Laser polishing method for large complex cylindrical surface

Abstract

The present invention discloses a laser polishing method for a large complex cylindrical surface, which relates to the field of laser processing technology and includes the following steps: S1, constructing a roughness database of the laser polished surface; S2, determining the optional range of the laser defocus amount and the optional range of the incident angle according to the roughness database; S3, dividing the complex cylindrical surface to be polished into a plurality of sub-cylinders based on the optional range of the laser defocus amount and the optional range of the incident angle; S4, polishing the plurality of sub-cylinders. The defocus amount value range that meets the laser polishing requirements obtained by the present invention through experimental optimization design and the principle of laser positive and negative defocus symmetry is several times the laser focal depth, which can overcome the problem of low processing efficiency caused by the limitation of focal depth in the existing laser polishing method.

Description

Technical Field

[0001] The invention relates to the technical field of laser processing, and in particular to a laser polishing method for a large and complex cylindrical surface. Background Art

[0002] A cylinder refers to a curved surface formed by a moving straight line moving parallel to a fixed curve. The moving straight line is called the straight generatrix of the cylinder, and the fixed curve is called the directrix of the cylinder. When the directrix is ​​a complex curve, the cylinder formed is a complex cylinder. A complex cylinder is a typical complex curved surface. Parts with complex cylinders are easy to obtain excellent static / dynamic properties and are widely used in engineering fields such as aerospace, ships, automobiles, and molds. In order to further improve the wear resistance, corrosion resistance, and mechanical properties of parts, it is often necessary to polish the complex cylinder to obtain the required surface roughness. Currently, commonly used polishing methods include mechanical polishing, electrochemical polishing, magnetorheological polishing, ion beam polishing, etc. When these methods are applied to complex cylinders, they will inevitably cause problems such as complex processes, low efficiency, and poor environmental protection.

[0003] Laser polishing has the characteristics of high precision, high flexibility and environmental protection, and has become a new type of surface polishing technology. When processing curved surfaces, the incident angle and defocus of the laser will directly affect the process performance, and the influence of these two factors must be considered. At present, there are mainly the following laser polishing technologies suitable for complex curved surfaces of parts:

[0004] The first is to use a laser scanning galvanometer and a three-axis motion table to control the laser processing path. For example, patent CN201010115968.0 discloses a projection laser etching method on a free-form surface. This method uses the characteristics of laser processing that the spot shape size, energy distribution and other processing characteristics remain unchanged within the focal depth of the focusing mirror, and converts the free-form surface into several sub-surfaces. Because when dividing the sub-surfaces, it must be ensured that the maximum difference in the Z coordinates within the sub-surface is less than the focal depth of the laser, otherwise the processing quality cannot be guaranteed. Therefore, when dividing the sub-surfaces of complex surfaces with large curvatures, the blocks are extremely small, resulting in a huge number of sub-surfaces, which causes the three-axis motion table to frequently start and stop, resulting in low processing efficiency.

[0005] The second is to use a laser processing head with a scanning galvanometer and a Z-axis moving mechanism, and to control the processing path in conjunction with a five-axis linkage CNC machine tool. For example, patent CN 201110048935.3 discloses a laser processing method and device suitable for complex surfaces. The solution adopts a processing step of dividing the complex surface into surface patches and establishing the coordinate system of each surface patch, so that in the subsequent processing steps of dividing the sub-surfaces and parallel projection of the processed graphics, each surface patch can be processed separately according to the coordinate system, thereby effectively solving the limitation that the prior art can only use a single coordinate system for overall projection, and the surface that is back against the laser incident direction or parallel to the optical axis direction cannot be processed. However, this solution is still limited by the focal depth of the laser beam. When dividing the complex surface with a large curvature into sub-surfaces, the number of blocks is still large, and the five-axis linkage CNC machine tool also needs to be started and stopped frequently, resulting in low processing efficiency. Summary of the invention

[0006] In order to solve the problem of low processing efficiency in the existing laser polishing method, the present invention proposes a laser polishing method for a large and complex cylindrical surface.

