An electric field-assisted spline cold forging method and machine tool

Abstract

This invention discloses an electric field-assisted spline cold forming method and machine tool; this invention belongs to the technical field of machining and metal plastic forming equipment; it aims to solve the problems of high load, rapid mold wear and poor forming quality in the cold forming of splines of difficult-to-deform materials such as high-strength alloy steel and titanium alloy; the positive terminal of the pulse power supply forms a circuit with the workpiece through the center and the negative terminal through the brush, so that the high-frequency pulse current flows directly through the cold forming deformation zone, inducing the electroplastic effect, reducing the yield strength of the material and improving plasticity; on this basis, the symmetrically arranged cold forming tools apply radial force to the workpiece as the spindle rotates, and the spline teeth are formed by the axial feed and rotation of the workpiece; this method deeply couples electric field softening with mechanical forming, fundamentally reducing the forming load, extending the mold life and improving the spline dimensional accuracy and surface quality.

Description

Technical Field

[0001] This invention belongs to the technical field of machining and metal plastic forming equipment, and relates to an electric field-assisted spline cold forming method and machine tool. Specifically, it is an electric field-assisted spline cold forming machine tool and cold forming method that utilizes the electroplastic effect to assist in the forming of difficult-to-deform materials. Background Technology

[0002] Splines are core components in mechanical transmission systems, and cold forging has become the mainstream manufacturing process due to its high production efficiency and continuous material fibers. However, with the increasing trend towards lightweight high-end equipment, drive shafts are increasingly using high-strength alloy steel, titanium alloys, and other difficult-to-deform materials, leading to serious technical bottlenecks in traditional room-temperature cold forging processes. Because these materials have high room-temperature yield strength and poor plasticity, they exhibit significant deformation resistance during cold forging. This not only requires machine tools with extremely high forming tonnage, accelerating fatigue damage to the spindle and transmission system, but also causes the cold forging die to experience extremely high contact stress and severe wear, significantly shortening die life and increasing production costs. Furthermore, severe plastic deformation easily leads to severe stress concentration and springback, making it extremely difficult to control the dimensional accuracy of splines and easily causing micro-cracks to develop at the tooth root and other locations, creating a potential safety hazard of fatigue fracture.

[0003] Theoretical studies have shown that applying high-density pulsed current or electric field to metallic materials can induce an "electroplastic effect," significantly reducing the material's yield strength and increasing its plasticity. However, in the current field of spline cold forging equipment, there is a lack of dedicated equipment and mature processes capable of safely and deeply coupling an electric field system with a high-speed, heavy-duty cold forging machine. How to safely and efficiently introduce a high-frequency pulsed electric field precisely into the local deformation zone and synchronize it with the mechanical forming action in a complex mechanical extrusion environment is a technological gap that urgently needs to be addressed. Therefore, there is an urgent need to develop a new electric field-assisted spline cold forging machine and forming method to fundamentally solve the problems of high cold forging loads, short die life, and poor forming quality of difficult-to-deform materials. Summary of the Invention

[0004] To address the problems in the background art, the present invention adopts the following technical solution: This invention provides an electric field-assisted spline cold forging method, the method comprising the following steps: S1: Push the workpiece into the machine tool from the loading and unloading device, start the clamping chuck to clamp the front end of the workpiece, control the clamping slide to move the workpiece to the center point through the controller, start the tailstock chuck to clamp the end of the workpiece, control the tailstock drive motor and the center point drive motor to fix the front and end of the workpiece axially by the center point and the tailstock chuck, and release the clamping chuck. S2: Control the tailstock drive motor to drive the tailstock chuck to rotate the workpiece, and stop rotating after ensuring that the workpiece does not jump significantly. S3: Start the hydraulic cylinders of the center brush and the rod brush, control the center brush to contact the rear end of the center, and the rod brush to contact the workpiece, and continuously apply a certain pressure to ensure that there is no gap between the contact surfaces; S4: Start the pulse power supply and tailstock drive motor to ensure that a continuous current is applied to the workpiece during rotation; S5: Start the input motor to control the rotary spindle to drive the cold forming tool to rotate, start the tailstock drive motor to control the tailstock slide to move and the tailstock chuck to rotate, realize the axial feeding and rotation of the workpiece, and complete the cold forming of the workpiece. S6: After the cold forging process is completed, control the clamping slide and clamping chuck to remove the workpiece from the loading and unloading device.

