Method for manufacturing a spherical cap part using single point incremental forming

Abstract

The application discloses a method for manufacturing a spherical crown part by using a single-point incremental forming technology, and comprises the following steps: step 1, determining basic forming parameters according to material performance and a target shape; step 2, performing first-pass forming according to a first-pass path, the forming depth is less than the target depth, and an axial compensation amount is reserved; step 3, performing second-pass forming according to a second-pass path on the basis of step 2, so that the radial direction approaches the final profile, and the depth direction reaches the target depth; and step 4, performing third-pass forming according to a third-pass path from the bottom of the spherical crown part to the edge direction of the top on the basis of step 3, so that the spherical crown part is obtained. The application solves the problems of breakage and low precision of existing alloys in the process of single-point incremental forming of a deep-cavity spherical crown part.

Description

Technical Field

[0001] This invention belongs to the field of material forming and preparation technology, specifically relating to a method for manufacturing spherical crown parts using single-point incremental forming technology. Background Technology

[0002] Aluminum alloys are widely used in aerospace, automotive, rail transportation, and equipment manufacturing due to their advantages such as low density, high strength, good corrosion resistance, and ease of lightweight design. High-strength aluminum alloys, in particular, combine high strength reserves with excellent service performance, effectively reducing component weight while ensuring structural load-bearing capacity. Therefore, they are of significant application value in aircraft skins, thin-walled enclosures, and other complex lightweight thin-walled components. High-strength aluminum alloys, represented by AA7075-T6, have become important materials for aerospace thin-walled components due to their high hardness, high specific strength, and excellent fatigue resistance.

[0003] However, high-strength aluminum alloys also face significant challenges in forming. Due to their poor room-temperature plasticity and significant work hardening, traditional sheet metal forming processes often result in problems such as high deformation resistance, severe local thinning, significant stress concentration, and high cracking sensitivity. This is especially true in the manufacture of complex curved surfaces and large-angle components, where it is often difficult to simultaneously achieve forming limits, wall thickness uniformity, and geometric accuracy. Single-point incremental forming technology, with its moldless, highly flexible, adaptable to complex curved surfaces, and suitable for small-batch customized manufacturing characteristics, can significantly shorten product development cycles and reduce mold investment costs.

[0004] For difficult-to-form materials such as high-strength aluminum alloys, traditional single-pass, single-point incremental forming still suffers from problems in practical applications, including low forming limits, severe local thinning, susceptibility to cracking, difficulty in controlling springback, and unstable forming quality. These issues severely limit its further application in the flexible manufacturing of complex thin-walled components. Among existing improvement methods, domestic and international scholars have adopted multi-pass forming to enhance the formability of parts, and some have used auxiliary processes to improve forming quality, but these methods mostly rely on increasing the number of passes. Summary of the Invention

[0005] The purpose of this invention is to provide a method for manufacturing spherical crown parts using single-point incremental forming technology, which solves the problems of cracking and low precision in the process of single-point incremental forming of deep cavity spherical crown parts using existing alloys.

[0006] The technical solution adopted in this invention is a method for manufacturing a spherical crown part using single-point incremental forming technology, comprising the following steps: Step 1: Determine the basic forming parameters based on material properties and target shape; Step 2: Perform the first forming according to the first forming path, with the forming depth less than the target depth and allowance for axial compensation. Step 3: Based on Step 2, perform a second shaping pass according to the second pass path to make the radial direction approach the final contour, while the depth direction reaches the target depth; Step 4: Based on Step 3, perform a third forming process from the bottom of the spherical crown part to the top edge according to the third forming path to obtain the spherical crown part.

[0007] The invention is further characterized by: Ultrasonic vibration is applied to assist forming during the forming process in steps 1, 3 and 4; the ultrasonic vibration is applied to the forming tool, causing the forming tool to generate high-frequency reciprocating vibration in the axial direction.

