A laser hybrid manufacturing method for friction stir welding tool micro-texture

Abstract

The application relates to a laser composite manufacturing method for a friction stir welding tool micro-texture, comprising the following steps: S1, using CAD to design the structure and appearance of the micro-texture of a to-be-processed stirring head; S2, layer-by-layer slicing and layering the processed part and outputting a two-dimensional graph; S3, importing the two-dimensional graph into laser processing software, using laser to perform layer-by-layer ablation on the part, removing redundant materials, and only leaving a working area and a heat affected zone compared with a standard part; and S4, milling the processed part again to remove the oxidation area and the heat affected layer of the laser processing, and completing fine processing of the micro-texture. Compared with the prior art, the laser ablation technology and the traditional mechanical processing method are combined, the workpiece is ablated by laser first, part of the material is removed, then the oxidation area and the heat affected layer are removed through milling processing, so that the problem of poor quality of the part processed by the traditional mechanical processing is solved, the precision of the processed workpiece is high, and the processing efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of microtexturing of friction stir welding tools, and in particular to a laser composite manufacturing method for microtexturing friction stir welding tools. Background Technology

[0002] Friction stir welding tools are mostly made of extremely hard materials. By processing the tool surface with microtextures, friction can be increased during the friction stir welding process, and heat input can also be increased. Appropriate microtextures help promote material flow during welding and improve the quality of the weld.

[0003] Most friction stir welding tools are made of cemented carbide, which is a high-hardness, high-wear-resistant material made by powder metallurgy with refractory metal hard compounds (such as tungsten carbide, titanium carbide, etc.) as the matrix and metals (such as cobalt, nickel, etc.) as the binder.

[0004] Cemented carbide is also known as a cermet material because its structure contains both a hard ceramic phase and a tough metallic phase. The hardness of cemented carbide can reach 69–81 HRC at room temperature, and it maintains high hardness and excellent wear resistance even at high temperatures of 900–1000°C.

[0005] The performance characteristics of cemented carbide include high hardness, wear resistance, good strength and toughness, heat resistance, and corrosion resistance. These properties make cemented carbide widely used in cutting tools, impact tools, and wear- and corrosion-resistant parts, such as turning tools, milling cutters, planing tools, drill bits, and boring tools, for cutting materials such as cast iron, non-ferrous metals, plastics, synthetic fibers, graphite, glass, stone, and ordinary steel. It is widely used in aerospace, military, machinery manufacturing, electronics, and automotive manufacturing, and is a mainstay material in modern industry, production, and technology.

[0006] The difficulty in machining cemented carbide stems primarily from its unique series of physical and mechanical properties. While these properties endow cemented carbide with excellent application performance, they also present challenges in machining. Specialized machining techniques and tools are typically required for effective machining of cemented carbide.

[0007] Laser processing, as an advanced manufacturing technology, has many significant advantages, such as non-contact processing and high precision. This has led to its widespread application in various industrial fields. Laser processing can achieve extremely fine machining with high precision and small tolerances. This is particularly important for parts requiring high precision and is suitable for micro-texturing of stirring heads.

[0008] Laser processing is a technology that uses the high energy of lasers to remove material from its surface. In this process, a laser beam is focused on the material surface, generating high temperatures that cause the material to evaporate or vaporize, thus achieving precise material removal. Laser ablation technology has many advantages, including high precision, high efficiency, strong controllability, and non-contact processing, and is therefore widely used in the field of micro- and nano-fabrication.

[0009] Laser ablation is a complex process involving multiple phase transitions and varying durations, influenced by factors such as laser pulse width, pulse energy distribution, repetition frequency, and material properties. By precisely monitoring the transient evolution of the thermodynamic properties of the material surface, the accuracy of laser ablation can be better controlled.

[0010] During laser processing, a laser beam is focused on the surface of the material, generating high temperatures that cause the material to melt, evaporate, or undergo phase changes locally. In this process, not only does the area directly irradiated by the laser undergo physical and chemical changes, but the surrounding area also forms a heat-affected zone due to heat conduction and radiation.

