Ultra-precision polishing method for gear

Abstract

The invention provides an ultra-precision polishing method for a gear, which comprises the following steps: carrying out laser rough polishing on the tooth surface of the gear, and then carrying out laser-assisted chemical mechanical polishing; and in the laser-assisted chemical mechanical polishing process, the chemical polishing solution is dripped into the tooth surface of the gear dynamically, and laser parameters are controlled so that the temperature of the tooth surface can be maintained at 35-85 DEG C. According to the ultra-precision polishing method for the gear, uniform nanoscale ultra-precision polishing of the whole tooth profile of the gear can be achieved, the surface roughness is remarkably reduced, the polishing efficiency can be improved, the overall machining efficiency is improved by 50% or above compared with that of a traditional technology, gear surface damage can be reduced, residual stress and microcracks are avoided, and the performance of the gear is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of surface precision machining, and particularly relates to a super-precision polishing method of a gear. BACKGROUND

[0002] Gears are the core basic components in mechanical transmission systems, and are widely used in the fields of aerospace, automobile industry, precision instruments, etc. The surface quality of gears, especially the roughness, waviness and surface integrity of the tooth surface, directly determines the transmission efficiency, running noise, fatigue life and working reliability of the entire transmission system. Therefore, in the last process of gear manufacturing, it is usually necessary to carry out finishing and polishing to obtain a high-quality surface.

[0003] At present, the commonly used gear finishing methods in industry mainly include traditional mechanical polishing and electrolytic polishing, etc. However, these traditional methods have many limitations. Traditional mechanical polishing, such as using abrasive or abrasive belt for grinding, has poor accessibility of the tool for the regions with complex geometry such as gear tooth root and transition curve, and is easy to cause machining interference, resulting in uneven polishing. In addition, mechanical contact will introduce residual stress and surface micro-cracks, which may damage the fatigue performance of the part. Electrolytic polishing is a non-contact machining method, but it has high requirements for the profile consistency of the gear. In the deep concave area of the tooth surface, it is easy to cause over-corrosion or insufficient polishing due to uneven current density distribution. At the same time, this method usually needs to use strong acid or strong base as electrolyte, which has environmental pollution and safety risk, so its application is limited.

[0004] In order to overcome the shortcomings of traditional methods, some advanced non-contact or micro-damage polishing technologies have been developed, such as laser polishing and chemical mechanical polishing.

[0005] Laser polishing utilizes a high-energy-density laser beam to melt a very thin layer of material on the surface in a very short time. Under the action of surface tension, the molten metal will flow from the convex peak to the concave valley, thereby rapidly reducing the surface roughness. This method has the advantages of no tool wear and can process complex curved surfaces. However, single laser polishing technology also has obvious defects when applied to metal gears, especially high-hardness materials. Improper heat input control is easy to cause the formation of a relatively thick micro-molten recast layer and heat-affected zone on the surface, and even micro-pores and micro-cracks, which will seriously affect the mechanical properties and fatigue strength of the gear. In addition, for surfaces with larger initial roughness, laser polishing requires higher energy input, resulting in lower efficiency.

[0006] Chemical mechanical polishing is an ultra-precision machining technology combining the synergistic effect of chemical corrosion and mechanical grinding, which can realize global planarization and obtain a nanoscale ultra-smooth and low-damage surface. Although its machining precision is high, its shortcomings are also very prominent, mainly including high cost of equipment and consumables, complex process and the need for precise control, and low overall efficiency, which is difficult to meet the production requirements of gears in large quantities and high efficiency.

[0007] In summary, the existing gear polishing technology, whether it is a traditional method or a single advanced machining method, is difficult to simultaneously meet all the requirements of efficient, high-precision, low-damage and uniform polishing of complex gear surfaces. Therefore, there is an urgent need in the field to develop a new ultra-precision polishing method that can efficiently, uniformly and low-damage polish the full gear surface. SUMMARY

[0008] The present application provides an ultra-precision polishing method for gears to solve the defects of the existing gear polishing technology that is difficult to simultaneously meet the requirements of efficient, high-precision, low-damage and uniform polishing of complex gear surfaces, and to realize efficient, uniform and low-damage ultra-precision polishing of the full gear surface.

[0009] The present application provides a polishing method for gears, comprising: laser rough polishing of the gear, and then laser-assisted chemical mechanical polishing; during the laser-assisted chemical mechanical polishing, dynamically dropping chemical polishing liquid on the gear, and controlling the laser parameters to maintain the temperature of the gear at 35-85℃.