[0008] The basic forming parameters in step 1 include the tool head diameter, feed rate, tool head rotation speed, and ultrasonic vibration parameters; the tool head is a ball head tool head with a diameter of 8–12 mm, a feed rate of 400–600 mm / min, a tool head rotation speed of 1000–1400 r / min, and ultrasonic vibration parameters of amplitude 0.02–0.06 mm and frequency 20–40 kHz.

[0009] Both the first and second passes are tangent curve paths with concave and convex arcs. A tangent curve path with concave and convex arcs is a continuous curve path formed by connecting concave and convex arcs tangent to each other.

[0010] During the first pass of forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the initial entry angle during the first pass is less than the forming limit angle of the material to be formed. The initial entry angle during the first pass is 45° to 55°. The entry angle is the angle between the tool head feed direction and the normal direction of the sheet metal plane, and the forming limit angle is the maximum entry angle at which the material will not break during a single pass of incremental forming.

[0011] During the second pass forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the entry angle of the second pass is greater than the average of the entry angles of the first and third passes; the entry angle of the second pass is 65° to 75°.

[0012] The third pass path is an arc path that matches the final shape of the spherical crown part, and the cutting angle of the third pass is the final forming angle of the spherical crown part. During the third pass forming, the tool head cuts down from the bottom center of the spherical crown part and moves layer by layer towards the top edge to complete the final contour trimming.

[0013] The axial compensation in step 2 is 1-3 mm, which is used to counteract the bottom accumulation caused by the downward flow of material during the forming process. After the first forming pass, a pit contour is formed. The second forming pass is to radially expand the pit contour based on the first forming pass, so that the sidewall angle increases and approaches the target contour. The third forming pass is to trim the surface contour based on the second forming pass, so that the surface of the final part is consistent with the target spherical crown surface.

[0014] The beneficial effects of this invention are: The present invention provides a method for manufacturing spherical crown parts using single-point incremental forming technology. By combining ultrasonic vibration with path planning, the number of forming passes for this type of material is reduced, improving forming efficiency. The tangential path trajectory of the concave and convex arc segments allows for flexible adjustment of axial and radial deformation, achieving a reasonable distribution of deformation across the three passes. Axial compensation is set in the first pass to prevent excessive material accumulation and the formation of a slab during the second pass, thus improving forming accuracy. The first and second passes use a path trajectory from the top edge to the bottom center, while the third pass uses a path trajectory from the bottom center to the top edge. This change in forming direction effectively controls the material flow direction, improving wall thickness uniformity and forming accuracy, and preventing cracking due to excessive thinning. Applying ultrasonic vibration with appropriate parameters effectively reduces forming force, promotes material flow, and lowers residual stress, thereby improving forming accuracy. Attached Figure Description

[0015] Figure 1 The forming principle diagram in Embodiment 8 of the present invention; Figure 2 The target part shape and size diagram in Embodiment 8 of the present invention; Figure 3 The three-path trajectory diagram in Embodiment 8 of the present invention.

[0016] In the diagram, 1. Upper pressure plate, 2. Lower pressure plate, 3. Ultrasonic generator, 4. Forming tool, 5. Sheet material, 6. First pass, 7. Second pass, 8. Third pass. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0018] The present invention provides a method for manufacturing a spherical crown using single-point incremental forming technology, comprising the following steps: Step 1: Determine the basic forming parameters based on material properties and target shape; by reasonably matching the basic forming parameters, control the mechanical conditions of the forming process from the source, and provide a stable process window for subsequent multi-pass deformation.

[0019] The basic forming parameters in step 1 include the tool head diameter, feed rate, tool head rotation speed, and ultrasonic vibration parameters. The tool head is a ball-end tool head with a diameter of 8–12 mm, a feed rate of 400–600 mm / min, a tool head rotation speed of 1000–1400 r / min, and ultrasonic vibration parameters of amplitude 0.02–0.06 mm and frequency 20–40 kHz. Among these, the ball-end tool head diameter affects the local contact stress and deformation zone range, the feed rate and tool head rotation speed together determine the number of loading cycles and friction state per unit area, and the ultrasonic vibration parameters reduce forming force and improve material flowability through high-frequency fretting effect.

