Technological method for improving machining precision of external gear

Abstract

The invention provides a process method for improving the machining precision of an external gear. The process method comprises the following steps: S1, preparing materials; s2, rough machining; s3, heat treatment; s4, the gear blank is subjected to semi-finish machining; s5, gear blank rough gear hobbing is carried out; s6, gear blank finish machining; s7, first-time accurate gear grinding machining is carried out; s8, surface hardening treatment; s9, second-time accurate gear grinding machining is carried out; and S10, finishing and deburring are conducted. By improving the process method, the manufacturing precision and efficiency of the high-precision gear are effectively improved, the manufacturing cost of the high-precision gear is reduced, and the product quality of the high-precision gear is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of gear processing and manufacturing, and specifically relates to a process method for improving the machining accuracy of external gears. The accuracy of the machined gears can reach above grade 3. Background Art

[0002] As a key component in the mechanical transmission system, the machining accuracy and surface roughness of gears directly affect the transmission efficiency, noise, and service life. Traditional gear machining methods such as hobbing and shaping can meet certain accuracy requirements, but in the manufacturing of high-precision gears, there are still problems of insufficient machining accuracy and relatively high surface roughness. In the prior art, finishing processes such as gear grinding and honing are usually used to improve the accuracy and surface quality of gears, but these methods have disadvantages such as low machining efficiency and high costs. In view of this, the following improved technical solutions are proposed. Summary of the Invention

[0003] The technical problem solved by the present invention: Provide a process method for improving the machining accuracy of external gears, and solve the technical problems of low manufacturing efficiency, high cost, and poor quality of high-precision gears.

[0004] The technical solution adopted by the present invention: A process method for improving the machining accuracy of external gears, including the following steps: S1. Prepare materials; S2. Rough machining; S3. Heat treatment; S4. Semi-finishing of the gear blank; S5. Rough hobbing of the gear blank; S6. Finishing of the gear blank; S7. First precision gear grinding; S8. Surface hardening treatment; S9. Second precision gear grinding; S10. Deburring and finishing.

[0005] Further: In step S2, the method of leaving uniform allowances on each outer shape and inner hole is adopted to ensure the stability of the basic shape and dimensions of the gear blank of the gear part.

[0006] Further: In step S3, the gear blanks made of stainless steel are treated by solution + aging heat treatment to ensure that the matrix hardness of the gear blanks is not less than 40HRC.

[0007] Further: Step S4 includes the following steps:

[0008] S401. Release and eliminate the residual stress generated inside the gear blank during heat treatment;

[0009] S402. Remove the excess dimensions of the gear blank;

[0010] S403. Improve the surface roughness or oxidation problem of the gear blank after heat treatment;

[0011] S404. Remove the hardened layer and oxidation layer generated by heat treatment through semi-finishing;

[0012] S405. Control the machining allowance during semi-finishing;

[0013] S406. Semi-finishing reduces machining time, improves machining efficiency, and ensures machining dimensions.

[0014] Furthermore: In step S5, a CNC hobbing machine is used for rough tooth cutting. By optimizing the hobbing process parameters, machining errors are reduced.

[0015] Furthermore: Step S6 includes the following steps:

[0016] S601. Establish a finishing reference, ensuring that the finishing reference coincides with the design reference and the measurement and inspection reference in height;

[0017] S602. The clamping and positioning are accurate, ensuring that the clamping and positioning reference coincides with the equipment machining reference; High-precision tools are used, and the tools are regularly calibrated and replaced to ensure that the machining accuracy meets the design requirements of the workpiece; High-precision equipment is used, and real-time monitoring and compensation are carried out through a grating scale to ensure the machining accuracy and geometric dimension stability of the workpiece, and to prepare a good machining reference for finishing the teeth.

[0018] Furthermore: Step S7 includes the following steps:

[0019] S701. Use a high-precision gear grinding machine to ensure the geometric accuracy, rigidity, and stability of the machine tool;

[0020] S702. Select a suitable grinding wheel according to the gear material and hardness, dress the grinding wheel, and maintain the tooth profile, helix angle accuracy, and sharpness of the grinding wheel;

[0021] S703. Use a high-precision fixture to ensure accurate clamping and positioning of the gear workpiece, and ensure the firm clamping of the gear workpiece;

[0022] S704. Optimize the machining parameters according to the gear material and accuracy, reasonably set the grinding speed, feed rate, and cutting depth to avoid overheating and burning of the gear workpiece;

[0023] S705. Pay attention to cooling and lubrication to ensure effective cooling of the gear workpiece during grinding and sufficient flushing of the grinding chips, so that the finishing allowance in the common normal direction of the gear is 0.10 - 0.15 mm.

