Positioning arm manufacturing method

Abstract

The invention relates to the field of additive welding, and provides a positioning arm manufacturing method. The positioning arm manufacturing method comprises the steps that an electric arc additive manufacturing system is used for conducting additive manufacturing on a preset area of a positioning arm workpiece; in the additive manufacturing process, molten pool state information of a molten pool in a preset area is collected in real time through a sensing system; based on the collected molten pool state information, at least two welding process parameters of the welding current, the welding voltage and the wire feeding speed are cooperatively regulated and controlled at the millisecond-level response speed through a high-frequency dynamic controller, so that the physical behavior of the molten pool is actively managed, and a near-net forming additive layer is formed on a positioning arm workpiece; active management of physical behaviors of the molten pool comprises inhibition of falling or flowing of the molten pool caused by gravity in the all-position additive manufacturing process, so that a near-net formed additive layer does not need to be subjected to a subsequent grinding and finishing procedure. The manufacturing method of the positioning arm can break through the automation bottleneck of geometric mutation positions; gravity influence is actively inhibited, and welding forming defects are eliminated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of additive welding, and provides a positioning arm manufacturing method. BACKGROUND

[0002] In the manufacturing and repairing process of the positioning arm of the high-speed railway bogie side beam, due to the unique geometric structure and complex performance requirements of the component, it has become a technical difficulty.

[0003] Firstly, the complex geometric structure of the positioning arm brings great challenges to manufacturing. The saddle-shaped weld on it not only has a complex spatial curved surface with continuous changes, but also contains difficult-to-handle corners, steep slopes and saddle point areas. The traditional arc welding process is limited by the accessibility of the welding gun, and it is difficult to achieve high-quality continuous welding in all positions in these areas. Although the existing automatic equipment improves the efficiency to some extent, it is still difficult to avoid forming deviations due to insufficient degrees of freedom or limitations of trajectory planning algorithms, which seriously affects the dimensional accuracy and assembly fit of the component.

[0004] Secondly, the saddle point of the saddle-shaped weld is a stress concentration area, which is extremely sensitive to penetration quality and internal defects. The existing welding technology lacks real-time and accurate penetration control capability, and the problem of insufficient penetration or overburning is likely to occur in this area, thereby affecting the fatigue life and running safety of the positioning arm under high-speed and high-load working conditions. In addition, even if the high-strength manual polishing can partially solve these problems, it not only greatly prolongs the manufacturing cycle and increases the cost, but also may change the microstructure of the positioning arm base material or weld due to local high temperature, further reducing its strength and toughness, and ultimately leading to component scrap.

[0005] Finally, the positioning arm is prone to wear, cracks and other damage during service, and the repair technology can provide a certain degree of remedy, but it still relies on the experience of technicians to ensure the metallurgical bonding quality and geometric accuracy of the repaired layer and the base. Such repair technology is inefficient and difficult to ensure the consistency of quality, and a large amount of polishing is still required after repair, thereby increasing the cost and reducing the repair efficiency.

[0006] In summary, the bogie manufacturing industry urgently needs an innovative technology that can automatically and accurately complete the manufacturing of complex structures to solve various bottleneck problems of existing manufacturing and repair technologies. SUMMARY

[0007] The embodiment of the present application provides a positioning arm manufacturing method to achieve the purpose of automatically and accurately completing the manufacturing and repair of the positioning arm.

[0008] The present application provides a positioning arm manufacturing method, comprising: using an electric arc additive manufacturing system to additively manufacture a predetermined area of the positioning arm workpiece; In the process of additive manufacturing, the molten pool state information of the predetermined region is collected in real time by a sensing system; Based on the collected molten pool state information, at least two of the welding process parameters of welding current, welding voltage and wire feeding speed are cooperatively regulated by a high-frequency dynamic controller with millisecond-level response speed, so as to actively manage the physical behavior of the molten pool, thereby forming a near-net-shape additive layer on the positioning arm workpiece. Among them, the active management of the physical behavior of the molten pool includes: in the process of full-position additive manufacturing, the gravity-induced sinking or flowing of the molten pool is inhibited, so that the near-net-shape additive layer does not need to be polished and trimmed in the subsequent process.

[0009] According to the embodiment of the present application, the molten pool state information includes at least one selected from the following: visual image of the molten pool, spectral information of the arc, and electrical signal information of the arc.

