A method for manufacturing high-precision needle roller bearings for arc-shaped cam indexing mechanisms

Abstract

This application discloses a manufacturing method for high-precision needle roller bearings used in arc-face cam indexing mechanisms, belonging to the field of precision bearing manufacturing technology. This invention achieves metallographic streamline orientation control of rollers and bushings through closed-die forging, matches the component matrix properties through co-furnace heat treatment, achieves sub-micron level concentricity control through synchronous pairing grinding with dual grinding heads, eliminates batch precision deviations through group selection and assembly, and ensures indexing accuracy stability through working condition simulation and running-in calibration. The resulting full-needle roller bearing has an overall rotational concentricity ≤0.8μm. When applied to arc-face cam indexing mechanisms, the rotary table indexing and repeatability accuracy error is ≤1.8 arcseconds, the first-pass yield is ≥98.5%, and the service life is extended by more than 40%. This completely solves the industry pain points of insufficient concentricity, large indexing errors, and poor precision retention in existing needle roller bearings, and is suitable for high-end CNC machining, precision automation equipment, and other fields.

Description

Technical Field

[0001] This invention relates to the field of precision bearing machining technology, specifically to a method for manufacturing high-precision needle roller bearings for arc-shaped cam indexing mechanisms. It is particularly suitable for arc-shaped cam indexing mechanisms in high-end CNC rotary tables and five-axis machining centers, and can meet the stringent requirements of high-precision indexing, high repeatability, and heavy-load impact resistance for machining complex parts in aerospace, precision molds, medical devices and other fields. Background Technology

[0002] The arc-face cam indexing mechanism is a core functional component of CNC rotary tables and precision automated equipment. It achieves intermittent indexing motion through the backlash-free meshing of the cam and driven wheel. Its indexing accuracy and repeatability directly determine the machining accuracy and operational stability of the final equipment. Needle roller bearings, as the core support and transmission component of the arc-face cam indexing mechanism, must simultaneously meet stringent requirements such as high coaxiality, low radial runout, high wear resistance, long service life, and resistance to intermittent impacts. Their manufacturing precision directly determines the final performance of the indexing mechanism.

[0003] In existing technologies, machining solutions for precision bearings mostly focus on optimizing the machining of individual rolling elements. For example, the prior art document CN103008994A discloses a method for producing steel balls for high-speed, high-precision CNC machine tool bearings. It only optimizes the process for machining a single spherical steel ball for bearings, and the core technical problem it solves is reducing the spherical error and diameter variation of the steel ball, thereby reducing the vibration and noise of high-speed rotating bearings. The application scenario is high-speed rotating CNC machine tool spindle bearings. This prior art document does not cover the entire process of manufacturing a complete set of full-length needle roller bearings, nor does it provide customized process design for the special working conditions of low-speed heavy-load, intermittent indexing, and clearanceless meshing of the arc-face cam indexing mechanism. It cannot solve the problem of excessive indexing error caused by insufficient concentricity between the rollers and bushings of the needle roller bearing.

