A laser processing method and apparatus for the inner surface of a hemispherical titanium alloy workpiece.

Abstract

This invention belongs to the field of laser processing technology and discloses a laser processing method and apparatus for the inner surface of a hemispherical titanium alloy workpiece. The invention first studies the laser polishing of Ti-6Al-4V titanium alloy flat plates, investigating the influence of laser parameters and the laser incident angle on the surface roughness of the polished material. Optimized laser parameters and the maximum laser incident angle that meets processing requirements are obtained and applied to the laser processing of hemispherical workpieces. A segmented method for the inner surface of the hemispherical workpiece is designed, and a five-axis motion system sequentially completes the laser processing of each segmented area. The laser incident angle at any point within each processing area does not exceed the maximum laser incident angle that meets processing requirements. Dynamic focusing technology is employed to ensure that the laser processing distance is the same at each point within the processing area, avoiding differences in laser energy due to varying processing point heights and improving processing uniformity.

Description

Technical Field

[0001] This invention belongs to the field of laser processing technology, and specifically relates to a laser processing method and apparatus for the inner surface of a hemispherical titanium alloy workpiece. Background Technology

[0002] Laser remelting is a widely used processing technology for key components in aerospace, marine engineering, and medical devices. It features high precision, low pollution, and a high degree of automation, enabling the fine machining of complex parts with special surfaces. Laser remelting alters the surface morphology of a part without removing the base material. It involves irradiating the material surface with a laser of a certain energy density, causing the surface protrusions to reach their melting point and melt into a liquid state. Under the influence of surface tension and gravity, the molten portion flows to lower areas, filling in surface depressions. When the laser beam leaves, the molten portion cools and solidifies, resulting in a smooth surface. Laser remelting allows for precise control over the microstructure and properties of materials. Lasers can process almost all metallic materials and are also used in the processing of ceramics and glass, so there are few limitations on the materials used.

[0003] Titanium alloys, especially Ti-6Al-4V, possess advantages such as low density, high strength, good toughness, corrosion resistance, and high biocompatibility, making them suitable for manufacturing aircraft engine casings, subsea pipelines, and human implants. However, titanium alloys also exhibit poor thermal conductivity, high chemical reactivity, high hardness, and high shear strength. Traditional machining methods accelerate tool wear, resulting in low processing efficiency and environmental pollution. Furthermore, traditional machining processes for complex curved titanium alloy parts suffer from low processing freedom, low efficiency, and low automation, failing to meet practical processing requirements. Therefore, compared to traditional machining methods, laser processing is more suitable for titanium alloys.

[0004] Most research on laser processing of titanium alloys has been conducted on planar materials. However, when polishing complex curved workpieces, variations in the laser incident angle and defocusing amount can affect the processing results. This is especially true for hemispherical workpieces with large curvature variations. Directly processing their inner surfaces with lasers cannot ensure perpendicular laser incidence, and the varying laser processing distance at each point affects the laser energy density, leading to unsatisfactory processing results. For example, in the biomedical field, the acetabular cup used in hip replacement surgery requires post-processing polishing to reduce surface roughness and wear. Therefore, it is necessary to explore laser processing methods for the inner surfaces of hemispherical titanium alloy workpieces. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a laser processing method for the inner surface of a hemispherical titanium alloy workpiece.

[0006] This invention first studies the laser polishing of Ti-6Al-4V titanium alloy flat plates, investigating the effects of laser parameters and laser incident angle on the surface roughness of the polished material. Optimized laser parameters and the maximum laser incident angle meeting processing requirements are obtained and applied to the laser processing of hemispherical workpieces. A segmentation method for the inner surface of the hemispherical workpiece is designed, and a five-axis motion system sequentially completes the laser processing of each segment. The laser incident angle at any point within each processing area does not exceed the maximum laser incident angle that meets processing requirements. Dynamic focusing technology is employed to ensure that the laser processing distance is the same at each point within the processing area, avoiding differences in laser energy due to varying processing point heights and improving processing uniformity.

