A method for machining a transfer case ball cam

Abstract

This invention discloses a method for machining a transfer case ball cam, comprising the following steps: CNC turning before quenching; hobbing the CNC-turned workpiece; CNC milling the hobbed workpiece for spiral ball grooves and deduplication holes; carburizing and quenching the CNC-milled workpiece before quenching; hard turning the left end face, inner hole, and chamfer of the workpiece after quenching; grinding the surface of the gear on the workpiece; hard milling the spiral ball groove on the quenched workpiece; and wire cutting the workpiece using a one-sided, two-pin positioning method. This invention not only ensures the phase relationship between the outer contour of the ball cam gear and the spiral ball groove, as well as the accuracy and quenching layer depth of the carburizing and quenching of the tooth surface and the spiral ball groove surface, but also effectively improves the machining efficiency and yield of the drive ball cam.

Description

Technical Field

[0001] This invention belongs to the field of automotive parts processing, and specifically relates to a method for processing a transfer case ball cam. Background Technology

[0002] The four-wheel drive transfer case is a crucial transmission assembly widely used in mid-to-high-end four-wheel drive vehicles, its function being to transmit the torque output from the transmission to all four wheels. The drive ball cam is the core component of the actuator mechanism in the four-wheel drive transfer case, its main function being to control the engagement of the clutch. Firstly, the drive ball cam combines the machining features of an irregular gear outer contour and a helical ball groove. Secondly, to ensure the high wear resistance and high strength requirements of the helical ball groove, its surface needs to be carburized and quenched before machining. Summary of the Invention

[0003] To address the aforementioned problems in existing technologies, this invention provides a transfer case ball cam machining method for ball cam parts requiring carburizing and quenching, as well as for machining parts with irregular gear outer contours. This method not only ensures the phase relationship between the outer contour of the ball cam gear and the helical ball groove, as well as the accuracy and quenching layer depth of the carburizing and quenching on the tooth surface and the helical ball groove surface, but also effectively improves the machining efficiency and yield of the active ball cam.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A method for machining a transfer case ball cam includes the following steps:

[0006] S1. CNC turning before quenching: Clamp the ball cam blank on the three-jaw chuck of the CNC lathe, position the left end face of the blank, and clamp the outer circle with hard jaws; turn the right end face, outer circle and outer contour; loosen the three-jaw chuck, remove the workpiece, turn it around and clamp it, clamp it and finish turn the outer circle in sequence, using the finish turn right end face as the positioning, finish turn the left end face, outer circle and outer contour;

[0007] S2. Gear hobbing: Gear hobbing is performed on the workpiece after it has been completed by CNC turning. The workpiece inner hole is tightened by a hydraulic expansion sleeve clamp, the left end face of the workpiece is positioned, and the workpiece is hobbing.

[0008] S3. CNC milling before quenching: The workpiece after gear hobbing is subjected to CNC milling of spiral ball groove and de-weighting hole; CNC milling is performed by using special CNC milling fixture to clamp the workpiece, and after milling the spiral ball groove, the de-weighting hole and positioning hole are machined.

[0009] S4. Carburizing and quenching: Carburizing and quenching is a surface treatment performed on the workpiece that has been CNC milled before quenching.

[0010] S5. Hard turning after quenching: Clamp the quenched workpiece onto the three-jaw chuck, clamp the outer circle of the tooth tip with soft jaws, position the right end face of the workpiece, and CNC hard turn the left end face, inner hole and chamfer of the workpiece.

[0011] S6. Gear grinding: A hydraulic expansion sleeve fixture is used to press the left end face of the hard-turned workpiece against the end face of the fixture. After the expansion sleeve tightens the inner hole of the workpiece, the surface of the gear is finished.

[0012] S7. Hard milling: The workpiece is finished by spiral ball groove after quenching. The hard milling is also performed by clamping the workpiece using the CNC milling fixture.

[0013] S8. Wire EDM: Wire EDM uses a one-sided two-pin positioning method. The workpiece to be cut is placed on a special wire EDM fixture for wire EDM processing.

[0014] Further, step S1 includes:

[0015] S11. First clamping of CNC lathe before quenching: Clamp the blank on the three-jaw chuck of the CNC lathe, clamp the outer circle D1 of the blank with hard jaws, position the left end face T1 of the blank, start the CNC lathe turning function, call the outer circle roughing tool to perform rough turning on the right end face, outer circle and outer contour of the workpiece, and call the outer circle finish turning tool to perform finish turning on the outer circle, right end face and outer contour of the workpiece.