[0004] The existing conventional needle roller bearing manufacturing process has the following core technical defects: 1. Non-directional design of blank forming process: cold heading or open forging are mostly used. The flow lines of the metallographic structure are discontinuous and non-directionally distributed, and the matrix is ​​not dense enough. Under the heavy load intermittent impact conditions of the arc surface cam indexing mechanism, fatigue failure at the flow line cut-off point is likely to occur, resulting in short service life. 2. Lack of coordinated matching in heat treatment processes: Rollers, bushings, and needle rollers are mostly heat treated in batches, resulting in large differences in hardness, expansion coefficient, and residual stress among parts in the same batch. This leads to severe springback in precision after subsequent grinding, large concentricity deviation after assembly, and poor precision retention. 3. Grinding process without pairing control: Single parts are often ground independently without synchronous pairing processing control. The dimensional matching between the outer circle of the roller and the inner circle of the bushing is poor. The concentricity of the roller and bushing in conventional products can only reach more than 3μm, which cannot achieve submicron level precision control. 4. No precision compensation in assembly process: Without the selection and matching of needle roller groups and preload control, the full needle type structure is prone to uneven force on the needle rollers, resulting in large assembly deformation and a significant decrease in the rotational accuracy of the finished bearing. 5. Lack of working condition simulation verification: Only static accuracy testing was performed, without simulating the running-in and accuracy calibration of the intermittent indexing conditions of the arc-face cam indexing mechanism. After the bearing was installed, the accuracy decayed rapidly under actual working conditions, resulting in an indexing error of more than 10 arcseconds caused by the bearing itself alone. This could not meet the requirement of indexing error ≤2 arcseconds for high-end CNC equipment. At the same time, there were problems such as low batch product qualification rate (only about 75%), short service life, and poor accuracy stability under heavy load conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a manufacturing method for high-precision needle roller bearings for arc-shaped cam indexing mechanisms. The invention features a fully customized process design for the special working conditions of arc-shaped cam indexing mechanisms, forming a closed-loop precision control system from blank forging, heat treatment, grinding, assembly to testing and calibration. This method completely solves the core industry pain points of existing needle roller bearings, such as insufficient concentricity, large indexing error, poor precision retention, and low finished product qualification rate.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for manufacturing a high-precision needle roller bearing for an arc-faced cam indexing mechanism, wherein the needle roller bearing is a full-needle type structure adapted to the backlash-free meshing condition of the arc-faced cam indexing mechanism, including coaxially mating rollers and bushings, as well as needle rollers and retaining rings, comprising the following closed-loop process: S1, Directional Streamline Blank Forging: GCr15SiMn bearing steel is selected as raw material. After precise CNC blanking, the roller blank and sleeve blank are formed by closed-die forging at 1100-1150℃. The forging deformation is controlled at 60%-70%. After forging, the blank is cooled in the furnace to below 200℃ before being removed from the furnace. During the closed-die forging process, the forging streamlines are controlled to be directionally and continuously distributed along the axial direction of the roller and the circumferential direction of the sleeve, so that the metallographic structure of the blank is dense and streamlined, and the raw material utilization rate is ≥85%. S2, Composite Precision Deburring: First, the blank is mechanically ground at a speed of 800-1000 r / min using a 400# diamond grinding wheel to remove burrs. After grinding, the surface roughness of the blank Ra≤1.6μm; then, a high-pressure water jet of 80-100MPa and a moving speed of 5-8mm / s is used to directionally flush the fine burrs on the roller end face and the retaining ring groove of the roller sleeve, controlling the rounding radius of the blank's sharp corners R≤0.05mm, with no processing stress concentration at the rounding point and no residual burrs on the surface; S3, Customized Heat Treatment for Matched Batches: Roller, bushing, and needle roller blanks are placed in a nitrogen-protected atmosphere furnace with an oxygen content ≤50ppm, and quenching and low-temperature tempering are performed simultaneously. Quenching is carried out at 8-10℃ / min to 840-860℃, held for 2-2.5 hours, and then oil-cooled, controlling the surface hardness of the blanks to HRC61-63. Tempering is carried out at 5℃ / min to 160-180℃, held for 3-4 hours, and then air-cooled, controlling the hardness uniformity of parts in the same batch to ≤HRC0.5 and the decarburized layer depth to ≤0.01mm. After heat treatment, a deep cryogenic-tempering cycle is performed, placing the blanks in a... Keep the blank in a cryogenic oven at 60℃~-70℃ for 2-3 hours, then air-cool it to room temperature, and then place it in an oven at 150-170℃ for 2-3 hours to cool it in the oven. Repeat the cryogenic-tempering cycle twice to control the residual austenite content of the blank to ≤1% and completely eliminate the residual internal stress of the matrix. S4, Synchronous Paired Stepped Precision Grinding: A dedicated dual-head CNC grinding machine with a centering accuracy ≤0.001mm and a polyurethane elastic pneumatic centering fixture are used to synchronously pair and grind rollers and bushings after heat treatment in the same furnace. The process involves three stages: rough grinding, fine grinding, and precision grinding. Each stage strictly matches the diamond grinding paste of the corresponding grit size, grinding pressure, and rotation speed. After each stage of rough grinding, fine grinding, and precision grinding, the rollers and bushings are cleaned for 10-15 minutes using a 28-40kHz ultrasonic cleaner with anhydrous ethanol as the cleaning medium. After cleaning, they are dried with hot air at 40-50℃ and their concentricity and cylindricity are tested using a laser interferometer with a detection accuracy ≤0.0001mm. Defective products are returned to the corresponding grinding stage for rework. Ultimately, the concentricity of the paired rollers and bushings is controlled to ≤0.5μm, the outer cylindricity to ≤1μm, and the dimensional deviation of the paired parts to ≤0.2μm. S5, high-precision assembly by group selection: Assembly is carried out in a Class 1000 cleanroom under constant temperature and humidity conditions of 20±2℃ and 40%-60% relative humidity; the needle rollers are first grouped according to their diameter tolerance, with each group having a diameter tolerance of ≤0.0005mm, and all needle rollers assembled in the same batch are selected from the same group; pneumatic pressing equipment is used to center and assemble the paired rollers and bushings, precisely controlling the needle roller clearance of 0.002-0.003mm, pressing force of 500-800N, pressing speed of 1-2mm / s, and the clearance between the retaining ring and the bushing ≤0.001mm. After assembly, the bearing axial preload deviation is checked and found to be ≤5%; S6, Working Condition Simulation Finished Product Inspection and Calibration: Using a high-precision roundness meter with a measurement accuracy of ≤0.0005μm and a laser goniometer with an angle measurement accuracy of ≤0.1 arcseconds, the assembled bearings are first subjected to initial accuracy testing; then the bearings are installed on a dedicated running-in table to simulate the intermittent indexing conditions of the arc-face cam indexing mechanism. The bearings are run-in without load for 30 minutes at 100-150r / min, and then run-in for 60 minutes with an axial load of 50-100N at 300r / min. After the running-in is completed, a full accuracy test is performed again at a test speed of 300r / min and with ≥1000 sampling points. For bearings with a concentricity of 0.8-1μm, 0.0005-0.001mm local micro-fine grinding calibration is performed using 4000# diamond grinding paste. Ultimately, the overall rotational concentricity of the finished bearing is guaranteed to be ≤1μm and the radial runout ≤1μm. After application to the arc-face cam indexing mechanism, the rotary table indexing and repeatability accuracy error is ≤2 arcseconds.

[0007] In a preferred embodiment, in step S1, the dimensional error of CNC blanking is ≤ ±0.1mm, the machining accuracy of the die cavity for closed die forging is ≤0.005mm, and the die cavity is provided with a streamline guide structure along the roller axis and the bushing circumference to ensure that the forging streamline is oriented and continuously distributed, without streamline cut-off or eddy defects.

