A worm manufacturing process method applied to a humanoid robot dexterous hand

Abstract

This invention relates to the field of mechanical manufacturing technology and discloses a manufacturing process for a worm gear used in the dexterous hand of a humanoid robot, comprising the following specific steps: Step 1: Material selection and pretreatment; Step 2: Rough turning and semi-finish turning; Step 3: Thread forming; Step 4: Heat treatment process, placing the worm gear formed in Step 3 into a vacuum heat treatment furnace for further processing; Step 5: Fine grinding and polishing; Step 6: Cleaning and rust prevention treatment. This invention achieves austenitization by heating the worm gear to 820℃~880℃ at a rate of 8℃ / min~12℃ / min in a vacuum heat treatment furnace, holding it at that temperature for 20min~40min, followed by high-pressure gas quenching, with the cooling rate controlled at 60℃ / s~100℃ / s. A closed-loop control using an infrared thermometer ensures an axial temperature difference ≤15℃, effectively solving the problem of uneven temperature distribution caused by differences in cross-sectional dimensions.

Description

Technical Field

[0001] This invention relates to the field of mechanical manufacturing technology, specifically to a manufacturing process for a worm gear used in the dexterous hand of a humanoid robot. Background Technology

[0002] With the continuous evolution of humanoid robot technology, dexterous hands, as the core execution unit for achieving precise operations and natural human-robot interaction, place extremely high demands on the precision and reliability of their internal transmission components. Dexterous hands typically consist of multiple highly free-degree-of-freedom finger joints, each relying on a precision reduction mechanism for accurate motion control. Worm gear drives, with their advantages of large transmission ratio, compact structure, smooth operation, and low noise, have become one of the key technological approaches for dexterous hand joint reducers. Among these, the miniature annular envelope worm gear structure has already been practically applied in high-degree-of-freedom dexterous hands.

[0003] Among them, the worm gear used in the dexterous hand of humanoid robots is a small-size, small-module (m<1.0mm) precision transmission component, with a typical diameter range of Φ2mm to Φ30mm. It must meet the stringent tolerance requirements of P1 grade helix accuracy and a mean diameter variation of no more than 0.01mm. These worm gears are usually made of materials such as 9Mn2V, T10A, or 45 steel, and are hardened to obtain a surface hardness of HRC45-62 to ensure wear resistance and dimensional stability during long-term use.

[0004] However, existing worm gear manufacturing processes face technical bottlenecks in the heat treatment stage, specifically:

[0005] Traditional machining processes include blanking, rough turning, semi-finish turning, thread forming (turning or milling), heat treatment, and subsequent fine grinding. However, when quenching slender worm gears, uneven temperature distribution during heating and cooling due to differences in cross-sectional dimensions leads to significant thermal and structural stresses, causing workpiece bending deformation or localized thread distortion, with deformation often reaching 0.02–0.05 mm. This deformation not only severely degrades the geometric accuracy obtained from previous machining but also leads to an imbalance in the allowance distribution during the fine grinding stage, reducing machining efficiency and increasing the scrap rate. Especially for multi-start worm gears, the consistency deviation of each helix caused by heat treatment directly damages transmission smoothness and meshing accuracy, making it difficult to meet the demands of dexterous hands for high dynamic response and micron-level positioning performance. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a manufacturing process for a worm gear in the dexterous hand of a humanoid robot, thus solving the aforementioned problems in the background technology.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: a manufacturing process for a worm gear used in the dexterous hand of a humanoid robot, comprising the following specific steps:

[0010] Step 1: Material selection and pretreatment. 9Mn2V or T10A steel is selected as the worm gear blank. The material composition is confirmed to meet the standard through spectral analysis. Then, the blank is cut to the preset length and the cut end face is chamfered and deburred.

[0011] Step 2: Rough turning and semi-finish turning. The outer diameter of the worm gear blank processed in Step 1 is rough turned on a precision CNC lathe, with a single-sided allowance of 0.3mm to 0.8mm. Then, the finishing tool is switched to perform semi-finish turning, controlling the outer diameter dimensional tolerance within ±0.05mm and ensuring that the coaxiality error of each shaft section is <0.01mm.

[0012] Step 3: Thread forming process. Use a multi-start worm gear CNC milling machine or cyclone milling device, then preset the helix angle and lead, and according to the preset helix angle and lead, use a forming tool to mill the tooth part of the worm gear blank processed in Step 2 in layers. The cutting depth of each layer is 0.05~0.1mm. Coolant is continuously applied during the milling process to control the temperature rise, and the formed worm gear is obtained.

[0013] Step 4: Heat treatment process. The worm gear formed in Step 3 is placed in a vacuum heat treatment furnace. First, the temperature is raised to 820℃~880℃ at a rate of 8℃ / min~12℃ / min, and held for 20min~40min to complete austenitization. Then, high-pressure gas quenching is performed, and the cooling rate is controlled at 60℃ / s~100℃ / s. Finally, it is tempered at 160℃~200℃ for 1.5h~2.5h.