[0020] Step 2: Perform the first forming according to the first forming path. The forming depth is less than the target depth, and axial compensation is reserved. The first forming bears most of the macroscopic deformation. By reserving the compensation amount, material reserves are provided for subsequent forming, avoiding local breakage caused by one-time forming.

[0021] During the first pass of forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the initial entry angle during the first pass is less than the forming limit angle of the material to be formed. The initial entry angle during the first pass is 45° to 55°. The entry angle is the angle between the tool head feed direction and the normal direction of the sheet metal plane. The forming limit angle is the maximum entry angle at which the material will not crack in a single pass of incremental forming. This top-down movement direction is conducive to the material flowing layer by layer from the edge to the center. By controlling the entry angle below the forming limit angle, it can be ensured that the deformation of the first pass is completed within the allowable safety margin of the material, and cracking is avoided in the initial pass.

[0022] The axial compensation amount in step 2 is 1 to 3 mm, which is used to offset the bottom accumulation caused by the downward flow of material during the forming process. After the first forming pass, a pit contour is formed. The second forming pass is based on the pit contour of the first passing pass and radially expands it to increase the sidewall angle and approach the target contour. The third forming pass is based on the second forming pass and the surface contour is trimmed so that the surface of the final part is consistent with the target spherical crown surface. This compensation amount offsets the bottom thickening caused by the downward flow of material in the first passing pass by reserving axial allowance, and prevents the bottom forming accuracy from being reduced due to the accumulation of material forming a platform in subsequent passes.

[0023] Step 3: Based on Step 2, perform the second forming according to the second pass path to make the radial direction approach the final contour, while the depth direction reaches the target depth; the second pass is a transitional deformation pass, which focuses on radial expansion based on the first pass pit contour, further increasing the side wall angle, so that the shape of the part gradually approaches the target spherical crown contour, while completing the final dimension in the depth direction, providing an intermediate state close to the final shape for the third finishing pass.

[0024] Both the first and second pass paths are tangent concave and convex arc curve paths, which are continuous curve paths formed by the tangent connection of concave and convex arcs. This path form achieves flexible distribution of axial and radial deformation through the alternating connection of concave and convex arcs, avoiding local stress concentration caused by straight or single curvature paths, and making the deformation transition of each pass more uniform and smooth.

[0025] During the second pass forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the entry angle of the second pass is greater than the average of the entry angles of the first and third passes; the entry angle of the second pass is 65° to 75°; the entry angle of the second pass is set to the relatively high position of the three, which is used to significantly improve the sidewall angle in the middle pass, and at the same time, the entry angle greater than the average value compensates for the work hardening effect of the material after the first pass forming, ensuring the effectiveness of radial expansion.

[0026] Step 4: Based on Step 3, perform the third forming from the bottom to the top edge of the spherical crown part according to the third forming path to obtain the spherical crown part; the third forming is the final finishing forming, and adopts the forming direction opposite to the second forming. The reverse movement guides the material to flow in the opposite direction, corrects the uneven wall thickness caused by the deformation of the first two forming, and completes the final geometric accuracy adjustment.

[0027] Ultrasonic vibration is applied to assist forming in steps 1, 3 and 4. The ultrasonic vibration is applied to the forming tool, causing the forming tool to generate high-frequency reciprocating vibration in the axial direction. The ultrasonic vibration generates local micro-disturbance in the contact area, which effectively reduces the frictional resistance between the forming tool and the sheet, promotes the movement of dislocations inside the material grains, and reduces the residual stress level, thereby improving the wall thickness uniformity and geometric accuracy while reducing the number of passes.

[0028] The third pass is an arc path that matches the final shape of the spherical crown part, and the entry angle of the third pass is the final forming angle of the spherical crown part. During the third forming pass, the tool head cuts down from the center of the bottom of the spherical crown part and moves layer by layer towards the top edge to complete the final contour trimming. This arc path is completely consistent with the final target shape, and is refined layer by layer from top to bottom in conjunction with the final forming angle to ensure that the surface contour of the part matches the design surface perfectly.