[0008] In a preferred embodiment, in step S2, the high-pressure water jet uses pure water as the medium, with a nozzle diameter of 0.3-0.5mm and a spray angle of 30°-45° to the sharp corner of the blank. This is used to perform targeted rinsing of the chamfered end face of the roller and the root of the retaining ring groove of the roller sleeve, thereby preventing corrosion and secondary damage to the surface of the blank.

[0009] In a preferred embodiment, during step S3, the blanks for rollers, bushings, and needle rollers are positioned and clamped using special tooling throughout the quenching, tempering, and cryogenic treatment processes. The rollers are placed vertically in the axial direction and the bushings are placed horizontally in the circumferential direction to avoid deformation due to their own weight during heat treatment and to ensure that the deformation deviation of parts in the same batch is ≤0.003mm.

[0010] In a preferred embodiment, in step S4, the rough grinding uses 800# diamond grinding paste, with a grinding pressure of 0.15-0.2MPa and a grinding speed of 500-600r / min, removing a machining allowance of 0.05-0.1mm and controlling the cylindricity of the outer circle to ≤5μm; the fine grinding uses 1500# diamond grinding paste, with a grinding pressure of 0.1-0.15MPa and a grinding speed of 700-800r / min, removing a machining allowance of 0.01-0.02mm and controlling the cylindricity of the outer circle to ≤1μm; the precision grinding uses 3000# diamond grinding paste, with a grinding pressure of 0.05-0.08MPa and a grinding speed of 900-1000r / min, removing a machining allowance of 0.002-0.005mm, achieving a concentricity of ≤0.5μm for the mating parts.

[0011] In a preferred embodiment, the stepped precision grinding process in step S4 is carried out in an environment with a cleanliness level of 10,000, a constant temperature of 20±1℃, and a relative humidity of 45%-55%. During the grinding process, an online laser diameter gauge is used to monitor the workpiece size in real time, and the size fluctuation is controlled within ±0.0002mm. Before each batch of grinding, the radial runout of the grinding machine spindle is calibrated, and after calibration, the radial runout of the spindle is ≤0.0003mm.

[0012] In a preferred embodiment, in step S5, the needle roller is made of GCr15SiMn bearing steel, which is the same material and heat-treated in the same furnace as the roller and the bushing. The diameter tolerance of the needle roller is ≤ ±0.001mm and the length tolerance is ≤ ±0.002mm. Before assembly, the needle roller, roller, bushing and retaining ring are all ultrasonically cleaned and dried, and there are no impurities left on the surface. The entire assembly process avoids bumps and scratches on the surface of the parts.

[0013] In a preferred embodiment, after the finished product inspection and calibration in step S6, the bearing raceway surface is subjected to plasma nitriding treatment, with the nitriding layer thickness controlled at 0.01-0.02mm, surface hardness at HV800-900, and the surface roughness of the raceway after nitriding Ra≤0.2μm, and the bearing operating friction coefficient≤0.0015. After nitriding treatment, the bearing is subjected to rotational concentricity testing again to ensure that the accuracy is without deviation.

[0014] In one preferred embodiment, during the running-in process of step S6, clean bearing-specific grease is continuously sprayed onto the bearing raceway. After the running-in is completed, the bearing is subjected to a second ultrasonic cleaning to remove the wear debris generated during the running-in process. Then, a full-size accuracy inspection is performed to reject products with out-of-tolerance accuracy after the running-in process.

[0015] In one preferred embodiment, after the testing and calibration in step S6, a clean and rust-proof packaging process is performed: the qualified finished product is ultrasonically cleaned in anhydrous ethanol for 5 minutes, dried with hot air at 40°C, and then aerospace-grade rust-proof lubricating grease with a thickness of 0.01~0.02mm is evenly coated on the bearing raceway and needle roller surface. The product is then sealed in a vacuum aluminum-plastic bag in a Class 1000 clean environment, with nitrogen gas filling the bag for protection. The residual oxygen content is ≤100ppm to ensure that the product is free from rust and has no loss of precision during storage.

[0016] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are as follows: 1. Order-of-magnitude improvement in precision: The overall rotational concentricity of the manufactured needle roller bearing is ≤1μm, which is more than 83% higher than that of existing mainstream products. When applied to CNC rotary tables, the indexing and repeatability accuracy error is ≤2 arcseconds. The indexing error caused by the bearing itself is reduced from 10 arcseconds to less than 2 arcseconds, an 80% reduction in error. This completely solves the problem of excessive machining accuracy on rotary tables caused by insufficient precision of traditional needle roller bearings.

[0017] 2. Significantly improved reliability and service life: Through closed-die forging, customized heat treatment, cryogenic stabilization, and plasma nitriding strengthening, the density of the bearing matrix is ​​increased by more than 50%, wear resistance is increased by more than 40%, service life is extended by more than 35%, fatigue impact resistance under heavy load conditions is increased by more than 50%, and the precision retention rate after grinding is ≥99.5%.

[0018] 3. Significantly improved batch consistency and yield: Standardized closed-loop management throughout the entire process increases the first-pass yield of finished products from 75% in traditional processes to over 98%, and the precision error between batches is ≤0.2μm, improving precision consistency by over 90%, completely solving the problem of large precision fluctuations between batches in traditional processes. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic flowchart illustrating a method for manufacturing a high-precision needle roller bearing for an arc-shaped cam indexing mechanism according to the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0024] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0025] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] Please see the appendix Figure 1 To make the technical solution, advantages and effects of the present invention clearer and easier to understand, the following detailed description is provided in conjunction with three sets of embodiments of different specifications and one set of prior art comparative examples. All performance tests adopt unified standard testing methods and equipment.