[0014] Step 5: Fine grinding and polishing. Use a CNC thread grinding machine to fine grind the worm gear teeth after heat treatment in step 4. Use a cubic boron nitride grinding wheel and a grinding speed of 30m / s to 40m / s. The grinding path is fed back and corrected in real time through an online measurement system to ensure that the accuracy of the helix reaches P1 level and the variation of the mean diameter does not exceed 0.01mm.

[0015] Step Six: Cleaning and Rust Prevention Treatment. The worm gear, after fine grinding in Step Five, is ultrasonically cleaned to remove residual abrasive particles and oil stains. Then, it is dipped in rust-preventive oil and dried at 70℃~90℃ to complete the entire manufacturing process.

[0016] Preferably, in the material selection and pretreatment of step one, the blanking is carried out using a slow wire EDM machine with a cutting speed of 8mm / min to 12mm / min and a surface roughness controlled within Ra1.6μm. After cutting, the worm blank is subjected to magnetic particle testing to ensure that there are no internal cracks or inclusion defects.

[0017] Preferably, in the roughing and semi-finishing processes of step two, the spindle speed is 600 rpm to 1000 rpm and the feed rate is 0.15 mm / r to 0.25 mm / r during roughing, and the spindle speed is increased to 1200 rpm to 1800 rpm and the feed rate is reduced to 0.08 mm / r to 0.12 mm / r during semi-finishing. Ceramic-coated tools are used to extend the tool life of roughing and semi-finishing.

[0018] Preferably, in the thread forming process of step three, the rake angle of the forming tool is 8° to 12° and the clearance angle is 5° to 8°. In addition, during the milling process, the tool wear is monitored in real time by a laser interferometer. When the wear exceeds 0.015mm to 0.025mm, an alarm is automatically triggered and the tool is replaced.

[0019] Preferably, in the heat treatment process of step four, the ultimate vacuum degree of the vacuum heat treatment furnace is better than 1×10-3 Pa, the gas quenching medium is nitrogen with a purity of 99.999% or higher, the quenching pressure is 0.4MPa~0.8MPa, and the surface hardness of the worm gear after tempering reaches HRC56~64, and the core hardness is HRC43~52.

[0020] Preferably, in the fine grinding and polishing of step five, the cubic boron nitride grinding wheel has a grit size of 100-150 mesh, the binder is a ceramic binder, constant force grinding technology is used during the grinding process, the grinding force is controlled between 40N and 90N, and the tooth surface profile is sampled and tested every 5 pieces processed by a white light interferometer.

[0021] Preferably, in step six, the cleaning and rust prevention treatment, the ultrasonic cleaning frequency is 35kHz to 45kHz, the cleaning solution is a water-based environmentally friendly cleaning agent, the cleaning time is 8min to 12min, the rust-preventive oil thickness is 4μm to 10μm, and the surface resistivity of the worm gear after drying is >1×10⁻⁶. 12 Ω.

[0022] Preferably, the process further includes a stress-relieving annealing step between step three and step four, in which the worm gear blank is heated to 520°C to 580°C, held at that temperature for 3 to 5 hours, cooled to 280°C to 320°C in a vacuum heat treatment furnace, and then air-cooled to room temperature to release the residual stress introduced by the cutting process.

[0023] Preferably, the method further includes dynamic balancing correction after step five. The formed worm is placed on a dynamic balancing machine, and the imbalance is detected at a speed of 2500 rpm to 3500 rpm. If the imbalance exceeds 0.5 g·mm, it is corrected by weight removal.

[0024] Preferably, all machining processes in the humanoid robot dexterous hand worm gear manufacturing process are carried out in a constant temperature workshop, with the ambient temperature controlled at 20℃±1℃ and the relative humidity <50%, to reduce the impact of thermal deformation on machining accuracy. In addition, the humanoid robot dexterous hand worm gear manufacturing process is integrated into a flexible manufacturing system, and the automatic transfer of the worm gear between each process is realized through a six-axis industrial robot. The repeatability of the six-axis industrial robot is ±0.02mm, and the overall cycle time of the flexible manufacturing system is <30min / piece.

[0025] (III) Beneficial Effects

[0026] This invention provides a manufacturing process for a worm gear used in the dexterous hand of a humanoid robot. It offers the following advantages:

[0027] (1) This invention achieves austenitization by heating the temperature to 820℃~880℃ at a rate of 8℃ / min~12℃ / min in a vacuum heat treatment furnace, holding it at that temperature for 20min~40min, followed by high-pressure gas quenching. The cooling rate is controlled at 60℃ / s~100℃ / s, and the axial temperature difference is ensured to be ≤15℃ by closed-loop control using an infrared thermometer. This effectively solves the problem of uneven temperature field distribution caused by differences in cross-sectional dimensions. After heat treatment, the bending of the worm gear along its entire length is ≤0.015mm, and the variation in the thread pitch diameter is <0.008mm, which is lower than the deformation of 0.02~0.05mm in the prior art. This ensures that the geometric accuracy of the worm gear meets the stringent tolerance requirements of P1 grade helical accuracy and pitch diameter variation not exceeding 0.01mm.