[0011] In laser processing, controlling and reducing the heat-affected zone (HAZ) is crucial for improving processing quality. For example, in laser cutting, the size of the HAZ can be reduced by optimizing cutting parameters (such as laser power, cutting speed, and assist gas), resulting in smoother cut edges and less thermal deformation. The HAZ can be minimized by changing the laser's processing parameters.

[0012] The grain structure of materials in the heat-affected zone (HAZ) may change due to rapid heating and cooling, such as abnormal grain growth or the formation of non-equilibrium phases. The mechanical properties of the HAZ material, such as hardness, strength, and toughness, may differ from the original material, and sometimes deformation hardening may occur. Due to rapid heating and cooling, uneven thermal expansion and contraction occur within the material, leading to the generation of residual stress.

[0013] Machining cemented carbide involves stringent requirements for equipment and processes due to its high hardness, brittleness, and thermal sensitivity. The high hardness of cemented carbide also leads to rapid wear of traditional cutting tools. Especially during high-speed cutting, the wear on the tool's flank increases, and cracks and chipping may occur on the cutting edge, thus shortening the tool's lifespan.

[0014] Due to the brittleness of cemented carbide, cracks and fractures are easily generated during machining, affecting machining accuracy and surface quality. To address these issues, existing technology discloses a laser-assisted machining apparatus and method. This laser-assisted surface machining machine tool includes: a bed, a five-axis linkage surface machining system, a spatial laser area scanning system, and a corresponding control system. This laser-assisted cutting machining utilizes a high-energy laser beam to heat the workpiece material, generating localized high temperatures that thermally soften the material in the machining area, reducing its hardness and increasing its plasticity, thereby improving the material's machinability. However, the design of this laser-assisted machining apparatus does not consider the heating depth during the laser beam heating process. Insufficient heating depth may lead to excessive wear on the machining tool. Conversely, if the heating depth exceeds the thickness to be cut, a heat-affected zone may form on the workpiece, resulting in a decrease in the workpiece's mechanical properties. Summary of the Invention

[0015] The purpose of this invention is to overcome the shortcomings of existing technologies, such as the difficulty in machining microtextures in friction stir welding tools, and to provide a laser composite manufacturing method for microtextures in friction stir welding tools. This method combines laser ablation technology with traditional machining methods. First, the workpiece is ablated with a laser to remove part of the material. Then, the oxidized area and heat-affected layer are removed by milling. This solves the problem of poor quality of parts produced by traditional machining, resulting in high precision and high processing efficiency.

[0016] The objective of this invention can be achieved through the following technical solutions: This invention proposes a novel process that combines advanced laser fabrication technology with conventional machining to improve the forming quality of parts and achieve high-efficiency manufacturing. Traditional cutting methods achieve high-precision machining of hard and brittle materials through precision cutting, but due to their hardness, brittleness, and poor fracture toughness, precision cutting is difficult to achieve. Therefore, a new composite machining mode is proposed, which can effectively solve the cutting problems of cemented carbide and other hard and brittle materials, thereby improving their machining quality and promoting the development and progress of cemented carbide parts. Laser ablation is used to remove some material from the microtexture of the friction stir welding tool, followed by milling to finish the laser-processed part, removing the laser-processed working area and heat-affected zone.

[0017] This invention provides a laser composite manufacturing method for microtextures of friction stir welding tools, comprising the following steps: S1: Design the workpiece using CAD: Design the structure and morphology of the microtexture of the stirring head of the friction stir welding tool using CAD; S2: Slice the workpiece layer by layer and output a two-dimensional image; S3: Import the 2D drawing into the laser processing software, use the laser to ablate the part layer by layer to remove excess material, and compared with the standard part, only the working area and heat-affected zone are left. S4: The workpiece is then milled to remove the oxidized area and heat-affected layer from the laser processing, thus completing the finishing of the microtexture.

[0018] Furthermore, in S2, the depth of laser processing on cemented carbide at different powers is measured, and the microtextured part of the stirring head is sliced ​​and layered according to the laser processing depth each time. The layered model is then converted into a two-dimensional image according to the size of each layer.

[0019] Furthermore, in S1, using CAD software, a conventional friction stir welding tool is first drawn, and then a microtexture that can enhance friction and material flowability is designed based on the conventional friction stir welding tool (2).

[0020] Furthermore, the microtexture in S1 is a swirling streamlined structure, which can increase the fluidity of the material during rotation.

