A heat input regulation method for magnetron plasma arc additive manufacturing

Abstract

The present invention relates to a heat input regulation method and system for magnetron plasma arc additive manufacturing. In order to solve the problems of heat input accumulation and uneven temperature distribution in plasma arc additive manufacturing, which easily lead to thermal cracks, incomplete melting, and pores, the present invention relates to a heat input regulation method for magnetron plasma arc additive manufacturing. The method comprises: it mainly consists of a plasma welding gun, a magnetron swinging arc device, an infrared thermometer, an infrared thermal imager and a control processor system. The key points of the technical solution are that the infrared thermal imager scans the upper surface of the formed part to obtain the real-time temperature distribution of each layer of the sample, and feeds back the temperature information distribution to the control processor system to adjust the excitation current and use the magnetic field to control the position and shape of the plasma arc; the infrared thermometer measures the temperature distribution of the molten pool in real time, and feeds back the molten pool temperature information to the control processor system to adjust the wire feeding speed and the local heat input of the molten pool, thereby realizing adaptive regulation and uniform distribution of heat input in the magnetron plasma arc additive manufacturing process.

Description

Technical Field

[0001] The present invention specifically relates to a heat input regulation method for magnetron plasma arc additive manufacturing, which controls heat input and regulates temperature distribution during the additive manufacturing process to reduce additive manufacturing defects. The method belongs to the field of plasma arc additive manufacturing. Background Art

[0002] The structure, performance, and availability of high-quality parts produced by wire arc additive manufacturing (WAAM) today depend on various process parameters, such as wire feed speed, wire diameter, travel speed, and arc power. Higher metal deposition rates pave the way for achieving high-performance and efficient components, but this translates to higher heat inputs that negatively impact the WAAM process. Heat input buildup leads to uneven temperature distribution, which can lead to defects such as thermal cracking, incomplete melting, and porosity, limiting high-quality production.

[0003] A search for heat input control and detection in additive manufacturing revealed that patent document CN113579253A discloses a device and method for online monitoring of multi-scale temperature fields in additive manufacturing. This method monitors cracks, spatter, holes, and geometric deformation defects that occur in parts during the additive manufacturing process using three parameters: substrate temperature, melt pool temperature, and sample temperature per layer. Process parameters are controlled in real time through temperature feedback, improving print quality. Patent document CN114083086A provides a method and device for controlling the stability of arc additive manufacturing processes. This method adjusts at least one of the wire feed speed and arc length to ensure stable wire transition even with large variations in process parameters, reducing spatter and wire sticking during the forming process and thereby improving the accuracy of arc additive manufacturing. Patent document CN112059384A discloses a method for adaptively controlling the distance between a magnetron plasma arc, the wire end, and the melt pool. This method addresses the key technical issues of adaptively controlling the distance between the wire end, the melt pool, and the plasma arc, as well as regulating the local heat input in the melt pool, during magnetron plasma arc additive manufacturing.

[0004] Although the above-mentioned existing schemes propose control and detection of heat input in additive manufacturing, they still have the following defects or shortcomings: First, the process parameters in the additive manufacturing process are controlled by three scales: substrate temperature, molten pool temperature, and temperature of each layer of the sample. The process is complicated and time-consuming; second, the wire feeding speed and arc length are controlled by obtaining the welding current and welding voltage in additive manufacturing, which is easily affected by various signal interference factors and cannot accurately obtain the thermal distribution image and law of the molten pool; finally, the distance control between the wire end, molten pool, and plasma arc based on magnetron plasma can only solve the problem of keeping the positional relationship between the wire end, molten pool, and plasma arc in dynamic balance, and fails to solve the heat accumulation and heat distribution problems caused by continuous arc swing and wire feeding in the additive manufacturing process, which can easily lead to defects such as thermal cracks, incomplete melting, and pores. Summary of the Invention

[0005] In response to at least some of the above shortcomings, the present invention provides a heat input regulation method for magnetron plasma arc additive manufacturing. The method aims to perform online temperature detection and heat input regulation through infrared thermal imagers, infrared thermometers, and magnetron sensors, and to perform online detection of the slice layer temperature and the molten pool temperature during the forming process, thereby performing real-time regulation of the heat input and improving heat input accumulation, thereby solving the technical problem of molding defects caused by abnormal temperature distribution in plasma arc additive manufacturing.