[0028] (2) The present invention adds a stress-relieving annealing process between step three and step four. The worm blank is heated to 520℃~580℃, held for 3h~5h and then cooled to 280℃~320℃ in a vacuum heat treatment furnace, and then air-cooled to room temperature. This makes the absolute value of the tensile stress and the absolute value of the compressive stress on the surface after annealing <50MPa, effectively releasing the residual stress introduced by the thread forming process, avoiding the bending deformation of the workpiece or the local distortion of the thread caused by the superposition of thermal stress and structural stress, ensuring the geometric accuracy obtained by the previous processing, improving processing efficiency and reducing the scrap rate.

[0029] (3) This invention uses a CNC thread grinding machine in conjunction with an online measurement system to finely grind the heat-treated worm gear teeth. A cubic boron nitride grinding wheel is used, and the grinding linear speed is 30m / s to 40m / s. The grinding path is fed back and corrected in real time by a white light interferometer and a high-precision encoder. The correction cycle is ≤0.5s, ensuring that the helix accuracy reaches P1 level, the mean diameter variation is ≤0.01mm, the tooth profile error is <0.003mm, and the tooth direction error is <0.004mm. This effectively solves the problem of consistency deviation of each helix caused by heat treatment of multi-head worm gears and meets the needs of dexterous hands for high dynamic response and micron-level positioning performance. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall process flow of the present invention.

[0031] Figure 2 This is a schematic diagram illustrating the detailed process of material selection and pretreatment in this invention.

[0032] Figure 3 This is a detailed flowchart illustrating the roughing and semi-finishing processes of the present invention.

[0033] Figure 4 This is a schematic diagram illustrating the detailed process of thread forming in this invention.

[0034] Figure 5 This is a detailed flow chart of the heat treatment process of the present invention.

[0035] Figure 6 This is a detailed schematic diagram of the fine grinding and polishing process of the present invention.

[0036] Figure 7 This is a detailed flowchart illustrating the cleaning and rust prevention process of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Please see Figure 1 - Figure 7 This invention provides a manufacturing process for a worm gear used in the dexterous hand of a humanoid robot, specifically including the following steps:

[0039] Step 1: Material selection and pretreatment. Specifically, 9Mn2V or T10A steel is selected as the worm gear blank. The material composition is confirmed to meet the standard through spectral analysis. Then, the blank is cut to the preset length and the cut end face is chamfered and deburred.

[0040] Furthermore, the blanking is performed using a slow wire EDM machine with a cutting speed set to 8mm / min~12mm / min, ensuring that the perpendicularity error of the cut surface is <0.01mm and the surface roughness is controlled within Ra1.6μm. After cutting, the worm gear blank is immediately subjected to magnetic particle testing with a testing sensitivity level ≥MT-2 to eliminate metallurgical defects such as internal cracks, inclusions, or shrinkage cavities. The chamfering is performed using a CNC chamfering machine with a chamfer angle of 40°~50° and a chamfer width of 0.3mm~0.8mm. Deburring is completed by high-pressure water jet with a water pressure of 15MPa and a nozzle movement speed of 50mm / min to ensure that there are no micro-burr residues on the end face and to prevent subsequent clamping and positioning deviations.

[0041] In material selection and pretreatment, all operations are carried out in a constant temperature workshop, with the ambient temperature maintained at 20℃±1℃ and the relative humidity <50%, to avoid material dimensional drift caused by temperature and humidity fluctuations.

[0042] Step 2: Rough turning and semi-finish turning. The outer diameter of the worm gear blank is rough turned on a precision CNC lathe, with a single-sided allowance of 0.3mm to 0.8mm. Then, the finishing tool is switched to perform semi-finish turning, controlling the outer diameter dimensional tolerance within ±0.05mm and ensuring that the coaxiality error of each shaft section is <0.01mm.

[0043] Specifically, in the roughing stage, the spindle speed is set to 600 rpm to 1000 rpm, the feed rate is 0.15 mm / r to 0.25 mm / r, the depth of cut is 1.0 mm, and a carbide tool with a tool tip radius of 0.4 mm is used. In the semi-finishing stage, a ceramic-coated tool is switched, the spindle speed is increased to 1200 rpm to 1800 rpm, the feed rate is reduced to 0.08 mm / r to 0.12 mm / r, the depth of cut is 0.3 mm, and the process is completed in two passes. Roughing and semi-finishing... Equipped with a high-rigidity spindle unit and hydrostatic guide rails, the repeatability is better than ±0.002mm. During machining, the radial runout of the workpiece is monitored in real time by a capacitive displacement sensor mounted on the turret, with a sampling frequency of 1kHz. When the runout value is >0.008mm, the machine automatically pauses and triggers the tool compensation program. The coaxiality is detected by using a double-center clamping system with a laser alignment instrument. The measurement points are evenly distributed at ≥5 locations along the axial direction. The data are fitted using the least squares method to calculate the maximum deviation value, ensuring that the requirement of <0.01mm is met.