[0007] The technical solution of the present invention is: a laser polishing method for a large complex cylindrical surface comprises the following steps:

[0008] S1. Construct a roughness database of laser polished surfaces;

[0009] S2. Determine the optional range of the laser defocus amount and the optional range of the incident angle according to the roughness database;

[0010] S3, dividing the complex cylindrical surface to be polished into a plurality of sub-cylinder surfaces based on the optional range of the laser defocus amount and the optional range of the incident angle;

[0011] S4. Polishing is performed on a plurality of sub-cylinder surfaces.

[0012] Furthermore, S1 includes the following sub-steps:

[0013] S11, when the defocus amount of the laser is 0 and the incident angle is 0°, polishing the planar substrate, and obtaining the optimal laser polishing parameters by an experimental optimization method, wherein the optimal laser polishing parameters include the pulse energy, pulse width, pulse frequency, scanning speed and scanning spacing of the laser;

[0014] S12. Based on the optimal laser polishing parameters, the roughness of the laser polished surface at different defocus amounts and different incident angles is determined through a full factorial experiment as a roughness database.

[0015] Further, in S2, the method for determining the optional range of the incident angle is: in the intervals formed by different defocus amounts and the intervals formed by different incident angles, the interval with the most consecutive values ​​is selected to determine the optional range of the incident angle;

[0016] In S2, the method for determining the optional range of the laser defocus amount is: determine the positive defocus amount optional range corresponding to the optional range of the incident angle, and determine whether there is a negative defocus amount optional range based on the positive defocus amount optional range; if there is a negative defocus amount optional range, determine the optional range of the laser defocus amount based on the positive defocus amount optional range and the negative defocus amount optional range; if there is no negative defocus amount optional range, determine the optional range of the laser defocus amount based on the positive defocus amount optional range.

[0017] Furthermore, S3 includes the following sub-steps:

[0018] S31, dividing the complex cylindrical surface to be polished into a plurality of sub-areas;

[0019] S32. Based on the optional range of the laser defocus amount and the optional range of the incident angle, the plurality of sub-areas are divided into a plurality of sub-cylinders in sequence.

[0020] Furthermore, in S32, the constraint condition for dividing the plurality of sub-areas into a plurality of sub-cylinders is:

[0021] ;

[0022] ;

[0023] ;

[0024] ;

[0025] In the formula, is the radius of curvature of the ith sub-region, is the projection length of the arc side of the j-th sub-cylinder of the i-th sub-region in the horizontal direction, is the maximum value of the optional range of laser defocus, is the minimum value of the optional range of laser defocus, is the side length of the telecentric field mirror scanning range, is the projection length of the straight edge of the j-th sub-cylinder of the i-th sub-region in the longitudinal direction, is the maximum incident angle when the laser polishes the j-th sub-cylinder of the i-th sub-region, is the maximum value of the optional range of laser incident angle, is the curvature radius of the j-th sub-cylinder of the i-th sub-region, .

[0026] Further, S4 includes the following sub-steps:

[0027] S41, rotating the longitudinal axis of the four-axis worktable so that the normal of the center point of the first sub-cylinder of the first sub-region is parallel to the vertical axis; moving the transverse axis and the longitudinal axis of the four-axis worktable so that the coordinate values ​​of the laser origin on the transverse axis and the longitudinal axis correspond to the coordinate values ​​of the center point of the first sub-cylinder of the first sub-region on the transverse axis and the longitudinal axis; controlling the vertical axis movement of the four-axis worktable to determine that the position of the laser focus on the vertical axis reaches the optimal vertical axis position;

[0028] S42, according to the projection area of ​​the first sub-cylinder of the first sub-region on the horizontal and vertical planes, controlling the size of the scanning area when the laser polishes the first sub-cylinder of the first sub-region, and completing the polishing process of the first sub-cylinder of the first sub-region;

[0029] S43, repeat S41-S42 to complete the polishing process on the remaining sub-cylindrical surfaces.