[0016] S12. Second clamping of CNC lathe before quenching: Turn around and clamp the workpiece on the three-jaw chuck. The hard jaws clamp the outer circle of the workpiece and position the right end face of the workpiece. Start the CNC lathe turning function, call the roughing tool to perform rough turning on the left end face and outer circle of the workpiece, call the outer circle finishing tool to finish turning the outer circle and right end face of the workpiece, call the inner hole roughing tool to rough turn the inner hole, and call the inner hole finishing tool to finish turn the inner hole.

[0017] Furthermore, in step S11, an external turning tool is used to rough machine the right end face, outer circle, and outer contour of the workpiece, leaving a finishing allowance of 0.5mm on each side; an external turning tool is used to finish machine the outer circle, right end face, and outer contour of the workpiece, ensuring that the outer circle runs out of 0.015mm relative to the right end face.

[0018] Further, in step S12, a roughing tool is used to rough machine the left end face and outer diameter of the workpiece, leaving a 0.5mm allowance on each side; an outer diameter finishing tool is used to finish machine the outer diameter and right end face of the workpiece, leaving a 0.15mm hard turning allowance on the left end face; an inner hole roughing tool is used to rough machine the inner hole, leaving a 0.5mm finish turning allowance on each side; an inner hole finishing tool is used to finish machine the inner hole, leaving a 0.015mm hard turning allowance on each side, with a cylindricity requirement of 0.015mm and a relative end face runout requirement of 0.015mm.

[0019] Furthermore, the CNC milling fixture includes a three-axis worktable, a fixture body, a pressure plate, pads, and a cover plate. The fixture body is provided with a boss. First, the fixture body is placed on the three-axis worktable, then the pressure plate is placed on both sides of the fixture body, and the pads are used to assist in supporting the pressure plate. Then, the fixture body is fixed to the worktable by passing the pressure plate bolts through the pressure plate. The center of the outer circle of the boss of the fixture body is measured with a probe as the origin of the machining x and y directions, and the lower surface of the boss is measured with a probe as the origin of the z direction. The inner hole of the workpiece to be milled is placed on the outer circle of the boss. After the lower surface of the boss mates with the left end face of the workpiece to be milled, the cover plate is placed on the workpiece to be milled and fastened to the fixture body with the cover plate bolts.

[0020] Furthermore, the outer circle of the fixture body and the inner hole of the workpiece to be milled adopt a clearance fit of H6 / h6 based on the shaft system. The runout of the outer circle of the boss and the lower end face of the boss body is required to be 0.015mm, and the runout of the lower end face of the boss and the lower end face of the fixture S2 is required to be 0.015mm.

[0021] Further, in step S7, the workpiece clamping process using the CNC milling fixture is as follows: after fixing the fixture body to the worktable, the coordinate origin is measured, and the workpiece to be hard-milled is placed on the fixture body. The lower end face of the fixture body boss positions the left end face of the workpiece hard-turned. After placing the workpiece to be hard-milled on the fixture body, a dial indicator is installed on the machine spindle, with the dial indicator needle in contact with the right side of the straightening groove. The machine spindle is moved in the y-direction to adjust the angle of the workpiece placement fixture body so that the change in the dial indicator dial is less than 0.02mm. Then, the workpiece to be hard-milled is fastened to the fixture body with a cover plate.

[0022] Furthermore, in step S3, for the machining of the spiral ball groove, a two-stage machining process is adopted. The first stage uses a φ8 end mill for deburring, and the second stage uses a φ6 ball end mill for finishing before quenching of the spiral ball groove. For the machining of the deduplication hole, a φ10R2 rounded end mill is used for machining. For the machining of the straightening groove, after machining the spiral ball groove, a φ8 end mill is used to machine the straightening groove used for part alignment after quenching.

[0023] Further, in step S8, the wire EDM fixture includes a fixture body, a locating pin, and a cover plate. First, the fixture body is placed on the wire EDM worktable, and then a dial indicator is used to move it in the y-direction until the dial indicator's runout is less than 0.01 mm. Then, the fixture body is fixed to the wire EDM worktable, and the locating pin is placed in the locating hole of the fixture body. After the locating hole of the CNC-machined workpiece to be cut is matched with the upper part of the locating pin, it is fastened to the fixture body by the cover plate. The wire EDM wire is passed through the wire threading hole, and the wire EDM equipment is started to perform wire EDM.