[0007] Another object of the present invention is to provide a laser processing apparatus for the inner surface of a hemispherical titanium alloy workpiece that implements the above-described processing method.

[0008] The device of the present invention can ensure that the change of laser incident angle is within a reasonable range during the laser processing of curved surfaces, and that the laser processing distance of processing points at different heights is consistent, which greatly reduces the unevenness of laser energy caused by spot distortion and defocusing, and improves the processing quality.

[0009] The objective of this invention is achieved through the following solution:

[0010] A laser processing method for the inner surface of a hemispherical titanium alloy workpiece includes the following steps:

[0011] (1) Determination of laser parameters: Laser parameter experiments were conducted on flat titanium alloy materials to determine the influence of laser parameters on the processing effect and the maximum laser incident angle that meets the processing requirements;

[0012] (2) Region division of the inner surface of the hemispherical titanium alloy workpiece: According to the maximum laser incident angle in step (1), the inner surface of the hemispherical titanium alloy workpiece is divided into zone one, zone two and zone three. Then, zone two and zone three are further divided into blocks. The divided regions satisfy the following: the laser incident angle at each point in the processing area is less than the maximum laser incident angle.

[0013] (3) Determination of processing trajectory: The shape of the area divided in step (2) is transformed by the principle of parallel projection to obtain the planar pattern of laser processing, and the laser processing trajectory of each area is generated.

[0014] (4) Determining the position of the laser and the workpiece: Place the workpiece in the preset position, draw the pattern obtained in step (3) using laser processing software, turn on the red light mode of the laser, move the laser so that the red light pattern coincides with the processing pattern of the workpiece, and record the coordinates of the laser.

[0015] (5) Laser processing: After moving the laser and the workpiece to the processing position determined in step (4), the laser, according to the laser processing trajectory determined in step (3), completes the processing of the inner surface of the hemispherical titanium alloy workpiece by moving the platform, rotating the platform and cooperating with the laser; wherein, the laser has a dynamic focusing system, which can achieve dynamic focusing within a height range of ±20mm.

[0016] The laser parameters mentioned in step (1) include laser power P, repetition frequency f, defocusing amount z, scanning speed v and scanning spacing d; wherein, different roughness ranges of processing surfaces can be obtained by adjusting the laser parameters, thereby realizing the roughness control of the inner surface of the hemispherical workpiece.

[0017] The laser parameters mentioned in step (1) are specifically: laser power P = 100W, f = 80kHz, defocus z = +9mm, scanning speed v = 200mm / s, and scanning spacing d = 0.02mm.

[0018] The maximum laser incident angle in step (1) satisfies the following condition: the maximum value of the laser incident angle whose change in surface roughness after laser processing is within 30% compared to the surface roughness after laser processing on the plane.

[0019] The maximum laser incident angle in step (1) is 35°.

[0020] The correspondence of the planar patterns in step (3) is as follows: the two-dimensional planar processing pattern of partition one is a circle; the two-dimensional planar processing patterns after partition two and partition three are divided into blocks are fan rings, and the fan ring blocks of partition two and partition three are of different sizes.

[0021] The determination of the laser and workpiece positions in step (4) is as follows: When performing laser processing in zone one, the workpiece is placed horizontally. A circular pattern with the same inner diameter as the hemispherical workpiece is drawn in the laser processing software. The laser red light mode is turned on, and the laser is moved so that the circular red light coincides with the inner circle of the hemispherical workpiece. At this time, the laser coordinate position is the processing position of zone one. When performing laser processing in zone two, the workpiece needs to be tilted 30° along the y-axis. The fan-ring pattern of zone two is irradiated onto the inner surface of the hemispherical workpiece through the laser red light mode. The laser is controlled to translate a corresponding distance along the x-axis. When the edge of the fan-ring red light pattern coincides with the edge of the circular area of ​​zone one, the z-axis height is adjusted. At this time, the laser coordinate position is the processing position of zone two. Similarly, the laser processing coordinate position of zone three can be obtained. Record the coordinates of each position to complete the processing program. Start the program to make the laser and workpiece automatically move to the positions of each processing area.