[0024] Furthermore: In step S8, the carbonitriding technology is used to increase the surface hardness of the gear, making the surface hardness of the gear greater than 60 HRC, and the remaining parts of the gear are protected.

[0025] Furthermore: Step S9 includes the following steps:

[0026] S901. Use a high-precision gear grinding machine to ensure the geometric accuracy, rigidity, and stability of the machine tool;

[0027] S902. Dress the grinding wheel to maintain the tooth profile and helix angle accuracy of the grinding wheel;

[0028] S903. Clamp the gear workpiece using a high-precision hydraulic expansion mandrel fixture to ensure accurate clamping and positioning of the gear workpiece, and at the same time ensure the firm clamping of the workpiece.

[0029] S904. Place a dial indicator on a high-precision gear grinding machine, reasonably set the grinding speed, feed rate, and cutting depth, control the feed depth of cut from the dial indicator reading and observe the grinding wheel sparks to ensure uniform cutting of the upper and lower tooth surfaces of the gear workpiece, effectively control the gear accuracy, and monitor the gear workpiece accuracy in real time during the processing to ensure that the gear workpiece accuracy meets the high-precision requirements in the standard.

[0030] S905. Pay attention to cooling and lubrication to ensure effective cooling of the gear workpiece during grinding and sufficient flushing of the grinding chips.

[0031] Furthermore: In step S10, the gear workpiece is subjected to chamfering and finishing treatment at sharp corners by combining a finishing equipment and manual deburring to ensure that the gear workpiece meets the drawing accuracy requirements and has no scratches or impact defects on the surface.

[0032] Advantages of the present invention compared with the prior art: By optimizing the process route, optimizing the blank accuracy of gear parts, and machining parameters, and introducing new processing technologies, the present invention significantly improves the machining accuracy and surface quality of gears. Specific Embodiments

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work fall within the scope of protection of the present invention.

[0034] A process method for improving the machining accuracy of external gears includes the following steps:

[0035] S1. Prepare materials. When selecting materials, it is preferred to use forgings or precision castings to reduce internal defects (such as pores and inclusions) and improve material uniformity. For high-precision gears, it is recommended to use alloy steel (such as 20CrMnTi) and perform quenching and tempering treatment.

[0036] S2. Rough machining; Furthermore: In step S2, the basic shape and size of the gear blank of the gear part are ensured to be stable by leaving uniform allowances on each outer shape and inner hole.

[0037] It should be noted that: Avoid local stress concentration caused by the hindrance of reserved machining allowances. For example: If the outer diameter of the gear blank needs to be machined to Φ100mm, the size after rough machining is controlled at Φ101mm to ensure uniform distribution of the allowances. Uniform allowances can also reduce the cutting force fluctuation, prevent the gear blank from bending or twisting, provide a consistent reference for subsequent finish machining, and reduce cumulative errors.

[0038] S3. Heat treatment; further: In step S3, the tooth blank made of stainless steel is treated by solution + aging heat treatment to ensure that the hardness of the tooth blank matrix is not less than 40 HRC.

[0039] It should be noted that: Solution treatment can heat the stainless steel material to the high-temperature single-phase region, fully dissolve the excess phase into the solid solution, and then obtain a supersaturated solid solution through rapid cooling, which helps to evenly distribute the chemical elements in the material, improve the strength and corrosion resistance of the steel. Aging treatment, on the basis of solution treatment, keeps the metal elements in the solid solution redistributed at a certain temperature for a period of time to form strengthening phases, thereby further improving the hardness and strength of the material, and ensuring that the hardness of the tooth blank matrix is not less than 40 HRC. Solution treatment can refine austenite grains, make the precipitated phases (such as carbides and sulfides) more evenly distributed, and help to improve the mechanical properties and corrosion resistance of the material. Aging treatment further optimizes the microstructure by controlling the temperature and time, reduces the number and size of precipitated phases, and enhances the grain uniformity, thereby improving the overall performance of the material. During the solution treatment process, the distorted lattice inside the material is restored, and the elongated and broken grains are recrystallized, thereby effectively eliminating internal stress, reducing the risk of deformation and cracking in subsequent processing, and improving the dimensional stability and machining accuracy of the tooth blank. Solution + aging heat treatment can significantly improve the wear resistance and corrosion resistance of the tooth blank made of stainless steel. This benefits from the optimization of the internal structure of the material and the formation of strengthening phases during the treatment process, enabling the tooth blank to maintain good performance in a harsh working environment.