[0024] The present invention has the following beneficial effects:

[0025] This invention provides a method for machining a transfer case ball cam, which is suitable for small-batch trial production and manufacturing processes, effectively ensuring the machining efficiency and finished product accuracy of this type of part.

[0026] A clamping scheme for spiral ball groove before and after quenching is proposed. By using a special clamping fixture, the parts can be repeatedly clamped by simply removing the clamping bolts and cover plate. Only one positioning is required, which improves the workpiece processing efficiency.

[0027] Regarding the assembly method between the fixture body and the workpiece, the positioning accuracy of the clamping is improved by controlling the precision requirements of the outer circle of the boss of the fixture body, the lower end face of the boss and the lower end face of the workpiece, as well as the matching method between the boss and the inner hole and end face of the workpiece, so that the positioning error of the workpiece clamping before and after quenching is less than 0.02mm.

[0028] A method for aligning a spiral ball groove after carburizing and quenching is provided. Before quenching, the workpiece is machined with a straight groove by CNC milling. After quenching, the clamping state of the workpiece is controlled by the runout of a dial indicator, and the positioning accuracy of the spiral ball groove before and after quenching is controlled to be less than 0.03mm.

[0029] Methods for CNC machining of spiral ball grooves before and after quenching are provided. For the features of the spiral ball grooves before quenching, programming machining strategies of clearing the model area with φ8 end mill and offsetting the 3D contour with φ6 ball cutter are adopted respectively. The machining allowance after carburizing and quenching is controlled.

[0030] A machining method is provided to ensure the phase relationship between the spiral ball groove and the incomplete gear. Only the bolts and cover plate need to be removed to achieve repeated clamping of parts, ensuring the positioning accuracy of wire EDM machining. The repeatability of the workpiece positioning accuracy is less than 0.02mm, and only the runout of the fixture end face and the machining coordinates need to be confirmed before the first machining, thus improving the workpiece machining efficiency.

[0031] For wire EDM, the system provides wire EDM paths and methods, ensuring that the workpiece remains clamped during the wire EDM process, both during entry and exit, and preventing deformation of the workpiece and the wire EDM fixture body. This also ensures the phase relationship between the gear shape and the helical ball groove. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the transfer case ball cam structure;

[0034] Figure 2 This is a schematic diagram of the process for machining a transfer case ball cam according to the present invention;

[0035] Figure 3 This is a schematic diagram of a forging blank;

[0036] Figure 4 A schematic diagram showing how a CNC milling fixture clamps the workpiece to be milled before quenching.

[0037] Figure 5 Exploded view of the CNC milling fixture structure;

[0038] Figure 6 A schematic diagram of the fixture body structure for CNC milling machine tools;

[0039] Figure 7 This is a schematic diagram of the straightening groove after quenching;

[0040] Figure 8 This is a schematic diagram of the clamping of a CNC lathe workpiece after quenching.

[0041] Figure 9 This is a schematic diagram of the alignment of a CNC milling workpiece after quenching.

[0042] Figure 10 Schematic diagram of the positioning hole for a wire-cut workpiece;

[0043] Figure 11 Exploded view of a tooling fixture specifically for wire EDM;

[0044] Figure 12 This is a schematic diagram of the machining path for a wire EDM workpiece.

[0045] In the picture:

[0046] 1-Cover plate bolt; 2-Cover plate; 3-Pressure plate bolt; 4-Workpiece to be milled; 5-Pressure plate; 6-Clamp body; 7-Padded block; 8-Worktable; 10-Workpiece to be cut; 11-Positioning pin; 12-Clamp body. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0048] Example

[0049] Active ball cam structure as follows Figure 1As shown, compared to the structure of general gear parts, this type of part not only includes the characteristic structure of a helical ball groove, but also, due to its transmission requirements, has an incomplete gear structure in its outer contour, with a phase angle relationship between the gear contour and the helical ball groove. To meet the high wear resistance and high hardness requirements of both the gear and the helical ball groove, this type of part requires carburizing and quenching. Since carburizing and quenching has requirements for the depth of the surface hardness layer, to ensure the surface accuracy requirements of the helical ball groove and gear, the gear and helical ball groove need to be machined before carburizing and quenching, and the heat-treated deformed surfaces need to be finished after quenching. This ensures that the required carburizing depth is met while satisfying the surface accuracy and roughness requirements of the helical ball groove and gear.