[0028] Unified testing standards and equipment: Metallographic structure and forging flow line inspection: Olympus GX53 metallographic microscope was used; Concentricity / cylindricity inspection: using a Taylor-Hopson PGI 1240 laser interferometer, with an inspection accuracy of ≤0.0001mm; Hardness testing: Rockwell hardness tester HR-150A was used, with a testing accuracy of ±0.5HRC; Bearing rotation accuracy testing: A Tokyo Seimitsu RONDCOM 60A high-precision roundness tester was used, with a measurement accuracy of ≤0.0005μm; Turntable indexing accuracy testing: using a Renishaw XL-80 laser interferometer, with an angle measurement accuracy of ≤0.1 arcseconds; Wear life test: The bearing life tester was used to run continuously for 1000 hours under rated load to detect wear and accuracy decay.

[0029] Example 1 This embodiment provides a manufacturing method for a high-precision needle roller bearing for a 200-type five-axis CNC rotary table arc cam indexing mechanism, applicable to a 200-type five-axis CNC rotary table used for precision machining of aerospace engine blades, with core requirements of ultra-high positioning accuracy and high stability.

[0030] Bearing specifications: roller diameter φ8mm, length 20mm; roller sleeve inner diameter φ40mm, outer diameter φ50mm, length 20mm; full needle type structure, number of needles 36.

[0031] The entire manufacturing process is as follows: S1, Directional Streamline Blank Forging: GCr15SiMn bearing steel bars are selected and precisely cut by CNC lathe with a blanking dimensional error ≤ ±0.1mm; closed-die forging process is used for roller and bushing blanks, with die cavity machining accuracy ≤ 0.005mm, and axial / circumferential streamline guiding structure is set; forging temperature is 1120℃, forging deformation is 65%, and after forging, it is cooled to 180℃ in the furnace before being taken out of the furnace. The forging streamlines are controlled to be directional and continuous along the axial direction of the roller and the circumferential direction of the bushing, without streamline cut-off or eddy current defects. The metallographic structure of the blank is dense and streamlined, and the raw material utilization rate is 88%. S2, Composite Precision Deburring: First, a 400# diamond grinding wheel is used to mechanically grind the blank at a speed of 900 r / min to remove burrs. After grinding, the surface roughness Ra≤1.6μm. Then, a 90MPa high-pressure water jet is used with a nozzle diameter of 0.4mm, a spray angle of 40°, and a moving speed of 6mm / s to directionally rinse the chamfer of the roller end face and the root of the roller retaining ring groove. Pure water is used as the medium. The rounding radius of the blank's sharp corners is R=0.03mm. There is no stress concentration at the rounding point, and no residual burrs on the surface. S3, Customized Heat Treatment for Paired Parts in the Same Batch: Roller, sleeve, and needle roller blanks are positioned and clamped using special tooling. The rollers are placed vertically in the axial direction and the sleeves are placed horizontally in the circumferential direction. They are placed in a nitrogen protective atmosphere furnace with an oxygen content of ≤50ppm in the same batch and quenching + low-temperature tempering are completed simultaneously. The quenching temperature is increased to 850℃ at 9℃ / min, held for 2.2h, and then oil-cooled. The surface hardness of the blank is HRC62. The tempering temperature is increased to 170℃ at 5℃ / min, held for 3.5h, and then air-cooled. The hardness uniformity of the parts in the same batch is controlled to be ≤HRC0.4, and the decarburized layer depth is ≤0.008mm. After heat treatment, a deep cryogenic-tempering cycle is performed. The blank is placed in a -65℃ deep cryogenic box and held for 2.5h. After air-cooling to room temperature, it is placed in a 160℃ oven and held for 2.5h. It is then cooled with the furnace. This cycle is repeated twice to control the residual austenite content of the blank to be ≤0.9% and completely eliminate the residual internal stress in the matrix. S4, Synchronous Paired Stepped Precision Grinding: Performed in a Class 10,000 cleanroom environment, constant temperature 20±1℃, and relative humidity 50%, using a dedicated dual-head CNC grinding machine with a centering accuracy ≤0.001mm, equipped with a polyurethane elastic pneumatic centering fixture. Before each batch of grinding, the spindle radial runout is calibrated to ≤0.0003mm. Rollers and bushings heat-treated in the same furnace are synchronously paired and ground in three stages: Coarse grinding uses 800# diamond grinding paste, grinding pressure 0.18MPa, grinding speed 550r / min, removing 0.08mm of material, and controlling the outer diameter cylindricity ≤5μm; Fine grinding uses 1500# diamond grinding paste, grinding pressure 0.12MPa, grinding speed 750r / min, removing 0.015mm of material, and controlling the outer diameter cylindricity ≤5μm. Cylindricity ≤1μm; fine grinding uses 3000# diamond grinding paste, grinding pressure 0.06MPa, grinding speed 950r / min, removing 0.003mm of excess material; after each stage, it is ultrasonically cleaned for 12min using 35kHz, dried with 45℃ hot air using anhydrous ethanol as the medium, and inspected by a laser interferometer. Defective products are reworked. The concentricity of the finally paired rollers and bushings is ≤0.4μm, cylindricity is ≤0.8μm, and the dimensional deviation of the parts in the same pairing group is ≤0.15μm; the grinding process is monitored in real time by an online laser diameter gauge, and the dimensional fluctuation is ≤±0.0002mm; S5, high-precision assembly and placement by group selection: This is carried out in a cleanroom with a Class 1000 cleanliness level, 20±2℃, and 50% relative humidity. First, the needle rollers are grouped according to diameter tolerance, with each group having a diameter tolerance of ≤0.0005mm. All 36 needle rollers assembled in this batch are selected from the same group. The needle rollers are made of GCr15SiMn bearing steel, the same material and heat-treated in the same furnace as the rollers and bushings, with a diameter tolerance of ≤±0.001mm and a length tolerance of ≤±0.002mm. After ultrasonic cleaning and drying, all components are assembled using pneumatic pressing equipment to center and assemble the paired rollers and bushings. The needle roller gap is controlled at 0.0025mm, the pressing force at 650N, and the pressing speed at 1.5mm / s. The clearance between the retaining ring and the bushing is ≤0.001mm. After assembly, the bearing axial preload deviation is checked and found to be ≤4%. S6, Simulated Finished Product Inspection and Calibration under Working Conditions: Using a high-precision roundness tester and laser goniometer, the assembled bearings are first subjected to initial precision testing. Then, the bearings are installed on a dedicated running-in table to simulate the intermittent indexing conditions of the arc-face cam indexing mechanism. The bearings are run-in at 120 r / min without load for 30 minutes, and then at 300 r / min with an 80 N axial load for 60 minutes, with clean bearing-specific grease continuously sprayed during the running-in process. After running-in, a second ultrasonic cleaning is performed, followed by full precision testing at a speed of 300 r / min. At a speed of r / min and 1200 sampling points, local micro-fine grinding calibration was performed on products with concentricity of 0.8-1μm. After ultrasonic cleaning and drying, qualified products underwent plasma nitriding treatment on the raceway surface, with the nitriding layer thickness controlled at 0.015mm and the surface hardness at HV850. The surface roughness of the raceway after nitriding was Ra≤0.2μm, and the concentricity was checked again without deviation. Finally, 0.015mm of aerospace-grade anti-rust lubricating grease was applied, and the products were vacuum-sealed in a Class 1000 clean environment using aluminum-plastic bags and nitrogen gas, with the residual oxygen content inside the bag ≤100ppm.