[0044] Step 3: Thread forming process. Use a multi-start worm gear CNC milling machine or a cyclone milling device. Then, preset the helix angle and lead, and according to the preset helix angle and lead, use a forming tool to mill the worm gear teeth in layers. The cutting depth of each layer is 0.05 to 0.1 mm. Coolant is continuously applied during the milling process to control the temperature rise.

[0045] Specifically, in step three, the rake angle of the forming tool is set to 8°–12°, the clearance angle to 5°–8°, the blunt radius of the cutting edge is controlled within 2μm, the tool material is ultra-fine grain cemented carbide, and the coating is a TiAlN composite film with a thickness of 3μm; milling adopts five-axis linkage control, with X, Y, and Z axis positioning accuracy better than ±0.001mm, and A and C rotation axis angular resolution ≥0.001°; the layering strategy is dynamically adjusted according to the number of worm heads, with worm heads classified as single-start worm, double-start worm, triple-start worm, and worms with more than three heads. Single-start worms are divided into 3 layers, double-start worms into 4 layers, and triple-start worms into 5 layers, with the cutting depth of each layer increasing in a gradient of 0.05mm, 0.07mm, and 0.1mm; cooling... The fluid is a synthetic cutting fluid containing extreme pressure additives, with a flow rate of 8 L / min and a pressure of 0.3 MPa. The nozzle is 10 mm away from the cutting zone. Simultaneously, the tool wear is monitored in real time by a laser interferometer installed at the end of the spindle. The sampling interval is every 10 mm of axial length. When the radial wear exceeds 0.015 mm to 0.025 mm, the system automatically alarms and starts the tool change program. The pre-setting accuracy of the new tool is controlled within ±0.005 mm. This step yields the formed worm gear.

[0046] Step 4: Heat treatment process. The formed worm gear is placed in a vacuum heat treatment furnace. The temperature is first increased to 820℃~880℃ at a rate of 8℃ / min~12℃ / min, and held for 20min~40min to complete austenitization. Then, high-pressure gas quenching is performed, with the cooling rate controlled at 60℃ / s~100℃ / s. Finally, tempering is carried out at 160℃~200℃ for 1.5h~2.5h. Specifically, in Step 4, the ultimate vacuum degree of the vacuum heat treatment furnace is better than 1×10⁻³ Pa. The vacuuming process is carried out in three stages: rough evacuation to 1 Pa, followed by starting the molecular pump to 10⁻² Pa, and finally maintaining the working vacuum degree by the ion pump. The gas quenching medium is high-purity nitrogen with a purity of 99.999% or higher, and the quenching pressure is controlled... The pressure is controlled at 0.4MPa to 0.8MPa, with a gas flow rate of 50m / s. Uniform circumferential cooling of the workpiece is achieved through a multi-directional nozzle array. The cooling rate is controlled by a closed-loop infrared thermometer, with the temperature measurement points located at the middle and both ends of the worm gear. The sampling frequency is 100 times / s to ensure that the axial temperature difference is ≤15℃. Tempering is carried out in a vacuum environment with a heating rate of 8℃ / min. During the holding period, a small amount of nitrogen is introduced to maintain a slight positive pressure to prevent surface oxidation. After heat treatment, the surface hardness of the worm gear reaches HRC56 to 64, and the core hardness is HRC43 to 52. The hardness gradient transition is smooth, and there is no obvious brittle layer. The deformation is detected by a coordinate measuring machine, with the total bending degree ≤0.015mm and the thread pitch diameter variation <0.008mm.

[0047] In addition, a stress-relief annealing process is added between steps three and four. The worm gear blank is heated to 520℃~580℃, held for 3h~5h, and then cooled to 280℃~320℃ in a vacuum heat treatment furnace, followed by air cooling to room temperature to release the residual stress introduced by the cutting process. The stress-relief annealing is carried out in a protective atmosphere furnace with an oxygen content of <20ppm and a heating rate of 4℃ / min~6℃ / min. During the holding period, the temperature fluctuation range is controlled within ±3℃. During the cooling stage in the protective atmosphere furnace, the cooling rate is ≤10℃ / min to ensure that the structural stress is released slowly. After annealing, the residual stress on the surface is detected by an X-ray stress analyzer. The absolute value of tensile stress is required to be <50MPa and the absolute value of compressive stress is required to be <80MPa. If the values ​​are exceeded, the annealing is repeated once.

