Vision-magnetic field low-frame same-frequency micro plasma arc fuse state monitoring method

Abstract

The invention discloses a method for monitoring the state of a micro-plasma arc fuse wire through vision-magnetic field low-frame common-frequency, and mainly solves the problems of high equipment cost and low efficiency in traditional arc additive manufacturing monitoring. Due to the fact that the time and the area of unstable metal transition in the wire fusing process are uncertain, only whole-course covering type monitoring can be achieved, mass data can be generated, and hysteresis exists. The method is technically characterized in that the shooting frame rate of a camera and the change frequency of a magnetic field are cooperatively controlled to monitor the metal transition state under the control of the magnetic field, a metal transition mode is recognized by shooting a small number of local area images, the magnetic field is dynamically adjusted according to the metal transition mode, and the shooting frame rate is correspondingly changed. According to the invention, the monitoring range is reduced from the fundamental principle, the data processing difficulty is reduced, the adjustment real-time performance is improved, and the low-cost and high-efficiency monitoring of the micro-plasma arc fuse wire additive process is realized.

Description

Technical Field

[0001] The present invention specifically relates to a method for visual-magnetic field low-frame co-frequency monitoring of micro plasma arc fuse status, and the method belongs to the field of arc fuse additive manufacturing process monitoring in intelligent manufacturing. Background Art

[0002] In the process of arc additive manufacturing and arc welding, the metal transition state directly affects the product quality, so it is necessary to monitor the metal transition state in real time in order to adjust the process parameters to maintain a stable transition. Monitoring the filament manufacturing process and adaptively adjusting the process are important means to improve the stability of metal transition.

[0003] In the manufacturing process of fuse deposition, the static stable metal transition mode is difficult to maintain for a long time, resulting in poor forming accuracy of fuse deposition. In order to ensure the forming quality of the workpiece, the process parameters are usually predicted and planned in advance, or the fuse process is monitored and adjusted. However, due to the inevitable "step effect" caused by factors such as heat accumulation deformation and time-varying process parameters, as well as the lack of current fuse process monitoring methods, the final forming quality is unsatisfactory. Therefore, for micro plasma arc fuse additive manufacturing, the unstable metal transition during the fuse deposition process causes internal defects in the workpiece and the reduction of workpiece contour accuracy, which is a bottleneck restricting the development of micro plasma arc fuse additive technology.

[0004] At present, the commonly used and effective monitoring method is to observe the fuse manufacturing process through vision + image intelligent processing, but high-frame rate cameras and high-performance image processing chips must be used, and high-performance computers and controllers must be equipped to monitor and control the manufacturing process in real time. The complexity of the algorithm and the huge equipment cost limit the long-term stable manufacturing capabilities of arc fuse additive technology. At the same time, traditional full-coverage passive monitoring will generate massive data and cannot achieve real-time regulation, which hinders the marketization of arc fuse additive technology. Therefore, it is urgent to seek new fluctuating metal transition state monitoring methods to achieve low-cost and efficient monitoring of microplasma arc fuse additive processes. This is another major challenge facing the development of magnetically controlled fluctuating stable fuse additive technology. Summary of the invention

[0005] The purpose of the present invention is to provide a visual-magnetic field frame rate joint control to monitor the change of the solid-liquid connection state in the micro plasma arc fuse additive process. In the fuse process, the magnetic field frequency and the visual image frame rate are optimally matched to provide a timely feedback method for later process adjustment and stable metal transition. The present invention designs a monitoring method with strong joint control and clear principles, simplifies passive monitoring, reduces the difficulty of data processing, and improves the monitoring efficiency of micro plasma arc fuse additive.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] See also Figure 1 This method is based on a micro-controlled plasma arc fuse manufacturing platform, which includes a wire feeder, a three-dimensional fixture, a metal wire, a micro plasma gun, a substrate, a magnetron device, and a camera. The magnetron device generates a magnetic field in the metal transition region that has a regulating effect on the micro plasma arc swing. The micro plasma gun releases a micro plasma torch to melt and deposit the metal wire. Before fuse deposition manufacturing, the distance between the end of the wire, the center of the plasma torch and the substrate is adjusted so that the wire conveying direction passes through the center below the micro plasma torch, the magnetic field acts in the metal transition area, the plasma arc is controlled to scan in the wire conveying direction, the wire feeding device is turned on, the plasma arc contacts the conveyed wire, the wire melts to produce molten metal, the plasma arc scans the substrate to partially melt the substrate in contact with the plasma arc, the locally melted substrate contacts the molten metal produced by the melting of the wire to form a molten pool, and then the plasma arc is controlled to perform periodic scanning between the end of the wire, the molten metal and the molten pool. Within a metal transition cycle, the camera takes a group of solid-liquid connection state pictures during the micro plasma arc scanning process, and all the images taken are divided in the order of shooting time with the number of images that are integer multiples of the magnetic field frequency as a group. In this group, it can be determined that the solid-liquid connection state changes and is determined as the camera shooting minimum frame rate. The optimal frame rate is selected to achieve the visual-magnetic field low frame co-frequency detection effect, so as to provide timely feedback for the subsequent adjustment of the fuse process and the magnetic field frequency.

