Device and method for regulating plasma arc thermal distribution to improve deposition layer morphology in plasma additive manufacturing

Abstract

The present invention discloses a device and method for regulating the thermal distribution of a plasma arc to improve the morphology of deposited layers in plasma additive manufacturing. Under plasma additive manufacturing conditions, the device dynamically controls the thermal distribution of the arc, adjusting the arc's thermal effects, influencing the arc's thermal distribution, the range of heat input, and the flow behavior of the molten pool, thereby improving the morphology of the deposited layer in plasma arc additive manufacturing. The device is also connected to a structured light camera. By comparing the surface signals captured by the camera with the preset deposited layer morphology, the resulting information is used as a control signal to control a dynamic push-pull mechanism, changing the tungsten electrode retraction, thereby altering the width and height of the deposited layer, achieving real-time control of the deposited layer morphology.

Description

Technical Field

[0001] The present invention relates to a device and method for regulating the thermal distribution of a plasma arc to improve the morphology of a deposited layer in a plasma additive manufacturing process, and belongs to the technical field of arc additive manufacturing. Background Art

[0002] Additive manufacturing (AM) is a new manufacturing technology developed in the late 1980s. AM transforms digital models into three-dimensional entities through the "discrete-accumulation" of materials. Arc AM, with its high melting efficiency and low cost, has attracted the attention of researchers both domestically and internationally. During the additive process, high-temperature liquid metal droplets accumulate layer by layer, transitioning smoothly to the surface of the part. As the number of metal layers increases, the increasing heat accumulation and increasingly poor heat dissipation conditions make it increasingly difficult to control the molten pool morphology and final dimensions.

[0003] In order to solve the above-mentioned problems, the present invention discloses a device and method for regulating the thermal distribution of a plasma arc to improve the morphology of a deposited layer in a plasma additive manufacturing process. The device is to dynamically control the thermal distribution of an arc under plasma additive manufacturing conditions, adjust the thermal effect of the arc, affect the thermal distribution of the arc and the range of heat input as well as the flow behavior of the molten pool, and improve the morphology of a deposited layer in plasma arc additive manufacturing. At the same time, the device is also connected to a structured light camera. By comparing the surface signal extracted by the camera with the preset morphology of the deposited layer, the information obtained is used as a control signal to control the dynamic push-pull device to change the amount of tungsten electrode retraction, change the width and height of the deposited layer, and achieve the goal of real-time control of the morphology of the deposited layer. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art by providing a device and method for regulating the thermal distribution of a plasma arc to improve the morphology of the deposited layer during plasma additive manufacturing. The device utilizes a dynamic push-pull mechanism to change the amount of tungsten electrode retraction, achieving dynamic control of the arc, adjusting the arc's restraining effect, affecting the arc's thermal distribution and the flow behavior of the molten pool, and improving the morphology of the deposited layer during plasma arc additive manufacturing. Simultaneously, a camera captures an image, compares it with a preset image, and transmits a feedback signal. This feedback signal is used to control the change in tungsten electrode retraction, achieving real-time control of the width and height of the deposited layer during the welding process.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions:

[0006] A device and method for regulating the heat distribution of a plasma arc to improve the morphology of a deposited layer in a plasma additive manufacturing process, characterized in that the device comprises a welding power source (1), an ion gas cylinder (2), a shielding gas cylinder (3), a plasma welding gun (4), a wire feeding device (5), a substrate (6), a computer control terminal (7), a structured light camera (8), a dynamic push-pull device (9), and a deposited layer (10); in the plasma additive manufacturing process, the structured light camera (8) is connected to the welding gun (4) through a clamping device, is located a certain distance behind the welding gun, and moves simultaneously with the welding gun; the dynamic push-pull device (9) is connected to the plasma welding gun (4) through a mechanical connection; and the wire feeding device (5) is connected to the welding gun (4) through a connecting plate, so that the welding gun and the wire feeding device move synchronously.