[0006] To achieve the above objectives, according to one aspect of the present invention, the following technical solution is provided: a system comprising a plasma welding gun, a magnetically controlled oscillating arc device, a wire feeder, an infrared thermometer, an infrared thermal imager, and a control processor. The system is characterized in that: during operation, the infrared thermal imager acquires the slice layer temperature distribution in real time, dividing the temperature characteristics into three regions: left, center, and right. This temperature information is compared and analyzed and fed back to the control processor, which then adjusts the excitation current, the direction and magnitude of the magnetic field, and the position and shape of the plasma arc based on the slice layer temperature distribution information to achieve uniform temperature distribution. Simultaneously, the infrared thermometer acquires the molten pool temperature information in real time, compares the molten pool temperature with the temperature in the middle of the slice layer, and feeds this back to the control processor, which then adjusts the wire feed speed of the wire feeder, corrects the problem of heat accumulation in the molten pool, and adjusts the local heat input of the molten pool.

[0007] The infrared thermal imager obtains the real-time temperature distribution of the slice layer and adjusts the printing parameters of the next layer in real time to prevent the phenomenon of over-burning of powder due to excessive temperature or incomplete melting of powder due to excessive temperature.

[0008] The molten pool temperature distribution obtained by the infrared thermometer is used to monitor the molten pool temperature disturbance during the printing process online, and the hole position and size of the sample are predicted, thereby adjusting the printing parameters in real time and eliminating abnormal temperature disturbances.

[0009] The magnetron plasma arc device can change the size and direction of the magnetic field generated by the device according to the required magnetic field function, thereby controlling the swing frequency and amplitude of the plasma arc and directly controlling the position and shape changes of the plasma arc.

[0010] The control processor can receive temperature information fed back by the temperature measuring instrument, has data analysis capability, and can output control data to the wire feeding device and the magnetron plasma arc device.

[0011] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art: the present invention provides a method for regulating heat input in magnetron plasma arc additive manufacturing, and various defects generated in plasma arc additive manufacturing are detected by temperature from multiple dimensions to regulate the corresponding heat input.

[0012] (1) The present invention generates a magnetic field through a magnetic control sensor and monitors the temperature of the slice layer in real time, which is then fed back to the control processor for temperature comparison. The control processor then regulates the size of the magnetic field generated by the excitation current. The Lorentz force generated by the arc in the transverse alternating magnetic field is used to swing the arc, so that the temperature of the slice layer is adjusted in real time, achieving a roughly uniform distribution of the layer temperature, thereby improving the forming process.

[0013] (2) The present invention collects the temperature of the molten pool in real time and then feeds it back to the control processor for temperature comparison. The control processor then controls the wire feeding speed, thereby adjusting the local heat input of the molten pool, avoiding heat accumulation, and realizing adaptive adjustment and stable operation of the heat input. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the device, 1 is the magnetron plasma device, 2 is the wire feeding device, 3 is the infrared thermometer, and 4 is the infrared thermal imager;

[0015] Figure 2 is a schematic diagram of adaptive control;

[0016] Figure 3 is a schematic diagram of temperature distribution; DETAILED DESCRIPTION

[0017] The present invention is described in further detail below with reference to the accompanying drawings and embodiments so that those skilled in the art can understand the present invention.

[0018] Example 1: Temperature control of the slice layer in plasma arc additive manufacturing. First, an infrared thermal imager is used to capture a real-time temperature image of the slice layer. The temperature distribution is fed back to the control processor, which sends instructions to adjust the excitation current and use the magnetic field to control the position of the plasma arc. The specific steps for the control processor to adjust the excitation current are as follows:

[0019] S1. Use infrared thermal imager to obtain real-time temperature distribution information of slice layer. The temperature of the center area of slice layer is T m , the temperature of the left side of the slice layer is recorded as T L , the temperature of the right side of the slice layer is recorded as T R ;

[0020] S2, if T m Greater than T L , adjust the excitation current, and magnetically control the swing arc device to make the arc deflect to the left. If T m Greater than T R , adjust the excitation current, and magnetically control the swing arc device to make the arc deflect to the right.

[0021] The layer temperature of plasma arc additive manufacturing is roughly evenly distributed, especially in scenarios where there are large temperature differences and uneven temperature distribution, which can easily lead to thermal cracks, incomplete melting, and pores. Self-starting identification and adaptive control of layer temperature distribution are achieved based on the difference in layer temperature, which greatly reduces the generation of defects and ensures stable deposition of the next layer of cladding.