[0029] Example 1 The method for manufacturing a spherical crown using single-point incremental forming technology proposed in this embodiment includes the following steps: Step 1: Determine the basic forming parameters based on material properties and target shape; Step 2: Perform the first forming according to the first forming path, with the forming depth less than the target depth and allowance for axial compensation. Step 3: Based on Step 2, perform a second shaping pass according to the second pass path to make the radial direction approach the final contour, while the depth direction reaches the target depth; Step 4: Based on Step 3, perform a third forming process from the bottom of the spherical crown part to the top edge according to the third forming path to obtain the spherical crown part.

[0030] Example 2 The method for manufacturing a spherical crown using single-point incremental forming technology proposed in this embodiment includes the following steps: Step 1: Determine the basic forming parameters based on material properties and target shape; Step 2: Perform the first forming according to the first forming path, with the forming depth less than the target depth and allowance for axial compensation. Step 3: Based on Step 2, perform a second shaping pass according to the second pass path to make the radial direction approach the final contour, while the depth direction reaches the target depth; Step 4: Based on Step 3, perform a third forming process from the bottom of the spherical crown part to the top edge according to the third forming path to obtain the spherical crown part; Ultrasonic vibration is applied to assist forming during the forming process in steps 1, 3 and 4; the ultrasonic vibration is applied to the forming tool, causing the forming tool to generate high-frequency reciprocating vibration in the axial direction.

[0031] Example 3 The method for manufacturing a spherical crown using single-point incremental forming technology proposed in this embodiment includes the following steps: Step 1: Determine the basic forming parameters based on material properties and target shape; The basic forming parameters in step 1 include the tool head diameter, feed rate, tool head rotation speed, and ultrasonic vibration parameters; the tool head is a ball head tool head with a diameter of 8–12 mm, a feed rate of 400–600 mm / min, a tool head rotation speed of 1000–1400 r / min, and ultrasonic vibration parameters of amplitude 0.02–0.06 mm and frequency 20–40 kHz; Step 2: Perform the first forming according to the first forming path, with the forming depth less than the target depth and allowance for axial compensation. Step 3: Based on Step 2, perform a second shaping pass according to the second pass path to make the radial direction approach the final contour, while the depth direction reaches the target depth; Step 4: Based on Step 3, perform a third forming process from the bottom of the spherical crown part to the top edge according to the third forming path to obtain the spherical crown part; Ultrasonic vibration is applied to assist forming during the forming process in steps 1, 3 and 4; the ultrasonic vibration is applied to the forming tool, causing the forming tool to generate high-frequency reciprocating vibration in the axial direction.

[0032] Example 4 The method for manufacturing a spherical crown using single-point incremental forming technology proposed in this embodiment includes the following steps: Step 1: Determine the basic forming parameters based on material properties and target shape; The basic forming parameters in step 1 include the tool head diameter, feed rate, tool head rotation speed, and ultrasonic vibration parameters; the tool head is a ball head tool head with a diameter of 8–12 mm, a feed rate of 400–600 mm / min, a tool head rotation speed of 1000–1400 r / min, and ultrasonic vibration parameters of amplitude 0.02–0.06 mm and frequency 20–40 kHz; Step 2: Perform the first forming according to the first forming path, with the forming depth less than the target depth and allowance for axial compensation. Step 3: Based on Step 2, perform a second shaping pass according to the second pass path to make the radial direction approach the final contour, while the depth direction reaches the target depth; Both the first and second passes are curved paths with concave and convex arcs tangent to each other. A curved path with concave and convex arcs tangent to each other is a continuous curved path formed by connecting concave and convex arcs tangent to each other. Step 4: Based on Step 3, perform a third forming process from the bottom of the spherical crown part to the top edge according to the third forming path to obtain the spherical crown part; Ultrasonic vibration is applied to assist forming during the forming process in steps 1, 3 and 4; the ultrasonic vibration is applied to the forming tool, causing the forming tool to generate high-frequency reciprocating vibration in the axial direction.