[0008] The solid-liquid connection state refers to the connection state between the wire and the molten pool in the material evolution path of the metal wire melting from the solid state to the liquid state and then cooling the molten pool to form a solid deposition layer. The metal transition mode division is based on the spatial position and shape of each substance in the metal transition area image captured by the camera within one cycle. The image processing module can sort and compare the solid-liquid connection state images captured by the camera to divide the current metal transition mode.

[0009] See also Figure 2 ,The metal transition modes within the scanning period of the magnetron microplasma arc are divided into (a) the wavy liquid bridge transition mode with continuous connection between solid and liquid, (b) the wavy contact transition mode with intermittent connection between solid and liquid, and (c) the wavy chaotic mode with no contact between solid and liquid by the image processing module.

[0010] The theoretical principle of building the visual-magnetic field low-frame co-frequency monitoring mechanism is as follows: in the microplasma arc fuse additive process, the metal transition process is actively visually monitored within a cycle of the magnetic field-controlled microplasma arc scanning. The periodic characteristics of the fluctuating metal transition are utilized, and all the images taken are grouped in the order of shooting time with the number of images of integer multiples of the magnetic field frequency (starting from 1) as a group. If it can be determined that the solid-liquid connection state has changed in a group of images, the number value of the group of images is the minimum frame rate of the camera that can observe the transition mode change. If it cannot be determined, the multiple is increased by one until the optimal frame rate that meets the shooting requirements is obtained. If the magnetic field frequency changes, the camera frame rate is adjusted in real time according to the joint control relationship to obtain the optimal frame rate of the camera at this time. In this way, the visual-magnetic field low-frame co-frequency monitoring joint control mechanism is constructed to shoot the contour image of the metal transition area. The image processing module divides the metal transition mode according to the solid-liquid connection state in the captured contour image, and determines whether the metal transition is stable according to the metal transition mode, and then adjusts the fuse process parameters and the magnetic field frequency to promote the stability of the microplasma arc fuse state. The above steps are repeated until the fuse process is completed.

[0011] The main features of the present invention are: there is a correlation between the shooting frame rate of the camera used to monitor the fused filament additive manufacturing process and the frequency of the applied magnetic field. During the manufacturing process, the shooting frame rate of the camera and the changing frequency of the magnetic field are jointly controlled to monitor the metal transition state under the control of the magnetic field. The metal transition mode is identified by shooting a small number of local area images, and the magnetic field is dynamically adjusted according to the metal transition mode and the shooting frame rate is changed accordingly.

[0012] See also Figure 3 The beneficial effect of the present invention is to provide a method for visual-magnetic field low-frame co-frequency monitoring of the solid-liquid connection state in micro plasma arc fuse additives. By utilizing the fluctuation regularity of the metal transition state, an active monitoring method is proposed to determine the shooting frame rate according to the magnetic field frequency. Only a small amount of image data needs to be collected and processed, which greatly reduces the amount of calculation; only an ordinary low-frame camera is needed to reduce the cost of purchasing a high-frame rate camera; process adjustment and fluctuation transition mode conversion are carried out simultaneously within the fluctuation period, which fundamentally reduces the monitoring range, reduces the difficulty of data processing and avoids subsequent adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A monitoring platform for magnetron micro plasma arc fuse manufacturing.

[0014] Figure 2 Schematic diagram of the connection between the wire and the molten pool during the magnetron micro plasma arc scanning cycle.

[0015] Figure 3 This is a comparison chart of fuse process monitoring methods.

[0016] Figure 4Implementation flow chart. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0018] See also Figure 1 , Figure 4 This method is based on a micro-controlled plasma arc fuse manufacturing platform. The platform includes a wire feeder, a three-dimensional fixture, a metal wire, a micro plasma gun, a substrate, a magnetron, and a camera. The magnetron can generate a magnetic field that has a regulating effect on the fuse process. The micro plasma gun generates a micro plasma torch to melt and deposit the metal wire. Before the fuse manufacturing begins, the relative position of the wire and the molten pool is adjusted so that the wire head is placed directly below the micro plasma gun. The power is turned on to start the equipment. The micro plasma gun generates a micro plasma arc that periodically scans between the wire and the molten pool to provide a stable heat source for the fuse process. The magnetron generates a magnetic field in the metal transition region to regulate the swing of the micro plasma arc. The visual-magnetic field low-frequency same-frame mechanism groups all the images taken in the order of shooting time with the number of images that are integer multiples of the magnetic field frequency (starting from 1) as a group. If the solid-liquid connection state can be determined to have changed in a group of images, the number value of the group of images is the lowest frame of the camera that can observe the transition mode change. If the determination cannot be made, the multiple is increased by one until the optimal frame rate that meets the shooting requirements is obtained to capture the contour image of the metal transition area. The image is sorted and divided into the current metal transition mode by the image processing module, namely (a) the wavy liquid bridge transition mode with continuous solid-liquid connection, (b) the wavy contact transition mode with intermittent solid-liquid connection, and (c) the wavy chaotic mode with no solid-liquid contact. Then, it is determined whether the metal transition state is stable. If it is unstable, the metal fuse process and the magnetic field frequency generated by the magnetron device are adjusted. The camera frame rate is adjusted in real time with the change of the magnetic field frequency. Otherwise, the fuse is manufactured according to the current parameters, and the above monitoring steps are repeated until the fuse manufacturing is completed.