[0021] Furthermore, in S2, because the laser processing depth remains constant within a given pattern area and corresponding focal length, and since the microtexture of this friction stir welding tool has curved surfaces, to improve the accuracy of laser processing, it is necessary to process patterns of different sizes. Therefore, the microtexture portion needs to be sliced ​​to obtain layers of different sizes. The thickness of the slice depends on the laser processing depth; the smaller the processing depth, the more slice layers are needed, resulting in higher processing quality.

[0022] Furthermore, in S3, the drawn two-dimensional diagram is imported into the laser processing software, and the path and size of the lines filling the pattern are set so that the processing depth of each area is the same during the ablation process. The laser (3) is used to perform subtractive processing on the cemented carbide.

[0023] Due to the laser ablation effect, a trace oxide layer and heat-affected zone exist on the surface of the processed material. These can be machined using tiny cutting tools. Because only the oxide layer and heat-affected zone need to be removed, tool wear is reduced, and processing efficiency is increased. Machining not only removes the oxide layer and heat-affected zone from the workpiece surface but also improves the smoothness of the processed texture, resulting in an enhanced surface quality.

[0024] Furthermore, in S3, laser processing is a processing method that uses lasers to remove the material required to remove the microtexture of the stirring head; during laser processing, the workpiece material absorbs the high-energy laser, causing the material to evaporate, ablate, or vaporize, thereby achieving material subtraction processing.

[0025] Furthermore, in S3, laser processing offers high precision and efficiency. Laser energy is concentrated on the surface of the material being processed through air, enabling non-contact processing. The heat from the laser causes the material to evaporate, ablate, or vaporize. Theoretically, regardless of the hardness of the material, as long as the laser temperature reaches the point of evaporation and vaporization, laser processing can be used.

[0026] Furthermore, since laser processing utilizes the thermal effect of lasers, it creates a working area and a heat-affected zone on the surface of the microtexture. The mechanical properties of this area are lower than the base material; therefore, milling is required to remove these areas. In step S4, milling is used to remove the working area and heat-affected zone. The working area is 100 μm thick, and the heat-affected zone is 20 μm thick. A milling cutter is used to remove material from both areas. To improve the machining accuracy and surface quality of the workpiece, milling is used as a post-processing step on the tool surface after laser processing. Milling not only removes the oxide layer generated by laser ablation but also reduces and reshapes the material in the heat-affected zone, thereby minimizing the adverse effects of laser processing on the material.

[0027] Furthermore, in S4, it is assumed that the total thickness of the working area and the heat-affected zone is... During milling, the affected area is removed in two passes; the first pass is roughing to remove... The second cut is for finishing, removing... This achieves the purpose of precision machining of the mixing head. The amount removed during rough machining plus the amount removed during fine machining equals the total thickness.

[0028] Laser processing offers advantages in terms of high precision and high quality, achieving micron- or sub-micron-level accuracy. It also boasts flexibility and adaptability, capable of processing diverse materials and shapes. Furthermore, laser processing systems are easily integrated with automated equipment and computer control systems, enabling automated and intelligent production.

[0029] Laser processing does not require contact with the material being processed, thus avoiding mechanical stress and making it particularly suitable for machining high-hardness materials like cemented carbide. Using lasers to process cemented carbide reduces tool wear. Tungsten-cobalt cemented carbide, a typical difficult-to-machine material, possesses excellent overall properties. Traditional machining methods for this type of material suffer from drawbacks such as rapid tool wear, low machining accuracy, and low efficiency, failing to meet actual production requirements. Lasers pre-remove most of the material, reducing tool usage. Furthermore, the laser's working area and heat-affected zone have lower hardness compared to the base material, further reducing tool wear and extending tool life during machining.

[0030] Laser processing, with its high energy density and short thermal interaction time, results in a relatively small heat-affected zone (HAZ). This reduces thermal damage to cemented carbide materials, preventing performance degradation caused by heat. The small HAZ also minimizes the risk of deformation and cracking due to thermal stress, which is particularly important for heat-sensitive materials like cemented carbide. The small HAZ helps maintain the microstructure and mechanical properties of cemented carbide, thereby improving the quality of the processed workpiece.