[0030] Further, in S41, the optimal vertical axis position The calculation formula is:

[0031] ;

[0032] In the formula, is the maximum value of the vertical axis coordinate of the first sub-cylinder in the first sub-region, is the minimum value of the Z coordinate of the first sub-cylinder in the first sub-region.

[0033] The beneficial effects of the present invention are:

[0034] (1) The defocus value range that meets the laser polishing requirements obtained by the present invention through experimental optimization design and the principle of symmetry of positive and negative laser defocus is several times the laser focal depth, which can overcome the problem of low processing efficiency caused by the limitation of focal depth in the existing laser polishing method;

[0035] (2) The present invention obtains a range of laser incident angle values ​​that meets the polishing requirements through experimental optimization design, which can eliminate the influence of the change of the incident angle on the polishing accuracy when the laser polishes the curved surface. The area of ​​the divided sub-surface can be increased while ensuring the polishing accuracy, thereby reducing the number of sub-surface divisions, which can reduce the number of starts, stops or adjustments of the moving workbench, thereby improving the polishing efficiency;

[0036] (3) The present invention uses a laser scanning galvanometer and a four-axis motion worktable to control the laser polishing path, wherein the movement of the X-axis and the Y-axis can adjust the position of the part on the X-axis and the Y-axis, and the combined scanning galvanometer can expand the area of ​​the laser polishable region; the rotation of the Y-axis and the movement of the Z-axis can respectively adjust the laser incident angle and the focal position so that the laser can polish cylinders with different curvature radii or spatial positions. The combination of the two can enable the laser to polish large and complex cylinders. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A flow chart of the laser polishing method for large and complex cylindrical surfaces;

[0038] Figure 2 Schematic diagram of laser polishing of large and complex cylindrical surfaces;

[0039] Figure 3 It is a schematic diagram of the projection of the sub-cylinder on the XY plane;

[0040] Figure 4 Schematic diagram of the maximum incident angle when laser polishing a sub-cylinder;

[0041] Figure 5 It is a schematic diagram of the end face of a cylindrical part and its divided sub-areas;

[0042] In the figure, 1. base, 2. axis moving module, 3. Y-axis moving module, 4. Z-axis moving module, 5. Y-axis rotation module, 6. large and complex cylindrical parts to be polished, 7. laser beam, 8. Y-axis scanning galvanometer, 9. X-axis scanning galvanometer, 10. telecentric field mirror. DETAILED DESCRIPTION

[0043] The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0044] like Figure 1 As shown, the present invention provides a laser polishing method for a large complex cylindrical surface, comprising the following steps:

[0045] S1. Construct a roughness database of laser polished surfaces;

[0046] S2. Determine the optional range of the laser defocus amount and the optional range of the incident angle according to the roughness database;

[0047] S3, dividing the complex cylindrical surface to be polished into a plurality of sub-cylinder surfaces based on the optional range of the laser defocus amount and the optional range of the incident angle;

[0048] S4. Polishing is performed on a plurality of sub-cylinder surfaces.

[0049] In this embodiment of the present invention, S1 includes the following sub-steps:

[0050] S11, when the defocus amount of the laser is 0 and the incident angle is 0°, polishing the planar substrate, and obtaining the optimal laser polishing parameters by an experimental optimization method, wherein the optimal laser polishing parameters include the pulse energy, pulse width, pulse frequency, scanning speed and scanning spacing of the laser;

[0051] S12. Based on the optimal laser polishing parameters, the roughness of the laser polished surface at different defocus amounts and different incident angles is determined through a full factorial experiment as a roughness database.

[0052] In S11, experimental optimization design method: the optimal parameters of a certain processing technology are obtained through experimental optimization design methods such as orthogonal or response surface.