[0040] S4. Semi-finishing of the tooth blank.

[0041] Further: Step S4 includes the following steps:

[0042] S401. Release and eliminate the residual stress generated inside the tooth blank during heat treatment.

[0043] Among them, vibration aging or thermal aging treatment can be used to reduce the internal residual stress of the tooth blank (up to 30% - 50%), avoid dimensional deviation or cracking caused by stress release during finish machining. Eliminate stress concentration areas, enable the tooth blank to maintain shape stability during long-term service, and extend the service life.

[0044] S402. Remove the excess dimensions of the tooth blank.

[0045] Among them, the excess allowance after heat treatment (such as the thickened part of the oxide scale) is removed through processes such as milling and turning to ensure that the dimensions of the tooth blank are close to the final design value, leaving a reasonable allowance (such as 0.5 - 1 mm on each side), reducing the finish machining load, and improving the overall efficiency.

[0046] S403. Improve the surface roughness or oxidation problem of the tooth blank after heat treatment.

[0047] Among them, by using sandblasting, pickling or polishing process, the surface roughness is reduced from Ra6.3 to below Ra3.2 to reduce tool wear in subsequent finishing. Thoroughly remove the oxide scale generated by heat treatment (the thickness can reach 0.1 - 0.3 mm) to prevent it from mixing into the coolant or scratching the machined surface.

[0048] S404. Semi-finishing removes the hardened layer and oxide layer generated by heat treatment.

[0049] Among them, the surface hardened layer (the hardness may exceed the matrix by 20 - 30 HRC) is removed by cutting to avoid tool chipping or surface burning during finishing. Expose the fresh metal matrix to improve the adhesion of subsequent surface treatments such as carburizing and nitriding.

[0050] S405. Semi-finishing controls the machining allowance.

[0051] Among them, according to the shape of the gear blank (such as the tooth tip and tooth root), the allowance is reserved differently (such as 0.8 mm for the tooth tip and 0.5 mm for the tooth root) to ensure uniform material removal during finishing. Through allowance control, the dimensional tolerance of the gear blank is reduced from ±0.5 mm to ±0.1 mm to improve the consistency of finishing.

[0052] S406. Semi-finishing reduces the machining time, improves the machining efficiency, and ensures the machining dimensions. Specifically, through efficient processes (such as high-speed milling and powerful turning), the semi-finishing time is reduced by 20% - 30% compared with the traditional method.

[0053] S5. Rough hobbing of the gear blank. Further: In step S5, a CNC hobbing machine is used to rough cut the teeth, and the machining error is reduced by optimizing the hobbing process parameters.

[0054] It should be noted that: The feed rate is precisely controlled by the numerical control system (such as 0.1 - 0.3 mm / tooth) to reduce the tooth profile error; The cutting speed is adjusted according to the material hardness (such as 80 - 120 m / min for stainless steel) to avoid tooth surface burning or tool wear. A hydraulic fixture or a thermal expansion and contraction fixture is used to reduce the clamping deformation, and the tooth ring runout error ≤ 0.03 mm. The thermal deformation of the machine tool and tool wear are compensated in real time by numerical control to improve the machining consistency. The pitch cumulative error of the traditional hobbing machine is 0.08 mm, and it is reduced to 0.03 mm after optimization of the numerical control hobbing machine. High-speed steel or carbide-coated tools are used, and the cutting speed is increased by 30%, and the single-piece machining time is shortened by 20%. The numerical control hobbing machine supports the one-time forming of complex tooth profiles (such as helical teeth, spiral teeth) to reduce the process conversion time. For example: When machining a helical gear with a module m = 5 and a number of teeth Z = 40, the traditional method takes 2 hours, and only 1.2 hours are required after optimization of the numerical control hobbing machine. The high-pressure internal cooling technology (pressure ≥ 5 MPa) of the numerical control hobbing machine reduces the cutting temperature, and the tool life is extended by 50%. The feed rate and cutting depth are adjusted according to the tool material (such as TiAlN coating) to reduce tool wear. The same hob can machine 800 - 1000 pieces under optimized parameters, which is 40% higher than the traditional method. The numerical control hobbing machine is integrated with a laser probe or a vision sensor to monitor the tooth profile error in real time and automatically correct the machining path. The machining process is simulated by CAM software to discover potential problems in advance (such as interference, undercutting). After optimization, the scrap rate is reduced from 5% to less than 1%.

