drive motor and a wire outlet nozzle, and the wire outlet nozzle is located below a heat source for melting the metal wire.

[0010] Furthermore, the temperature measuring device is used to measure the temperature of multiple points of the workpiece, and the temperature measuring device is a non-contact temperature measuring device, which is evenly distributed in an area with uniform temperature and can represent the temperature of the molded part.

[0011] Furthermore, there are one or two welding guns, which serve as an arc device for melting the metal wire and a workpiece heating device respectively or simultaneously.

[0012] Furthermore, the temperature measuring device is a thermocouple or an infrared thermometer.

[0013] An additive manufacturing method for a plasma arc fuse additive manufacturing device comprises the following steps:

[0014] Step 1), setting the additive manufacturing parameters and the workpiece temperature adjustment target value in the control system, the control system collects and measures the temperature of each point in the workpiece substrate area in real time through the temperature measuring device, and the temperature measuring device feeds back the temperature control signal to the control system;

[0015] Step 2), when the set workpiece temperature adjustment target value is lower than the temperature control signal feedback value, the motion system cooperates with the plasma arc heat source to heat the workpiece in the low temperature area;

[0016] Step 3) During the welding or additive process, when the set workpiece temperature adjustment target value is higher than the temperature control signal feedback value, the motion system cooperates with the plasma arc heat source and the wire feeding mechanism to perform wire melting deposition; the temperature control printing process is completed layer by layer in a reciprocating manner.

[0017] Furthermore, the additive manufacturing parameters set in the control system include welding current, heating current, wire feeding speed, welding movement speed of the robot arm or machine tool, and heating movement speed of the robot arm or machine tool.

[0018] Furthermore, during the first layer of molten deposition, when the set workpiece temperature adjustment target value is higher than the temperature control signal feedback value, the motion actuator quickly scans and heats with the set heating current and heating movement speed; when the set workpiece temperature adjustment target value is lower than the temperature control signal feedback value, the motion actuator deposits the first layer of wire with the set welding current, welding movement speed and wire feeding speed.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] The present invention discloses a plasma arc fuse additive manufacturing device. A control system and a motion actuator, a temperature measuring device, a welding gun, a wire feeding mechanism, a working platform and a plasma arc generator connected to the control system are used to form a plasma heating welding system. The welding gun is fixed to the end of the motion actuator, the welding gun is connected to the plasma arc generator, the wire feeding mechanism is installed on the motion actuator, and the wire outlet of the wire feeding mechanism is located at the lower end of the welding gun heat source. The control system is used to control the plasma arc generator to provide current and voltage for welding and control the motion path of the motion actuator. The control system is used to combine the welding gun with the plasma arc generator to realize the use as a heat source for molten wire and arc heating. At the same time, a temperature measuring device fixed to one side of a to-be-formed area of ​​the working platform is used to feed back the workpiece temperature to the control system. By changing the welding gun temperature through the control system, the stress generated by the temperature gradient during the welding of large components or fuse additive can be reduced, and the deformation or cracking caused by the stress can be reduced or avoided. The device has high temperature field steady-state control accuracy and dynamic response characteristics.

[0021] A plasma arc fuse additive manufacturing method converts the temperature value into an electrical signal through a monitoring process and feeds it back to a control system in real time. The control system compares the set temperature with the real-time temperature. When the real-time temperature is lower than the workpiece adjustment target value, the plasma arc moves to a low-temperature area for heating, which can effectively reduce the deformation and cracking of printed parts caused by uneven temperature distribution during the temperature printing of large components. The method of the invention has high equipment utilization rate and strong flexibility, and reduces the setting of auxiliary components. The method is simple to operate and has strong feasibility. Metal wire is used as raw material, and a heat source melts the metal wire to continuously form a molten pool, which solidifies to form a deposition surface. This is repeated and finally completed by melting and solidifying layer by layer. The manufacturing process has lower raw material cost than powder, an open processing environment and fast deposition efficiency, and is more suitable for the processing and manufacturing of large structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a simplified structural diagram of the present invention.