[0022] The laser processing described in step (5) is as follows: The workpiece is fixed in the fixture and placed horizontally. The processing program is started. Taking the initial position of the laser as the origin, when the five-axis motion system moves the laser to the processing position of partition one, the laser will receive a pulse signal from the five-axis motion system. After receiving the signal, the laser will generate a processing trajectory according to the processing pattern of partition one and perform laser scanning processing. After the laser completes the laser processing of partition one, it will send a pulse signal to the five-axis motion system. At this time, the five-axis motion system will control the moving platform to move the laser to the processing position of partition two and control the rotating platform to tilt the workpiece by 30°. After the laser and the workpiece reach the designated position, the five-axis motion system will send a signal to the laser again, and the laser will start to perform the block processing of partition two. After each block is processed, a signal is sent to the five-axis motion system to control the workpiece to rotate, so that the unprocessed block is rotated into the laser processing range, and finally the processing of partition two is completed. The processing method of partition three is the same as that of partition two.

[0023] A laser processing apparatus for processing the inner surface of a hemispherical titanium alloy workpiece using the above processing method includes a fixture, a laser, a five-axis motion system, and a control system.

[0024] The laser has a dynamic focusing system, including a scanning galvanometer and a dynamic focusing mirror;

[0025] The five-axis motion system includes a moving platform and a rotating platform; wherein, the moving platform is connected to the laser and can drive the laser to move along the x, y, and z axes; the rotating platform is connected to the fixture and can tilt or rotate the fixture, including a servo motor, a rotary axis, and an angular displacement axis;

[0026] The control system includes a motion control card, a motor driver, and an industrial computer.

[0027] The laser processing device specifically includes a moving platform, a rotating platform, a fixture 9, a laser 4, and a laser emission source 6. The moving platform includes an x-axis moving platform 3, a y-axis moving platform 1, and a z-axis moving platform 8. The rotating platform includes a rotation axis 10 and an angular displacement axis 11. The fixture 9 is used to load a hemispherical titanium alloy workpiece and is connected to the rotating platform to enable the workpiece to move in the angular displacement axis and rotation axis directions. The laser 4 is an infrared nanosecond fiber laser; the laser beam is emitted from the laser emission source 6, passes through a dynamic focusing lens and a scanning galvanometer in the laser 4, and reaches the processing point to perform laser processing on the inner surface of the hemispherical workpiece. The laser 4 is connected to the z-axis moving platform 8 to achieve lifting and lowering.

[0028] The mechanism of this invention is as follows:

[0029] The key to this invention's method for machining the inner surface of hemispherical titanium alloy workpieces lies in the linkage between a five-axis motion system and a laser to ensure that the laser incident angle remains within a reasonable range during laser processing. Specifically, compared to the surface roughness after laser processing on a flat surface, the change in surface roughness after processing is within 30% of the laser incident angle. Maintaining a consistent laser processing distance significantly reduces energy variations during the laser processing of the inner surface of the hemispherical workpiece. First, laser parameterization experiments are conducted on the surface of a flat titanium alloy material to investigate the influence of laser parameters on the surface roughness of the processed titanium alloy. A set of optimized parameters is obtained that can be directly applied to the laser processing of the inner surface of hemispherical workpieces. By fixing the laser parameters and continuously changing the tilt angle of the flat titanium alloy material, the influence of the laser incident angle on the surface roughness of the processed titanium alloy is investigated. Based on the comparison of the surface roughness value when the laser is incident perpendicularly, the maximum laser incident angle within the acceptable range for roughness value variation is obtained. During the laser processing of the inner surface of the hemispherical workpiece, the laser incident angle at each point in the processing area must be less than the maximum laser incident angle. Based on the experimentally obtained laser incident angle range, the inner surface of the hemispherical workpiece is divided into processing areas. Two-dimensional planar patterns for processing different areas are obtained through parallel projection transformation. The workpiece can be tilted by rotating the platform to change the laser incident angle of the processing area. A laser with dynamic focusing function is used to complete the processing of each area in sequence.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] The method of this invention can realize laser processing of the inner surface of hemispherical titanium alloy workpieces, effectively reducing its surface roughness (under the parameters of laser power P = 100W, f = 80kHz, defocusing amount z = +9mm, scanning speed v = 200mm / s, and scanning spacing d = 0.02mm, the surface roughness of the inner surface of the hemispherical workpiece can be reduced from Sa = 25μm to Sa = 2.312μm, a reduction of 90.75%), improving the surface morphology, and ensuring the uniformity of processing quality in all areas of the inner surface.