[0010] According to the embodiment of the present application, the cooperative regulation includes at least one of adjusting the peak-to-base ratio of the pulse current, instantaneously compensating the welding voltage, and controlling the amplitude of the micro-oscillation of the wire feeding speed.

[0011] According to the embodiment of the present application, the predetermined region includes a saddle-shaped region or a corner region on the positioning arm.

[0012] According to the embodiment of the present application, before the step of additive manufacturing, the method further comprises: based on the three-dimensional digital model of the positioning arm workpiece, planning an equidistant additive path for the saddle-shaped region.

[0013] According to the embodiment of the present application, when additive manufacturing is performed at the saddle point or the arc-receiving region of the saddle-shaped region, the cooperative regulation is used to ensure complete fusion of the weld and smooth transition at the arc-receiving position.

[0014] According to the embodiment of the present application, when the predetermined region is in an overhead welding position, the step of cooperative regulation includes increasing the frequency of the pulse current to enhance the surface tension of the molten pool, thereby inhibiting the sinking of the molten metal.

[0015] According to the embodiment of the present application, when the predetermined region is in an upright welding position, the method further comprises: using a cable-stayed bead strategy for surfacing to prevent the molten pool from flowing.

[0016] According to the embodiment of the present application, the surface roughness Ra of the near-net-shape additive layer is not greater than 6.3 microns.

[0017] According to the embodiment of the present application, the geometric accuracy error of the near-net-shape additive layer is not greater than 0.5 millimeters.

[0018] According to an embodiment of the present application, the electric arc additive manufacturing system comprises a multi-axis robot and a positioner, and during the process of additive manufacturing, the multi-axis robot and the positioner move cooperatively to keep the welding torch in an optimal working pose.

[0019] According to an embodiment of the present application, the step of cooperative regulation specifically comprises: inputting the molten pool state information into a penetration prediction model, and determining the regulation amount of the welding process parameters according to the output result of the penetration prediction model.

[0020] According to the positioning manufacturing method provided by the embodiment of the present application, the multi-axis robot and the positioner of the electric arc additive manufacturing system move cooperatively, which solves the problems of poor reachability of the welding torch and difficulty in adapting to complex areas of the positioning arm (such as saddle-shaped curved surfaces and corner mutations) in the traditional arc welding process, realizes full-position continuous additive manufacturing in the predetermined area, avoids local incomplete welding and uneven thickness of the additive layer caused by improper pose of the welding torch in the traditional process, and lays a foundation for the formation of subsequent high-quality additive layers. The sensing system collects multiple types of molten pool state information in real time, which comprehensively reflects the real-time state of the molten pool from three dimensions of morphology, temperature and energy, and avoids one-sidedness of state judgment caused by single information collection. Accurate molten pool state information provides a reliable regulation basis for the high-frequency dynamic controller, prevents regulation deviation caused by misjudgment of the molten pool state, and ensures the pertinence and accuracy of subsequent process parameter adjustment. The millisecond-level response speed of the high-frequency dynamic controller and the multi-parameter cooperative regulation can quickly respond to changes in the physical behavior of the molten pool, actively suppress the molten pool from falling or flowing caused by gravity, and avoid defects such as welding spatter, undercutting and size out-of-tolerance caused by unstable molten pool in the traditional process. The finally formed near-net-shape additive layer does not need subsequent polishing and finishing process, which on the one hand greatly shortens the manufacturing cycle and reduces the labor cost and material cost caused by manual polishing; on the other hand, avoids the damage of local high temperature in the polishing process to the microstructure of the parent material and the additive layer of the positioning arm, ensures the mechanical properties such as strength and toughness of the positioning arm, and at the same time ensures that the surface quality and geometric accuracy of the additive layer meet the standards, and improves the structural reliability and assembly adaptability of the whole positioning arm. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0022] Figure 1 is a schematic flowchart of the positioning arm manufacturing method provided by the present application. DETAILED DESCRIPTION

[0023] The embodiments of the present application will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the present application, but cannot be used to limit the scope of the present application.

[0024] As shown in the drawings, Figure 1 The present application provides a positioning arm manufacturing method, comprising: Step 10, using an electric arc additive manufacturing system to additively manufacture a predetermined region of the positioning arm workpiece; Step 20, during the additive manufacturing process, collecting the molten pool state information of the predetermined region in real time through the sensing system; Step 30, based on the collected molten pool state information, at least two of the welding process parameters of the welding current, the welding voltage and the wire feeding speed are cooperatively controlled by the high-frequency dynamic controller at a millisecond level response speed, to actively manage the physical behavior of the molten pool, so as to form a near-net-shape additive layer on the positioning arm workpiece; Wherein, the active management of the physical behavior of the molten pool includes: in the full-position additive manufacturing process, the gravity-induced molten pool sinking or flowing is inhibited, so that the near-net-shape additive layer does not need to be subjected to subsequent polishing and finishing process.