[0050] This embodiment describes a method for machining a transfer case ball cam, including pre-quenching CNC turning (two-stage), gear hobbing, CNC milling, carburizing and quenching heat treatment, quenched hard turning, gear grinding, hard milling, and wire EDM machining; the machining equipment included in the process includes a CNC lathe, gear hobbing machine, three-axis vertical machining center, gear grinding machine, and wire EDM equipment. Figure 2 As shown, the specific steps include:

[0051] S1. CNC turning before quenching: Clamp the ball cam blank on the three-jaw chuck of the CNC lathe, position the left end face of the blank, and clamp the outer circle with hard jaws; turn the right end face, outer circle and outer contour, loosen the three-jaw chuck, remove the workpiece, turn it around and clamp it, clamp it and finish turn the outer circle in sequence, using the right end face as the positioning, finish turn the left end face, outer circle and outer contour; after completion, loosen the three-jaw chuck and remove the workpiece.

[0052] S11. First clamping of CNC lathe before quenching: Forged blank as follows Figure 3 As shown, the blank is clamped on the three-jaw chuck of the CNC lathe, and the outer circle D1 of the blank is clamped with the hard jaws. The left end face T1 of the blank is positioned. The CNC lathe turning function is started, and the outer diameter roughing tool is used to perform rough turning on the right end face, outer circle and outer contour of the workpiece. A finishing allowance of 0.5mm is left on each side. The outer diameter finishing tool is used to perform finish turning on the outer circle, right end face and outer contour of the workpiece, ensuring that the runout of the outer circle relative to the right end face is 0.015mm.

[0053] S12. Second clamping of CNC lathe before quenching: Turn around and clamp the workpiece on the three-jaw chuck. Clamp the outer diameter of the workpiece with the hard jaws and position the right end face of the workpiece. Start the CNC lathe turning function and use the roughing tool to rough turn the left end face and outer diameter of the workpiece, leaving 0.5mm on each side. Use the outer diameter finishing tool to finish turn the outer diameter and right end face of the workpiece, leaving 0.15mm of hard turning allowance on the left end face. Use the inner hole roughing tool to rough turn the inner hole, leaving 0.5mm of finish turning allowance on each side. Use the inner hole finishing tool to finish turn the inner hole, leaving 0.015mm of hard turning allowance on each side. Cylindricity requirement: 0.015mm. Relative end face runout requirement: 0.015mm.

[0054] S2. Gear hobbing: The workpiece after CNC turning is hobbed. The hobbing uses a hydraulic expansion sleeve fixture, which is close to the left end face of the CNC lathe in the first precision turning. The fixture expands the inner hole of the workpiece, positions the left end face of the workpiece, starts the hobbing function, and calls the hob to perform gear hobbing on the workpiece. After the machining is completed, the expansion sleeve is retracted and the hobbed workpiece is unloaded.

[0055] S3. CNC Milling Before Quenching: The workpiece after gear hobbing is subjected to CNC milling for spiral ball grooves and de-emphasis holes. CNC milling is performed using a dedicated CNC milling fixture. The workpiece is placed on the fixture body, ensuring the outer circle of the fixture body's boss mates with the inner hole of the workpiece. A cover plate is then used to clamp the workpiece, and bolts are used to secure it. The spiral ball groove is milled first, followed by the de-emphasis holes and positioning holes. After milling, the cover plate is removed, and the workpiece is taken off.

[0056] The CNC milling special tooling structure is as follows: Figure 4 , Figure 5 As shown, first place the fixture body 6 on the three-axis worktable 8, then place the pressure plate 5 on both sides of the fixture body, and use the pads 7 to assist in supporting the pressure plate. Then, use the pressure plate bolts 3 to pass through the pressure plate 5 to fix the fixture body 6 on the worktable 8. Use a probe to measure the center of the outer circle of the boss of the fixture body as the origin of the machining x and y directions, and use a probe to measure the lower surface of the boss as the origin of the z direction. Place the inner hole of the workpiece on the outer circle of the boss, and after the lower surface of the boss mates with the left end face of the workpiece, place the cover plate 2 on the workpiece 4 to be milled, and then tighten it to the fixture body 6 with the cover plate bolts 1. Start the machine tool, call the machining program to perform machining, and perform the feature machining of the spiral ball groove, the weight removal hole, and the straightening groove. After the machining is completed, loosen and tighten the cover plate bolts 1, remove the cover plate 2, and then remove the workpiece 4 to be milled.