[0023] In the figure, 1. motion actuator; 2. temperature measuring device; 3. welding gun; 4. wire feeding mechanism; 5. working platform; 6. plasma arc generator; 7. control system. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0025] like Figure 1 As shown, a plasma arc fuse additive manufacturing device comprises a control system 7 and a motion actuator 1 connected to the control system 7, a temperature measuring device 2, a welding gun 3, a wire feeding mechanism 4, a working platform 5 and a plasma arc generator 6; the welding gun 3 is fixed to the end of the motion actuator 1, the temperature measuring device 2 is fixed to one side of the to-be-molded area of ​​the working platform 5, and is used to measure the temperature of the molded part; the welding gun 3 is connected to the plasma arc generator 6, and the connection line between the welding gun 3 and the plasma arc generator 6 is fixed to the motion actuator 1 and moves with the motion actuator 1 to prevent influence in the additive manufacturing process; the wire feeding mechanism 4 is installed on the motion actuator 1, and the wire outlet of the wire feeding mechanism 4 is located at the lower end of the heat source of the welding gun 3;

[0026] The motion actuator 1 is a mechanical arm or a machine tool, which is used to carry the wire feeding mechanism 4 and the welding gun 3 to move according to the set planned path;

[0027] The welding gun 3 is an operating device for generating a plasma arc. There are one or two welding guns, which are used as an arc device for melting metal wire and a workpiece heating device respectively or simultaneously. The arc for heating the workpiece is used for preheating the workpiece before melting the wire (or supplying heat) and slow cooling of the workpiece in the solidified area behind the melting wire (or supplying heat). The heat sources used by the arc device for melting the wire and the workpiece heating device are both plasma arcs.

[0028] The plasma arc generator 6 provides current and voltage for welding, and is characterized in that the plasma arc generator can be one or two, and the plasma arc generator is electrically connected to the welding gun.

[0029] The wire feeding mechanism 4 includes a wire feeding disc, a wire feeding drive motor and a wire outlet nozzle, and the wire outlet nozzle is located below a heat source for melting metal wires.

[0030] The temperature measuring device 2 is used to measure the temperature of multiple points of the workpiece. The temperature measuring device 2 is a non-contact temperature measuring device, which is evenly distributed in an area with uniform temperature and can represent the temperature of the molded part, and its measuring point position is constant. The temperature measuring device 2 is a thermocouple or an infrared thermometer. The temperature measuring device is an online real-time temperature dynamic monitoring device. The temperature measuring device and the plasma arc are electrically connected to the control system to form a closed-loop control unit of the temperature field, which ensures the real-time and accurate dynamic stability of the temperature field.

[0031] The control system 7 is electrically connected to the wire feeding motor, the driving system of the motion mechanism 1, the plasma arc generator and the temperature measuring device. The control system 7 is used to control the switch of the wire feeding motor and the wire feeding amount, control the motion switch of the robot arm or machine tool, control the switch of the plasma arc generator, and read and feedback the temperature value of the temperature measuring device.

[0032] A plasma arc fuse additive manufacturing method comprises the following steps:

[0033] Step 1), input and set welding current, heating current, wire feeding speed, robot arm or machine tool welding movement speed, robot arm or machine tool heating movement speed, and workpiece temperature adjustment target value in the control system;

[0034] Step 2), the control system turns on the temperature measuring device to measure the temperature at various points in the workpiece substrate area;

[0035] Step 3), the control system collects the temperature signals of each temperature measuring device in real time and inputs the control signal. During the first layer of molten deposition, when the set workpiece temperature adjustment target value is higher than the temperature control signal feedback value, the control system only turns on the plasma arc heating device and the motion system carrying the plasma arc heating device. The motion system carries the plasma arc heating device to quickly scan and heat at the set heating current and heating motion speed;