[0048] Step 5: Fine grinding and polishing. The heat-treated worm gear teeth are finely ground using a CNC thread grinding machine with a cubic boron nitride wheel at a grinding speed of 30m / s to 40m / s. An online measurement system provides real-time feedback and corrects the grinding path to ensure the helix accuracy reaches P1 level, with a mean diameter variation ≤0.01mm. Specifically, in step 5, the cubic boron nitride wheel grit is 100-150 mesh, the bonding agent is ceramic, and the wheel dynamic balance reaches G0.4 level. Constant force grinding technology is used during grinding, with a piezoelectric force sensor monitoring the grinding force in real-time, controlling the range to 40N to 90N, and a force fluctuation standard deviation <3N. The online measurement system consists of a white light interferometer and a high-precision encoder. The interferometer is vertically mounted on the opposite side of the grinding wheel, with a measurement spot diameter of 50μm and a sampling interval of 0.1mm. A full tooth surface scan is performed after each grinding revolution. The measurement data is compared with the theoretical tooth profile in real time by the embedded processor, the deviation vector is calculated, and the grinding wheel feed is dynamically adjusted by the servo system, with a correction cycle of ≤0.5s. After processing 5 worm gears, the online measurement system automatically triggers a sampling inspection program, and the tooth surface profile is evaluated using a white light interferometer. The tooth profile error is required to be <0.003mm and the tooth direction error to be <0.004mm. Polishing is performed using a soft resin grinding wheel with a grit size of W20, the linear speed is reduced to 15m / s, and the removal amount is controlled within 1μm to ensure a surface roughness Ra <0.2μm.

[0049] Furthermore, after step five, dynamic balancing is performed. The worm gear is placed on a dynamic balancing machine, and the imbalance is measured at a speed of 2500 rpm to 3500 rpm. If the imbalance exceeds 0.4 g·mm to 0.6 g·mm, it is corrected using a weight reduction method. The dynamic balancing machine is equipped with a double-sided measuring system with a sensitivity of 0.01 g·mm. The correction plane is located at the journals at both ends of the worm gear. Weight reduction is achieved by micro-beam plasma drilling with a hole diameter of 0.2 mm to 0.4 mm and a depth of 0.3 mm to 0.7 mm. The position is precisely calculated by the balancing algorithm to ensure that the imbalance after correction is <0.3 g·mm. After correction, a high-speed rotation test is performed again, with the speed increased to 5000 rpm for 10 minutes, and the peak vibration acceleration is monitored to be ≤2 m / s². 2 .

[0050] Step Six: Cleaning and Rust Prevention. The finely ground worm gear undergoes ultrasonic cleaning to remove residual abrasive particles and oil. It is then immersed in rust-preventive oil and dried at 70℃~90℃, completing the entire manufacturing process. Specifically, in Step Six, the ultrasonic cleaning tank frequency is 35kHz~45kHz, and the power density is 0.5W / cm². 2The cleaning solution is a water-based environmentally friendly cleaning agent with a pH of 7.5. The cleaning time is 8-12 minutes, followed by two 3-minute rinses with pure water. Before drying, the worm gear is centrifuged at 2000 rpm for 2 minutes. The rust-preventive oil is a sulfonate-based rust inhibitor with a viscosity of 30 cSt. The immersion time is 30 seconds, and the lifting speed is 50 mm / min to form a uniform oil film. Drying is carried out in a vacuum oven at 80℃ and 100 Pa for 30 minutes to ensure an oil film thickness of 4-10 μm. After drying, the surface resistivity of the worm gear is >1×10⁻⁶. 12 Ω, meeting high insulation requirements; finished products are inspected under an optical microscope and the surface is free of scratches, rust spots or oil stains.

[0051] In this invention, all machining processes are carried out in a constant temperature workshop with an ambient temperature controlled at 20℃±1℃ and a relative humidity of <50%. The workshop is equipped with an air filtration system, achieving a cleanliness level of ISO Class 8, effectively isolating dust and vibration interference. The entire process is integrated into a flexible manufacturing system, and the automatic transfer of worm gears between processes is achieved through a six-axis industrial robot. The end effector of the six-axis industrial robot is equipped with a vacuum suction cup and a vision positioning module, with a repeatability of ±0.02mm. Each device is connected to the central control system via the OPCUA protocol, uploading process parameters and quality data in real time.

[0052] Example 1

[0053] The worm gear for the dexterous hand of a humanoid robot is manufactured using the process method of this invention, with the following specific parameters:

[0054] Step 1: Select 9Mn2V steel, cut length 120mm, slow wire EDM speed 10mm / min, chamfer angle 45°, chamfer width 0.5mm, high-pressure water jet deburring water pressure 15MPa.

[0055] Step 2: Rough turning spindle speed 800 rpm, feed rate 0.2 mm / r, depth of cut 1.0 mm; semi-finish turning spindle speed 1500 rpm, feed rate 0.1 mm / r, depth of cut 0.3 mm, outer diameter tolerance ±0.05 mm.

[0056] Step 3: Adopt a double-headed worm gear design with a helix angle of 15° and a lead of 6mm. Mill in 4 layers with cutting depths of 0.05mm, 0.05mm, 0.07mm, and 0.07mm for each layer. The coolant flow rate is 8L / min and the pressure is 0.3MPa.

[0057] Between steps three and four: stress-relief annealing temperature 550℃, hold for 4 hours.

[0058] Step 4: Vacuum heat treatment with a heating rate of 10℃ / min, an austenitizing temperature of 850℃, a holding time of 30min, a gas quenching pressure of 0.6MPa, a cooling rate of 80℃ / s, a tempering temperature of 180℃, and a holding time of 2h.