[0031] Compared with the prior art, the present invention has the following advantages: (1) This invention uses laser to process hard alloy materials. The high-energy laser beam acts on the material, causing it to vaporize or sublimate, thus removing the material and effectively solving the problem of traditional processing methods being difficult to process hard and brittle materials. Simultaneously, the laser spot size can be very small, reaching the micrometer or even submicrometer level. The laser processing diameter is much smaller than that of traditional machining, thus ensuring high precision. This allows for fine-tuning operations, enabling parts to maintain excellent accuracy during processing.

[0032] (2) This invention uses lasers to process hard, brittle, and heat-sensitive materials, so controlling the heat-affected zone (HAZ) during processing is particularly important. This design reduces heat diffusion by changing the laser processing parameters, thereby reducing the HAZ. This reduces thermal deformation and thermal damage, preserving the original characteristics of the processed area. Experimental data shows that the faster the processing speed, the greater the heat input per unit time, and the larger the size of the HAZ.

[0033] (3) This invention combines laser processing with traditional machining. The laser can be controlled by software, making it easy to adjust the laser processing parameters and adapt to the processing of various complex shapes and sizes of cemented carbide workpieces. At the same time, laser processing can achieve more precise material removal. When used in combination with traditional machining, it can reduce material waste and improve material utilization. Furthermore, for some complex shapes or materials that are difficult to process using traditional machining, laser processing can be used as a supplement, and vice versa. The combination of the two can expand the processing range.

[0034] (4) The present invention has a wide range of applications. Lasers can process a variety of materials, including difficult-to-process materials such as metals, plastics, ceramics, glass and composite materials, and have a wide range of applications. Attached Figure Description

[0035] Figure 1 This is a flowchart of the microtexturing method of the present invention; Figure 2 The present invention relates to a conventional stirring head and a processed stirring head with microtexturation; Figure 3 This is a schematic diagram of a slice of the microtexture according to the present invention; Figure 4 This is a schematic diagram of the laser processing process of the present invention; Figure 5 This is a schematic diagram showing the laser processing completed according to the present invention; Figure 6 This is a schematic diagram of different areas after laser processing according to the present invention; Figure 7 This is a schematic diagram illustrating the removal of the laser processing working area and heat-affected zone using a milling teaching method according to the present invention; Figure reference numerals: 1. Stirring head tip, 2. Microtexture, 3. Laser, 4. Laser-processed area, 5. Working area, 6. Heat-affected zone, 7. Base material, 8. Milling cutter. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0037] Example 1 This embodiment provides a laser composite manufacturing method for microtexturing of friction stir welding tools, such as... Figure 1 As shown, it includes the following steps: S1: Design the workpiece using CAD: Design the structure and morphology of the microtexture 2 of the stirring head of the friction stir welding tool using CAD; S2: Slice the workpiece layer by layer and output a two-dimensional image; S3: Import the 2D drawing into the laser processing software, use laser 3 to ablate the part layer by layer to remove excess material, and compared with the standard part, only the working area 5 and the heat-affected zone 6 are left. S4: The workpiece is then milled to remove the oxidized area and heat-affected layer from the laser 3 process, thus completing the finishing of the microtexture 2.

[0038] like Figure 3 As shown, in a specific embodiment, in S2, the depth of the cemented carbide processed by the laser 3 at different powers is measured, and the microtexture 2 part of the stirring head is sliced ​​and layered according to the processing depth of the laser 3 each time. The layered model is then converted into a two-dimensional image according to the size of each layer.

[0039] In a specific implementation, in S1, using CAD software, a conventional friction stir welding tool is first drawn, and then, based on the conventional friction stir welding tool, a microtexture 2 that can enhance friction and material flowability is designed.

[0040] In specific implementations, such as Figure 2 As shown in the diagram on the right, the microtexture 2 in S1 is a swirling streamlined structure, which increases the fluidity of the material during rotation. Ordinary stirring tools, such as... Figure 2 As shown in the left-hand diagram, the tip of the stirring head (needle 1) is conical. In a specific implementation, in step S2, because the processing depth of laser 3 remains constant within a certain pattern area and corresponding focal length, and because the microtexture of this friction stir welding tool has curved surfaces, to improve the processing accuracy of laser 3, it is necessary to process patterns of different sizes using laser 3. Therefore, the microtexture 2 portion needs to be sliced ​​to obtain layers of different sizes. The thickness of the slices depends on the processing depth of laser 3; the smaller the processing depth, the more slices are needed, and the higher the processing quality.