[0025] According to the positioning manufacturing method provided by the embodiment of the present application, the multi-axis robot of the electric arc additive manufacturing system cooperates with the positioner to solve the problem of poor weld gun accessibility and difficulty in adapting to complex regions of the positioning arm (such as saddle-shaped curved surface, corner mutation) in the traditional arc welding process, realizes full-position continuous additive manufacturing of the predetermined region, avoids defects such as local incomplete welding and uneven thickness of the additive layer caused by improper weld gun pose in the traditional process, and lays a foundation for the formation of subsequent high-quality additive layer. The sensing system collects multiple types of molten pool state information in real time, which comprehensively reflects the real-time state of the molten pool from three dimensions of shape, temperature and energy, avoiding the one-sidedness of state judgment caused by single information collection. Accurate molten pool state information provides a reliable control basis for the high-frequency dynamic controller, preventing control deviation caused by misjudgment of the molten pool state, and ensuring the pertinence and accuracy of subsequent process parameter adjustment. The millisecond level response speed of the high-frequency dynamic controller and the multi-parameter cooperative control can quickly respond to changes in the physical behavior of the molten pool, actively inhibit the gravity-induced molten pool sinking or flowing, and avoid defects such as welding spatter, undercutting and size out-of-tolerance caused by unstable molten pool in the traditional process. The finally formed near-net-shape additive layer does not need subsequent polishing and finishing process, which on the one hand greatly shortens the manufacturing cycle and reduces the labor cost and material cost brought by manual polishing; on the other hand, avoids the damage of local high temperature in the polishing process to the microstructure of the positioning arm base material and the additive layer, ensures the mechanical properties such as strength and toughness of the positioning arm, and at the same time ensures that the surface quality and geometric accuracy of the additive layer meet the standards, and improves the overall structural reliability and assembly adaptability of the positioning arm.

[0026] Please continue to seeFigure 1 The positioning arm manufacturing method provided by the embodiments of the present application mainly includes the following three steps: When the step 10 is performed, the electric arc additive manufacturing system is used as a core operation unit, which includes a multi-axis robot, a positioner and a welding torch. The multi-axis robot is provided with a welding torch at the tail end and has a multi-degree-of-freedom spatial motion capability; the positioner is fixedly connected with the positioning arm workpiece and can drive the workpiece to adjust the posture. Before the operation, the additive manufacturing path is planned according to the geometric characteristics of the predetermined region (such as a saddle-shaped region or an angular region) of the positioning arm workpiece; during the operation, the multi-axis robot and the positioner move cooperatively, the multi-axis robot drives the welding torch to move along the planned path, and the positioner synchronously adjusts the posture of the positioning arm workpiece, so as to ensure that the welding torch is always aligned with the predetermined region and to deliver the electric arc energy and the welding wire to the region, thereby realizing the additive manufacturing.

[0027] The step 20 is performed synchronously with the step 10, and the sensing system collects the molten pool state information in real time throughout the whole process. The sensing system includes a visual detection component, a spectral detection component and an electrical signal detection component: the visual detection component captures the shape, size and spreading state of the molten pool by high-definition imaging; the spectral detection component is close to the electric arc region and collects the spectral signals generated by the electric arc combustion, reflecting the temperature change of the molten pool; the electrical signal detection component is connected with the welding circuit and collects the current and voltage fluctuation signals of the electric arc. All the collected molten pool state information is transmitted to the high-frequency dynamic controller in real time through a data line, thereby providing a basis for subsequent regulation and control.