[0007] The dynamic push-pull device comprises a motor (9-1), an eccentric connecting rod (9-3), a moving stroke fixing device (9-5), a gear 1 (9-2), a gear 2 (9-4), and a tungsten pole connecting rod (9-6); the motor (9-1) is matched and connected with the gear 1 (9-2), the gear 1 (9-2) is meshed and connected with the gear 2 (9-4), the gear 1 (9-2) is connected with the eccentric connecting rod (9-3), the eccentric connecting rod (9-3) is fixedly connected with the tungsten pole connecting rod (9-7), and the moving stroke fixing device (9-4) is slidably connected with the tungsten pole connecting rod (9-7) via a slide rail. The motor drives the gear to rotate, and the eccentric connecting rod converts the rotation into movement, thereby driving the tungsten pole connecting rod to move up and down, thereby achieving the purpose of controlling the tungsten pole to retract.

[0008] The dynamic push-pull device is fixedly connected to the plasma welding torch. The tungsten electrode connecting rod in the dynamic push-pull device is secured to the tungsten electrode in the welding torch via a specially designed tungsten electrode clamp. By controlling the dynamic push-pull device to vary the tungsten electrode retraction, the thermal distribution of the plasma arc is regulated, thereby controlling the morphology of the deposited layer during the additive process. During deposition, increasing the tungsten electrode retraction increases arc restraint, increasing both arc force and heat input, improving both fuse efficiency and deposition efficiency. As the deposited layer height increases, its width gradually narrows. Reducing the tungsten electrode retraction allows the arc to diverge, reducing the range of arc force and heat input, and widening the deposited layer.

[0009] The dynamic push-pull device (9), the computer control terminal (7), and the structured light camera (8) are connected to form a feedback control circuit. The structured light camera is clamped on the rear side of the welding gun and detects the surface contour of the deposited layer in conjunction with the filter. The contour information is transmitted to the computer control terminal for comparison with the set geometric shape. The comparison result is output as a control signal to control the change of the tungsten electrode retraction amount, regulate the thermal distribution state of the plasma arc, control the width and height of the deposited layer, improve the uneven morphology defects of the deposited layer during the additive manufacturing process, and obtain a deposited layer with a smooth surface and good shape.

[0010] The motor has an adjustable frequency of 50Hz to 1000Hz, and the dynamic push-pull mechanism can adjust the tungsten electrode retraction from -4mm to 1mm, with an accuracy of 0.1mm (based on the plasma welding torch nozzle). The dynamic push-pull mechanism is connected to an external computer control terminal, which can adjust the motor frequency, control the gear rotation degree and speed, and control the speed and extent of tungsten electrode extension and retraction according to experimental requirements.

[0011] The gas types in the ion gas cylinder (2) are argon gas and argon-helium mixed gas; the gas types in the protective gas cylinder (3) are argon gas, helium gas and helium-argon mixed gas.

[0012] A device and method for regulating the thermal distribution of a plasma arc to improve the morphology of a deposited layer during plasma additive manufacturing comprises the following steps:

[0013] Step 1: Assemble the welding gun with the dynamic push-pull device and connect it to the plasma additive manufacturing equipment. Securely connect the structured light camera and wire feeder to the welding gun so that they can move synchronously with the welding gun. Set the initial welding current and wire feed speed, and adjust experimental conditions such as the camera angle and wire feed height.

[0014] Step 2: Start the plasma welding power supply and other necessary equipment, and perform additive deposition according to the predetermined trajectory. The surface profile of the deposited layer detected by the structured light camera is compared in real time with the preset profile. If the deposited layer width exceeds the preset controllable range, the tungsten electrode retraction is increased, increasing the arc force and reducing the heat input range to reduce the deposited layer width. If the deposited layer width is less than the preset width, the tungsten electrode retraction is reduced, reducing the arc force and increasing the arc force range to increase the deposited layer width.

[0015] Step 3: Return to the initial position and raise the welding gun to a certain height.

[0016] Step 4: Repeat the operations of step 2 and step 3, and continuously repeat the deposition cycle to obtain the desired structural parts.

[0017] Beneficial effects of the present invention:

[0018] (1) Compared with the existing invention, the present invention uses a dynamic push-pull device to regulate the retraction of the tungsten electrode, realizes dynamic control of the arc thermal distribution, adjusts the restraining effect of the welding gun on the arc, affects the arc force and the range of heat input and the flow behavior of the molten pool, and improves the morphology of the deposited layer in plasma arc additive manufacturing.

[0019] (2) The present invention connects a camera and a computer to a dynamic push-pull device to form a feedback control circuit, thereby achieving real-time control of the deposited layer morphology during the additive process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is a schematic diagram of a device for regulating the thermal distribution of a plasma arc to improve the morphology of a deposited layer during plasma additive manufacturing, using a side-axis wire feeding method.