[0055] S6. Finish machining of the gear blank.

[0056] Furthermore: Step S6 includes the following steps:

[0057] S601. Establish a finish machining reference to ensure that the finish machining reference coincides with the design reference and the measurement and inspection reference in height.

[0058] Among them, by unifying the reference, the error superposition caused by reference conversion is avoided (such as the 0.03 - 0.05 mm error caused by non-coincidence of references in the traditional method). The consistency of the workpiece position during the machining process is ensured, and the dimensional fluctuation range of the gear blank is reduced from ±0.05 mm to ±0.01 mm. The key methods to achieve reference coincidence: Machine a high-precision process hole (positional tolerance ≤ 0.01 mm) on the end face of the gear blank as the finish machining reference; Use a composite machining center to complete the machining of the tooth profile, tooth direction and end face in one clamping to avoid repeated positioning errors. For example: In the finish machining of a certain aviation gear, through the reference coincidence technology, the tooth ring runout error is reduced from 0.04 mm to 0.01 mm, and the tooth profile accuracy is improved by 40%.

[0059] S602. The clamping and positioning are accurate to ensure that the clamping and positioning reference coincides with the equipment processing reference. High-precision cutting tools are used, and the cutting tools are regularly calibrated and replaced to ensure that the processing accuracy meets the design requirements of the workpiece. High-precision equipment is utilized, and real-time monitoring and compensation are carried out through grating scales to ensure the processing accuracy and geometric dimension stability of the workpiece, and to establish a good processing reference for precision teeth.

[0060] It should be noted that: to ensure that the clamping and positioning reference coincides with the equipment processing reference, when using high-precision cutting tools, a hydraulic expansion fixture is adopted, and zero-clearance clamping of the workpiece is achieved through uniform pressure (such as 6 - 8 MPa), and the positioning accuracy reaches ±0.002 mm. The hot clamping technology is adopted, and the temperature difference between the fixture and the workpiece is ≤1 °C by induction heating to eliminate the influence of thermal deformation. When regularly calibrating the cutting tools, CBN (cubic boron nitride) or diamond-coated cutting tools are used, and the tool life is extended to more than 2000 pieces. The calibration mechanism is that the tool runout is calibrated by a laser interferometer every 50 pieces processed (the error ≤0.003 mm), and a new cutting tool is replaced every 200 pieces. When using high-precision equipment, the X / Y / Z axes of the machine tool are equipped with grating scales (resolution 0.001 μm) to compensate for thermal deformation and mechanical errors in real time. Through temperature sensors and force sensors, the cutting parameters (such as feed rate, cutting force) are adjusted in real time. Compared with traditional technologies, this process can improve the tooth profile error (mm) by 50% - 70%, the helix error (mm) by 50% - 67%, the surface roughness by 50%, and the processing speed by 33%.

[0061] Therefore, the S6 reference coincidence technology eliminates the reference conversion error, and the dimensional consistency of the gear blank is improved by 80%. The real-time monitoring and compensation technology dynamically corrects the processing error through grating scales and sensors, and the tooth profile accuracy reaches IT5 level. Multiple processes are carried out in one clamping, reducing the repeated positioning time, and the single-piece processing time is shortened by 30%. The tool life is extended, the CBN cutting tools reduce the tool change times, and the equipment utilization rate is increased by 25%. The scrap rate decreases, the finishing scrap rate drops from 5% to less than 1%, and the annual material cost savings exceed 300,000 yuan (calculated based on an annual output of 1 million pieces). The energy consumption is optimized, high-precision processing reduces rework, and the energy consumption per unit workpiece is reduced by 15%.

[0062] S7. The first precision gear grinding process.

[0063] Furthermore: Step S7 includes the following steps:

[0064] S701. Utilize a high-precision gear grinding machine tool to ensure the geometric accuracy, rigidity, and stability of the machine tool.

[0065] Among them, when using a high-precision gear grinding machine tool, the straightness of the machine tool ≤0.003 mm / m, the angular deviation ≤2″, to ensure that the tooth profile error ≤0.01 mm. A mineral casting bed (such as S200), the anti-vibration performance is improved by 40%, and the grinding vibration is reduced. During stability control, the thermal deformation error of the machine tool is ≤0.005 mm / °C, which is achieved through a constant-temperature workshop (20±1°C) and a thermally symmetric structure.