[0028] In the step 30, the high-frequency dynamic controller starts the cooperative regulation and control with a millisecond-level response speed after receiving the molten pool state information transmitted by the sensing system. The molten pool physical behavior is judged according to the molten pool state information: if it is detected that the molten pool has a downward trend (such as an overhead welding position), the pulse frequency of the welding current and the wire feeding speed are regulated; if it is detected that the molten pool has a flowing trend (such as an upright welding position), the peak ratio of the welding voltage and the welding current is regulated. During the regulation and control process, at least two parameters selected from the welding current, the welding voltage and the wire feeding speed are cooperatively adjusted, so as to actively manage the physical behavior of the molten pool by changing the heat input and the welding wire supply rate, thereby inhibiting the downward trend or the flowing trend of the molten pool caused by gravity. Finally, a near-net-shape additive layer with a smooth surface and accurate size is formed in the predetermined region of the positioning arm workpiece, and the additive layer can meet the use requirements without subsequent polishing and finishing.

[0029] According to the embodiments of the present application, the molten pool state information includes at least one selected from the following: a visual image of the molten pool, spectral information of the electric arc and electrical signal information of the electric arc.

[0030] In the embodiment of the present application, the sensing system comprises multiple detection components for collecting molten pool state information. Among them, the visual detection component is aligned with the predetermined area of the molten pool of the positioning arm workpiece, captures the visual image of the molten pool in real time, and clearly presents the shape, size and spreading of the molten pool; the spectral detection component is close to the arc area, collects the spectral information generated during the arc combustion process, and reflects the energy state of the arc and the temperature change of the molten pool through the spectral characteristics; the electrical signal detection component is connected with the welding circuit of the arc additive manufacturing system, and collects the electrical signal information of the arc, which can reflect the real-time fluctuation of the welding current and voltage. The above-mentioned three kinds of molten pool state information can be collected separately or combined, and the collected information is transmitted to the high-frequency dynamic controller in real time to provide basis for subsequent process parameter regulation.

[0031] Through the collection of multiple types of molten pool state information, the real-time state of the molten pool can be comprehensively reflected from multiple dimensions of visual form, energy temperature and electrical fluctuation, avoiding the judgment deviation caused by single information collection. The visual image can intuitively identify the shape defects such as flow and drop of the molten pool, the spectral information can accurately judge whether the temperature of the molten pool is suitable, and the electrical signal information can timely perceive the welding energy fluctuation. The combination of the three can make the high-frequency dynamic controller more accurately grasp the physical behavior of the molten pool, provide comprehensive and reliable basis for coordinated regulation, and further improve the accuracy of regulation and reduce the forming defects caused by insufficient state judgment.

[0032] According to the embodiment of the present application, the coordinated regulation comprises at least one of adjusting the peak-to-base ratio of the pulse current, instantaneously compensating the welding voltage, and controlling the micro-oscillation amplitude of the wire feeding speed. The present application also provides a.

[0033] In the embodiment of the present application, the coordinated regulation of the high-frequency dynamic controller is realized in multiple ways. When adjusting the peak-to-base ratio of the pulse current, the controller judges the energy demand of the molten pool according to the molten pool state information. If the temperature of the molten pool is low, the peak-to-base ratio is increased to increase the instantaneous energy input, and if the molten pool has a flow trend, the ratio is reduced to reduce the heat input. When instantaneously compensating the welding voltage, the controller immediately outputs a compensation signal to adjust the voltage to a preset range to ensure the stability of the arc when the electrical signal information shows that the voltage fluctuates. When controlling the micro-oscillation amplitude of the wire feeding speed, the controller adjusts the fluctuation range of the wire feeding speed according to the change of the molten pool size. When the molten pool is large, the micro-oscillation amplitude is reduced to avoid excessive supply of welding wire, and when the molten pool is small, the micro-oscillation amplitude is increased to ensure timely replenishment of welding wire. The above-mentioned regulation methods can be executed separately or combined to adapt to different molten pool state requirements.

[0034] The peak value and the base value ratio of the pulse current are adjusted, the heat input of the molten pool is accurately controlled, the molten pool is prevented from flowing due to too high heat input, or the fusion is prevented from being insufficient due to too low heat input, the instantaneous compensation of the welding voltage is performed, the influence of voltage fluctuation on the arc is quickly eliminated, the arc is ensured to burn stably, and the abnormal droplet transfer caused by unstable arc is reduced, and the micro-oscillation amplitude of the wire feeding speed is controlled, so that the welding wire supply amount is matched with the molten pool consumption, and the welding wire accumulation or insufficient supply is avoided. The three kinds of regulation and control modes work together, the problems of the molten pool in different states can be solved, the physical behavior of the molten pool is actively managed, and the forming quality of the additive layer is improved.

[0035] According to an embodiment of the present application, the predetermined region comprises a saddle-shaped region or a corner region on the positioning arm.