[0032] The finished bearings produced in this embodiment, after testing, have the following characteristics: overall rotational concentricity of 0.7 μm, radial runout of 0.8 μm, and when applied to a 200-type arc-face cam indexing mechanism, the turntable indexing error is 1.6 arcseconds, the repeatability error is 1.2 arcseconds, the first-pass yield is 98.8%, and after 1000 hours of continuous operation under rated load, the accuracy decay rate is ≤0.5%, and the service life is 1.4 times that of products manufactured using traditional processes.

[0033] Example 2 This embodiment provides a manufacturing method for a high-precision needle roller bearing for the arc-surface cam indexing mechanism of a 320-type heavy-duty four-axis CNC rotary table. It is applicable to a 320-type heavy-duty four-axis CNC rotary table used for milling automotive engine cylinder blocks. The core requirements are heavy-duty impact resistance, long service life, and precision stability.

[0034] Bearing specifications: roller diameter φ12mm, length 30mm; roller sleeve inner diameter φ60mm, outer diameter φ75mm, length 30mm; full needle type structure, number of needles 48.

[0035] The entire manufacturing process is as follows: S1, Directional Streamline Blank Forging: CNC blanking dimension error ≤ ±0.1mm, closed die forging cavity machining accuracy ≤ 0.005mm, forging temperature 1100℃, forging deformation 60%, furnace cooling to 190℃ after forging, controlling the continuous directional distribution of forging streamlines along the roller axis and the bushing circumference, raw material utilization rate 86%; S2, Composite Precision Deburring: Mechanical grinding speed 800r / min, high-pressure water jet pressure 80MPa, moving speed 5mm / s, nozzle diameter 0.5mm, spray angle 45°, blank corner rounding radius R=0.04mm, no residual burrs on the surface; S3, customized heat treatment for the same batch: simultaneous quenching and tempering in the same furnace, quenching heating rate 8℃ / min, quenching temperature 840℃, holding for 2.5h and oil cooling, surface hardness HRC61; tempering heating rate 5℃ / min, tempering temperature 160℃, holding for 4h and air cooling, hardness uniformity of parts in the same batch ≤HRC0.5, decarburized layer depth ≤0.01mm; cryogenic-tempering cycle: cryogenic holding at -60℃ for 3h, tempering holding at 150℃ for 3h, cycled twice, retained austenite content ≤1%; S4, Synchronous Paired Stepped Precision Grinding: Coarse grinding uses 800# grinding paste, pressure 0.15MPa, speed 500r / min, removal allowance 0.05mm, cylindricity ≤5μm; Fine grinding uses 1500# grinding paste, pressure 0.1MPa, speed 700r / min, removal allowance 0.01mm, cylindricity ≤1μm; Finish grinding uses 3000# grinding paste, pressure 0.05MPa, speed 900r / min, removal allowance 0.002mm; Finally, the concentricity of the paired rollers and bushings is ≤0.5μm, cylindricity is ≤1μm, and the dimensional deviation of the same pairing group is ≤0.2μm; S5, high-precision assembly and placement by group selection: needle rollers are grouped according to diameter tolerance, with each group having a tolerance zone of ≤0.0005mm. All assembled needle rollers are from the same group, with needle roller clearance controlled at 0.002mm, pressing force at 500N, pressing speed at 1mm / s, and preload deviation ≤5%. S6, Working condition simulation finished product testing and calibration: Simulated working condition running-in: 100r / min no load running-in for 30min, 300r / min, 50N load running-in for 60min; testing speed 300r / min, sampling points 1000 points, qualified products undergo plasma nitriding treatment and rust-proof packaging.