[0005] An electric field-assisted spline cold forging machine tool using the method described in the claims includes a machine bed, a clamping slide, a clamping chuck, a rod brush hydraulic cylinder, a transmission mechanism, an input motor, a gearbox, a machine column, a cold forging mechanism, a center brush, a center brush hydraulic cylinder, a center drive motor, a center, a pulse power supply, a controller, a rod brush, a workpiece, a tailstock chuck, a loading and unloading device, a tailstock drive motor, a tailstock slide, and a guide rail. The transmission mechanism includes a cylindrical gear pair, a bracket, and a bevel gear pair. The cold forging mechanism includes a rotary spindle, a tool spindle base, a tool spindle, a tool spindle end cover, and a cold forging tool. The machine column, input motor, gearbox, transmission mechanism, pulse power supply, controller, center brush hydraulic cylinder, and cold forging mechanism are mounted on the machine bed. The input motor is connected to the gearbox, the gearbox is connected to the transmission mechanism, and the transmission mechanism is connected to the cold forging mechanism for transmission. The clamping slide and tailstock slide are mounted on the guide rails of the machine tool bed. The clamping chuck and the rod brush hydraulic cylinder are mounted on the clamping slide. The loading / unloading device and the tailstock chuck are mounted on the tailstock slide. The tailstock drive motor is mounted on the side of the loading / unloading device for controlling the movement of the tailstock slide and the rotation of the tailstock chuck. The center and the center drive motor are mounted on the machine tool column. The center drive motor is connected to the center for controlling the extension and retraction of the center. The center brush and the rod brush are respectively mounted on the center brush hydraulic cylinder and the end of the rod brush. The contact surfaces of the brushes are in contact with the center and the workpiece, respectively.

[0006] Preferably, the transmission mechanism includes a bracket, a cylindrical gear pair, and a bevel gear pair. The gears in the cylindrical gear pair are respectively mounted on the bracket and the gearbox, and the bevel gear pair is respectively mounted on the bracket and the rotary spindle. The synchronous rotation of the rotary spindle is achieved through the meshing of the gears in the transmission mechanism.

[0007] Preferably, the cold forging mechanism includes a rotary spindle, a tool spindle chassis, a tool spindle, a tool spindle end cap, and a cold forging tool. The rotary spindle is mounted on the machine tool bed, the tool spindle chassis, the tool spindle, and the tool spindle end cap are mounted on the rotary spindle, and the cold forging tool is mounted on the tool spindle. The mounting positions of the tool spindle with the tool spindle chassis and the tool spindle end cap use insulated bearings and insulated gaskets.

[0008] Compared with the prior art, the present invention has the following beneficial effects: This invention provides an electric field-assisted spline cold forging method and machine tool. Its basic principle utilizes the electroplastic effect induced by high-frequency pulsed current to generate in-situ modification within the workpiece material. As shown in the figure, the device combines a pulsed power supply and a cold forging mechanism through an electrical path, allowing them to work synergistically on the workpiece. Specifically, the positive terminal of the pulsed power supply is connected to the tip in contact with the workpiece via a wire, and the negative terminal is connected to the brush in contact with the workpiece via a wire. This allows a high-density, high-frequency pulsed current to directly enter the workpiece from the tip, flow through the local deformation zone, and then exit through the brush, thereby forming a specific high-frequency pulsed electric field within the workpiece section located in the cold forging tool's action zone. When this high-frequency pulsed electric field acts on the workpiece, its high-density electron flow interacts with dislocations within the metal, accelerating dislocation movement and activating new dislocation sources, inducing an electroplastic effect. This significantly reduces the material's yield strength (deformation resistance) macroscopically, increasing its plasticity. Meanwhile, based on the softening of the material by the electric field, two symmetrically arranged cold forging tools rotate under the drive of their respective rotary spindles and apply radial force to the workpiece deformation zone. Combined with the workpiece moving along the feed direction and the synchronous rotation of the workpiece itself, the spline tooth profile is cold forged and formed. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope.