[0041] like Figure 4 , Figure 5 As shown, this is the stirring head after laser processing. In a specific embodiment, in S3, the drawn two-dimensional image is imported into the laser processing software, and the path and size of the lines filling the pattern are set so that the processing depth of each area is the same during the ablation process. The hard alloy is processed by laser 3 to obtain the laser-processed area 4.

[0042] Due to the ablation effect of laser 3D, a trace oxide layer and heat-affected zone exist on the surface of the processed material. This allows for machining with tiny cutting tools. Since only the oxide layer and heat-affected zone need to be removed, tool wear is reduced, and processing efficiency is increased. Machining not only removes the oxide layer and heat-affected zone from the workpiece surface but also improves the smoothness of the processed texture, resulting in an enhanced surface quality.

[0043] In a specific implementation, S3, laser processing is a processing method that uses laser 3 to remove the material required to be removed from the microtexture 2 of the stirring head; during laser processing, the workpiece material absorbs the high-energy laser 3, causing the material to evaporate, ablate or vaporize, thereby achieving material reduction processing.

[0044] In a specific implementation, in step S3, laser processing achieves high precision and efficiency. Laser energy is concentrated on the surface of the material being processed via air, enabling non-contact processing. The heat from the laser causes the material to evaporate, ablate, or vaporize. Theoretically, regardless of the hardness of the material, as long as the laser temperature reaches the temperature required for material evaporation and vaporization, laser processing can be employed.

[0045] like Figure 6 As shown, in a specific embodiment, since laser processing utilizes the thermal effect of laser 3, a working area 5 and a heat-affected zone 6 are generated on the surface of the microtexture 2. Compared to the base material 7, the mechanical properties of this part of the material are reduced; therefore, milling is required to remove the working area 5 and the heat-affected zone 6. In S4, milling is used to remove the working area 5 and the heat-affected zone 6; the thickness of the working area is 100 μm, and the thickness of the heat-affected zone is 20 μm. A milling cutter 8 is used to remove the material from the working area 5 and the heat-affected zone 6, such as... Figure 7 As shown. To improve the machining accuracy and surface quality of the workpiece, milling is used as a post-processing step on the tool surface after laser 3 machining. Milling not only removes the oxide layer generated by laser 3 ablation, but also reduces and reshapes the material in the heat-affected zone, thereby reducing the adverse effects of laser 3 machining on the material.

[0046] In a specific implementation, in S4, it is assumed that the total thickness of the working area 5 and the heat-affected zone 6 is [missing information]. During milling, the affected area is removed in two passes; the first pass is roughing to remove... The second cut is for finishing, removing... This achieves the purpose of precision machining of the mixing head. The amount removed during rough machining plus the amount removed during fine machining equals the total thickness.

[0047] Laser 3D processing offers advantages in high precision and quality, achieving micron- or sub-micron-level accuracy. It also boasts flexibility and adaptability, capable of processing diverse materials and shapes. Furthermore, laser 3D processing systems are easily integrated with automated equipment and computer control systems, enabling automated and intelligent production.

[0048] Laser machining (laser 3) does not require contact with the workpiece, thus avoiding mechanical stress and making it particularly suitable for machining high-hardness materials like cemented carbide. Using laser 3 to machine cemented carbide reduces tool wear. Tungsten-cobalt cemented carbide, a typical difficult-to-machine material, possesses excellent overall performance. Traditional machining methods for this type of material suffer from severe tool wear, low machining accuracy, and low efficiency, failing to meet actual production requirements. Laser 3 pre-removes most of the material, reducing tool usage. Furthermore, the hardness of the laser's working area and heat-affected zone is lower than that of the base material (7), further reducing tool wear and extending tool life during machining.

[0049] Laser processing, with its high energy density and short thermal interaction time, results in a relatively small heat-affected zone (HAZ). This reduces thermal damage to cemented carbide materials, preventing performance degradation caused by heat. The small HAZ also minimizes the risk of deformation and cracking due to thermal stress, which is particularly important for heat-sensitive materials like cemented carbide. The small HAZ helps maintain the microstructure and mechanical properties of the cemented carbide, thereby improving the quality of the processed workpiece.