[0036] The finished bearings produced in this embodiment, after testing, have the following characteristics: overall rotational concentricity of 0.9 μm, radial runout of 0.9 μm, and when applied to a 320-type arc-face cam indexing mechanism, the turntable indexing error is 1.8 arcseconds, the repeatability error is 1.3 arcseconds, the first-pass yield is 98.2%, and after 1000 hours of continuous operation under rated load, the accuracy decay rate is ≤0.6%, and the impact resistance is improved by 55% compared to traditional processes.

[0037] Example 3 This embodiment provides a manufacturing method for large-size, high-precision needle roller bearings for a 400-type APC horizontal cam exchange table. It is applicable to 400-type APC horizontal dual-station exchange tables used for batch processing of automotive parts. The core requirements are dual-station synchronous accuracy and high-frequency exchange stability.

[0038] Bearing specifications: roller diameter φ15mm, length 40mm; roller sleeve inner diameter φ80mm, outer diameter φ100mm, length 40mm; full needle type structure, number of needles 56.

[0039] The entire manufacturing process is as follows: S1 Directional Streamline Blank Forging: CNC blanking dimensional error ≤ ±0.1mm, closed die forging temperature 1150℃, forging deformation 70%, furnace cooling to 170℃ after forging, forging streamlines are continuously distributed directionally along the roller axis and the sleeve circumferential direction, and the raw material utilization rate is 85%; S2, Composite Precision Deburring: Mechanical grinding speed 1000r / min, high-pressure water jet pressure 100MPa, moving speed 8mm / s, nozzle diameter 0.3mm, spray angle 30°, blank corner rounding radius R=0.02mm, no residual burrs on the surface; S3, customized heat treatment for the same batch: simultaneous quenching and tempering in the same furnace, quenching heating rate 10℃ / min, quenching temperature 860℃, holding for 2 hours and oil cooling, surface hardness HRC63; tempering heating rate 5℃ / min, tempering temperature 180℃, holding for 3 hours and air cooling, hardness uniformity of parts in the same batch ≤HRC0.45, decarburized layer depth ≤0.009mm; cryogenic-tempering cycle: cryogenic holding at -70℃ for 2 hours, tempering holding at 170℃ for 2 hours, cycled twice, retained austenite content ≤0.8%; S4, Synchronous Paired Stepped Precision Grinding: Coarse grinding uses 800# grinding paste, pressure 0.2MPa, speed 600r / min, removal of 0.1mm, cylindricity ≤5μm; Fine grinding uses 1500# grinding paste, pressure 0.15MPa, speed 800r / min, removal of 0.02mm, cylindricity ≤1μm; Finish grinding uses 3000# grinding paste, pressure 0.08MPa, speed 1000r / min, removal of 0.005mm; The final concentricity of the paired rollers and bushings is ≤0.45μm, cylindricity is ≤0.9μm, and the dimensional deviation of the same paired group is ≤0.18μm; S5, high-precision assembly and placement by group selection: needle rollers are grouped according to diameter tolerance, with each group having a tolerance zone of ≤0.0005mm. All assembled needle rollers are from the same group, with needle roller clearance controlled at 0.003mm, pressing force at 800N, pressing speed at 2mm / s, and preload deviation ≤4.5%. S6, Working condition simulation finished product testing and calibration: Simulated working condition running-in: 150r / min no load running-in for 30min, 300r / min, 100N load running-in for 60min; test speed 300r / min, sampling points 1500 points, qualified products undergo plasma nitriding treatment, nitriding layer thickness 0.02mm, surface hardness HV900, and finally complete rust-proof encapsulation.

[0040] The finished bearings produced in this embodiment, after testing, have the following characteristics: overall rotational concentricity of 0.8 μm, radial runout of 0.85 μm. When applied to a 400-type arc-face cam indexing mechanism, the turntable indexing error is 1.7 arcseconds, the repeatability error is 1.1 arcseconds, the first-pass yield is 98.5%, and after 1000 hours of continuous operation under high-frequency turntable changing conditions, the accuracy decay rate is ≤0.4%, the wear resistance is improved by 45%, and the service life is extended by 40%.

[0041] Comparative Example 1 This comparative example uses the existing conventional needle roller bearing manufacturing process. The raw materials and bearing specifications are completely consistent with those in Example 1. The process is as follows: conventional open forging blank forming, ordinary filing to remove burrs, conventional box furnace batch heat treatment, single-stage conventional single-part grinding, ordinary workshop assembly without grouping, conventional static testing, without paired processing, closed-loop control and working condition simulation.

[0042] The finished bearings produced in this comparative example were tested and found to have an overall rotational concentricity of 3.5 μm and a radial runout of 4 μm. When applied to the same type of arc-shaped cam indexing mechanism, the turntable indexing error was 11 arcseconds, the repeatability error was 8 arcseconds, the first-pass yield was 72%, and after 1000 hours of continuous operation under rated load, the accuracy decay rate was ≥8%, and the service life was only 60% of that of Example 1.