[0033] Example 5 The method for manufacturing a spherical crown using single-point incremental forming technology proposed in this embodiment includes the following steps: Step 1: Determine the basic forming parameters based on material properties and target shape; The basic forming parameters in step 1 include the tool head diameter, feed rate, tool head rotation speed, and ultrasonic vibration parameters; the tool head is a ball head tool head with a diameter of 8–12 mm, a feed rate of 400–600 mm / min, a tool head rotation speed of 1000–1400 r / min, and ultrasonic vibration parameters of amplitude 0.02–0.06 mm and frequency 20–40 kHz; Step 2: Perform the first forming according to the first forming path, with the forming depth less than the target depth and allowance for axial compensation. During the first pass of forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the initial entry angle during the first pass is less than the forming limit angle of the material to be formed. The initial entry angle during the first pass is 45° to 55°. The entry angle is the angle between the tool head feed direction and the normal direction of the sheet metal plane, and the forming limit angle is the maximum entry angle at which the material will not break in a single pass of incremental forming. Step 3: Based on Step 2, perform a second shaping pass according to the second pass path to make the radial direction approach the final contour, while the depth direction reaches the target depth; Both the first and second passes are curved paths with concave and convex arcs tangent to each other. A curved path with concave and convex arcs tangent to each other is a continuous curved path formed by connecting concave and convex arcs tangent to each other. Step 4: Based on Step 3, perform a third forming process from the bottom of the spherical crown part to the top edge according to the third forming path to obtain the spherical crown part; Ultrasonic vibration is applied to assist forming during the forming process in steps 1, 3 and 4; the ultrasonic vibration is applied to the forming tool, causing the forming tool to generate high-frequency reciprocating vibration in the axial direction.

[0034] Example 6 The method for manufacturing a spherical crown using single-point incremental forming technology proposed in this embodiment includes the following steps: Step 1: Determine the basic forming parameters based on material properties and target shape; The basic forming parameters in step 1 include the tool head diameter, feed rate, tool head rotation speed, and ultrasonic vibration parameters; the tool head is a ball head tool head with a diameter of 8–12 mm, a feed rate of 400–600 mm / min, a tool head rotation speed of 1000–1400 r / min, and ultrasonic vibration parameters of amplitude 0.02–0.06 mm and frequency 20–40 kHz; Step 2: Perform the first forming according to the first forming path, with the forming depth less than the target depth and allowance for axial compensation. During the first pass of forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the initial entry angle during the first pass is less than the forming limit angle of the material to be formed. The initial entry angle during the first pass is 45° to 55°. The entry angle is the angle between the tool head feed direction and the normal direction of the sheet metal plane, and the forming limit angle is the maximum entry angle at which the material will not break in a single pass of incremental forming. Step 3: Based on Step 2, perform a second shaping pass according to the second pass path to make the radial direction approach the final contour, while the depth direction reaches the target depth; Both the first and second passes are curved paths with concave and convex arcs tangent to each other. A curved path with concave and convex arcs tangent to each other is a continuous curved path formed by connecting concave and convex arcs tangent to each other. During the second pass forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the entry angle of the second pass is greater than the average of the entry angles of the first and third passes; the entry angle of the second pass is 65° to 75°. Step 4: Based on Step 3, perform a third forming process from the bottom of the spherical crown part to the top edge according to the third forming path to obtain the spherical crown part; Ultrasonic vibration is applied to assist forming during the forming process in steps 1, 3 and 4; the ultrasonic vibration is applied to the forming tool, causing the forming tool to generate high-frequency reciprocating vibration in the axial direction; The third pass path is an arc path that matches the final shape of the spherical crown part, and the cutting angle of the third pass is the final forming angle of the spherical crown part. During the third pass forming, the tool head cuts down from the bottom center of the spherical crown part and moves layer by layer towards the top edge to complete the final contour trimming.