[0066] S702. Select a suitable grinding wheel according to the gear material and hardness, dress the grinding wheel, and maintain the tooth profile, tooth direction accuracy, and sharpness of the grinding wheel.

[0067] Among them, when selecting the grinding wheel, for carburized steel with a hardness of 58-62 HRC, a cubic boron nitride (CBN) grinding wheel is recommended, with a grain size of 80-120#, and the binder is resin. For quenched steel with a hardness of 45-55 HRC, an alumina ceramic grinding wheel is recommended, with a grain size of 60-100#, and the binder is ceramic. When dressing the grinding wheel, a single-point diamond pen (tip radius ≤0.1 mm) is used, and the tooth profile error of the dressed grinding wheel is ≤0.005 mm. When dressing parameters, the feed rate is 0.01-0.02 mm / time, and the dressing frequency is once every 50 pieces processed. For the detection of the sharpness of the grinding wheel state, the wear of the grinding wheel is monitored by an acoustic emission sensor, and the grinding wheel is forced to be replaced when the cutting force increases by 10%.

[0068] S703. Use a high-precision fixture to ensure accurate clamping and positioning of the gear workpiece and ensure the stable clamping of the gear workpiece.

[0069] Among them, a hydraulic expansion mandrel is used, with an expansion pressure of 6-8 MPa, a positioning accuracy of ±0.002 mm, and a clamping repeatability of ≤0.003 mm. The end positioning pin of the hydraulic expansion mandrel: the diameter tolerance of the pin is ±0.001 mm, ensuring that the radial runout of the tooth circle is ≤0.01 mm. The clamping force (such as 8-10 kN) is monitored in real time through a pressure sensor to avoid workpiece deformation.

[0070] S704. Optimize the machining parameters according to the gear material and accuracy, reasonably set the grinding speed, feed rate, and cutting depth, and avoid overheating and burning of the gear workpiece.

[0071] Specifically: the grinding speed of the CBN grinding wheel is 30-45 m / s, avoiding burning and improving the surface quality. The feed rate is 0.01-0.03 mm / tooth, controlling the tooth profile error ≤0.01 mm. The cutting depth is 0.02-0.05 mm, ensuring the grinding efficiency and avoiding grinding wheel overload. Taking the example of machining 20CrMnTi carburized steel material, before optimization, the grinding speed was 25 m / s, the feed rate was 0.04 mm / tooth, and the tooth surface burning rate was 15%. After optimization, the grinding speed was 35 m / s, the feed rate was 0.02 mm / tooth, and the tooth surface burning rate dropped to 2%.

[0072] S705. Pay attention to cooling and lubrication to ensure effective cooling of the gear workpiece during grinding and sufficient flushing of the grinding chips, so that the fine grinding allowance in the normal direction of the gear common normal is 0.10-0.15 mm.

[0073] Among them, a high-pressure cooling system is adopted, with a pressure ≥ 8 MPa and a flow rate ≥ 50 L / min to ensure that the temperature in the grinding area ≤ 80 °C. A fully synthetic grinding fluid is selected as the coolant, with the lubricity improved by 30%. A 5-μm filter element is used, and the residual amount of grinding chips ≤ 0.1 g / L to avoid scratching the tooth surface. A finishing allowance of 0.10 - 0.15 mm is left in the common normal direction to ensure uniform final machining allowance. Therefore, the tooth profile accuracy is improved from IT7 level to IT5 - IT6 level, and the tooth profile error ≤ 0.01 mm. The surface roughness of the tooth surface Ra ≤ 0.8 μm, and the tooth surface burn rate ≤ 2%. The single-piece machining time is shortened by 20%. The service life of the CBN grinding wheel is extended to more than 1000 pieces, and the number of tool changes is reduced by 50%. The scrap rate is reduced from 8% to 1.5%, and the annual material cost savings exceed 500,000 yuan (calculated based on an annual output of 1 million pieces). The high-pressure cooling system reduces the grinding energy consumption by 15%.

[0074] S8. Surface hardening treatment.

[0075] Furthermore: In step S8, the carbonitriding technology is adopted to increase the surface hardness of the gear, making the surface hardness of the gear greater than 60 HRC, and the rest of the gear is protected.