[0043] The comparison between the above embodiments and comparative examples clearly shows that, through the customized process design of the entire process, the present invention has achieved a significant improvement in bearing rotation accuracy, indexing accuracy, finished product qualification rate, service life, and accuracy retention compared with the existing conventional process, achieving unexpected and remarkable technical effects and completely solving the core pain points of the existing technology.

[0044] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a high-precision needle roller bearing for an arc-faced cam indexing mechanism, wherein the needle roller bearing is a full-needle type structure adapted to the backlash-free meshing condition of the arc-faced cam indexing mechanism, comprising coaxially mating rollers and bushings, as well as needle rollers and retaining rings, characterized in that, Includes the following closed-loop processes: S1, Directional Streamline Blank Forging: GCr15SiMn bearing steel is selected as raw material. After precise CNC blanking, the roller blank and sleeve blank are formed by closed-die forging at 1100-1150℃. The forging deformation is controlled at 60%-70%. After forging, the blank is cooled in the furnace to below 200℃ before being removed from the furnace. During the closed-die forging process, the forging streamlines are controlled to be directionally and continuously distributed along the axial direction of the roller and the circumferential direction of the sleeve, so that the metallographic structure of the blank is dense and streamlined, and the raw material utilization rate is ≥85%. S2, Composite Precision Deburring: First, the blank is mechanically ground at a speed of 800-1000 r / min using a 400# diamond grinding wheel to remove burrs. After grinding, the surface roughness of the blank Ra≤1.6μm; then, a high-pressure water jet of 80-100MPa and a moving speed of 5-8mm / s is used to directionally flush the fine burrs on the roller end face and the retaining ring groove of the roller sleeve, controlling the rounding radius of the blank's sharp corners R≤0.05mm, with no processing stress concentration at the rounding point and no residual burrs on the surface; S3, Customized Heat Treatment for Matched Batches: Roller, bushing, and needle roller blanks are placed in a nitrogen-protected atmosphere furnace with an oxygen content ≤50ppm, and quenching and low-temperature tempering are performed simultaneously. Quenching is carried out at 8-10℃ / min to 840-860℃, held for 2-2.5 hours, and then oil-cooled, controlling the surface hardness of the blanks to HRC61-63. Tempering is carried out at 5℃ / min to 160-180℃, held for 3-4 hours, and then air-cooled, controlling the hardness uniformity of parts in the same batch to ≤HRC0.5 and the decarburized layer depth to ≤0.01mm. After heat treatment, a deep cryogenic-tempering cycle is performed, placing the blanks in a... Keep the blank in a cryogenic oven at 60℃~-70℃ for 2-3 hours, then air-cool it to room temperature, and then place it in an oven at 150-170℃ for 2-3 hours to cool it in the oven. Repeat the cryogenic-tempering cycle twice to control the residual austenite content of the blank to ≤1% and completely eliminate the residual internal stress of the matrix. S4, Synchronous Paired Stepped Precision Grinding: A dedicated dual-head CNC grinding machine with a centering accuracy ≤0.001mm and a polyurethane elastic pneumatic centering fixture are used to synchronously pair and grind rollers and bushings after heat treatment in the same furnace. The process involves three stages: rough grinding, fine grinding, and precision grinding. Each stage strictly matches the diamond grinding paste of the corresponding grit size, grinding pressure, and rotation speed. After each stage of rough grinding, fine grinding, and precision grinding, the rollers and bushings are cleaned for 10-15 minutes using a 28-40kHz ultrasonic cleaner with anhydrous ethanol as the cleaning medium. After cleaning, they are dried with hot air at 40-50℃ and their concentricity and cylindricity are tested using a laser interferometer with a detection accuracy ≤0.0001mm. Defective products are returned to the corresponding grinding stage for rework. Ultimately, the concentricity of the paired rollers and bushings is controlled to ≤0.5μm, the outer cylindricity to ≤1μm, and the dimensional deviation of the paired parts to ≤0.2μm. S5, high-precision assembly by group selection: Assembly is carried out in a Class 1000 cleanroom under constant temperature and humidity conditions of 20±2℃ and 40%-60% relative humidity; the needle rollers are first grouped according to their diameter tolerance, with each group having a diameter tolerance of ≤0.0005mm, and all needle rollers assembled in the same batch are selected from the same group; pneumatic pressing equipment is used to center and assemble the paired rollers and bushings, precisely controlling the needle roller clearance of 0.002-0.003mm, pressing force of 500-800N, pressing speed of 1-2mm / s, and the clearance between the retaining ring and the bushing ≤0.001mm. After assembly, the bearing axial preload deviation is checked and found to be ≤5%; S6, Working condition simulation finished product inspection and calibration: Using a high-precision roundness meter with a measurement accuracy of ≤0.0005μm and a laser goniometer with an angle measurement accuracy of ≤0.1 arcsecond, the assembled bearing is first subjected to initial accuracy testing; then the bearing is installed on a special running-in table to simulate the intermittent indexing condition of the arc cam indexing mechanism, running-in without load for 30 minutes at a speed of 100-150r / min, and running-in with an axial load of 50-100N at a speed of 300r / min for 60 minutes; After the running-in is completed, a full-precision test is performed again. The test speed is 300 r / min and the number of sampling points is ≥1000. For bearings with concentricity of 0.8-1μm, 0.0005-0.001mm local micro-fine grinding calibration is performed using 4000# diamond grinding paste. Finally, it is ensured that the overall rotational concentricity of the finished bearing is ≤1μm and the radial runout is ≤1μm. After being applied to the arc-face cam indexing mechanism, the indexing and repeatability accuracy error of the turntable is ≤2 arcseconds.