[0053] In S12, according to the principle of equal step size, different defocus amounts (0≤f≤3mm or -3mm≤f≤0, i.e., positive defocus or negative defocus range, preferably positive defocus range) and incident angles (α≤50°) are selected as the horizontal values ​​of f and α, and other parameters are set to be the same as the optimal laser polishing parameters in S11.

[0054] In the embodiment of the present invention, in S2, the method for determining the optional range of the incident angle is: in the intervals formed by different defocus amounts and the intervals formed by different incident angles, the interval with the most consecutive values ​​is selected to determine the optional range of the incident angle;

[0055] In S2, the method for determining the optional range of the laser defocus amount is: determine the positive defocus amount optional range corresponding to the optional range of the incident angle, and determine whether there is a negative defocus amount optional range based on the positive defocus amount optional range; if there is a negative defocus amount optional range, determine the optional range of the laser defocus amount based on the positive defocus amount optional range and the negative defocus amount optional range; if there is no negative defocus amount optional range, determine the optional range of the laser defocus amount based on the positive defocus amount optional range.

[0056] When determining the optional range of the incident angle, for example, there are multiple values ​​of the laser incident angle and defocus amount that meet the polishing requirements obtained from the full factorial experiment, some of which are continuous, and some are separated by values ​​that do not meet the requirements, so that these values ​​that meet the requirements have multiple intervals formed by continuous values, and the number of continuous values ​​in each interval is also different. It is necessary to select the interval with the most continuous values ​​that meet the polishing requirements. In this way, the range of values ​​of the laser incident angle and defocus amount can be maximized, thereby increasing the area of ​​the sub-cylinders divided subsequently and reducing the number of sub-cylinders.

[0057] When determining the optional range of the laser defocus amount, the laser defocus amount is divided into positive and negative, and the positive defocus and negative defocus are symmetrical. If a certain positive defocus amount range meets the laser polishing requirements, the corresponding negative defocus amount range also meets the laser polishing requirements. For example, in the example, the positive defocus amount optional range corresponding to the optional range of the laser incident angle is f=0~1mm, including 0mm, then there is a negative defocus range, and the corresponding negative defocus range is f=0~-1mm, which also meets the polishing requirements, so according to the principle of symmetry of laser positive and negative defocus, f=-1~1mm can be selected as the final value range of the defocus amount that meets the polishing requirements. In the example, the positive defocus amount optional range corresponding to the optional range of the laser incident angle is f=1~2mm, excluding 0mm, then there is no negative defocus range, so f=1~2mm can be selected as the final value range of the defocus amount that meets the polishing requirements.

[0058] In this embodiment of the present invention, S3 includes the following sub-steps:

[0059] S31, dividing the complex cylindrical surface to be polished into a plurality of sub-areas;

[0060] S32. Based on the optional range of the laser defocus amount and the optional range of the incident angle, the plurality of sub-areas are divided into a plurality of sub-cylinders in sequence.

[0061] In S31, the complex cylindrical surface to be polished is divided into different sub-areas according to the curvature radius.

[0062] In the embodiment of the present invention, in S32, the constraint condition for dividing the plurality of sub-areas into a plurality of sub-cylinders is:

[0063] ;

[0064] ;

[0065] ;

[0066] ;

[0067] In the formula, is the radius of curvature of the ith sub-region, is the projection length of the arc side of the j-th sub-cylinder of the i-th sub-region in the horizontal direction, is the maximum value of the optional range of laser defocus, is the minimum value of the optional range of laser defocus, is the side length of the telecentric field mirror scanning range, is the projection length of the straight edge of the j-th sub-cylinder of the i-th sub-region in the longitudinal direction, is the maximum incident angle when the laser polishes the j-th sub-cylinder of the i-th sub-region, is the maximum value of the optional range of laser incident angle, is the curvature radius of the j-th sub-cylinder of the i-th sub-region, .