[0035] Example 7 The method for manufacturing a spherical crown using single-point incremental forming technology proposed in this embodiment includes the following steps: Step 1: Determine the basic forming parameters based on material properties and target shape; The basic forming parameters in step 1 include the tool head diameter, feed rate, tool head rotation speed, and ultrasonic vibration parameters; the tool head is a ball head tool head with a diameter of 8–12 mm, a feed rate of 400–600 mm / min, a tool head rotation speed of 1000–1400 r / min, and ultrasonic vibration parameters of amplitude 0.02–0.06 mm and frequency 20–40 kHz; Step 2: Perform the first forming according to the first forming path, with the forming depth less than the target depth and allowance for axial compensation. During the first pass of forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the initial entry angle during the first pass is less than the forming limit angle of the material to be formed. The initial entry angle during the first pass is 45° to 55°. The entry angle is the angle between the tool head feed direction and the normal direction of the sheet metal plane, and the forming limit angle is the maximum entry angle at which the material will not break in a single pass of incremental forming. The axial compensation in step 2 is 1 to 3 mm, which is used to counteract the bottom accumulation caused by the downward flow of material during the forming process. After the first forming pass, a pit contour is formed. The second forming pass is to expand radially on the basis of the pit contour of the first passing pass, so that the sidewall angle increases and approaches the target contour. The third forming pass is to trim the surface contour on the basis of the second forming pass, so that the surface of the final part is consistent with the target spherical crown surface. Step 3: Based on Step 2, perform a second shaping pass according to the second pass path to make the radial direction approach the final contour, while the depth direction reaches the target depth; Both the first and second passes are curved paths with concave and convex arcs tangent to each other. A curved path with concave and convex arcs tangent to each other is a continuous curved path formed by connecting concave and convex arcs tangent to each other. During the second pass forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the entry angle of the second pass is greater than the average of the entry angles of the first and third passes; the entry angle of the second pass is 65° to 75°. Step 4: Based on Step 3, perform a third forming process from the bottom of the spherical crown part to the top edge according to the third forming path to obtain the spherical crown part; Ultrasonic vibration is applied to assist forming during the forming process in steps 1, 3 and 4; the ultrasonic vibration is applied to the forming tool, causing the forming tool to generate high-frequency reciprocating vibration in the axial direction; The third pass path is an arc path that matches the final shape of the spherical crown part, and the cutting angle of the third pass is the final forming angle of the spherical crown part. During the third pass forming, the tool head cuts down from the bottom center of the spherical crown part and moves layer by layer towards the top edge to complete the final contour trimming.

[0036] Example 8 The method for manufacturing a spherical crown using single-point incremental forming technology proposed in this embodiment includes a forming device comprising an upper pressure plate 1, a lower pressure plate 2, an ultrasonic generator 3, a forming tool 4, and a sheet metal 5. The upper pressure plate 1 and lower pressure plate 2 clamp and fix the sheet metal 5, and the ultrasonic generator 3 provides high-frequency vibration to the forming tool 4. The forming tool 4 achieves the forming of the target part by processing the sheet metal 5 layer by layer.

[0037] like Figure 2 As shown, this embodiment involves forming a thin sheet of AA7075-T6 aluminum alloy with a diameter of 136 mm and a thickness of 1 mm. The forming target is a deep cavity spherical crown shape with a forming angle of 80°, formed in three passes. The formed part has an opening diameter of 83.4 mm and a depth of 35 mm.

[0038] In this embodiment, the tool head is a ball head with a diameter of 10 mm, the feed speed is 500 mm / min, the tool head rotation speed is 1200 r / min, and the ultrasonic vibration parameters are: amplitude 0.04 mm and frequency 30 kHz.

[0039] like Figure 3 As shown, the forming tool shapes the initial sheet material, creating a concave shape. The initial forming angle for the first pass (6) is 50°, connected by three arc segments: concave-convex-concave, with a forming depth of 33 mm. A 2 mm depth compensation is included because the tool head moves downwards during forming, causing material to flow downwards. This compensation effectively counteracts material buildup, preventing bottom settling and improving forming accuracy.