[0059] Step 5: Use a 120-grit cubic boron nitride grinding wheel, grinding speed of 35 m / s, grinding force control of 60 N, polishing wheel grit of W20, and a grinding speed of 15 m / s. Perform dynamic balancing at 3000 rpm.

[0060] Step Six: Ultrasonic cleaning frequency 40kHz, power density 0.5W / cm³ 2 Cleaning time: 10 min; rust-preventive oil viscosity: 30 cSt; drying temperature: 80℃; drying time: 30 min.

[0061] Example 2

[0062] Step 1: Select T10A steel, cut to a length of 150mm, and keep the other parameters the same as in Example 1.

[0063] Step 2: Rough turning spindle speed 750 rpm, feed rate 0.25 mm / r, depth of cut 1.2 mm; semi-finish turning spindle speed 1600 rpm, feed rate 0.08 mm / r, depth of cut 0.25 mm.

[0064] Step 3: Use a three-head worm gear design with a helix angle of 18° and a lead of 9mm. Mill in 5 layers with cutting depths of 0.05mm, 0.05mm, 0.07mm, 0.07mm and 0.1mm for each layer, and coolant flow rate of 9L / min.

[0065] Between steps three and four: stress-relief annealing temperature 550℃, hold for 4 hours.

[0066] Step 4: Austenitizing temperature 860℃, holding temperature for 35 min, gas quenching pressure 0.65 MPa, cooling rate 85℃ / s, tempering temperature 190℃, holding temperature for 2.5 h.

[0067] Step 5: Grinding speed 36m / s, grinding force control 65N, polishing speed 16m / s. Dynamic balancing correction speed 3500rpm.

[0068] Step 6: Ultrasonic cleaning time 12min, rust-preventive oil viscosity 32cSt, drying time 35min.

[0069] Example 3

[0070] Step 1: Select 9Mn2V steel, cut to a length of 100mm, and keep the other parameters the same as in Example 1.

[0071] Step 2: Rough turning spindle speed 850 rpm, feed rate 0.18 mm / r, depth of cut 0.9 mm; semi-finish turning spindle speed 1450 rpm, feed rate 0.12 mm / r, depth of cut 0.35 mm.

[0072] Step 3: Use a single-head worm gear design with a helix angle of 12° and a lead of 4mm. Mill in 3 layers with cutting depths of 0.05mm, 0.07mm, and 0.1mm for each layer, and coolant flow rate of 7.5L / min.

[0073] Between steps three and four: stress-relief annealing temperature 550℃, hold for 4 hours.

[0074] Step 4: Austenitizing temperature 840℃, holding temperature for 28 min, gas quenching pressure 0.55 MPa, cooling rate 75℃ / s, tempering temperature 175℃, holding temperature for 1.8 h.

[0075] Step 5: Grinding speed 34m / s, grinding force control 55N, polishing speed 14m / s. Dynamic balancing correction speed 2800rpm.

[0076] Step 6: Ultrasonic cleaning time 9 min, rust-preventive oil viscosity 28 cSt, drying time 28 min.

[0077] Comparative Example 1

[0078] The worm gear is manufactured using traditional methods without stress-relief annealing. The specific steps are as follows:

[0079] Step 1: 9Mn2V steel was selected and cut using a regular saw without magnetic particle testing.

[0080] Step 2: Machining on a conventional lathe, with an outer diameter tolerance of ±0.1mm, without real-time monitoring.

[0081] Step 3: Traditional milling, without using a layering strategy, single cutting depth of 0.3mm, and without real-time monitoring of tool wear.

[0082] Step 4: Ordinary box furnace heat treatment, air quenching, without precise temperature control.

[0083] Step 5: The ordinary thread grinding machine is not equipped with an online measurement system and has not undergone dynamic balancing correction.

[0084] Step 6: Simple washing, air dry at room temperature.

[0085] Comparative Example 2

[0086] The worm gear was manufactured using a partially improved process, with a vacuum furnace used only in the heat treatment stage, but stress-relief annealing was not performed.

[0087] Steps one through three: Same as Comparative Example one.

[0088] Step 4: Vacuum heat treatment, but the heating rate is relatively fast (20℃ / min), and the gas quenching pressure is only 0.4MPa.

[0089] Steps five and six: Same as Comparative Example 1.

[0090] The performance test yielded the following results:

[0091]

[0092] Further durability tests were conducted, and the results are shown in the table below:

[0093] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Fatigue life (10,000 cycles) 85 92 80 28 45 Wear amount (μm / 10,000 cycles) 0.8 0.7 0.9 3.8 2.2 Transmission efficiency (%) 94.5 95.2 93.8 85.3 88.7 Noise level (dB) 52 51 53 68 62 <![CDATA[Peak vibration acceleration (m / s 2 )]]> 1.5 1.3 1.7 8.5 5.2 Operating temperature rise (°C) 18 16 20 45 32

[0094] Experimental results:

[0095] Accuracy Comparison: The worm gears manufactured using the process method of this invention in Examples 1-3 all achieved a helix accuracy of P1 grade, with a pitch diameter variation of ≤0.009mm, tooth profile error <0.003mm, and tooth direction error <0.004mm, all meeting the standard requirements. Comparative Example 1, using a traditional process, achieved a helix accuracy of only P5 grade, with a pitch diameter variation of 0.045mm, exceeding the standard requirement by 4.5 times. Although Comparative Example 2 made improvements in the heat treatment process, its accuracy was lower than that of the present invention due to the lack of a complete precision machining system and stress-relief annealing.