[0021] Figure 2 It is a dynamic push-pull device.

[0022] In the figure, 1. welding power supply; 2. ion gas cylinder; 3. shielding gas cylinder; 4. plasma welding gun; 5. wire feeding device; 6. substrate; 7. computer control terminal; 8. structured light camera; 9. dynamic push-pull device: motor (9-1), eccentric connecting rod (9-3), moving stroke fixing device (9-5), gear 1 (9-2), gear 2 (9-4), tungsten electrode connecting rod (9-6); 10. deposition layer.

[0023] Figure 3 Schematic diagram of the morphology change of the additive deposition layer caused by the change in shrinkage. DETAILED DESCRIPTION

[0024] In order to further understand the content, features and effects of the present invention, the following embodiments are listed and described in detail with reference to the accompanying drawings:

[0025] The basic concept of this invention is to utilize a dynamic push-pull mechanism to adjust the tungsten electrode retraction, achieving dynamic control of the arc and adjusting the arc's restraint, thereby influencing the arc's thermal distribution and the flow behavior of the molten pool, and improving the morphology of the deposited layer during plasma arc additive manufacturing. Simultaneously, a camera captures an image, compares it with a preset image, and generates a feedback signal. This feedback signal controls the tungsten electrode retraction, achieving real-time control of the deposited layer width and height during the welding process.

[0026] like Figure 1 A device for regulating the heat distribution of a plasma arc to improve the morphology of a deposited layer during a plasma additive manufacturing process is shown, comprising a welding power source (1), an ion gas cylinder (2), a shielding gas cylinder (3), a plasma welding gun (4), a wire feeding device (5), a base plate (6), a computer control terminal (7), a structured light camera (8), a dynamic push-pull device (9), and a deposited layer (10); during the plasma additive manufacturing process, the structured light camera (8) is connected to the welding gun (4) via a clamping device, is located a certain distance behind the welding gun, and moves simultaneously with the welding gun; the dynamic push-pull device (9) is connected to the plasma welding gun (4) via a mechanical connection; and the wire feeding device (5) is connected to the welding gun (4) via a connecting plate, so that the welding gun and the wire feeding device move synchronously.

[0027] like Figure 2The dynamic push-pull device includes a motor (9-1), an eccentric connecting rod (9-3), a moving stroke fixing device (9-5), a gear 1 (9-2), a gear 2 (9-4), and a tungsten pole connecting rod (9-6). The motor (9-1) is coupled to the gear 1 (9-2), the gear 1 (9-2) is meshed with the gear 2 (9-4), the gear 1 (9-2) is connected to the eccentric connecting rod (9-3), the eccentric connecting rod (9-3) is fixedly connected to the tungsten pole connecting rod (9-7), and the moving stroke fixing device (9-4) is slidably connected to the tungsten pole connecting rod (9-7) via a slide rail. The motor drives the gear to rotate, and the eccentric connecting rod converts the rotation into movement, thereby driving the tungsten pole connecting rod to move up and down, thereby achieving the purpose of controlling the tungsten pole to retract.

[0028] The dynamic push-pull device is fixedly connected to the plasma welding gun. The tungsten electrode connecting rod in the dynamic push-pull device is fixed to the tungsten electrode in the welding gun through a special tungsten electrode clamp. By controlling the dynamic push-pull device to change the tungsten electrode retraction, the purpose of regulating the heat distribution of the plasma arc and controlling the morphology of the deposited layer during the additive process is achieved. During the deposition process, by increasing the tungsten electrode retraction, the arc constraint is increased, the arc force and heat input are increased, and the fuse efficiency and deposition efficiency are improved; as the height of the deposited layer increases, the width of the deposited layer will gradually narrow. By reducing the tungsten electrode retraction, the arc diverges, the arc force and heat input range are reduced, and the width of the deposited layer is widened. The dynamic push-pull device (9), the computer control terminal (7), and the structured light camera (8) are connected to form a feedback control circuit. The structured light camera is clamped on the back side of the welding gun and cooperates with the filter to detect the surface contour of the deposited layer. The morphology information is transmitted to the computer control end for comparison with the set geometric morphology. The comparison result is output as a control signal to control the change of the tungsten electrode retraction amount, adjust the thermal distribution state of the plasma arc, control the width and height of the deposited layer, improve the uneven morphology defects of the deposited layer during the additive manufacturing process, and obtain a deposited layer with a smooth surface and good shape.