[0036] Step 4), when the set workpiece temperature adjustment target value is lower than the temperature control signal feedback value, the control system starts the arc device of the molten metal wire and the motion system of the arc device carrying the molten metal wire, and deposits the first layer of wire at the set welding current, welding motion speed, and wire feeding speed;

[0037] Step 5) During welding or additive manufacturing, the control signal is compared with the set target temperature value of the workpiece in real time. When the set target temperature value of the workpiece is higher than the temperature control signal, the plasma arc heating device is turned off and the control system turns on the arc device of the molten metal wire. When the set target temperature value of the workpiece is lower than the temperature control signal, the robot arm or machine tool cooperates with the plasma arc heating device to run to the low temperature zone and turns on the heating device. The temperature control printing process is completed layer by layer in a reciprocating manner.

[0038] When there is only one plasma arc generator and welding gun mentioned in the present invention, and the plasma arc is used as both an arc device for melting metal wire and a workpiece heating device, taking the melting of titanium alloy wire as an example, the following steps are included:

[0039] Step 1. Input the set welding current of 150A, heating current of 80A, wire feeding speed of 2m / min, welding movement speed of robot or machine tool of 200mm / min, heating movement speed of robot or machine tool of 1000mm / min, and workpiece temperature adjustment target value of 100℃ in the control system.

[0040] Step 2: The control system turns on the temperature measuring device to measure the temperature at various points in the workpiece substrate area.

[0041] Step 3. During the first layer of melt deposition, when the temperature control signal feedback value is lower than 100°C, the control system only turns on the plasma arc heating device and the motion system carrying the plasma arc heating device. The motion system carries the plasma arc heating device with a welding current of 80A and a speed of 1000mm / min to quickly scan and heat the substrate.

[0042] Step 4. When the temperature control signal feedback value is higher than 100°C, the control system starts the arc device of the molten metal wire and the motion system that carries the arc device of the molten metal wire. The motion system starts the first layer melting at 200mm / min, welding current 150A and wire feeding speed 2m / min.

[0043] Step 5. During the welding process, the control signal is compared with the set workpiece temperature adjustment target value in real time. When the temperature control signal feedback value is higher than 100°C, the welding current is switched to 150A, the welding speed is set to 200mm / min, and the wire feeding speed is set to 2m / min. When the temperature control signal is lower than 100°C, the current is switched to 80A, the welding speed is set to 1000mm / min, and the wire feeding system is turned off. The plasma arc quickly scans the low temperature zone to the set temperature, and the temperature control printing process is completed layer by layer in a reciprocating manner.

[0044] When the plasma arc generator and welding gun mentioned in the present invention are both in two groups, one group is used as an arc device for melting metal wire, and the other group is used as a workpiece heating device. Taking the melting of titanium alloy wire as an example, the following steps are included:

[0045] When a plasma arc is used as both an arc device for melting metal wire and a workpiece heating device, taking titanium alloy wire melting as an example, the following steps are included:

[0046] Step 1. Input the set welding current of 150A, heating current of 80A, wire feeding speed of 2m / min, welding movement speed of robot or machine tool of 200mm / min, heating movement speed of robot or machine tool of 1000mm / min, and workpiece temperature adjustment target value of 100℃ in the control system.

[0047] Step 2: The control system turns on the temperature measuring device to measure the temperature at various points in the workpiece substrate area.

[0048] Step 3. During the first layer of melt deposition, when the temperature control signal feedback value is lower than 100°C, the control system only turns on the plasma arc heating device and the motion system carrying the plasma arc heating device. The motion system carries the plasma arc heating device with a welding current of 80A and a speed of 1000mm / min to quickly scan and heat the substrate.

[0049] Step 4. When the temperature control signal feedback value is higher than 100°C, the control system starts the arc device of the molten metal wire and the motion system that carries the arc device of the molten metal wire. The motion system starts the first layer melting at 200mm / min, welding current 150A and wire feeding speed 2m / min.