[0096] 2. Comparison of mechanical properties: The surface hardness of Examples 1-3 is all within the range of HRC59-61, and the core hardness is 46-48 HRC, showing a reasonable hardness gradient. Comparative Example 1, due to the use of a conventional box furnace and air quenching, has a surface hardness of only 52 HRC, failing to meet the standard requirements. Comparative Example 2, although using vacuum heat treatment, has a surface hardness of only 56 HRC due to excessively rapid heating rate and insufficient air quenching pressure, also failing to meet the standard.

[0097] 3. Stress State Comparison: By adding a stress-relieving annealing process after thread forming and before heat treatment, the residual stress in Examples 1 and 3 is controlled at a compressive stress state of 45-48 MPa, which is beneficial to improving fatigue strength. The residual tensile stress in Comparative Example 1 is as high as 180 MPa, and Comparative Example 2 also has a tensile stress of 125 MPa, which will significantly reduce the fatigue life and reliability of the parts.

[0098] 4. Durability Comparison: The fatigue life of Examples 1 and 3 is 800,000-920,000 cycles, with a wear rate of only 0.7-0.9 μm / 10,000 cycles and a transmission efficiency of 93.8%-95.2%. Comparative Example 1 has a fatigue life of only 280,000 cycles, less than one-third of the present invention's solution, with a wear rate as high as 3.8 μm / 10,000 cycles and a transmission efficiency of only 85.3%. Although Comparative Example 2 shows some improvement, its fatigue life of 450,000 cycles is still significantly lower than the present invention's solution, demonstrating that a complete process system is crucial for product performance.

[0099] 5. Comparison of operational quality: In Examples 1 and 3, through dynamic balancing correction, the imbalance was controlled within 0.22-0.28 g·mm, the operating noise was 51-53 dB, and the peak vibration acceleration was 1.3-1.7 m / s². 2 The temperature rise was 16-20℃. Comparative Example 1, which lacked dynamic balancing correction, had an imbalance of 2.5 g·mm, resulting in a noise level of 68 dB and a vibration rate of 8.5 m / s². 2 The temperature rises by 45°C, which seriously affects the precision control performance of the dexterous hand.

[0100] 6. Surface Quality Comparison: Examples 1 and 3 employed online measurement feedback correction and soft resin wheel polishing, achieving a surface roughness Ra of 0.15-0.18 μm. Comparative Example 1, without online measurement and precision polishing, had a surface roughness of 0.85 μm, exceeding the standard by more than four times, which would exacerbate wear and reduce transmission efficiency.

[0101] In conclusion, this invention, through a complete process system including precision material pretreatment, layered thread forming, stress-relief annealing, precise heat treatment, online measurement feedback grinding, and dynamic balancing correction, enables the worm gear to achieve superior dimensional accuracy, mechanical properties, stress state, surface quality, and operational quality compared to traditional and some improved processes. Fatigue life is increased by 2-3 times, and transmission efficiency is improved by 8-10 percentage points, fully meeting the high precision and high reliability requirements of humanoid robot dexterity hands.

[0102] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A manufacturing process for a worm gear used in the dexterous hand of a humanoid robot, characterized in that, Includes the following steps: Step 1: Material selection and pretreatment. 9Mn2V or T10A steel is selected as the worm gear blank. Spectral analysis confirms that the material composition meets the standards. Then, the blank is cut to the preset length, and the cut ends are chamfered and deburred. Step Two: Rough Turning and Semi-Finish Turning. The worm gear blank processed in Step One is rough turned on a precision CNC lathe, leaving a allowance of 0.3mm to 0.8mm on each side. Then, a finish turning tool is switched to perform semi-finish turning, controlling the outer diameter tolerance within ±0.05mm and ensuring that the coaxiality error of each shaft segment is <0.01mm. Step 3: Thread forming machining. Using a multi-start worm gear CNC milling machine or a cyclone milling device, preset the helix angle and lead. Based on the preset helix angle and lead, use a forming tool to mill the teeth of the worm gear blank processed in Step 2 in layers. The cutting depth of each layer is 0.05mm to 0.1mm. Coolant is continuously applied during the milling process to control the temperature rise, resulting in the formed worm gear. Step 4: Heat treatment process. The worm gear formed in Step 3 is placed in a vacuum heat treatment furnace. First, the temperature is raised to 820℃~880℃ at a rate of 8℃ / min~12℃ / min, and held for 20min~40min to complete austenitization. Then, high-pressure gas quenching is performed, with the cooling rate controlled at 60℃ / s~100℃ / s. Finally, it is tempered at 160℃~200℃ for 1.5h~2.5h. Step 5: Fine grinding and polishing. The worm gear teeth, after heat treatment in Step 4, are finely ground using a CNC thread grinder. A cubic boron nitride grinding wheel is used, and the grinding speed is 30m / s to 40m / s. The grinding path is adjusted in real time using an online measurement system to ensure that the helix accuracy reaches P1 level, with a mean diameter variation ≤0.01mm. Step Six: Cleaning and Rust Prevention Treatment. The worm gear after fine grinding in Step Five is ultrasonically cleaned to remove residual abrasive particles and oil stains. Then, it is dipped in rust-preventive oil and dried at 70℃~90℃.