[0057] For the fixture body 6, such as Figure 6 As shown, the outer circle and the inner hole of the workpiece to be milled adopt a clearance fit of H6 / h6 based on the shaft system. For the fixture body, in order to ensure the machining accuracy requirements, the runout of the outer circle D2 of the boss and the lower end face S1 of the boss is required to be 0.015mm, and the runout of the lower end face S1 of the boss and the lower end face S2 of the fixture is required to be 0.015mm.

[0058] For CNC milling, Powermill machining software is used for contour programming. For spiral ball groove machining, a two-stage machining process is employed: the first stage uses an 8mm end mill for material removal, and the second stage uses a 6mm ball end mill for pre-quenching finishing, leaving a 0.15mm machining allowance after quenching. For removing excess holes, a 10R2 rounded end mill is used. For straightening groove machining, such as... Figure 7 As shown, after machining the spiral ball groove, a φ8 end mill is used to machine the straightening groove C1, which is used for part alignment after quenching. After the program is written, the machining program is imported into the machine tool.

[0059] S4. Carburizing and quenching: The workpiece that has been CNC milled before quenching is placed in a vacuum furnace for carburizing and quenching surface treatment.

[0060] S5. Hard turning after quenching: such as Figure 8 As shown, the quenched workpiece is clamped onto the three-jaw chuck, and the outer circle of the tooth tip is clamped with soft jaws to position the right end face of the workpiece. The turning function is started, and the left end face, inner hole and chamfer of the workpiece are hard-turned by CNC, ensuring that the runout of the left end face relative to the inner hole is less than 0.015mm; after machining, the three-jaw chuck is released and the workpiece is unloaded.

[0061] S6. Gear Grinding: Gear grinding also uses a hydraulic expansion sleeve fixture. After hard turning, the workpiece is placed on the expansion sleeve fixture with its left end face close to the end face of the fixture. After the expansion sleeve tightens the inner hole of the workpiece, the gear grinding function is started to perform fine machining on the surface of the workpiece gear. After the machining is completed, the expansion sleeve is retracted and the workpiece is removed.

[0062] S7. Hard Milling: The hardened workpiece undergoes helical ball groove finishing. The hard milling is also performed using the CNC milling fixture. The hard-turned inner hole and positioning hole of the workpiece are placed on the boss of the fixture body of the CNC milling fixture. After the left end face of the workpiece is pressed against the fixture body, the workpiece is pressed with a cover plate and fixed with bolts. The helical ball groove is then finished with hard milling, and the positioning hole is machined by wire cutting. After the milling is completed, the bolts are loosened and the cover plate is removed to unload the workpiece.

[0063] like Figure 9 As shown, after fixing the fixture body to the worktable, the coordinate origin is measured, and the measurement position is consistent with S3. After measuring the machining origin, the workpiece to be hard-milled is placed on the fixture body. The outer circle of the boss on the fixture body mates with the inner hole of the hard-turned part, and the fit level is consistent with S3. The lower end face of the boss on the fixture body positions the left end face of the workpiece for hard turning. After placing the workpiece on the fixture body, the dial indicator is installed on the machine spindle, with the dial indicator needle in contact with the right side of the straightening groove. The machine spindle is moved in the y-direction to observe the change in the dial indicator dial. By adjusting the angle of the workpiece placement fixture body, the change in the dial indicator dial is made less than 0.02mm. The workpiece is then secured to the fixture body with a cover plate and bolts. The machine tool is started, and the spiral ball groove finishing program is called to perform finishing of the spiral ball groove features. Then, the wire-cut positioning hole is machined. The wire-cut positioning hole D4 is shown in the figure. Figure 10 As shown, two positioning holes are machined along the y-axis of the workpiece for wire EDM positioning. After milling, the bolts are loosened and the cover plate is removed, and the workpiece is unloaded.