[0032] This invention divides the processing area of ​​the inner surface of a hemispherical workpiece based on the laser incident angle, ensuring that the laser incident angle at each point within the processing area is within a reasonable range, thus avoiding severe distortion of the laser spot due to an excessively large laser incident angle.

[0033] The laser used in this invention has a dynamic focusing system that can dynamically adjust the laser focus position within a height range of ±20mm according to the different heights of the processing point, ensuring that the laser processing distance is consistent in all areas of the inner surface of the hemispherical workpiece during processing, and avoiding changes in laser energy due to different laser processing distances.

[0034] This invention utilizes a five-axis motion system linked with a laser to jointly complete the laser processing of the inner surface of a hemispherical workpiece. The five-axis motion system and the laser have signal transmission capabilities, allowing them to receive and send pulse signals to each other, thus automating the processing and ensuring processing accuracy. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the device structure in the laser processing method for the inner surface of a hemispherical titanium alloy workpiece according to the present invention;

[0036] Among them, 1 is the y-axis moving platform, 2 is the y-axis linear motor, 3 is the x-axis moving platform, 4 is the laser, 5 is the x-axis linear motor, 6 is the laser emission source, 7 is the z-axis motor, 8 is the z-axis moving platform, 9 is the fixture, 10 is the rotary axis, and 11 is the angular displacement axis.

[0037] Figure 2 This is a schematic diagram of the processing area division in the laser processing method for the inner surface of the hemispherical titanium alloy workpiece of the present invention.

[0038] Figure 3 This is a schematic diagram illustrating the calculation of the processing pattern dimensions for each section / block in the laser processing method for the inner surface of the hemispherical titanium alloy workpiece of the present invention.

[0039] Figure 4 This is a flowchart of the laser processing method for the inner surface of a hemispherical titanium alloy workpiece according to the present invention. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0041] Unless otherwise specified, all reagents used in the examples are commercially available.

[0042] Example

[0043] This embodiment describes a laser processing device for the inner surface of a hemispherical titanium alloy (Ti-6Al-4V) workpiece, such as... Figure 1As shown, the system includes a moving platform, a rotating platform, a fixture 9, a laser 4, and a laser emission source 6. The moving platform includes an x-axis moving platform 3, a y-axis moving platform 1, and a z-axis moving platform 8. The rotating platform includes a rotation axis 10 and an angular displacement axis 11. The fixture 9 is used to load the hemispherical titanium alloy workpiece. The fixture 9 is connected to the rotating platform to enable the workpiece to move in the angular displacement axis and rotation axis directions. The laser 4 is preferably an infrared nanosecond fiber laser. The laser beam is emitted from the laser emission source 6, passes through the dynamic focusing lens and scanning galvanometer in the laser 4, and reaches the processing point to perform laser processing on the inner surface of the hemispherical workpiece. The laser 4 is connected to the z-axis moving platform 8 to achieve lifting.