[0010] In the present application, the temperature of the gear is maintained at 35-85℃, for example, it can be 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃ or 85℃, and specific point values between the above point values. Due to the limitation of space and the consideration of simplicity, the present application does not exhaustively list the specific point values included in the range.

[0011] The ultra-precision polishing method for gears provided by the present application first performs laser rough polishing on the gear, and then performs laser-assisted chemical mechanical polishing. Through laser rough polishing, the macroscopic unevenness (such as turning and milling tool marks) on the gear surface can be efficiently removed, and the metal surface is activated to prepare for subsequent fine polishing. Then, through laser-assisted chemical mechanical polishing, the chemical reaction rate is accurately controlled by laser temperature control (35-85℃), and mechanical grinding is used to realize nanoscale fine material removal. The polishing method of the present application can realize efficient, uniform and low-damage ultra-precision polishing of complex gear surfaces.

[0012] The laser parameter in the laser-assisted chemical mechanical polishing process is controlled in the present application, and the laser parameter is as follows: power 10-50 W, scanning speed 3000-6000 mm / s, and repetition frequency 10-10000 Hz.

[0013] In the present application, the laser parameter is controlled as follows: power 10-50 W, for example, 10 W, 15 W, 20 W, 25 W, 30 W, 35 W, 40 W, 45 W or 50 W, and specific point values between the above point values, and the specific point values included in the range are not listed in the present application due to the limited length and the consideration of simplicity.

[0014] In the present application, the laser parameter is controlled as follows: scanning speed 3000-6000 mm / s, for example, 3000 mm / s, 3500 mm / s, 4000 mm / s, 4500 mm / s, 5000 mm / s, 5500 mm / s or 6000 mm / s, and specific point values between the above point values, and the specific point values included in the range are not listed in the present application due to the limited length and the consideration of simplicity.

[0015] In the present application, the laser parameter is controlled as follows: repetition frequency 10-10000 Hz, for example, 10 Hz, 50 Hz, 100 Hz, 200 Hz, 500 Hz, 800 Hz, 1000 Hz, 2000 Hz, 3000 Hz, 4000 Hz, 5000 Hz, 6000 Hz, 7000 Hz, 8000 Hz, 9000 Hz or 10000 Hz, and specific point values between the above point values, and the specific point values included in the range are not listed in the present application due to the limited length and the consideration of simplicity.

[0016] In the present application, the laser parameter in the laser-assisted chemical mechanical polishing process is controlled in a specific range, so that the gear temperature of 35-85 DEG C can be stably and accurately realized, and then the synergistic effect of the laser thermal effect and the chemical reaction can be realized, the reaction efficiency of the chemical polishing liquid can be effectively accelerated, the thermal damage of the material surface caused by the excessively high temperature or the failure of the polishing liquid can be avoided, and thus the stability of the fine polishing process and the final surface quality are ensured.

[0017] In the present application, the laser parameter in the laser-assisted chemical mechanical polishing process is controlled in a specific range, so that the gear temperature of 35-85 DEG C can be stably and accurately realized, and then the synergistic effect of the laser thermal effect and the chemical reaction can be realized, the reaction efficiency of the chemical polishing liquid can be effectively accelerated, the thermal damage of the material surface caused by the excessively high temperature or the failure of the polishing liquid can be avoided, and thus the stability of the fine polishing process and the final surface quality are ensured.

[0018] In the present application, the Y-axis feed amount is 0.3-0.6mm, for example, it can be 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm or 0.6mm, and the specific point values between the above point values, limited to the length and for the sake of simplicity, the present application will not be listed in the range of specific point values included.

[0019] In the present application, the flow rate is 40-60ml / min, for example, it can be 40ml / min, 45ml / min, 50ml / min, 55ml / min or 60ml / min, and the specific point values between the above point values, limited to the length and for the sake of simplicity, the present application will not be listed in the range of specific point values included.

[0020] In the present application, the polishing pressure is 0.05-0.2MPa, for example, it can be 0.05MPa, 0.06MPa, 0.07MPa, 0.08MPa, 0.09MPa, 0.1MPa, 0.11MPa, 0.12MPa, 0.13MPa, 0.14MPa, 0.15MPa, 0.16MPa, 0.17MPa, 0.18MPa, 0.19MPa or 0.2MPa, and the specific point values between the above point values, limited to the length and for the sake of simplicity, the present application will not be listed in the range of specific point values included.