[0036] In an embodiment of the present application, the predetermined region of the positioning arm is a saddle-shaped region or a corner region. The saddle-shaped region has a continuously changing complex spatial curved surface structure, including a saddle point and a steep slope section, a multi-axis robot of the arc additive manufacturing system and a positioner cooperatively move, the pose of the welding torch is adjusted according to the curved surface form of the region, and it is ensured that the welding torch is always adapted to the normal direction of the curved surface; the corner region is a position with a sudden change in geometric form on the positioning arm, such as the intersection of a vertical edge and a plane, the welding torch moves along the corner contour through accurate path planning, and it is ensured that the additive layer completely covers the corner surface. When additive manufacturing is performed on the two regions, the sensing system continuously collects molten pool state information, and the high-frequency dynamic controller synchronously performs parameter regulation and control.

[0037] For the complex curved surface of the saddle-shaped region, through the cooperative adjustment of the multi-axis robot and the positioner, the poor reachability of the welding torch in the traditional arc welding process and the difficulty in all-position welding are solved, and it is ensured that uniform additive layers can be obtained at each part of the curved surface; for the geometric mutation characteristics of the corner region, through accurate path planning and parameter regulation and control, the defects such as incomplete welding and undercutting that are prone to occur at the corner in the traditional process are avoided, and the forming integrity of the corner region is ensured. The targeted operation of the two regions breaks through the bottleneck of manufacturing the complex structure of the positioning arm, and improves the overall manufacturing quality of the positioning arm.

[0038] According to an embodiment of the present application, before the step of performing additive manufacturing, the method further comprises: based on a three-dimensional digital model of the positioning arm workpiece, planning an equidistant additive path for the saddle-shaped region.

[0039] In an embodiment of the present invention, before additive manufacturing of the positioning arm workpiece, a three-dimensional digital model of the workpiece is first obtained. This model is generated through 3D scanning or computer-aided design and can fully represent the curved surface contour and dimensional parameters of the saddle-shaped region. Based on this three-dimensional digital model, a path planning algorithm is used to plan equidistant additive manufacturing paths for the saddle-shaped region. The path spacing is determined according to the preset additive layer thickness to ensure that there are no gaps or overlaps between adjacent paths. The planned additive manufacturing paths are imported into the control unit of the arc additive manufacturing system, which controls the multi-axis robot to move the welding torch along the planned paths to realize the additive manufacturing of the saddle-shaped region.

[0040] Precise data of the saddle-shaped region is obtained through a 3D digital model, providing a reliable basis for path planning and avoiding path deviations caused by manual planning. Equidistant additive paths ensure uniform additive layer thickness in all parts of the saddle-shaped region, avoiding local over-thickness or under-thinness and improving the geometric consistency of the additive layer. Pre-planning and importing the path into the system makes the welding torch movement more precise and orderly, reducing path adjustment time during operation, improving additive manufacturing efficiency, and avoiding forming defects caused by chaotic paths.

[0041] According to an embodiment of the invention, when additive manufacturing is performed at the saddle point or arc termination region of a saddle-shaped area, synergistic control is used to ensure complete fusion of the weld and a smooth transition at the arc termination.

[0042] In an embodiment of the invention, the saddle point of the saddle-shaped region is a location where curved surfaces intersect and stress is easily concentrated, while the arc-ending region is the area where the additive manufacturing process is about to end. During additive manufacturing at the saddle point, the high-frequency dynamic controller appropriately increases the ratio of the peak to the base value of the welding current based on the molten pool state information collected by the sensor system, thereby increasing the arc energy. Simultaneously, it fine-tunes the wire feed speed to ensure sufficient melting of the welding wire, allowing the weld to fully fuse with the base material of the positioning arm. During additive manufacturing in the arc-ending region, the controller gradually reduces the welding current and voltage to lower the heat input, while simultaneously controlling the wire feed speed to decrease slowly until the additive manufacturing process ends. This allows the additive layer at the arc-ending point to gradually transition to the surface of the positioning arm, preventing depressions or protrusions.

[0043] The coordinated control of the saddle point improves the penetration depth in this area, avoids stress concentration risks caused by insufficient fusion, enhances the structural strength of the positioning arm at the saddle point, and ensures its reliability under high-speed and high-load conditions. The gradual control of the arc termination area eliminates defects such as arc craters and depressions that are prone to occur in the traditional arc termination process, achieves a smooth transition at the arc termination, improves the surface quality of the additive layer, and avoids the risk of cracks caused by arc termination defects, further ensuring the overall performance of the positioning arm.