[0076] It should be noted that: By using the carbonitriding technology, the surface hardness can reach 60 - 65 HRC after treatment, which is 10% - 15% higher than that of traditional carburizing (58 - 62 HRC). The increase in hardness improves the wear resistance of the gear tooth surface by 30% - 50% and extends the service life. The surface-to-core hardness gradient transitions (such as 62 HRC at the surface → 50 HRC at 0.5 mm → 35 HRC at the core), avoiding brittle fracture. The retention of core toughness improves the gear's ability to resist impact loads by 20%, making it suitable for heavy-duty working conditions (such as construction machinery gears). After carbonitriding, a residual compressive stress is formed on the surface (about -200 to -400 MPa), inhibiting crack initiation and increasing the fatigue limit by 15% - 20%. The synergistic effect of surface hardness and compressive stress increases the contact strength by 25%. When protecting the rest of the gear, copper plating, coating with high-temperature resistant paint or mechanical masking is used to ensure that non-hardened areas (such as splines, shaft holes) are not affected by carburizing. The dimensional change of the protected area ≤ 0.02 mm, avoiding assembly interference (such as the spline fit clearance is maintained at 0.05 - 0.1 mm). The carburizing temperature is 820 - 860 °C (the carbonitriding temperature is 20 - 30 °C lower than that of traditional carburizing, reducing the risk of grain growth). Atmosphere control: carbon potential 1.0% - 1.2%, nitrogen potential 0.2% - 0.4%, ammonia flow rate 5 - 10 L / min. The case depth is 0.5 - 0.8 mm (adjusted according to the module, such as the case depth of a gear with m = 3 is 0.6 mm).

[0077] S9. Second precision gear grinding.

[0078] Furthermore: Step S9 includes the following steps:

[0079] S901. Use a high-precision gear grinding machine to ensure the geometric accuracy, rigidity, and stability of the machine tool.

[0080] Among them, the geometric accuracy of the machine tool performance: straightness ≤ 0.002 mm / m, angular deviation ≤ 1″, ensuring that the tooth profile error ≤ 0.005 mm. Rigid design: Adopt a mineral casting bed (such as S200), the anti-vibration performance is improved by 50%, reducing grinding vibration. Stability control: The thermal deformation error of the machine tool ≤ 0.003 mm / °C, achieved through a constant temperature workshop (20 ± 1°C) and a thermally symmetric structure.

[0081] S902. Dress the grinding wheel to maintain the tooth profile and tooth direction accuracy of the grinding wheel.

[0082] Dressing tool: single-point diamond pen (tip radius ≤ 0.05 mm), the tooth profile error of the dressed grinding wheel ≤ 0.003 mm. Dressing parameters: feed rate 0.005 - 0.01 mm / time, dressing frequency once every 20 pieces processed. Sharpness detection, monitor the wear of the grinding wheel through an acoustic emission sensor, and forcefully replace the grinding wheel when the cutting force increases by 15%. Tooth profile accuracy maintenance: Use a laser profilometer to detect the tooth profile of the grinding wheel, ensuring that the tooth profile error ≤ 0.005 mm.

[0083] S903. Use a high-precision hydraulic expansion mandrel fixture to clamp the gear workpiece, ensuring accurate clamping and positioning of the gear workpiece, and at the same time ensuring the stable clamping of the workpiece.

[0084] Among them, the hydraulic expansion pressure: 8 - 10 MPa, positioning accuracy ±0.001 mm, clamping repeatability ≤ 0.002 mm. End face positioning pin: pin diameter tolerance ±0.0005 mm, ensuring that the radial runout of the tooth circle ≤ 0.005 mm. Clamping force control: Real-time monitor the clamping force through a pressure sensor (such as 12 - 15 kN) to avoid workpiece deformation. Clamping efficiency: The clamping time of the hydraulic fixture ≤ 30 seconds, and the efficiency is increased by 40% compared with the traditional fixture.

[0085] S904. Place a dial indicator on the high-precision gear grinding machine, reasonably set the grinding speed, feed rate, and cutting depth, control the feed depth of cut from the dial indicator reading and observe the grinding wheel sparks, ensure uniform cutting of the upper and lower tooth surfaces of the gear workpiece, effectively control the gear accuracy, and monitor the gear workpiece accuracy in real time during the processing to ensure that the gear workpiece accuracy meets the high-precision requirements in the standard.