[0050] Step 5. During the welding process, the control signal is compared with the set workpiece temperature adjustment target value in real time. When the temperature control signal feedback value is higher than 100°C, the arc device of the molten metal wire and the motion system carrying the arc device of the molten metal wire start the welding current of 150A, the welding speed is run to 200mm / min, and the wire feeding speed is run to 2m / min; when the temperature control signal is lower than 100°C, the plasma arc heating device and the motion system carrying the plasma arc heating device are turned on with a current of 80A and a welding speed of 1000mm / min, and the plasma arc is quickly scanned to the set temperature in the low temperature area. At the same time, the arc device of the molten metal wire and the motion system carrying the arc device of the molten metal wire also start the welding current of 150A, the welding speed is run to 200mm / min, and the wire feeding speed is run to 2m / min.

[0051] The temperature-controlled printing process is completed layer by layer in a reciprocating manner.

Claims

1. An additive manufacturing method based on a plasma arc fuse additive manufacturing device, characterized in that: The plasma arc fused wire additive manufacturing device comprises a control system (7) and a motion actuator (1), a temperature measuring device (2), a welding gun (3), a wire feeding mechanism (4), a working platform (5) and a plasma arc generator (6) connected to the control system (7); the welding gun (3) is fixed to the end of the motion actuator (1), the temperature measuring device (2) is fixed to one side of the to-be-molded area of ​​the working platform (5), the welding gun (3) is connected to the plasma arc generator (6), the wire feeding mechanism (4) is mounted on the motion actuator (1), the wire outlet nozzle of the wire feeding mechanism (4) is located at the lower end of the heat source of the welding gun (3), and the control system (7) is used to control the plasma arc generator (6) to provide current and electricity for welding. The motion actuator (1) is configured to press and control the motion path of the motion actuator (1), wherein the motion actuator (1) is a mechanical arm or a machine tool, and is used to carry the wire feeding mechanism (4) and the welding gun (3) to move according to a set planned path, wherein the wire feeding mechanism (4) comprises a wire feeding disc, a wire feeding drive motor and a wire outlet nozzle, wherein the wire outlet nozzle is located below a heat source for melting metal wire, and the temperature measuring device (2) is used to measure the temperature of multiple positions of the workpiece, and the temperature measuring device (2) is a non-contact temperature measuring device, which is evenly distributed in an area with uniform temperature and can represent the temperature of the workpiece, and the welding gun is a single unit, which is used as an arc device for melting the metal wire and a workpiece heating device at the same time, and the temperature measuring device (2) is a thermocouple or an infrared thermometer; The additive manufacturing method comprises the following steps: Step 1) Input the set welding current 150A, heating current 80A, wire feeding speed 2m / min, robot or machine welding movement speed 200mm / min, robot or machine heating movement speed 1000mm / min, and workpiece temperature adjustment target value 100℃ in the control system; Step 2), the control system turns on the temperature measuring device to measure the temperature at various points in the workpiece area; Step 3), during the first layer of melt deposition, when the temperature control signal feedback value is lower than 100°C, the motion actuator quickly scans and heats the workpiece with a heating current of 80A and a heating movement speed of 1000mm / min; Step 4), when the temperature control signal feedback value is higher than 100°C, the motion actuator starts the first layer melting at a welding speed of 200mm / min, a welding current of 150A, and a wire feeding speed of 2m / min; Step 5) During the welding process, the temperature control signal is compared with the set workpiece temperature adjustment target value in real time. When the temperature control signal feedback value is higher than 100°C, the current is switched to the welding current of 150A, the movement speed is set to the welding movement speed of 200mm / min, and the wire feeding speed is set to 2m / min; when the temperature control signal is lower than 100°C, the current is switched to the heating current of 80A, the movement speed is switched to the heating movement speed of 1000mm / min, and the wire feeding system is turned off. The plasma arc quickly scans the low temperature area to the set workpiece temperature adjustment target value, and completes the temperature control printing process layer by layer in sequence.

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