[0044] According to an embodiment of the present invention, when the predetermined area is in the overhead welding position, the coordinated control step includes: increasing the frequency of the pulse current to enhance the surface tension of the molten pool, thereby suppressing the molten metal from falling.

[0045] In an embodiment of the invention, when the predetermined area of ​​the positioning arm is in the overhead welding position, the molten metal is prone to falling downwards due to gravity, forming weld beads or incomplete welds. At this time, the high-frequency dynamic controller initiates coordinated regulation based on the molten pool state information fed back by the sensing system, increasing the frequency of the pulse current. After the pulse current frequency is increased, the force of the arc on the molten pool is enhanced, causing the metal molecules in the molten pool to move more rapidly, thereby increasing the surface tension of the molten pool and confining the molten metal within the molten pool, making it less likely to fall due to gravity. Simultaneously, the controller synchronously fine-tunes the welding voltage to ensure stable arc combustion, and in conjunction with a stable wire feed speed, ensures the formation of the additive layer in the overhead welding position.

[0046] Increasing the pulse current frequency enhances the surface tension of the molten pool, physically suppressing the downward tendency of molten metal in the overhead welding position. This avoids defects such as weld beads and incomplete penetration commonly found in traditional overhead welding processes, ensuring the geometric accuracy and surface flatness of the additive layer in the overhead welding area. The stable arc and wire feeding further ensure the fusion quality in the overhead welding position, making the additive layer firmly bonded to the base material, improving the structural reliability of the overhead welding part, and breaking through the bottleneck of poor forming quality in the overhead welding position in traditional processes.

[0047] According to an embodiment of the present invention, when the predetermined area is in a vertical welding position, the method further includes: using a slanted weld bead strategy for overlay welding to prevent the molten pool from flowing.

[0048] In an embodiment of the invention, when the predetermined area of ​​the positioning arm is in the vertical welding position, the molten pool is prone to flow vertically due to gravity, resulting in uneven additive layer thickness. In this case, during additive manufacturing, a slanted weld bead strategy is used for surfacing. That is, the planned additive path extends upwards at an angle along the vertical welding area, the welding torch moves along this slanted path, and a high-frequency dynamic controller adjusts the welding parameters to control the size of the molten pool and the solidification rate. During the surfacing process, starting from the bottom of the vertical welding area, surfacing is performed layer by layer upwards along the slanted weld bead. Subsequent weld beads partially overlap with previous weld beads to ensure coverage of the entire vertical welding area.

[0049] The inclined welding strategy changes the force direction of the molten pool at the vertical welding position, reducing the influence of gravity on the flow of the molten pool. Combined with parameter control to regulate the solidification rate of the molten pool, it ensures that the molten pool maintains a stable shape during the forming process, avoiding defects such as flow and accumulation. Welding is carried out layer by layer from the bottom up with partial overlap of weld beads, ensuring that the additive layer in the vertical welding area is continuous, complete, and of uniform thickness, thus improving the forming quality of the vertical welding part. This strategy does not require additional auxiliary tooling, simplifies the vertical welding operation process, and improves the efficiency and reliability of additive manufacturing at the vertical welding position.

[0050] According to an embodiment of the present invention, the surface roughness Ra of the near-net-shape additive layer is no greater than 6.3 micrometers.

[0051] In embodiments of the present invention, the control of surface roughness of the near-net-shape additive layer is achieved through multi-stage collaborative processes. Before additive manufacturing, a precise equidistant additive path is planned based on a three-dimensional digital model to ensure uniform welding torch movement. During operation, a sensing system collects molten pool status information in real time, and a high-frequency dynamic controller adjusts the welding current, voltage, and wire feed speed with millisecond-level response speed to suppress defects such as molten pool sagging and flowing, ensuring uniform molten pool spreading. Targeted control strategies and weld bead strategies are adopted for different positions (such as overhead welding, vertical welding, and saddle points) to avoid local surface protrusions or depressions. Through the combined effect of the above stages, the final additive layer surface is smooth, and the roughness meets the preset requirements.