2. The manufacturing method of the high-precision needle roller bearing for the arc-surface cam indexing mechanism according to claim 1, characterized in that, In step S1, the dimensional error of CNC blanking is ≤ ±0.1mm, the machining accuracy of the die cavity of closed die forging is ≤0.005mm, and the die cavity is equipped with a streamline guide structure along the roller axis and the roller sleeve circumferential direction to ensure that the forging streamline is oriented and continuously distributed, without streamline cut-off or eddy defects.

3. The manufacturing method of the high-precision needle roller bearing for the arc-surface cam indexing mechanism according to claim 1, characterized in that, In step S2, the high-pressure water jet uses pure water as the medium, with a nozzle diameter of 0.3-0.5mm and a spray angle of 30°-45° to the sharp corner of the blank. It performs targeted rinsing on the chamfer of the roller end face and the root of the roller retaining ring groove to avoid corrosion and secondary damage to the blank surface.

4. The manufacturing method of the high-precision needle roller bearing for the arc-shaped cam indexing mechanism according to claim 1, characterized in that, In step S3, throughout the quenching, tempering, and cryogenic treatment process, the blanks of rollers, bushings, and needle rollers are positioned and clamped using special tooling. The rollers are placed vertically in the axial direction and the bushings are placed horizontally in the circumferential direction to avoid deformation due to their own weight during heat treatment and to ensure that the deformation deviation of parts in the same batch is ≤0.003mm.

5. The manufacturing method of the high-precision needle roller bearing for the arc-surface cam indexing mechanism according to claim 1, characterized in that, In step S4, rough grinding uses 800# diamond grinding paste, with a grinding pressure of 0.15-0.2MPa and a grinding speed of 500-600r / min, removing 0.05-0.1mm of machining allowance and controlling the cylindricity of the outer circle to ≤5μm; fine grinding uses 1500# diamond grinding paste, with a grinding pressure of 0.1-0.15MPa and a grinding speed of 700-800r / min, removing 0.01-0.02mm of machining allowance and controlling the cylindricity of the outer circle to ≤1μm; and precision grinding uses 3000# diamond grinding paste, with a grinding pressure of 0.05-0.08MPa and a grinding speed of 900-1000r / min, removing 0.002-0.005mm of machining allowance, achieving a concentricity of ≤0.5μm for mating parts.

6. The method for manufacturing a high-precision needle roller bearing for an arc-shaped cam indexing mechanism according to claim 1, characterized in that, The stepped precision grinding process in step S4 is carried out in an environment with a cleanliness level of 10,000, a constant temperature of 20±1℃, and a relative humidity of 45%-55%. During the grinding process, an online laser diameter gauge is used to monitor the workpiece size in real time, and the size fluctuation is controlled within ±0.0002mm. Before each batch of grinding, the radial runout of the grinding machine spindle is calibrated, and after calibration, the radial runout of the spindle is ≤0.0003mm.

7. The method for manufacturing a high-precision needle roller bearing for an arc-shaped cam indexing mechanism according to claim 1, characterized in that, In step S5, the needle rollers are made of GCr15SiMn bearing steel, which is the same material and heat-treated in the same furnace as the rollers and bushings. The diameter tolerance of the needle rollers is ≤ ±0.001mm and the length tolerance is ≤ ±0.002mm. Before assembly, the needle rollers, rollers, bushings and retaining rings are all ultrasonically cleaned and dried, and there are no impurities left on the surface. The entire assembly process avoids bumps and scratches on the surface of the parts.

8. The method for manufacturing a high-precision needle roller bearing for an arc-shaped cam indexing mechanism according to claim 1, characterized in that, After the finished product inspection and calibration in step S6 is completed, the bearing raceway surface is subjected to plasma nitriding treatment. The nitriding layer thickness is controlled at 0.01-0.02mm, the surface hardness is HV800-900, the surface roughness of the raceway after nitriding is Ra≤0.2μm, and the bearing operating friction coefficient is ≤0.0015. After nitriding treatment, the bearing is subjected to rotational concentricity test again to ensure that the accuracy is without deviation.

9. The method for manufacturing a high-precision needle roller bearing for an arc-shaped cam indexing mechanism according to claim 1, characterized in that, During the running-in process in step S6, clean bearing-specific grease is continuously sprayed onto the bearing raceway. After the running-in is completed, the bearing is subjected to a second ultrasonic cleaning to remove the wear debris generated during the running-in. Then, a full-dimensional accuracy inspection is performed, and products with out-of-tolerance accuracy after the running-in are rejected.

10. The method for manufacturing a high-precision needle roller bearing for an arc-shaped cam indexing mechanism according to claim 1, characterized in that, After the testing and calibration in step S6 are completed, a clean and rust-proof packaging process is carried out: the qualified finished product is placed in anhydrous ethanol for ultrasonic cleaning for 5 minutes, dried with hot air at 40℃, and then aerospace-grade anti-rust grease with a thickness of 0.01~0.02mm is evenly coated on the bearing raceway and needle roller surface. It is then sealed in a vacuum aluminum-plastic bag in a Class 1000 clean environment. The bag is filled with nitrogen for protection, and the oxygen residue is ≤100ppm to ensure that the product is free from rust and has no loss of precision during storage.

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