[0021] In the present application, the polishing head rotation speed is 100-1200rpm, for example, it can be 100rpm, 200rpm, 300rpm, 400rpm, 500rpm, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, 1100rpm or 1200rpm, and the specific point values between the above point values, limited to the length and for the sake of simplicity, the present application will not be listed in the range of specific point values included.

[0022] In the present application, the polishing time is 20-40s, for example, it can be 20s, 25s, 30s, 35s or 40s, and the specific point values between the above point values, limited to the length and for the sake of simplicity, the present application will not be listed in the range of specific point values included.

[0023] The present application optimizes the specific mechanical movement and fluid parameters in the process of laser-assisted chemical mechanical polishing, the constant polishing pressure and the precise feed amount can ensure uniform material removal for the gear profile; and the controlled polishing liquid flow rate, polishing head rotation speed and polishing time ensure that fresh chemical reactants can be continuously supplied and reaction products can be timely removed, and match the laser heating, mechanical grinding effect, together to achieve efficient and uniform polishing of the entire gear surface.

[0024] According to the ultra-precision polishing method for gears of the present invention, during the laser-assisted chemical mechanical polishing process, the polishing head used in the chemical mechanical polishing is a flexible polishing wheel or polishing belt, the material of which includes one or more of polyurethane or polyolefin.

[0025] This invention utilizes the adaptability of flexible materials to solve the problem of traditional rigid tools failing to fully conform to the complex curved surfaces of gears. The flexible polishing head can adapt to changes in the tooth profile, ensuring good and uniform contact with the tooth surface throughout the polishing process. This avoids over-polishing or under-polishing in localized areas, significantly improving the uniformity and consistency of polishing complex tooth surfaces.

[0026] According to the ultra-precision polishing method for gears of the present invention, during the laser rough polishing process, the laser parameters are controlled as follows: power 100-2000W, scanning speed 100-6000mm / s, repetition frequency 50-300kHz, and spot overlap rate 50%-90%.

[0027] This invention optimizes the specific process parameters of laser rough polishing, thereby significantly reducing the initial surface roughness (such as removing tool marks and burrs) in a short time, while creating a more uniform and activated substrate for subsequent fine polishing, thus improving the overall efficiency of the entire composite process.

[0028] According to the ultra-precision polishing method for gears of the present invention, a protective gas is coaxially blown during the laser rough polishing process. The protective gas includes N2 or Ar. This effectively prevents the gear metal surface from reacting with oxygen in the air and oxidizing under the high temperature generated by the laser, ensuring the cleanliness of the surface after rough polishing and the activity of subsequent chemical reactions.

[0029] According to the ultra-precision polishing method for gears of the present invention, during the laser rough polishing process, the laser melting depth is ≤20um (preferably 10-20um).

[0030] This invention limits the melting depth, which can effectively avoid the formation of an excessively thick recast layer and an excessively large heat-affected zone, thereby maximizing the preservation of the original excellent mechanical properties and metallographic structure of the gear matrix material, such as hardness, wear resistance and fatigue strength, and achieving the goal of low-damage processing.

[0031] The ultra-precision polishing method for gears according to the present invention includes the following steps: S1. Clamping and pretreatment: Clamp the gear to be polished on the multi-axis linkage CNC worktable and clean and dry it; S2. Laser rough polishing of the gear: control the laser parameters as follows: power 100-2000W, scanning speed 100-6000mm / s, repetition frequency 50-300kHz, and light spot overlap rate 50%-90%; adopt coaxial blowing of protective gas, which includes N2 or Ar; laser melting depth ≤20um; S3. Laser-assisted chemical mechanical polishing of the gear: during the laser-assisted chemical mechanical polishing process, dynamically drop the chemical polishing liquid on the gear, and control the laser parameters to maintain the temperature of the gear at 35-85℃; during the laser-assisted chemical mechanical polishing process, control the laser parameters as follows: power 10-50W, scanning speed 3000-6000mm / s, and repetition frequency 10-10KHz; the chemical mechanical polishing adopts constant pressure polishing, Y-axis feed amount is 0.3-0.6mm, flow rate is 40-60ml / min, polishing pressure is 0.05-0.2MPa, polishing head rotation speed is 100-1200rpm, and polishing time is 20-40s; the polishing head adopted by the chemical mechanical polishing is a flexible polishing wheel or a polishing belt, and the material thereof includes one or more of polyurethane or polyolefin; S4. Post-processing: after polishing, the gear is put into water to terminate the reaction, then ultrasonic cleaning is performed, and then dehydration and drying are performed.