[0044] Laser processing of the inner surface of a hemispherical titanium alloy workpiece includes the following steps:

[0045] (1) Laser parameterization experiments were conducted on a flat titanium alloy material (Ti-6Al-4V) placed on a rotating platform:

[0046] Laser parameters include laser power P, scanning spacing d, repetition frequency f, scanning speed v, and defocusing amount z. The influence of laser parameters on the surface roughness of titanium alloy machining was obtained through orthogonal experiments. Different roughness ranges of machined surfaces could be obtained by adjusting the laser parameters, thus achieving control over the surface roughness. The optimal laser parameters that minimized the surface roughness were selected (laser power P = 100W, repetition frequency f = 80kHz, defocusing amount z = +9mm, scanning speed v = 200mm / s, scanning spacing d = 0.02mm). Under these parameters, the surface roughness of the inner surface of the hemispherical workpiece decreased from Sa = 25μm to Sa = 2.312μm, a reduction of 90.75%. These optimized parameters were used as the parameters for subsequent laser machining experiments on the inner surface of the hemispherical workpiece. By changing the tilt angle of the flat titanium alloy material through the angular displacement axis 11 and fixing the laser parameters, the laser beam is made to act on the tilted surface. The effect of the laser incident angle on the surface roughness is observed. The maximum laser incident angle θ, which is within 30% of the roughness value compared with the vertically incident surface, is determined to be 35°.

[0047] (2) Divide the laser processing area:

[0048] Figure 2 In the diagram, 'a' represents a partitioning diagram; 'b' represents a block diagram of partition two; and 'c' represents a block diagram of partition three. For example... Figure 2As shown, the horizontally placed hemispherical workpiece is divided into three zones. In zone one, the laser incident angle at all points is between 0 and 30°, which is less than the maximum laser incident angle of 35°, so it can be directly processed by laser. When the workpiece is placed horizontally, there are areas in zones two and three where the laser incident angle is greater than θ, so they cannot be processed directly. By tilting the workpiece by 30°, there are areas in zone two where the laser incident angle is less than θ. Zone two is then divided into blocks to ensure that the laser incident angle at each point is less than θ when the blocks are processed by laser. The same applies to zone three.

[0049] (3) Determine the pattern of each section of the laser processing so that the laser can generate the processing trajectory:

[0050] Figure 3 In the diagram, a, b, and c represent the calculation diagrams for the processing pattern dimensions of zones one, two, and three, respectively. Figure 3 As shown, after parallel projection transformation, the laser processing pattern in partition one is circular, and the size of the circle is determined by the inner diameter of the hemispherical workpiece. The laser processing pattern in partition two is a fan ring. Let the shortest radius of the fan ring be r2, the longest radius be R2, the outer arc length be 2l (the model image of the hemispherical workpiece is a sectional view, so the actual arc length of the drawn pattern is 2l), and the central angle be 2a. The size of the fan ring can be calculated based on the size of the processing pattern in partition one, the inner diameter of the hemispherical workpiece, and the maximum laser incident angle θ. The laser processing pattern in partition three is also a fan ring, and the calculation method is the same as that in partition two. After the processing pattern is drawn, the pattern fill is set in the laser processing software. Select "bow-shaped scanning path" and set the scanning direction to 90°. After the fill is completed, the laser processing trajectory can be generated.

[0051] (4) Record the coordinate information of the laser and the workpiece during the machining of each zone on the inner surface of the hemispherical workpiece:

[0052] When performing laser processing on section one, the workpiece is placed horizontally. A circular pattern with the same inner diameter as the hemispherical workpiece is drawn in the laser processing software. The laser's red light mode is activated, and the laser is moved along the x and y axes until the circular red light coincides with the inner circle of the hemispherical workpiece. At this point, the center of the circular processing pattern in section one also coincides with the center of the hemispherical workpiece. The z-axis is adjusted so that the laser reaches the specified height position. The laser's coordinate position at this point is the processing position for section one; the laser's coordinates are recorded. The workpiece is then tilted 30° along the y-axis for section two processing. The sector of section two is processed... The ring pattern is irradiated onto the inner surface of the hemispherical workpiece using the red light mode of a laser. The laser is controlled to translate a corresponding distance along the x-axis. When the edge of the fan-shaped red light pattern coincides with the edge of the circular area in partition one, the z-axis height is adjusted. At this time, the laser coordinate position is the processing position in partition two, and the laser coordinates are recorded. Then, the workpiece is tilted 30° for partition three processing. The laser processing coordinate position in partition three is determined in the same way as in partition two, and the laser coordinates are recorded. The coordinates of each position are written into the processing program, and the laser processing of the inner surface of the hemispherical workpiece can be completed automatically thereafter.