[0052] Meeting the surface roughness standard of the additive layer means that the surface quality of the additive layer directly meets the technical standards of the positioning arm, eliminating the need for subsequent manual grinding and finishing processes. This completely eliminates the time and labor costs associated with manual grinding, while also preventing damage to the microstructure of the positioning arm's base material or additive layer caused by localized high temperatures during grinding, thus ensuring the strength and toughness of the positioning arm. The smooth surface reduces stress concentration points, improving the fatigue resistance of the positioning arm during service and extending its service life. It also enhances the appearance quality and assembly compatibility of the positioning arm.

[0053] According to an embodiment of the present invention, the geometric accuracy error of the near-net-shape additive layer is no greater than 0.5 mm.

[0054] In embodiments of the present invention, the control of the geometric accuracy of the near-net-shape additive layer relies on precise motion control and parameter adjustment. The multi-axis robot and positioner of the arc additive manufacturing system move in tandem. The multi-axis robot, with its high degree of freedom, can precisely adjust the welding torch posture according to the planned path, while the positioner adjusts the workpiece position of the positioning arm in real time to ensure the welding torch is always in the optimal working posture. A high-frequency dynamic controller adjusts the welding process parameters in real time based on the molten pool state information to avoid additive layer thickness deviations caused by parameter fluctuations. The additive path is planned based on a three-dimensional digital model to ensure that the path coverage is consistent with the preset dimensions. Through the synergy of motion control, parameter adjustment, and path planning, the error between the actual dimensions and the design dimensions of the additive layer is controlled within a preset range.

[0055] The small geometric accuracy error of the additive layer ensures that the dimensions of the positioning arm meet the design requirements, improves the assembly fit between the positioning arm and other components, avoids assembly difficulties or gaps caused by dimensional deviations, and guarantees the overall assembly accuracy and operational stability of the bogie. The precise geometric dimensions reduce subsequent correction processes, shorten the manufacturing cycle of the positioning arm, and reduce manufacturing costs. At the same time, the uniform thickness of the additive layer ensures that the force is evenly distributed in all parts of the positioning arm, avoids stress concentration caused by local dimensional deviations, and improves the structural reliability and load-bearing capacity of the positioning arm.

[0056] According to an embodiment of the present invention, the arc additive manufacturing system includes a multi-axis robot and a positioner, and during the additive manufacturing process, the multi-axis robot and the positioner move in coordination to keep the welding torch in the optimal working position at all times.

[0057] In embodiments of the present invention, the multi-axis robot of the arc additive manufacturing system is equipped with a welding torch and has multiple degrees of freedom of motion, enabling multi-angle adjustment of the welding torch in space. The positioner is connected to the workpiece of the positioning arm and can drive the workpiece to rotate around different axes. During the additive manufacturing process, the system control unit synchronously sends motion commands to the multi-axis robot and the positioner based on the position information of the additive path and the predetermined area: the multi-axis robot adjusts the spatial position and angle of the welding torch, and the positioner adjusts the posture of the workpiece of the positioning arm. The two work together to ensure that when working in different areas of the positioning arm (such as saddle-shaped areas, corner areas, overhead welding positions, and vertical welding positions), the welding torch always maintains a suitable distance and angle from the working surface and is in the optimal working posture.

[0058] The coordinated motion of the multi-axis robot and the positioner solves the problems of insufficient motion freedom and limited welding torch posture adjustment in traditional arc welding equipment. It ensures that the welding torch can operate in the optimal posture in all areas of the complex structure of the positioning arm, improving the consistency of welding quality. The optimal working posture allows the arc energy to be applied to the molten pool more accurately, reducing energy loss, while ensuring that the welding wire can be accurately delivered to the molten pool, avoiding welding wire waste or insufficient supply, and improving additive manufacturing efficiency. The coordinated motion of the two also expands the system's operating range, eliminating the need for manual adjustment of the workpiece or welding torch position, realizing fully automated additive manufacturing of the positioning arm, and reducing the error risk caused by human intervention.

[0059] According to an embodiment of the present invention, the steps of coordinated control specifically include: inputting the molten pool state information into the molten depth prediction model, and determining the amount of control on the welding process parameters based on the output of the molten depth prediction model.