[0022] Example 2: Adaptive control of melt pool heat input in plasma arc additive manufacturing. First, an infrared thermometer is used to collect real-time melt pool temperature information. The melt pool temperature is compared with the temperature in the middle of the slice layer and used as feedback to the control processor. By adjusting the wire feed speed, the heat accumulation problem in the melt pool is corrected and the local heat input in the melt pool is adjusted. The specific steps for controlling the processor to adjust the wire feed speed are as follows:

[0023] S1, obtain the molten pool temperature information in real time through the infrared thermometer, recorded as T P ;

[0024] S2, if T P Greater than T m , the control processor system adjusts the wire feeding structure to reduce the wire feeding speed. If T P Less than T m , the control processor system adjusts the wire feeding structure to increase the wire feeding speed.

[0025] S3, real-time temperature information of the molten pool T P The temperature of the center area of the slice layer is T m The wire feeding speed after adjustment is calculated based on the difference between the two values:

[0026] V w ′=V w ±(T P -T m )K p

[0027] Where V w ′ is the adjusted wire feeding speed, V w is the wire feeding speed before adjustment, Kp is the coefficient.

[0028] By real-time monitoring of the melt pool temperature information parameters, controlling the processor to quickly process comparative analysis and quickly adjust parameters such as wire feed speed, it is possible to achieve smooth heat input in plasma arc additive manufacturing. At the same time, it improves the problem of heat accumulation in the melt pool, adjusts the local heat input in the melt pool, avoids heat accumulation, realizes adaptive adjustment and stable heat input, avoids defects such as thermal cracks, incomplete melting, and porosity, and improves high-quality production efficiency.

[0029] Example 3, improves the forming of workpieces in additive manufacturing and reduces defects. It can be seen from relevant literature and experiments that the arc stirring the molten pool to a certain extent can improve the forming of the workpiece. At the same time, the alternating magnetic field can also stir the molten pool, refine the grains, and improve the mechanical properties of the molded parts. The present invention obtains the temperature distribution of the slice layer through a thermal imager. When printing, the control processor sends instructions to the magnetron plasma arc device to change the shape and position of the plasma arc by adjusting the excitation current, and controls the plasma arc to deflect with a certain arc and frequency to stir the molten pool. In addition, the molten pool temperature information is obtained through a thermometer, and the control processor adjusts the wire feeding speed of the wire feeding device to change the heat accumulation problem of the molten pool, adjust the local heat input of the molten pool, refine the grains, and improve the forming of the workpiece.

[0030] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, improvements, or combinations within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for regulating heat input in magnetron plasma arc additive manufacturing. The system comprises a plasma welding gun, a magnetron oscillating arc device, an infrared thermometer, an infrared thermal imager, and a control processor, and is characterized by: The infrared thermal imager obtains the temperature distribution of the slice layer in real time, which is divided into three regional temperature characteristics: left, middle, and right. The control processor adjusts the excitation current according to the temperature distribution information of the slice layer to change the position and shape of the plasma arc and adjust the heat distribution to be uniform. In addition, the infrared thermometer obtains the molten pool temperature information in real time, compares the molten pool temperature with the temperature in the middle of the slice layer, and feeds back the feedback to the control processor to adjust the wire feeding speed, change the heat accumulation problem in the molten pool, and adjust the local heat input of the molten pool.

2. The heat input regulation method for magnetron plasma arc additive manufacturing according to claim 1, characterized in that: The steps of feedback adjustment of slice layer temperature distribution information are as follows: S1, obtain the real-time temperature distribution information of the slice layer through the infrared thermal imager, and the temperature of the center area of the slice layer is T m , the temperature of the left side of the slice layer is recorded as T L , the temperature of the right side of the slice layer is recorded as T R ; S2, if T m >T L , adjust the excitation current, and magnetically control the swing arc device to make the arc deflect to the left. If T m >T R , adjust the excitation current, and magnetically control the swing arc device to make the arc deflect to the right.

3. The heat input regulation method for magnetron plasma arc additive manufacturing according to claim 1, characterized in that: The specific steps of adjusting the wire feeding speed by feedback of the molten pool temperature information are as follows: S1, obtaining the molten pool temperature information in real time through an infrared thermometer, denoted as T P ; S2, if T P >T m , the control processor system adjusts the wire feeding structure to reduce the wire feeding speed. If T P <T m , the control processor system adjusts the wire feeding structure to increase the wire feeding speed.

4. The heat input regulation method for magnetron plasma arc additive manufacturing according to claim 3, characterized in that: The real-time temperature information T of the molten pool P The temperature of the center area of the slice layer is T m The wire feeding speed after adjustment is calculated based on the difference between the two values: V w ′=V w ±(T P -T m )K p Where V w ′ is the adjusted wire feeding speed, V w is the wire feeding speed before adjustment, K p is the coefficient.

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