[0032] The formula of the chemical polishing liquid is adjusted according to the gear base material (such as steel, copper alloy, titanium alloy, etc.) to ensure the best polishing effect and controllable corrosion.

[0033] According to the ultra-precision polishing method of the gear, the material of the gear is carburized steel; the chemical polishing liquid includes nanoscale abrasive, oxidizing agent, complexing agent and water; and the pH value of the chemical polishing liquid is 2-5. The components in the formula synergistically act to produce efficient and controllable chemical corrosion and complex removal effect on the carburized steel under the condition of laser-assisted heating, realize the high matching of chemical action and mechanical grinding, and thus realize efficient and precise polishing of the high-hardness carburized steel gear.

[0034] In some specific embodiments, the material of the gear is 18Cr2Ni4WA gear steel.

[0035] Preferably, the nanoscale abrasive is SiO2, the particle size is 20-100nm, and the mass percentage content is 1-3%, preferably 1.5-2.5%; the oxidizing agent is H2O2, the mass percentage content is 0.1-1%, preferably 0.3-0.8%; the complexing agent is sodium citrate, the mass percentage content is 0.1-1%, preferably 0.5-0.8%, and the pH value is adjusted to 2-5.

[0036] In some specific embodiments, the nanoscale abrasive is SiO2 with a particle size of 20-100 nm and a mass percentage of 2%; the oxidizing agent is H2O2 with a mass percentage of 0.5%; and the complexing agent is sodium citrate with a mass percentage of 0.67%, and the pH value is adjusted to 3.

[0037] In the process of laser-assisted chemical mechanical polishing, the laser power is controlled to be 20-30 W, the scanning speed is 5000-6000 mm / s, and the repetition frequency is 900-1000 Hz, so that the temperature of the gear is maintained at 55-75 DEG C.

[0038] The present application provides a kind of gear ultra-precision polishing method, by the synergistic effect of laser rough polishing and laser-assisted chemical mechanical polishing, first utilize laser rough polishing to remove the macroscopic unevenness of gear surface and activate surface, then utilize laser-assisted chemical mechanical polishing to carry out fine smoothing treatment.Compared with the prior art, the present application combines the advantages of two processes, overcomes the limitations of single technology, and has the following remarkable beneficial effects: (1) ultra-high precision and uniformity: can realize uniform nanoscale ultra-precision polishing of gear tooth top, tooth surface, tooth root and other complex whole tooth profile, significantly reduce the surface roughness. (2) high efficiency: the laser treatment of the previous sequence greatly improves the material removal rate of the subsequent chemical mechanical polishing, so that the overall processing efficiency is improved by more than 50% compared with single chemical mechanical polishing process. (3) low damage: using the micro-removal method of "softening and removing", avoiding macroscopic cutting force, basically not introducing residual stress and micro-cracks, thereby greatly improving the fatigue performance and reliability of the gear. (4) high accessibility: using the flexible focusing characteristics of laser beam, effectively solving the machining interference problem of traditional mechanical tools in complex areas such as tooth root, realizing the no-dead-angle polishing of the whole surface of the gear. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0040] Figure 1 is the surface topography diagram of the gear before polishing in example 1 provided by the present application.

[0041] Figure 2 is the surface topography diagram of the gear after polishing in example 1 provided by the present application.

[0042] Figure 3is the surface topography diagram of the gear polished in the present application.

[0043] Figure 4 is the surface topography diagram of the gear polished in the present application. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0045] Embodiment 1 The present embodiment provides a method for ultra-precision polishing of a gear, the gear being a gear made of 18Cr2Ni4WA gear steel, the test equipment adopting a gear chemical mechanical polishing machine + laser auxiliary heating system, the X and Y axes selecting a sliding table module, the Z axis adopting a cast iron + motor lead screw structure, and a Cartesian coordinate system being constructed; the tool holder rotating shaft B selecting a high-precision composite bearing to meet the requirements of accurate positioning and high rigidity of the tool helix angle; the workpiece indexing shaft C adopting a servo torque motor to ensure the accuracy of indexing positioning; and the main shaft motor selecting a large-torque direct-current brushless motor with a rated torque of 1.28 N*m and a maximum speed of 3000 rpm, which can meet the linear speed requirements of the soft polyurethane polishing head.