[0060] In embodiments of the present invention, a weld depth prediction model is introduced during the collaborative control process. This model is constructed based on a large amount of additive manufacturing experimental data and can predict the current weld depth according to the weld pool state information (such as the size of the weld pool reflected in the visual image, the temperature reflected in the spectral information, and the energy reflected in the electrical signal information). During operation, the sensing system inputs the collected weld pool state information into the weld depth prediction model in real time. The model calculates and outputs the predicted result of the current weld depth. The high-frequency dynamic controller receives the prediction result and compares it with the preset target weld depth. If the predicted weld depth is less than the target weld depth, it determines to increase the peak welding current and increase the welding voltage to improve heat input and increase weld depth. If the predicted weld depth is greater than the target weld depth, it determines to decrease the peak welding current and decrease the welding voltage to reduce heat input and decrease weld depth, thereby achieving precise control of welding process parameters.

[0061] The introduction of the melt depth prediction model transforms melt depth control from "experience-based judgment" to "data-driven" control, improving the accuracy of melt depth judgment and avoiding melt depth control deviations caused by insufficient human experience. Determining the control amount based on the prediction results makes the high-frequency dynamic controller's control more targeted, avoiding blind parameter adjustments and reducing defects such as insufficient fusion or overheating caused by improper parameters. Precise melt depth control ensures good fusion between the additive layer and the base material, as well as between each additive layer, improving the metallurgical quality and mechanical properties of the positioning arm. Simultaneously, it avoids overheating damage to the base material caused by excessive melt depth, ensuring the overall performance stability of the positioning arm.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a positioning arm, characterized in that, include: An electric arc additive manufacturing system is used to perform additive manufacturing on a predetermined area of ​​the positioning arm workpiece. During the additive manufacturing process, the molten pool status information of the predetermined area is collected in real time through a sensing system. Based on the collected molten pool state information, at least two of the welding process parameters, namely welding current, welding voltage and wire feed speed, are coordinated and controlled by a high-frequency dynamic controller with a millisecond-level response speed to actively manage the physical behavior of the molten pool, thereby forming a near-net-shape additive layer on the positioning arm workpiece. The active management of the physical behavior of the molten pool includes: suppressing the molten pool from falling or flowing due to gravity during all-position additive manufacturing, so that the near-net-shape additive layer does not require subsequent grinding and finishing processes.

2. The method for manufacturing a positioning arm according to claim 1, characterized in that, The molten pool state information includes at least one of the following: a visual image of the molten pool, spectral information of the electric arc, and electrical signal information of the electric arc.

3. The method for manufacturing a positioning arm according to claim 1, characterized in that, The coordinated control includes at least one of the following: adjusting the ratio of the peak value to the base value of the pulse current, instantaneously compensating the welding voltage, and controlling the micro-oscillation amplitude of the wire feeding speed.

4. The method for manufacturing a positioning arm according to claim 1, characterized in that, The predetermined area includes a saddle-shaped area or an angular area on the positioning arm.

5. The method for manufacturing a positioning arm according to claim 4, characterized in that, Prior to the additive manufacturing step, the method further includes: planning equidistant additive paths for the saddle-shaped region based on a three-dimensional digital model of the positioning arm workpiece.

6. The method for manufacturing a positioning arm according to claim 4, characterized in that, When additive manufacturing is performed at the saddle point or arc termination area of ​​the saddle-shaped region, the coordinated control is used to ensure complete fusion of the weld and a smooth transition at the arc termination.

7. The method for manufacturing a positioning arm according to claim 1, characterized in that, When the predetermined area is in the overhead welding position, the coordinated control step includes: increasing the frequency of the pulse current to enhance the surface tension of the molten pool, thereby suppressing the molten metal from falling.

8. The method for manufacturing a positioning arm according to claim 1, characterized in that, When the predetermined area is in a vertical welding position, the method further includes: using a slanted weld bead strategy for surfacing to prevent the molten pool from flowing.

9. The method for manufacturing a positioning arm according to any one of claims 1 to 8, characterized in that, The surface roughness Ra of the near-net-shape additive layer is no greater than 6.3 micrometers.

10. The method for manufacturing a positioning arm according to any one of claims 1 to 8, characterized in that, The geometric accuracy error of the near-net-shape additive layer is no greater than 0.5 mm.

11. The method for manufacturing a positioning arm according to any one of claims 1 to 8, characterized in that, The electric arc additive manufacturing system includes a multi-axis robot and a positioner. During the additive manufacturing process, the multi-axis robot and the positioner move in coordination to keep the welding torch in the optimal working position at all times.

12. The method for manufacturing a positioning arm according to any one of claims 1 to 8, characterized in that, The steps of the coordinated control specifically include: inputting the molten pool state information into the weld depth prediction model, and determining the control amount of the welding process parameters based on the output of the weld depth prediction model.

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