[0050] The material used for machining friction stir welding tools is cemented carbide. It is necessary to machine features such as... Figure 2 The image on the right shows a microtextured pattern. Using a friction stir welding tool with a microtextured pattern to weld aluminum alloys can increase heat input during the welding process and also increase the fluidity of the aluminum alloy material, resulting in higher strength at the weld joint.

[0051] Mount the microtextured friction stir welding tool onto a dedicated machine tool, and clamp the aluminum alloy sheet to be welded. Set the welding tool to a speed of 1000 rpm, move it directly above the weld seam on the aluminum alloy sheet, and begin its descent. When the tool is 1 mm above the weld seam, begin descending at a speed of 0.1 mm / min. Hold the position at the designated location for 15 seconds, then move it along the weld seam at a speed of 500 mm / min until welding is complete. Finally, move the welding tool upwards and stop rotating. Welding is now complete.

[0052] Components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0053] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A laser composite manufacturing method for microtextures of friction stir welding tools, characterized in that, Includes the following steps: S1: Design the workpiece using CAD: Design the structure and morphology of the microtexture (2) of the stirring head of the friction stir welding tool using CAD; S2: Slice the workpiece layer by layer and output a two-dimensional image; measure the depth of the hard alloy processing by the laser (3) at different power, slice the microtexture (2) part of the stirring head according to the processing depth of the laser (3) each time, and convert the layered model into a two-dimensional image according to the size of each layer; the thickness of the slice depends on the processing depth of the laser (3). The smaller the processing depth, the more slices there are and the higher the processing quality. S3: Import the two-dimensional drawing into the laser processing software, use the laser (3) to ablate the part layer by layer to remove excess material, and compared with the standard part, only the working area (5) and the heat-affected zone (6) are left. S4: The workpiece is then milled to remove the oxidized area and heat-affected layer of the laser (3) and complete the finishing of the microtexture (2); the working area (5) and heat-affected zone (6) are removed by milling; the thickness of the working area is 100μm and the thickness of the heat-affected zone is 20μm. The material of the working area (5) and heat-affected zone (6) is removed by milling cutter (8).

2. The laser composite manufacturing method for microtexture of friction stir welding tools according to claim 1, characterized in that, In S1, using CAD software, a conventional friction stir welding tool is first drawn, and then a microtexture that can enhance friction and material flowability is designed based on the conventional friction stir welding tool (2).

3. The laser composite manufacturing method for microtexture of friction stir welding tools according to claim 1, characterized in that, The microtexture (2) in S1 is a swirling streamline structure, which can increase the fluidity of the material during rotation.

4. The laser composite manufacturing method for microtexture of friction stir welding tools according to claim 1, characterized in that, In S3, the drawn two-dimensional diagram is imported into the laser processing software, and the path and size of the lines filling the pattern are set so that the processing depth of each area is the same during the ablation process. The laser (3) is used to perform subtractive processing on the cemented carbide.

5. The laser composite manufacturing method for microtexture of friction stir welding tools according to claim 1, characterized in that, In S3, laser (3) processing is a processing method that uses laser (3) to remove the material required to remove the microtexture (2) of the stirring head; during the laser (3) processing, the workpiece material absorbs the high-energy laser (3) of the laser (3), causing the material to evaporate, ablate or vaporize, thereby realizing the material subtraction processing.

6. The laser composite manufacturing method for microtexture of friction stir welding tools according to claim 1, characterized in that, In S3, the laser (3) energy is concentrated on the surface of the material being processed through the air, which is a non-contact processing method. The heat from the laser (3) causes the material being processed to evaporate, ablate, or vaporize.

7. The laser composite manufacturing method for microtexture of friction stir welding tools according to claim 1, characterized in that, In S4, the total thickness of the working area (5) and the heat-affected zone (6) is: During milling, the working area (5) and the heat-affected zone (6) are removed in two passes; the first pass is roughing to remove... The second cut is for finishing, removing... This achieves the purpose of precision machining of the mixing head. The amount removed during rough machining plus the amount removed during fine machining equals the total thickness.

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