[0046] The method comprises the following steps: S1. Clamping and pretreatment: clamp the gear to be polished on the multi-axis linkage numerical control workbench and perform cleaning and drying.

[0047] S2. Laser rough polishing: scan the gear tooth surface to be polished by a laser beam according to a preset path, and set the laser parameters to make the surface layer of the tooth surface micro-fuse to form a polishing modification layer without significant ablation or deep melting, and the laser fusion depth is controlled within 10-20 um.

[0048] The laser used for laser rough polishing is a fiber laser, and the laser parameters are set as follows: power 160 W, scanning speed 4500 mm / s, repetition frequency 200 kHz, and spot overlap rate 80%.

[0049] The laser rough polishing aims to quickly remove the turning and milling tool marks and burrs to achieve rough polishing, and the laser action causes defects in the surface lattice to activate the surface and provide better reaction conditions for subsequent chemical mechanical polishing.

[0050] The laser scanning path in the laser rough polishing is generated by a numerical control system according to a gear CAD model, so as to ensure that the laser beam can cover all tooth surfaces and the beam vector always keeps a constant angle with the normal of the tooth surface.

[0051] In the laser rough polishing process, the coaxial blowing of the protective gas N2 is adopted to prevent the oxidation of the metal surface.

[0052] S3. Laser-assisted chemical mechanical polishing: after the laser polishing treatment, laser-assisted chemical mechanical polishing is performed, a polishing head is used and a polishing liquid is supplied, the gear tooth surface is subjected to chemical mechanical polishing, and in the tooth surface polishing, the laser head is moved downward and aligned with the side surface of the tooth surface to synchronously heat the tooth surface polishing area. The polishing liquid used is a mixed solution of 2% nanoscale abrasive (SiO2, particle size of 20-100 nm), 0.5% oxidant H2O2, 0.67% complexing agent sodium citrate and deionized water, and the pH value is adjusted to 3.

[0053] The polishing liquid is dynamically dropped onto the tooth surface. The polishing head for the laser-assisted chemical mechanical polishing is a flexible polishing wheel made of polyurethane; constant pressure polishing is adopted (polishing pressure is 0.1 MPa), the Y-axis feed amount is 0.52 mm, the flow rate is 50 ml / min, the polishing head rotation speed is 300 rpm, and the polishing time is 30 s.

[0054] In the laser-assisted chemical mechanical polishing, the laser-assisted heating laser parameter is set as: power 25 W, scanning speed 6000 mm / s, and repetition frequency 1000 Hz, so as to control the temperature of the tooth surface between 55-75℃ and more effectively improve the efficiency of the chemical mechanical polishing.

[0055] S4. Post-processing: the gear is taken out and immediately put into deionized water to terminate the reaction, then ultrasonic cleaning is performed to completely remove the residual liquid, anhydrous ethanol is used for dehydration and drying, and the surface roughness and morphology are detected.

[0056] Figure 1 The surface morphology of the gear after the polishing method of the embodiment is shown, and the surface three-dimensional roughness Sa value is 40.4 nm. Figure 2 The surface morphology of the gear after the polishing method of the embodiment is shown, and the surface three-dimensional roughness Sa value is 40.4 nm.

[0057] Comparative Example 1 The comparative example provides a polishing method of a gear, which is different from the embodiment 1 in that only steps S1 and S2 are included, and steps S3 and S4 are not included.

[0058] Figure 3 The surface morphology of the gear after the polishing method of the comparative example is shown, and the surface three-dimensional roughness Sa value is 185 nm.

[0059] Comparative Example 2 The present comparative example provides a polishing method of a gear, comprising the following steps: S1. Clamping and pretreatment: clamp the gear to be polished on a multi-axis linkage numerical control workbench, and clean and dry.

[0060] S2. Chemical mechanical polishing: after laser polishing treatment, use a polishing head and supply polishing liquid to perform chemical mechanical polishing on the gear tooth surface. The polishing liquid used is the same as in Example 1, and the polishing parameters are different from those in Example 1 in that the polishing time is 60 s.