[0064] S8. Wire EDM: Wire EDM uses a one-sided two-pin positioning method. The positioning hole of the workpiece to be cut is placed on the positioning pin of the wire EDM special tooling. After covering it with a cover plate, it is tightened with bolts to perform wire EDM.

[0065] Special tooling structure for wire EDM, such as Figure 11 As shown, first place the fixture body 12 on the wire EDM worktable, then move it in the y direction with a dial indicator until the dial indicator's runout is less than 0.01mm, then fix the fixture body 12 to the wire EDM worktable, place the positioning pin 11 in the positioning hole K1 of the fixture, then align the positioning hole of the CNC-machined workpiece 10 (after quenching) with the upper part of the positioning pin 11, then fasten the cover plate 2 to the fixture body 12 with bolts 1, then pass the wire-cut metal wire through the wire-threading hole K2, call the wire EDM cutting program, and start the wire EDM equipment function to perform wire cutting.

[0066] For wire EDM programs, the workpiece's rotation center is used as the programming origin, such as... Figure 12 As shown, the wire EDM program route is: K2 center L1 → entry point L2 → exit point L3 → K3 center L4. After the metal wire is passed through the wire threading hole K2, the wire EDM positioning program is called. After identifying the actual coordinates of the center of K2, it is set as the theoretical coordinates for the programming and the cutting process is performed. After the outer contour is cut, it exits from L3. When the metal wire reaches L4, the automatic wire bending setting is performed.

[0067] After completing the machining, loosen and tighten the cover plate bolts, remove the cover plate, and then unload the machined workpiece.

[0068] 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 method for machining a transfer case ball cam, characterized in that, Includes the following steps: S1. CNC turning before quenching: The ball cam blank is clamped on the three-jaw chuck of the CNC lathe, the left end face of the blank is positioned, and the outer circle is clamped with hard jaws; the right end face, outer circle, and outer contour are turned; the three-jaw chuck is released, the workpiece is unloaded, turned around and clamped, and the outer circle is finished in sequence. Using the right end face as a positioning, the left end face, outer circle, and outer contour are finished; Step S1 includes: S11. First clamping of CNC lathe before quenching: Clamp the blank on the three-jaw chuck of the CNC lathe, clamp the outer circle of the blank (D1) with the hard jaws, position the left end face of the blank (T1), start the CNC lathe turning function, call the outer circle roughing tool to perform rough turning on the right end face, outer circle and outer contour of the workpiece, and call the outer circle finish turning tool to perform finish turning on the outer circle, right end face and outer contour of the workpiece. S12. Second clamping of CNC lathe before quenching: Turn around and clamp the workpiece on the three-jaw chuck. The hard jaws clamp the outer circle of the workpiece and position the right end face of the workpiece. Start the CNC lathe turning function, call the roughing tool to perform rough turning on the left end face and outer circle of the workpiece, call the outer circle finishing tool to finish turning the outer circle and right end face of the workpiece, call the inner hole roughing tool to rough turn the inner hole, and call the inner hole finishing tool to finish turn the inner hole. S2. Gear hobbing: Gear hobbing is performed on the workpiece after it has been completed by CNC turning. The workpiece inner hole is tightened by a hydraulic expansion sleeve clamp, the left end face of the workpiece is positioned, and the workpiece is hobbing. S3. Pre-quenching CNC milling: The workpiece after gear hobbing undergoes CNC milling to create a spiral ball groove and a de-dust hole. The CNC milling process uses a dedicated CNC milling fixture for workpiece clamping. After milling the spiral ball groove, the de-dust hole and positioning hole are machined. The spiral ball groove machining is performed in two stages. The first stage uses… End mills are used for machining, and the second step uses... The ball end mill is used for finishing before quenching the spiral ball groove; for machining the deduplication hole, the following is adopted: The rounded end mill is used for machining; for straightening groove machining, after machining the spiral ball groove, a rounded end mill is used. A straightening groove, machined by an end mill and used for part alignment after quenching; S4. Carburizing and quenching: Carburizing and quenching is a surface treatment performed on the workpiece that has been CNC milled before quenching. S5. Hard turning after quenching: Clamp the quenched workpiece onto the three-jaw chuck, clamp the outer circle of the tooth tip with soft jaws, position the right end face of the workpiece, and CNC hard turn the left end face, inner hole and chamfer of the workpiece. S6. Gear grinding: A hydraulic expansion sleeve fixture is used to press the left end face of the hard-turned workpiece against the end face of the fixture. After the expansion sleeve tightens the inner hole of the workpiece, the surface of the gear is finished. S7. Hard milling: The workpiece is finished by spiral ball groove after quenching. The hard milling is also performed by clamping the workpiece using the CNC milling fixture. S8. Wire EDM: Wire EDM uses a one-sided two-pin positioning method. The workpiece to be cut is placed on a special wire EDM fixture for wire EDM processing.