[0010] Figure 1 A schematic diagram of an electric field-assisted spline cold forging machine; Figure 2 This is a schematic diagram of the machine tool's transmission mechanism and cold-pressing mechanism; Figure 3 Schematic diagram of the electric field-assisted cold spline forming principle; Figure 1-2: 1. Machine bed; 2. Clamping slide; 3. Clamping chuck; 4. Rod brush hydraulic cylinder; 5. Transmission mechanism; 6. Input motor; 7. Gearbox; 8. Machine column; 9. Cold forging mechanism; 10. Center brush; 11. Center brush hydraulic cylinder; 12. Center drive motor; 13. Center; 14. Pulse power supply; 15. Controller; 16. Rod brush; 17. Workpiece; 18. Tailstock chuck; 19. Loading and unloading device; 20. Tailstock drive motor; 21. Tailstock slide; 22. Guide rail; 23. Cylindrical gear pair; 24. Support; 25. Bevel gear pair; 26. Rotary spindle; 27. Tool spindle base; 28. Tool spindle; 29. ​​Tool spindle end cover; 30. Cold forging tool. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0012] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0013] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art. Specific implementation method one: This invention provides an electric field-assisted spline cold forging machine. Its main structure is based on a machine bed 1 as a support platform. A guide rail 22 is mounted on the machine bed 1, and a clamping slide 2 and a tailstock slide 21 are respectively arranged on the guide rail 22. A clamping chuck 3 and a rod brush hydraulic cylinder 4 are mounted on the clamping slide 2. A loading / unloading device 19 and a tailstock chuck 18 are mounted on the tailstock slide 21. A tailstock drive motor 20 is mounted on the side of the loading / unloading device 19 to synchronously control the axial movement of the tailstock slide 21 along the guide rail 22 and the rotation of the tailstock chuck 18. A machine tool column 8 is also fixedly mounted on the machine bed 1. A center drive motor 12 and a center 13 are mounted on the machine tool column 8. The center drive motor 12 is connected to the center 13 to control the extension and retraction of the center 13. A center brush hydraulic cylinder 11 is mounted on the side of the machine tool column 8, with its end brush 10 facing the rear end of the center 13. The machine tool bed 1 is also equipped with an input motor 6, a gearbox 7, a transmission mechanism 5, a cold-pressing mechanism 9, a pulse power supply 14, and a controller 15. The transmission mechanism 5 includes a cylindrical gear pair 23 and a bevel gear pair 25 mounted on a bracket 24. The cylindrical gear pair 23 is respectively mounted on the bracket 24 and the gearbox 7, and the bevel gear pair 25 is respectively mounted on the bracket 24 and the rotary spindle 26 of the cold-pressing mechanism 9. The power output from the input motor 6 via the gearbox 7 is transmitted to the rotary spindle 26 through the meshing of the two-stage gears.