[0029] The motor in the dynamic push-pull mechanism has an adjustable frequency of 50Hz to 1000Hz, and can adjust the tungsten electrode retraction from -4mm to 0mm with an accuracy of 0.1mm (based on the plasma welding torch nozzle). The dynamic push-pull mechanism is connected to an external computer control terminal, which adjusts the motor frequency, controls the gear rotation degree and speed, and controls the speed and extent of tungsten electrode extension and retraction according to experimental requirements.

[0030] Example 1:

[0031] Take the improved plasma arc additive manufacturing equipment to deposit an aluminum alloy layer with a height of 5 cm and a width of 8 mm as an example. Figure 1As shown in the figure, connect the required equipment according to the diagram. The power source used in the additive process is a plasma arc welding power source. The three-dimensional motion mechanism drives the plasma welding gun, wire feeder, and camera to move synchronously. The specific steps include:

[0032] Step 1: Secure the substrate to the desired additive manufacturing platform and set the ion gas flow rate to 1.0 L / min and the shielding gas flow rate to 20 L / min. Turn on the plasma arc welding power supply and set the plasma arc current to 120 A in the EN phase and 90 A in the EP phase. Using the 3D motion controller, adjust the relative position of the plasma welding gun and the aluminum plate to be welded so that it is 4 mm above the aluminum plate.

[0033] Step 2: Start the plasma welding power supply and camera, and perform additive deposition according to the predetermined trajectory. During the deposition process, the surface profile of the deposited layer detected by the structured light camera is compared in real time with the preset profile. If the deposited layer width exceeds 8.3mm, the tungsten electrode retraction is increased, increasing the arc force and reducing the heat input range to reduce the deposited layer width. If the deposited layer width is less than 7.7mm, the tungsten electrode retraction is reduced, reducing the arc force and increasing the arc force range to increase the deposited layer width.

[0034] Step 3: Return to the initial position and raise the welding gun 4mm.

[0035] Step 4: Repeat the operations of step 2 and step 3, and continuously repeat the deposition cycle to obtain the desired structural parts.

Claims

1. A device for regulating the thermal distribution of a plasma arc to improve the morphology of deposited layers in plasma additive manufacturing, characterized by: The invention comprises a welding power source (1), an ion gas cylinder (2), a shielding gas cylinder (3), a plasma welding gun (4), a wire feeding device (5), a substrate (6), a computer control terminal (7), a structured light camera (8), a dynamic push-pull device (9) and a deposition layer (10); the welding power source (1), the ion gas cylinder (2) and the shielding gas cylinder (3) are connected to the plasma welding gun (4); during the plasma additive manufacturing process, the structured light camera (8) is connected to the plasma welding gun (4) through a clamping device, is located at a certain distance behind the plasma welding gun (4) and moves simultaneously with the plasma welding gun (4); the dynamic push-pull device (9) is connected to the plasma welding gun (4) through a mechanical connection; the wire feeding device (5) is connected to the plasma welding gun (4) through a connecting plate, so that the plasma welding gun (4) and the wire feeding device (5) are connected. Synchronous movement; the deposition layer (10) is provided on the substrate (6), and the wire feeding device (5) and the dynamic push-pull device (9) are directly opposite to the deposition layer (10); the structured light camera (8) and the dynamic push-pull device (9) are connected to the computer control terminal (7); the dynamic push-pull device is fixedly connected to the plasma welding gun, and the tungsten electrode connecting rod in the dynamic push-pull device and the tungsten electrode in the plasma welding gun are assembled and fixed by a special tungsten electrode clamp, and the tungsten electrode retraction amount is changed by controlling the dynamic push-pull device to achieve the purpose of regulating the heat distribution of the plasma arc and controlling the morphology of the deposition layer during the additive process; the surface contour morphology of the deposition layer detected by the structured light camera is compared with the preset morphology in real time: if it is found that the width of the deposition layer exceeds the controllable range of the preset width, the tungsten electrode retraction amount is increased, the arc force is increased, and the heat input range is reduced, so that the width of the deposition layer is reduced; If the width of the deposited layer is found to be smaller than the preset width, the amount of tungsten electrode retraction is reduced, the arc force is reduced, and the range of arc force action is increased to increase the width of the deposited layer; The dynamic push-pull device (9), the computer control terminal (7), and the structured light camera (8) are connected to form a feedback control circuit; the structured light camera is clamped on the rear side of the plasma welding gun, and cooperates with the filter to detect the surface contour morphology of the deposited layer, transmits the morphology information to the computer control terminal for comparison with the set geometric morphology, and outputs the comparison result as a control signal to control the change of the tungsten electrode retraction amount, regulate the thermal distribution state of the plasma arc, and control the width and height of the deposited layer.