[0068] In this embodiment of the present invention, S4 includes the following sub-steps:

[0069] S41, rotating the longitudinal axis of the four-axis worktable so that the normal of the center point of the first sub-cylinder of the first sub-region is parallel to the vertical axis; moving the transverse axis and the longitudinal axis of the four-axis worktable so that the coordinate values ​​of the laser origin on the transverse axis and the longitudinal axis correspond to the coordinate values ​​of the center point of the first sub-cylinder of the first sub-region on the transverse axis and the longitudinal axis; controlling the vertical axis movement of the four-axis worktable to determine that the position of the laser focus on the vertical axis reaches the optimal vertical axis position;

[0070] S42, according to the projection area of ​​the first sub-cylinder of the first sub-region on the horizontal and vertical planes, controlling the size of the scanning area when the laser polishes the first sub-cylinder of the first sub-region, and completing the polishing process of the first sub-cylinder of the first sub-region;

[0071] S43, repeat S41-S42 to complete the polishing process on the remaining sub-cylindrical surfaces.

[0072] The present invention allows the laser to be polished with positive defocus, which can get rid of the problem of focal depth limitation of existing laser polishing methods, and can significantly reduce the number of divided sub-blocks to reduce the frequency of starting and stopping the moving workbench, thereby greatly improving processing efficiency.

[0073] In the embodiment of the present invention, in S41, the optimal vertical axis position The calculation formula is:

[0074] ;

[0075] In the formula, is the maximum value of the vertical axis coordinate of the first sub-cylinder in the first sub-region, is the minimum value of the Z coordinate of the first sub-cylinder in the first sub-region.

[0076] like Figure 2 As shown in the figure, a laser scanning galvanometer and a four-axis motion table (movement of the X, Y, and Z axes and rotation of the Y axis) are used to control the polishing path. This method is easy to control and operate, and can greatly improve the polishing efficiency while ensuring the polishing accuracy and stability of large and complex cylindrical surfaces.

[0077] In the laser scanning galvanometer and the four-axis motion workbench, the X-axis moving module 2 is placed on the base 1, the Y-axis moving module 3 is placed on the X-axis moving module 2, and the Z-axis moving module 4 is installed on the column set by the Y-axis moving module 3; the Y-axis rotation module 5 is installed on the Z-axis moving module 4 through a rotating shaft; the large and complex cylindrical part 6 to be polished is placed on the Y-axis rotation module 5; the Y-axis scanning galvanometer 8, the X-axis scanning galvanometer 9 and the far-field lens 10 constitute a laser scanning galvanometer, which is placed on the large and complex cylindrical part 6 to be polished; the laser beam 7 emitted from the laser is irradiated onto the processing surface of the large and complex cylindrical part 6 to be polished after passing through the laser scanning galvanometer for polishing.

[0078] like Figure 3 As shown, is the projection length of the arc edge of the j-th sub-cylinder of the i-th sub-region in the X-axis direction; is the projection length of the straight edge of the j-th sub-cylinder of the i-th sub-region in the Y-axis direction, are respectively the maximum and minimum values ​​of the Z coordinates of the first sub-cylinder in the first sub-region.

[0079] like Figure 4 As shown, is the maximum incident angle when the laser polishes the j-th sub-cylinder of the i-th sub-region.

[0080] This embodiment provides a specific example to illustrate the entire laser polishing method. This embodiment uses a TC4 titanium alloy complex cylindrical surface as the part to be polished. Figure 5 As shown, the polishing roughness requirement is 0.3~0.5μm; a fiber laser with a maximum average power of 60W, a maximum pulse energy of 1.5mJ, a wavelength of 1064nm, a pulse width of 2~500ns, and a frequency of 1~4000kHz is selected, equipped with a telecentric field mirror with a focusing spot diameter of 50μm, a focal length E of 160.3mm, a scanning range side length W of 100mm, and an XY scanning galvanometer, including the following steps:

[0081] (1) Establish a database of laser polishing surface roughness at different defocus values ​​f and incident angles α:

[0082] (i) The laser defocus f=0 and the incident angle α=0° were set to polish a flat TC4 titanium alloy plate (with the same surface texture characteristics as the complex cylindrical surface to be polished). The minimum roughness of laser polishing was obtained by orthogonal experimental optimization design to be 0.09 μm. The corresponding laser polishing parameters (optimal laser parameters) were as follows: pulse energy of 0.1 mJ, pulse width of 250 ns, pulse frequency of 400 kHz, scanning speed of 8000 mm / s, and scanning spacing of 20 μm.