[0086] Among them, the grinding speed of the CBN grinding wheel is 40 - 50 (m / s), which can avoid burning and improve the surface quality; the feed rate is 0.005 - 0.01 mm / tooth, controlling the tooth profile error ≤ 0.005 mm; the cutting depth is 0.01 - 0.02 mm, ensuring the grinding efficiency and avoiding overloading of the grinding wheel. Micrometer monitoring: Monitor the feed depth of cut in real time to ensure uniform cutting of the upper and lower tooth surfaces (error ≤ 0.002 mm). Spark observation: Judge the grinding state through the sparks of the grinding wheel and adjust the parameters in time to avoid burning. Online measurement: Use a laser gear measuring instrument to monitor the tooth profile error in real time and feedback to adjust the grinding parameters. Before processing: The tooth profile error is 0.015 mm, and the helix error is 0.02 mm. After processing: The tooth profile error ≤ 0.005 mm, and the helix error ≤ 0.003 mm. Effect: The gear transmission noise is reduced from 75 dB to 68 dB, and the transmission efficiency is increased by 2%.

[0087] S905. Pay attention to cooling and lubrication to ensure effective cooling of the gear workpiece during grinding and sufficient flushing of grinding chips.

[0088] Among them, configure a cooling system. High-pressure cooling: The pressure ≥ 10 MPa, and the flow rate ≥ 80 L / min to ensure that the temperature in the grinding area ≤ 60 °C. Selection of coolant: Fully synthetic grinding fluid, with a 40% improvement in lubricity. Filtration accuracy: Use a 3μm filter element, and the residual amount of grinding chips ≤ 0.05 g / L to avoid scratching the tooth surface. Flushing method: Multi-nozzle directional flushing to ensure complete removal of grinding chips at the bottom of the tooth groove.

[0089] S10. Finish deburring.

[0090] Furthermore: Step S10 uses a method combining a finishing device and manual deburring to chamfer and finish the sharp corners of the gear workpiece, ensuring that the gear workpiece meets the drawing accuracy requirements and has no scratches or impact defects on the surface.

[0091] It should be noted that: The combination of equipment and manual work has a synergistic effect, improving the processing efficiency. The combination of equipment and manual work has a synergistic effect. The finishing equipment can achieve batch processing (such as a vibratory finishing machine can process 500 pieces at a time); manual deburring for fine parts (such as tooth roots and keyways), with the overall efficiency increased by 40% and 100% coverage of complex parts. The chamfer dimension tolerance of the finishing equipment is ±0.05 mm, and the chamfer dimension tolerance of manual deburring is ±0.02 mm, with the comprehensive tolerance controlled within ±0.03 mm. The surface roughness Ra of the finishing equipment is ≤ 0.4 μm, and the surface roughness Ra of manual deburring is ≤ 0.2 μm, improving the surface consistency with no scratches or impact damage. The finishing equipment can have fixed process parameters; for manual deburring, it can adapt to different workpiece characteristics (such as special-shaped teeth). The combination of equipment and manual work has a synergistic effect, and the processing ability of complex workpieces is increased by 50%.

[0092] Through comparison, for the traditional method, the surface roughness (Ra) is 0.8 - 1.2 μm. With the combination of finishing and manual work, the surface roughness (Ra) ≤ 0.2 μm, and the surface quality is improved by 75% - 83%. For the chamfer size tolerance, the traditional method is ±0.1 mm, and with the combination of finishing and manual work, it is ±0.03 mm, with a 70% improvement. For the processing efficiency, the traditional method is 20 pieces per hour, and with the combination of finishing and manual work, it is 50 pieces per hour, with a 150% efficiency improvement. For the defect rate, the traditional method is 5% - 8%, and with the combination of finishing and manual work, it is ≤ 0.5%, and the qualified rate is improved by 90% - 94%. For the proportion of labor cost, the traditional method is 100%, and with the combination of finishing and manual work, the proportion of labor cost is 30%, reducing the equipment dependence by 70%.

[0093] In summary, by improving the process method, the present invention effectively improves the manufacturing precision and efficiency of high-precision gears, reduces the manufacturing cost of high-precision gears, and improves the product quality of high-precision gears.

[0094] Each embodiment in this specification is described in a related manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments.

[0095] The above description is only for the preferred embodiments of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A process method for improving the machining accuracy of external gears, characterized in that, It includes the following steps: S1. Prepare materials; S2. Rough machining; S3. Heat treatment; S4. Semi-finish machining of the gear blank; S5. Rough hobbing of the gear blank; S6. Finish machining of the gear blank; S7. First finish grinding of the gear teeth; S8. Surface hardening treatment; S9. Second finish grinding of the gear teeth; S10. Finishing and deburring.