2. The device for regulating plasma arc thermal distribution to improve deposition layer morphology in plasma additive manufacturing according to claim 1, characterized in that: The dynamic push-pull device comprises a motor (9-1), an eccentric connecting rod (9-3), a moving stroke fixing device (9-5), gear one (9-2), gear two (9-4), and a tungsten pole connecting rod (9-6); the motor (9-1) is cooperatively connected to gear one (9-2), gear one (9-2) is meshedly connected to gear two (9-4), gear one (9-2) is connected to the eccentric connecting rod (9-3), the eccentric connecting rod (9-3) is fixedly connected to the tungsten pole connecting rod (9-6), and the moving stroke fixing device (9-5) is slidably connected to the tungsten pole connecting rod (9-6) by means of a slide rail; the motor (9-1) drives gear one (9-2) to rotate, and the rotation is converted into movement through the eccentric connecting rod (9-3), thereby driving the tungsten pole connecting rod (9-6) to move up and down, thereby achieving the purpose of controlling the tungsten pole to retract.

3. The device for regulating plasma arc thermal distribution to improve deposition layer morphology in plasma additive manufacturing according to claim 1, characterized in that: During the deposition process, the arc force and heat input are increased by increasing the retraction of the tungsten electrode and the arc confinement, thereby improving the fuse efficiency and deposition efficiency. As the height of the deposited layer increases, the width of the deposited layer will gradually narrow. By reducing the retraction of the tungsten electrode, the arc is diverged, the range of arc force and heat input is reduced, and the width of the deposited layer is widened.

4. The device for regulating plasma arc thermal distribution to improve deposition layer morphology in plasma additive manufacturing according to claim 1, characterized in that: The dynamic push-pull device can adjust the tungsten electrode retraction amount to -4mm to 1mm, with an adjustment accuracy of 0.1mm; the dynamic push-pull device is externally connected to a computer control terminal, which can adjust the motor frequency according to experimental requirements, control the degree and speed of gear rotation, and control the speed and size of tungsten electrode extension and retraction.

5. The device for regulating plasma arc thermal distribution to improve deposition layer morphology in plasma additive manufacturing according to claim 1, characterized in that: The gas types in the ion gas cylinder (2) are argon gas and argon-helium mixed gas; the gas types in the shielding gas cylinder (3) are argon gas, helium gas and helium-argon mixed gas.

6. A method for controlling the thermal distribution of a plasma arc to improve the morphology of a deposited layer during plasma additive manufacturing according to any one of claims 1 to 5, characterized in that: The following steps are included: Step 1: Assemble the plasma welding gun and the dynamic push-pull device, connect the plasma additive manufacturing equipment, securely connect the structured light camera and wire feeder to the plasma welding gun, and synchronize their movement with the plasma welding gun. Set the initial welding current and wire feed speed, and adjust the camera angle and wire feed height experimental conditions. Step 2: Start the plasma welding power supply and other necessary equipment, and perform additive deposition according to the predetermined trajectory. The surface profile of the deposited layer detected by the structured light camera is compared with the preset profile in real time. If the width of the deposited layer exceeds the controllable range of the preset width, the tungsten electrode retraction is increased, the arc force is increased, and the heat input range is reduced to reduce the width of the deposited layer. If the width of the deposited layer is found to be smaller than the preset width, the amount of tungsten electrode retraction is reduced, the arc force is reduced, and the range of arc force action is increased to increase the width of the deposited layer; Step 3: Return to the initial position and raise the plasma welding gun to a certain height; Step 4: Repeat the operations of step 2 and step 3, and continuously repeat the deposition cycle to obtain the desired structural parts.

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