[0015] The cold forging mechanism 9 includes a rotary spindle 26, a tool spindle base 27, a tool spindle 28, a tool spindle end cap 29, and a cold forging tool 30. The rotary spindle 26 is mounted on the machine tool bed 1. The tool spindle base 27, tool spindle 28, and tool spindle end cap 29 are sequentially mounted on the rotary spindle 26. The cold forging tool 30 is mounted on the working end of the tool spindle 28. The connections between the tool spindle 28 and the tool spindle base 27 and tool spindle end cap 29 are electrically isolated using insulated bearings and insulated gaskets to prevent current from bypassing the internal circuitry of the cold forging mechanism 9. In terms of electrical connections, the positive terminal of the pulse power supply 14 is connected to the center point 13 via a wire, and the negative terminal is connected to the rod brush 16 via a wire. The rod brush 16 is mounted at the end of the rod brush hydraulic cylinder 4 and faces the outer surface of the workpiece 17. The controller 15 is electrically connected to the clamping chuck 3, clamping slide 2, tailstock drive motor 20, tailstock chuck 18, center drive motor 12, center brush hydraulic cylinder 11, rod brush hydraulic cylinder 4, input motor 6 and pulse power supply 14 respectively, to realize full-process automated coordinated control. The overall layout ensures that after the workpiece 17 is clamped, its deformation zone is located exactly between the center brush 10 and the rod brush 16, and the action position of the cold forging tool 30 is highly coincident with the electric field action area. Specific Implementation Method Two: In operation, the workpiece 17 is first pushed into the machine tool via the loading / unloading device 19. After the clamping chuck 3 clamps the front end of the workpiece 17, the controller 15 controls the clamping slide 2 to move the workpiece 17 along the guide rail 22 to the center point 13. The tailstock chuck 18 clamps the end of the workpiece 17. Then, the center point drive motor 12 drives the center point 13 to extend, and the tailstock drive motor 20 controls the tailstock chuck 18 to tighten, so that the front and end of the workpiece 17 are axially fixed by the center point 13 and the tailstock chuck 18 respectively. The clamping chuck 3 is then released. Next, the tailstock drive motor 20 drives the workpiece 17 to rotate at a low speed. The controller 15 judges the runout of the workpiece 17 based on the detection signal and stops the rotation after the runout is eliminated. Subsequently, the center brush hydraulic cylinder 11 and the rod brush hydraulic cylinder 4 are activated respectively. The center brush 10 is driven by the hydraulic cylinder to press against the rear end of the center point 13, and the rod brush 16 is pressed against the outer surface of the workpiece 17. Both continuously apply pressure to eliminate the contact gap and form a stable electrical contact path. At this time, the pulse power supply 14 is activated, and the high-frequency pulse current flows from the tip 13 through the inside of the workpiece 17 to the brush 16 of the rod. A high-frequency pulse electric field is established in the section of the workpiece where the cold forging tool 30 is about to be applied. The high-density electron flow interacts strongly with the dislocations inside the workpiece metal, accelerating the dislocation slip and activating new dislocation sources, producing a significant electroplastic effect. This significantly reduces the yield strength of the workpiece material and significantly increases its plasticity, meaning that the material has been softened in situ by the electric field before the mechanical cold forging action.

[0017] Based on the softening of the material by the electric field, the input motor 6 starts, and the power is transmitted to the transmission mechanism 5 after being accelerated by the gearbox 7. The two-stage meshing of the cylindrical gear pair 23 and the bevel gear pair 25 drives the rotary spindle 26 to rotate at high speed, and the cold forging tool 30 mounted on the tool shaft 28 rotates accordingly. At the same time, the tailstock drive motor 20 controls the tailstock slide 21 to feed along the guide rail 22 towards the cold forging tool 30, and drives the workpiece 17 to rotate synchronously. Under the action of radial force, the cold forging tool 30 applies impact extrusion to the surface of the workpiece 17. With the axial feed and rotation of the workpiece 17, the spline tooth profile is gradually formed by cold forging. Since the deformation zone of the workpiece 17 is always under the action of a high-frequency pulse electric field, the material deformation resistance remains at a low level. The forming force required by the cold forging tool 30 is greatly reduced, and the surface of the workpiece 17 is less prone to defects such as cracks and folds. The tooth profile accuracy and surface quality are significantly improved. After forming is completed, each actuator is reset in sequence, and the clamping slide 2 sends the workpiece 17 back to the unloading device 19 for unloading. The whole process realizes the spatiotemporal coordination of electric field softening and mechanical cold forming. The rotation of the cold forming tool 30 is stably driven by the input motor 6 through the gearbox 7 and the transmission mechanism 5. The feeding and rotation of the workpiece 17 are uniformly controlled by the tailstock drive motor 20. The two work together precisely under the coordination of the controller 15, giving full play to the promoting effect of electroplasticity on cold forming.