2. The process method according to claim 1, characterized in that: In step S2, the method of leaving uniform allowances on each outer shape and inner hole is adopted to ensure the stability of the basic shape and dimensions of the gear blank of the gear part.

3. The process method according to claim 2, characterized in that: In step S3, the gear blank made of stainless steel is treated by solution + aging heat treatment to ensure that the hardness of the gear blank matrix is not less than 40HRC.

4. The process method according to claim 3, characterized in that: Step S4 includes the following steps: S401. Release and eliminate the residual stress generated inside the gear blank during heat treatment. S402. Remove the excess dimensions of the gear blank. S403. Improve the surface roughness or oxidation problem of the gear blank after heat treatment. S404. Remove the hardened layer and oxidation layer generated by heat treatment through semi-finish machining. S405. Control the machining allowance during semi-finish machining. S406. Reduce the machining time, improve the machining efficiency and ensure the machining dimensions during semi-finish machining.

5. The process method according to claim 4, characterized in that: In step S5, a CNC hobbing machine is used for rough hobbing, and by optimizing the hobbing process parameters, the machining error is reduced.

6. The process method according to claim 5, characterized in that, Step S6 includes the following steps: S601. Establish a finish machining reference to ensure that the finish machining reference coincides with the design reference and the measurement and inspection reference in height. S602. The clamping and positioning are accurate to ensure that the clamping and positioning reference coincides with the equipment machining reference. High-precision tools are used, and the tools are calibrated and replaced regularly to ensure that the machining accuracy meets the design requirements of the workpiece; high-precision equipment is used, and real-time monitoring and compensation are carried out through grating scales to ensure the machining accuracy and geometric dimension stability of the workpiece and prepare a good machining reference for finish machining of the teeth.

7. The process method according to claim 6, characterized in that, Step S7 includes the following steps: S701. Use a high-precision gear grinding machine to ensure the geometric accuracy, rigidity and stability of the machine tool. S702. Select a suitable grinding wheel according to the gear material and hardness, dress the grinding wheel and maintain the tooth profile, tooth direction accuracy and sharpness of the grinding wheel. S703. Use a high-precision fixture to ensure accurate clamping and positioning of the gear workpiece and ensure the stable clamping of the gear workpiece. S704. Optimize the machining parameters according to the gear material and accuracy, reasonably set the grinding speed, feed rate and cutting depth to avoid overheating and burning of the gear workpiece. S705. Pay attention to cooling and lubrication to ensure effective cooling of the gear workpiece during the grinding process and sufficient flushing of the grinding chips, so that the finish grinding allowance in the common normal direction of the gear is 0.10 - 0.15mm.

8. The process method according to claim 7, characterized in that: In step S8, the carbonitriding technology is adopted to improve the surface hardness of the gear, so that the surface hardness of the gear is greater than 60HRC, and the rest of the gear is protected.

9. The process method according to claim 8, characterized in that, Step S9 includes the following steps: S901. Use a high-precision gear grinding machine to ensure the geometric accuracy, rigidity and stability of the machine tool. S902. Dress the grinding wheel to maintain the tooth profile and tooth direction accuracy of the grinding wheel. S903. Use a high-precision hydraulic expansion mandrel fixture to clamp the gear workpiece to ensure accurate clamping and positioning of the gear workpiece and at the same time ensure the stable clamping of the workpiece. S904. Place a dial indicator on a high-precision gear grinding machine, reasonably set the grinding speed, feed rate, and cutting depth, control the feed depth of cut based on the readings of the dial indicator, and observe the sparks of the grinding wheel to ensure uniform cutting of the upper and lower tooth surfaces of the gear workpiece, effectively control the gear accuracy, and monitor the accuracy of the gear workpiece in real time during the machining process to ensure that the accuracy of the gear workpiece meets the high-precision requirements in the standard. S905. Pay attention to cooling and lubrication to ensure effective cooling of the gear workpiece during grinding and sufficient flushing of the grinding chips.

10. The process method according to claim 9, characterized in that, In step S10, the gear workpiece is subjected to chamfering and finishing treatment at sharp corners by combining a finishing device and manual deburring to ensure that the gear workpiece meets the accuracy requirements of the drawing and has no scratches or impact defects on the surface.