[0053] (5) The five-axis motion system is linked with the laser 4 to complete the laser processing of the inner surface of the hemispherical workpiece:

[0054] Processing flow as follows Figure 4 As shown; connect the laser 4 to the signal line of the five-axis motion system to enable it to send and receive signals; move the laser to the processing position of partition one through the x-axis moving platform 3, y-axis moving platform 1 and z-axis moving platform 8 of the five-axis motion system, and send a signal to make the laser 4 start processing; after the laser 4 completes the processing of partition one, send a signal to make the five-axis motion system move the laser to the processing position of partition two, and at the same time, the angular displacement axis 11 drives the workpiece to tilt. After the laser completes the processing of each fan ring block, send a signal to make the rotary axis 10 drive the workpiece to rotate, and rotate the unprocessed block area into the laser processing range. This cycle is repeated to complete the processing of partition two; the same applies to partition three.

[0055] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A laser processing method for the inner surface of a hemispherical titanium alloy workpiece, characterized in that... Includes the following steps: Step 1: Determination of laser parameters: Conduct laser parameter experiments on flat titanium alloy materials to determine the influence of laser parameters on processing effect and the maximum laser incident angle that meets processing requirements; Step 2, Region division of the inner surface of the hemispherical titanium alloy workpiece: Based on the maximum laser incident angle in Step 1, the inner surface of the hemispherical titanium alloy workpiece is divided into three regions: region 1, region 2, and region 3. Then, region 2 and region 3 are further divided into blocks. The divided regions satisfy the following condition: the laser incident angle at each point in the processing area is less than the maximum laser incident angle. Step 3: Determining the processing trajectory: By transforming the shape of the area divided in Step 2 using the principle of parallel projection, a planar pattern for laser processing is obtained, generating the laser processing trajectory for each area; Step 4: Determining the position of the laser and the workpiece: Place the workpiece in the preset position, use the laser processing software to draw the pattern obtained in Step 3, turn on the red light mode of the laser, move the laser so that the red light pattern coincides with the processing pattern of the workpiece, and record the coordinates of the laser. Step 5, Laser Processing: After moving the laser and workpiece to the processing position determined in Step 4, the laser, according to the laser processing trajectory determined in Step 3, completes the processing of the inner surface of the hemispherical titanium alloy workpiece through the cooperation of the moving platform and the rotating platform; wherein, the laser is equipped with a dynamic focusing system, which can achieve dynamic focusing within a height range of ±20mm; The correspondence of the planar patterns described in step three is as follows: the two-dimensional planar processing pattern of partition one is a circle; the two-dimensional planar processing patterns after partition two and partition three are divided into fan rings, and the size of the fan ring blocks in partition two and partition three is different; wherein the laser incident angle of all points in partition one is less than the maximum laser incident angle. Step four, determining the laser and workpiece positions, is as follows: When performing laser processing in zone one, the workpiece is placed horizontally. A circular pattern with the same inner diameter as the hemispherical workpiece is drawn in the laser processing software. The laser's red light mode is activated, and the laser is moved until the circular red light coincides with the inner circle of the hemispherical workpiece. At this point, the laser's coordinate position is the processing position for zone one. When performing laser processing in zone two, the workpiece needs to be tilted 30° along the y-axis. The fan-ring pattern for zone two is irradiated onto the inner surface of the hemispherical workpiece using the laser's red light mode. The laser is then moved a corresponding distance along the x-axis. When the edge of the fan-ring red light pattern coincides with the edge of the circular area in zone one, the z-axis height is adjusted. At this point, the laser's coordinate position is the processing position for zone two. Similarly, the laser processing coordinate position for zone three can be obtained. The coordinates of each position are recorded to complete the processing program. Starting the program will automatically move the laser and workpiece to their respective processing areas.