[0018] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for cold forging splines with an electric field assisted, characterized in that, The method includes the following steps: S1: Push the workpiece (17) into the machine tool from the loading and unloading device (19), start the clamping chuck (3) to clamp the front end of the workpiece (17), control the clamping slide (2) through the controller (15) to move the workpiece (17) to the center (13), start the tailstock chuck (18) to clamp the end of the workpiece (17), control the tailstock drive motor (20) and the center drive motor (12) to make the front end and end of the workpiece (17) axially fixed by the center (13) and the tailstock chuck (18), and release the clamping chuck (3). S2: By controlling the tailstock drive motor (20) to drive the tailstock chuck (18) to rotate the workpiece (17), and stop rotating after ensuring that the workpiece (17) does not jump significantly; S3: Start the hydraulic cylinder (11) for the tip brush and the hydraulic cylinder (4) for the rod brush, control the tip brush (10) to contact the rear end of the tip (13), and the rod brush (16) to contact the workpiece (17), and continuously apply a certain pressure to ensure that there is no gap between the contact surfaces; S4: Start the pulse power supply (14) and tailstock drive motor (20) to ensure that the workpiece (17) is continuously current applied during rotation; S5: Start the input motor (6), control the rotary spindle (26) to drive the cold forging tool (30) to rotate, start the tailstock drive motor (20) to control the tailstock slide (21) to move and the tailstock chuck (18) to rotate, realize the axial feeding and rotation of the workpiece (17), and complete the cold forging of the workpiece (17); S6: After the cold forging process is completed, control the clamping slide (2) and clamping chuck (3) to remove the workpiece (17) from the loading and unloading device.

2. An electric field-assisted spline cold forging machine tool that can use the method described in claim 1, comprising a machine bed (1), a clamping slide (2), a clamping chuck (3), a rod brush hydraulic cylinder (4), a transmission mechanism (5), an input motor (6), a gearbox (7), a machine column (8), a cold forging mechanism (9), a center brush (10), a center brush hydraulic cylinder (11), a center drive motor (12), a center (13), a pulse power supply (14), a controller (15), a rod brush (16), a workpiece (17), a tailstock chuck (18), a loading and unloading device (19), a tailstock drive motor (20), a tailstock slide (21), and a guide rail (22), characterized in that, The transmission mechanism (5) includes a cylindrical gear pair (23), a bracket (24), and a bevel gear pair (25). The cold forging mechanism (9) includes a rotary spindle (26), a tool spindle chassis (27), a tool spindle (28), a tool spindle end cover (29), and a cold forging tool (30). The machine tool column (8), input motor (6), gearbox (7), transmission mechanism (5), pulse power supply (14), controller (15), center brush hydraulic cylinder (11), and cold forging mechanism (9) are mounted on the machine tool bed (1). The input motor (6) is connected to the gearbox (7), the gearbox (7) is connected to the transmission mechanism (5), and the transmission mechanism (5) is connected to the cold forging mechanism (9) for transmission. The clamping slide (2) and the tailstock slide (21) are mounted on the machine tool bed (1). On the guide rail (22), the clamping chuck (3) and the rod brush hydraulic cylinder (4) are mounted on the clamping slide (2). The loading and unloading device (19) and the tailstock chuck (18) are mounted on the tailstock slide (21). The tailstock drive motor (20) is mounted on the side of the loading and unloading device (19) to control the movement of the tailstock slide (21) and the rotation of the tailstock chuck (18). The center point (13) and the center point drive motor (12) are mounted on the machine tool column (8). The center point drive motor (12) is connected to the center point (13) to control the extension and retraction of the center point (13). The center point brush (10) and the rod brush (16) are respectively mounted on the end of the center point brush hydraulic cylinder (11) and the rod brush (16). The contact surfaces of the brushes are in contact with the center point (13) and the workpiece (17) respectively.

3. The electric field-assisted spline cold forging machine tool according to claim 2, characterized in that, The transmission mechanism (5) includes a bracket (24), a cylindrical gear pair (23), and a bevel gear pair (25). The gears in the cylindrical gear pair (23) are respectively mounted on the bracket (24) and the gearbox (7). The bevel gear pair (25) is respectively mounted on the bracket (24) and the rotary spindle (26). The synchronous rotation of the rotary spindle (26) is achieved by the meshing of the gears in the transmission mechanism (5).

4. The electric field-assisted spline cold forging machine tool according to claim 2, characterized in that, The cold forging mechanism (9) includes a rotary spindle (26), a tool spindle chassis (27), a tool spindle (28), a tool spindle end cap (29), and a cold forging tool (30). The rotary spindle (26) is mounted on the machine tool bed (1). The tool spindle chassis (27), the tool spindle (28), and the tool spindle end cap (29) are mounted on the rotary spindle (26). The cold forging tool (30) is mounted on the tool spindle (28). The mounting positions of the tool spindle (28) with the tool spindle chassis (27) and the tool spindle end cap (29) use insulated bearings and insulated gaskets.

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