[0083] (ii) Select a step size of 0.5 mm and 0 ≤ f ≤ 3 mm (i.e., select f = 0, 0.5, 1.0, 1.5, 2.0, 2.5 or 3.0 mm) and a step size of 10° and 0° ≤ α ≤ 50° (i.e., select α = 0°, 10°, 20°, 30°, 40° or 50°) as the horizontal values ​​of f and α, respectively. Set other parameters to be the same as the optimal laser polishing parameters in (i) (i.e., pulse energy of 0.1 mJ, pulse width of 250 ns, pulse frequency of 400 kHz, scanning speed of 8000 mm / s, and scanning spacing of 20 μm). The roughness values ​​of the laser polished surface under different defocus values ​​f and different incident angles α are obtained through full factor experiments, as shown in Table 1.

[0084] Table 1

[0085]

[0086] (2) Determine the selectable range of laser defocus f and incident angle α: In the database (Table 1) described in (1), select the roughness The values ​​of laser incident angle α and defocus f corresponding to less than 0.3μm; based on α and f that meet the requirements, firstly, according to the principle of the largest number of consecutive values ​​of α and f (when f is 0, 0.5 and 1.0 and α is 0°, 10°, 20°, 30° and 40° in Table 1), the optional range of α is determined to be α=0°~40°, and then according to the f corresponding to α=0°~40° (f=0~1mm) and the principle of symmetry of positive and negative defocus, the optional range of f is determined to be f=-1mm~1mm.

[0087] (3) Divide sub-regions and sub-cylinders according to given conditions: according to the radius of curvature =30mm, =40mm, =30mm, =50mm, =30mm Divide the TC4 titanium alloy complex cylindrical parts to be polished into , , , and The five different sub-regions are divided into different sub-cylinders according to f = -1mm~1mm and α = 0°~40° determined in (2).

[0088] (4) Control the movement or rotation of the four-axis worktable according to the spatial position of the sub-cylinder: control the Y-axis rotation of the four-axis worktable so that the normal of the center point of the first sub-cylinder in the first sub-region is parallel to the Z-axis; control the X-axis and Y-axis movement of the four-axis worktable so that the coordinate values ​​of the laser origin (i.e., the center point of the telecentric field mirror) on the X-axis and Y-axis are equal to the coordinate values ​​of the center point of the first sub-cylinder in the first sub-region on the X-axis and Y-axis respectively; control the Z-axis movement of the four-axis worktable so that the position of the laser focus on the Z-axis is Z= .in, and are respectively the maximum and minimum values ​​of the Z coordinates of the first sub-cylinder in the first sub-region.

[0089] (5) Adjusting the size of a single laser scanning area according to the projection area of ​​the sub-cylinder: According to the projection area of ​​the first sub-cylinder of the first sub-region on the XY plane, the size of the scanning area when laser polishing the first sub-cylinder of the first sub-region is adjusted to: , start the laser to polish the first sub-cylinder of the first sub-area.

[0090] (6) Repeat steps (4) and (5) to perform laser polishing on the sub-cylinder surfaces of the remaining sub-regions in turn until all sub-cylinder surfaces have been processed.