[0040] The entry point of the second pass 7 is the same as that of the first pass 6, with an initial forming angle of 70°. It connects through three arc segments—concave-convex-concave—achieving a forming depth of 35 mm, reaching the designed target depth. The second pass 7 adopts a top-down forming direction, forming from the edge of the part to the bottom center. Since the third pass 8 adopts a bottom-up forming direction, the second pass must form to the target depth.

[0041] In the third pass, the tool head cuts down from the center of the bottom of the part, gradually shaping it to the top edge. The third pass uses a complete circular arc path with a radius of 42.4 mm to achieve the final contour finishing.

Claims

1. A method for manufacturing a spherical crown part using single-point incremental forming technology, characterized in that, Includes the following steps: Step 1: Determine the basic forming parameters based on material properties and target shape; Step 2: Perform the first forming according to the first forming path, with the forming depth less than the target depth and allowance for axial compensation. Step 3: Based on Step 2, perform a second shaping pass according to the second pass path to make the radial direction approach the final contour, while the depth direction reaches the target depth; Step 4: Based on Step 3, perform a third forming process from the bottom of the spherical crown part to the top edge according to the third forming path to obtain the spherical crown part.

2. The method for manufacturing a spherical crown using single-point incremental forming technology according to claim 1, characterized in that, Ultrasonic vibration is applied to assist forming during the forming process in steps 1, 3 and 4; the ultrasonic vibration is applied to the forming tool, causing the forming tool to generate high-frequency reciprocating vibration in the axial direction.

3. The method for manufacturing a spherical crown using single-point incremental forming technology according to claim 1, characterized in that, The basic forming parameters mentioned in step 1 include the tool head diameter, feed rate, tool head rotation speed, and ultrasonic vibration parameters; the tool head is a ball head tool head with a diameter of 8-12 mm, a feed rate of 400-600 mm / min, a tool head rotation speed of 1000-1400 r / min, and ultrasonic vibration parameters of amplitude 0.02-0.06 mm and frequency 20-40 kHz.

4. The method for manufacturing a spherical crown using single-point incremental forming technology according to claim 1, characterized in that, Both the first and second secondary paths are curved paths with concave and convex arcs tangent to each other. The curved paths with concave and convex arcs tangent to each other are continuous curved paths formed by connecting concave and convex arcs tangent to each other.

5. The method for manufacturing a spherical crown using single-point incremental forming technology according to claim 4, characterized in that, During the first pass forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the initial entry angle during the first pass forming is less than the forming limit angle of the material to be formed. The initial entry angle during the first pass forming is 45° to 55°. The entry angle is the angle between the tool head feed direction and the normal direction of the sheet metal plane, and the forming limit angle is the maximum entry angle at which the material will not break during a single pass incremental forming.

6. The method for manufacturing a spherical crown using single-point incremental forming technology according to claim 4, characterized in that, During the second pass forming, the tool head moves from the top edge of the spherical crown part towards the bottom center, and the entry angle of the second pass is greater than the average of the entry angles of the first and third passes; the entry angle of the second pass is 65° to 75°.

7. The method for manufacturing a spherical crown using single-point incremental forming technology according to claim 4, characterized in that, The third pass path is an arc path that matches the final shape of the spherical crown part, and the cutting angle of the third pass is the final forming angle of the spherical crown part. During the third pass forming, the tool head cuts down from the bottom center of the spherical crown part and moves layer by layer towards the top edge to complete the final contour trimming.

8. The method for manufacturing a spherical crown using single-point incremental forming technology according to claim 1, characterized in that, The axial compensation in step 2 is 1-3 mm, which is used to counteract the bottom accumulation caused by the downward flow of material during the forming process. After the first forming pass, a pit contour is formed. The second forming pass is based on the pit contour of the first forming pass and radially expands it to increase the sidewall angle and approach the target contour. The third forming pass is based on the second forming pass and performs surface contour trimming so that the surface of the final part is consistent with the target spherical crown surface.

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