2. The laser processing method for the inner surface of a hemispherical titanium alloy workpiece according to claim 1, characterized in that: The laser parameters mentioned in step one include laser power P, repetition frequency f, defocusing amount z, scanning speed v, and scanning spacing d; wherein, by adjusting the laser parameters, processing surfaces with different roughness value ranges can be obtained, thereby realizing the roughness control of the inner surface of the hemispherical workpiece.

3. The laser processing method for the inner surface of a hemispherical titanium alloy workpiece according to claim 1 or 2, characterized in that: The laser parameters mentioned in step one are specifically: laser power P=100W, f=80kHz, defocus z=+9mm, scanning speed v=200mm / s, and scanning spacing d=0.02mm.

4. The laser processing method for the inner surface of a hemispherical titanium alloy workpiece according to claim 1, characterized in that: The maximum laser incident angle mentioned in step one satisfies the following condition: the maximum value of the laser incident angle whose change in surface roughness after laser processing is within 30% compared to the surface roughness after laser processing on the plane.

5. The laser processing method for the inner surface of a hemispherical titanium alloy workpiece according to claim 1 or 4, characterized in that: The maximum laser incident angle described in step one is 35°.

6. The laser processing method for the inner surface of a hemispherical titanium alloy workpiece according to claim 1, characterized in that: Step 5 of the laser processing is as follows: The workpiece is fixed in the fixture and placed horizontally. The processing program is started. Taking the initial position of the laser as the origin, when the five-axis motion system moves the laser to the processing position of partition one, the laser will receive a pulse signal from the five-axis motion system. After receiving the signal, it will generate a processing trajectory according to the processing pattern of partition one and perform laser scanning processing. After the laser completes the laser processing of partition one, it will send a pulse signal to the five-axis motion system. At this time, the five-axis motion system will control the moving platform to move the laser to the processing position of partition two, and control the rotating platform to tilt the workpiece by 30°. After the laser and the workpiece reach the designated position, the five-axis motion system will send a signal to the laser again, and the laser will start to process the blocks of partition two. After each block is processed, a signal is sent to the five-axis motion system to control the rotation of the workpiece, so that the unprocessed blocks are rotated into the laser processing range, and finally the processing of partition two is completed. The processing method of partition three is the same as that of partition two.

7. A laser processing apparatus for processing the inner surface of a hemispherical titanium alloy workpiece according to any one of claims 1-6, comprising a fixture, a laser, a five-axis motion system, and a control system; The laser has a dynamic focusing system, including a scanning galvanometer and a dynamic focusing mirror; The five-axis motion system includes a moving platform and a rotating platform; wherein... The mobile platform is connected to the laser and can drive the laser to move along the x, y, and z axes; the rotary platform is connected to the fixture and can tilt or rotate the fixture, including servo motors, rotary axes, and angular displacement axes. The control system includes a motion control card, a motor driver, and an industrial computer.

8. The laser processing apparatus for the inner surface of a hemispherical titanium alloy workpiece according to claim 7, characterized in that: Specifically, it includes a moving platform, a rotating platform, a fixture (9), a laser (4), and a laser emission source (6); wherein, the moving platform includes an x-axis moving platform (3), a y-axis moving platform (1), and a z-axis moving platform (8); the rotating platform includes a rotation axis (10) and an angular displacement axis (11); the fixture (9) is used to load a hemispherical titanium alloy workpiece, and the fixture (9) is connected to the rotating platform to realize the movement of the workpiece in the angular displacement axis and rotation axis direction; the laser (4) is an infrared nanosecond fiber laser, and the laser beam is emitted from the laser emission source (6), passes through the dynamic focusing lens and scanning galvanometer in the laser (4) to reach the processing point, and performs laser processing on the inner surface of the hemispherical workpiece; the laser (4) is connected to the z-axis moving platform (8) to realize lifting.

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