[0091] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A laser polishing method for large complex cylindrical surfaces, characterized in that: The following steps are involved: S1. Construct a roughness database of laser polished surfaces; S2. Determine the optional range of the laser defocus amount and the optional range of the incident angle according to the roughness database; S3, dividing the complex cylindrical surface to be polished into a plurality of sub-cylinder surfaces based on the optional range of the laser defocus amount and the optional range of the incident angle; S4, performing polishing treatment on a plurality of sub-cylinder surfaces; The S3 comprises the following sub-steps: S31, dividing the complex cylindrical surface to be polished into a plurality of sub-areas; S32, based on the optional range of the laser defocus amount and the optional range of the incident angle, sequentially dividing the plurality of sub-areas into a plurality of sub-cylinders; In S32, the constraint condition for dividing the plurality of sub-areas into a plurality of sub-cylinders is: ； ； ； ； In the formula, is the radius of curvature of the ith sub-region, is the projection length of the arc side of the j-th sub-cylinder of the i-th sub-region in the horizontal direction, is the maximum value of the optional range of laser defocus, is the minimum value of the optional range of laser defocus, is the side length of the telecentric field mirror scanning range, is the projection length of the straight edge of the j-th sub-cylinder of the i-th sub-region in the longitudinal direction, is the maximum incident angle when the laser polishes the j-th sub-cylinder of the i-th sub-region, is the maximum value of the optional range of laser incident angle, is the radius of curvature of the j-th sub-cylinder in the i-th sub-region.

2. The laser polishing method for large complex cylindrical surfaces according to claim 1, characterized in that: The S1 comprises the following sub-steps: S11, when the defocus amount of the laser is 0 and the incident angle is 0°, polishing the planar substrate, and obtaining the optimal laser polishing parameters by an experimental optimization method, wherein the optimal laser polishing parameters include the pulse energy, pulse width, pulse frequency, scanning speed and scanning spacing of the laser; S12. Based on the optimal laser polishing parameters, the roughness of the laser polished surface at different defocus amounts and different incident angles is determined through a full factorial experiment as a roughness database.

3. The laser polishing method for large complex cylindrical surfaces according to claim 1, characterized in that: In S2, the method for determining the optional range of the incident angle is: in the intervals formed by different defocus amounts and the intervals formed by different incident angles, the interval with the most consecutive values ​​is selected to determine the optional range of the incident angle; In S2, the method for determining the optional range of the laser defocus amount is: determining the positive defocus amount optional range corresponding to the optional range of the incident angle, and determining whether there is a negative defocus amount optional range according to the positive defocus amount optional range; If there is a negative defocus amount optional range, determining the laser defocus amount optional range according to the positive defocus amount optional range and the negative defocus amount optional range; If there is no optional range of negative defocus amount, the optional range of laser defocus amount is determined according to the optional range of positive defocus amount.

4. The laser polishing method for large complex cylindrical surfaces according to claim 1, characterized in that: The S4 comprises the following sub-steps: S41, rotating the longitudinal axis of the four-axis worktable so that the normal of the center point of the first sub-cylinder of the first sub-region is parallel to the vertical axis; moving the transverse axis and the longitudinal axis of the four-axis worktable so that the coordinate values ​​of the laser origin on the transverse axis and the longitudinal axis correspond to the coordinate values ​​of the center point of the first sub-cylinder of the first sub-region on the transverse axis and the longitudinal axis; controlling the vertical axis movement of the four-axis worktable to determine that the position of the laser focus on the vertical axis reaches the optimal vertical axis position; S42, according to the projection area of ​​the first sub-cylinder of the first sub-region on the horizontal and vertical planes, controlling the size of the scanning area when the laser polishes the first sub-cylinder of the first sub-region, and completing the polishing process of the first sub-cylinder of the first sub-region; S43, repeat S41-S42 to complete the polishing process on the remaining sub-cylindrical surfaces.

5. The laser polishing method for large complex cylindrical surfaces according to claim 4, characterized in that: In S41, the optimal vertical axis position The calculation formula is: ； In the formula, is the maximum value of the vertical axis coordinate of the first sub-cylinder in the first sub-region, is the minimum value of the Z coordinate of the first sub-cylinder in the first sub-region.

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