[0019] Implementation case 1, as a monitoring method for repairing the deposited layer of fused additive manufacturing. First, the automatic fused additive equipment composed of peripherals such as a drive motor, a gyroscope, and an encoder performs real-time repair of the deposited layer, and at the same time generates a magnetic field perpendicular to the wire feeding direction in the metal transition area. Then, the camera on the side of the deposited layer adjusts the position of the camera through an equal-width slide rail and a lifting structure to better observe the movement and deposition repair process of the automatic fused additive equipment in real time, and establishes a magnetic field-camera low-frame frequency synchronization mechanism to synchronously record the cross-sectional data of the deposited layer and feed it back to the image processing system. After sorting, processing, and analyzing the image data, the image processing system feeds back the parameters to the main control system. After receiving the data, the main control system controls the automatic fused additive equipment to adjust the parameters for repairing the deposited layer in real time, and the entire system forms positive feedback. In order to reduce the error in the process of repairing the deposited layer, the change in the magnetic field frequency can trigger the synchronous adjustment of the camera frame rate, and repeat the above steps.

[0020] Implementation case 2: as a monitoring method for micro plasma arc additive manufacturing of small parts. Figure 1 In the process of micro plasma arc fuse transition, the magnetron device applies a local magnetic field in the metal transition area that can adjust the swing of the micro plasma arc, establishes a low frame frequency mechanism of the magnetic field-camera, records the solid-liquid connection state of the wire-molten pool in real time and feeds it back to the image processing system. The picture is sorted and divided into the current metal transition mode by the image processing module. If it is stable, the fuse is manufactured according to the existing parameters. Otherwise, the metal transition state is stabilized by controlling the shape, direction and residence time of the micro plasma arc by changing the magnetic field size and frequency. At the same time, the camera frame rate is adjusted in real time with the change of the magnetic field frequency and generates image data to determine whether the current metal transition state is stable, maintain the dynamic stability of the metal transition process and repeat the above steps until the manufacturing of the tiny parts is completed.

Claims

1. A method for monitoring the state of a micro plasma arc fuse by using a visual-magnetic field at low frame and same frequency, characterized by: Taking advantage of the periodic characteristics of fluctuating metal transitions, a low-frame co-frequency joint control relationship between the image shooting frame rate and the magnetic field frequency required for judging the metal transition mode transition is constructed. The number of images that are integer multiples of the magnetic field frequency (starting from 1) is taken as a group, and all the images taken are grouped in order of shooting time. If it can be determined in a group of images that the solid-liquid connection state has changed, the number value of this group of images is the minimum frame rate of the camera that can observe the transition mode transition. If it cannot be determined, the multiple is increased by one until the optimal frame rate that meets the shooting requirements is obtained. If the magnetic field frequency changes, the camera frame rate is adjusted in real time according to the joint control relationship to obtain the optimal frame rate of the camera at this time, thereby constructing a visual-magnetic field low-frame co-frequency monitoring joint control mechanism.

2. A method for monitoring the state of a micro plasma arc fuse by using a visual-magnetic field at low frame and frequency, characterized in that: In the process of micro plasma arc fuse additive, the metal transition process is actively visually monitored within one cycle of magnetic field-controlled micro plasma arc scanning. The contour image of the metal transition area is captured by a camera at an optimal frame rate. The image processing module divides the metal transition mode according to the solid-liquid connection state in the captured contour image, and determines whether the metal transition is stable based on the metal transition mode, thereby adjusting the fuse process parameters and magnetic field frequency to promote the stability of the micro plasma arc fuse state.

3. The method for monitoring the state of a micro plasma arc fuse by using a visual-magnetic field at low frame and same frequency according to claim 2 is characterized by: The solid-liquid connection state refers to the connection state between the wire and the molten pool in the material evolution path in which the metal wire melts from the solid state to the liquid state and then transitions to the molten pool, and the molten pool cools to become a solid deposition layer.

4. The method for monitoring the state of a micro plasma arc fuse by using a visual-magnetic field at low frame and same frequency according to claim 2 is characterized by: The metal transition area includes the area space that can be scanned by the micro plasma arc under control, part of the wire, the molten metal, the molten pool and the substrate; the metal transition mode division is based on the spatial position and shape of each material in the metal transition area image captured by the camera within one cycle.

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