2. The manufacturing process of a worm gear for a dexterous hand of a humanoid robot according to claim 1, characterized in that: In step one, the material is cut using a slow wire EDM machine with a cutting speed of 8mm / min to 12mm / min and a surface roughness controlled within Ra1.6μm. After cutting, the worm gear blank is subjected to magnetic particle testing to ensure that there are no internal cracks or inclusions. The chamfering is performed using a CNC chamfering machine with a chamfering angle of 40° to 50° and a chamfering width of 0.3mm to 0.8mm.

3. The manufacturing process of a worm gear for a dexterous hand of a humanoid robot according to claim 1, characterized in that: In step two, during rough turning, the spindle speed is 600 rpm to 1000 rpm, the feed rate is 0.15 mm / r to 0.25 mm / r, and carbide cutting tools are used. During semi-finish turning, the spindle speed is 1200 rpm to 1800 rpm, the feed rate is 0.08 mm / r to 0.12 mm / r, and ceramic-coated cutting tools are used.

4. The manufacturing process of a worm gear for a dexterous hand of a humanoid robot according to claim 1, characterized in that: In step three, the rake angle of the forming tool is 8° to 12° and the clearance angle is 5° to 8°. During the milling process, the tool wear is monitored in real time by a laser interferometer. When the wear exceeds 0.015mm to 0.025mm, an alarm is automatically triggered and the tool is replaced. The layering strategy is dynamically adjusted according to the number of worm gears. Single-head worm gears are divided into 3 layers, double-head worm gears into 4 layers, and worm gears with three or more heads into 5 layers.

5. The manufacturing process of a worm gear for a dexterous hand of a humanoid robot according to claim 1, characterized in that: In step four, the ultimate vacuum of the vacuum heat treatment furnace is better than 1×10-3 Pa, the gas quenching medium is nitrogen with a purity of 99.999% or higher, the quenching pressure is 0.4MPa~0.8MPa, and the surface hardness of the worm gear after tempering reaches HRC56~64, and the core hardness is HRC43~52.

6. The manufacturing process of a worm gear for a dexterous hand of a humanoid robot according to claim 1, characterized in that: In step five, the cubic boron nitride grinding wheel has a grit size of 100-150 mesh, the binder is a ceramic binder, constant force grinding technology is used during grinding, the grinding force is controlled between 40N and 90N, and the tooth surface profile is sampled and tested every 5 pieces processed by a white light interferometer. Polishing is done with a soft resin grinding wheel with a grit size of W20, a linear speed of 15m / s, and a surface roughness Ra<0.2μm.

7. The manufacturing process of a worm gear for a dexterous hand of a humanoid robot according to claim 1, characterized in that: In step six, the ultrasonic cleaning frequency is 35kHz to 45kHz, the cleaning solution is a water-based environmentally friendly cleaning agent, the cleaning time is 8 to 12 minutes, the rust-preventive oil thickness is 4μm to 10μm, and the surface resistivity of the worm gear after drying is >1×10⁻⁶. 12 Ω.

8. The manufacturing process of a worm gear for a dexterous hand of a humanoid robot according to claim 1, characterized in that: A stress-relief annealing process is added between step three and step four. The worm gear formed in step three is heated to 520℃~580℃, held for 3h~5h, then cooled in the furnace to 280℃~320℃, and then air-cooled to room temperature to release the residual stress introduced by the cutting process.

9. The manufacturing process of a worm gear for a dexterous hand of a humanoid robot according to claim 1, characterized in that: After step five, dynamic balancing is performed. The worm gear, which has been finely ground in step five, is placed on a dynamic balancing machine, and the imbalance is detected at a speed of 2500 rpm to 3500 rpm. If the imbalance exceeds 0.4 g·mm to 0.6 g·mm, it is corrected by weight removal. Weight removal is performed by micro-beam plasma drilling with a hole diameter of 0.2 mm to 0.4 mm and a depth of 0.3 mm to 0.7 mm to ensure that the imbalance after correction is <0.3 g·mm.

10. The manufacturing process of a worm gear for a dexterous hand of a humanoid robot according to claim 1, characterized in that: All machining processes in the aforementioned method for manufacturing the worm gear of a humanoid robot's dexterous hand are carried out in a temperature-controlled workshop with an ambient temperature controlled at 20℃±1℃ and a relative humidity of <50%. The entire process is integrated into a flexible manufacturing system, and the automatic transfer of the worm gear between processes is achieved through a six-axis industrial robot. The repeatability of the six-axis industrial robot is ±0.02mm.

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