[0061] S3. Post-treatment: remove the gear and immediately place it in deionized water to terminate the reaction, then perform ultrasonic cleaning to completely remove residual chemicals, dehydrate with anhydrous ethanol, and dry, and detect the surface roughness and morphology.

[0062] Figure 4 The gear surface morphology after the gear is polished by the polishing method of the present comparative example is shown, and the surface three-dimensional roughness Sa value is 65 nm.

[0063] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for ultra-precision polishing of gears, characterized in that, include: The gear is subjected to laser rough polishing, followed by laser-assisted chemical mechanical polishing. During the laser-assisted chemical mechanical polishing process, chemical polishing liquid is dynamically dripped onto the gear, and the laser parameters are controlled to maintain the temperature of the gear at 35-85℃.

2. The ultra-precision polishing method for gears according to claim 1, characterized in that, During laser-assisted chemical mechanical polishing, the laser parameters are controlled as follows: power 10-50W, scanning speed 3000-6000mm / s, and repetition frequency 10-10000Hz.

3. The ultra-precision polishing method for gears according to claim 1 or 2, characterized in that, During laser-assisted chemical mechanical polishing (CMP), constant pressure polishing is used, with a Y-axis feed rate of 0.3-0.6 mm, a flow rate of 40-60 ml / min, a polishing pressure of 0.05-0.2 MPa, a polishing head rotation speed of 100-1200 rpm, and a polishing time of 20-40 s.

4. The ultra-precision polishing method for gears according to any one of claims 1-3, characterized in that, In the process of laser-assisted chemical mechanical polishing, the polishing head used in chemical mechanical polishing is a flexible polishing wheel or polishing belt, the material of which includes one or more of polyurethane or polyolefin.

5. The ultra-precision polishing method for gears according to any one of claims 1-4, characterized in that, During the laser rough polishing process, the laser parameters are controlled as follows: power 100-2000W, scanning speed 100-6000mm / s, repetition frequency 50-300kHz, and spot overlap rate 50%-90%.

6. The ultra-precision polishing method for gears according to any one of claims 1-5, characterized in that, During the laser rough polishing process, a protective gas is blown coaxially, and the protective gas includes N2 or Ar.

7. The ultra-precision polishing method for gears according to any one of claims 1-6, characterized in that, During laser rough polishing, the laser melting depth is ≤20um.

8. The ultra-precision polishing method for gears according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Clamping and pretreatment: Clamp the gear to be polished on the multi-axis linkage CNC worktable and clean and dry it; S2. Perform laser rough polishing on the gears: control the laser parameters as follows: power 100-2000W, scanning speed 100-6000mm / s, repetition frequency 50-300kHz, spot overlap rate 50%-90%; use coaxial blowing of protective gas, the protective gas including N2 or Ar; laser melting depth ≤20um; S3. Laser-assisted chemical mechanical polishing (CMP) of the gears: During CMP, the chemical polishing slurry is dynamically dripped onto the gears, and the laser parameters are controlled to maintain the gear temperature at 35-85℃. The laser parameters are controlled as follows: power 10-50W, scanning speed 3000-6000mm / s, repetition frequency 10-10000Hz. Constant pressure polishing is used, with a Y-axis feed of 0.3-0.6mm, flow rate of 40-60ml / min, polishing pressure of 0.05-0.2MPa, polishing head rotation speed of 100-1200rpm, and polishing time of 20-40s. The polishing head used in CMP is a flexible polishing wheel or polishing belt, made of one or more materials including polyurethane or polyolefin. S4. Post-treatment: After polishing, the gears are placed in water to stop the reaction, then ultrasonically cleaned, dehydrated and dried.

9. The ultra-precision polishing method for gears according to any one of claims 1-8, characterized in that, The gear is made of carburized steel; the chemical polishing solution includes nano-sized abrasives, oxidant, complexing agent and water; the pH value of the chemical polishing solution is 2-5; Preferably, the nano-abrasive is SiO2 with a particle size of 20-100nm and a mass percentage of 1-5%; the oxidant is H2O2 with a mass percentage of 0.5-5%; and the complexing agent is sodium citrate with a mass percentage of 0.5-2%.

10. The ultra-precision polishing method for gears according to claim 9, characterized in that, During laser-assisted chemical mechanical polishing, the laser power is controlled at 20-30W, the scanning speed at 5000-6000mm / s, and the repetition frequency at 900-1000Hz, so that the temperature of the gear is maintained at 55℃-75℃.

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