2. The method for machining a transfer case ball cam as described in claim 1, characterized in that, In step S11, the outer diameter roughing tool is used to rough machine the right end face, outer diameter and outer contour of the workpiece, leaving a 0.5mm finishing allowance on each side; the outer diameter finishing tool is used to finish machine the outer diameter, right end face and outer contour of the workpiece, ensuring that the outer diameter runs out 0.015mm relative to the right end face.

3. The method for machining a transfer case ball cam as described in claim 1, characterized in that, In step S12, a roughing tool is used to rough machine the left end face and outer diameter of the workpiece, leaving a 0.5mm allowance on each side; an outer diameter finishing tool is used to finish machine the outer diameter and right end face of the workpiece, leaving a 0.15mm hard turning allowance on the left end face; an inner hole roughing tool is used to rough machine the inner hole, leaving a 0.5mm finish turning allowance on each side; an inner hole finishing tool is used to finish machine the inner hole, leaving a 0.015mm hard turning allowance on each side, with a cylindricity requirement of 0.015mm and a relative end face runout requirement of 0.015mm.

4. The method for machining a transfer case ball cam as described in claim 1, characterized in that, The CNC milling fixture includes a three-axis worktable, a fixture body, a pressure plate, pads, and a cover plate. The fixture body has a boss. First, the fixture body is placed on the three-axis worktable. Then, the pressure plate is placed on both sides of the fixture body, and the pads are used to support the pressure plate. Then, the fixture body is fixed to the worktable by passing the pressure plate bolts through the pressure plate. The center of the outer circle of the boss on the fixture body is measured with a probe as the origin of the machining x and y directions, and the lower surface of the boss is measured with a probe as the origin of the z direction. The inner hole of the workpiece to be milled is placed on the outer circle of the boss. After the lower surface of the boss mates with the left end face of the workpiece to be milled, the cover plate is placed on the workpiece to be milled and fastened to the fixture body with the cover plate bolts.

5. The method for machining a transfer case ball cam as described in claim 4, characterized in that, The outer circle of the fixture body and the inner hole of the workpiece to be milled adopt a clearance fit of H6 / h6 based on the shaft system. The runout of the outer circle of the boss and the lower end face of the boss body is required to be 0.015mm, and the runout of the lower end face of the boss and the lower end face of the fixture S2 is required to be 0.015mm.

6. The method for machining a transfer case ball cam as described in claim 4, characterized in that, In step S7, the workpiece clamping process using the CNC milling fixture is as follows: After fixing the fixture body to the worktable, the coordinate origin is measured, and the workpiece to be hard-milled is placed on the fixture body. The lower end face of the fixture body boss positions the left end face of the workpiece hard-turned. After placing the workpiece to be hard-milled on the fixture body, the dial indicator is installed on the machine spindle, with the dial indicator needle in contact with the right side of the straightening groove. The machine spindle is moved in the y-direction to adjust the angle of the workpiece placement fixture body so that the change in the dial indicator dial is less than 0.02mm. Then, the workpiece to be hard-milled is fastened to the fixture body with a cover plate.

7. The method for machining a transfer case ball cam as described in claim 1, characterized in that, In step S8, the wire EDM fixture includes a fixture body, a locating pin, and a cover plate. First, the fixture body is placed on the wire EDM worktable. Then, a dial indicator is used to move it in the y-direction until the dial indicator's runout is less than 0.01 mm. The fixture body is then fixed to the wire EDM worktable, and the locating pin is placed in the locating hole of the fixture body. After the locating hole of the CNC-machined workpiece to be cut is aligned with the upper part of the locating pin, it is then fastened to the fixture body by the cover plate. The wire EDM wire is then passed through the wire threading hole, and the wire EDM equipment is started to perform wire EDM.

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