A slender pusher for machining U-shaped openings and its machining process

Abstract

This invention discloses a slender push cutter for machining U-shaped openings and its machining process. The slender push cutter includes cutting teeth and correcting teeth disposed on the broaching section of an elongated push cutter body. Viewed along the length direction parallel to the push cutter body, the outer contour of the cutting teeth and correcting teeth is a U-shaped outer contour with three cutting edges. The three cutting edges of the U-shaped outer contour include an arc-shaped cutting edge and a pair of parallel straight cutting edges connected to both ends of the arc-shaped cutting edge. A rectangular cross-section guide bar is longitudinally disposed on the back side of the elongated push cutter body. The cutting edge contour plane formed by the arc-shaped cutting edge and the pair of straight cutting edges is inclined laterally relative to the elongated push cutter body. In the machining process of the slender push cutter, the chip groove is ground using a grinding method with alternating back-and-forth movement of the grinding head, which can reduce the temporal unevenness of the heat distribution on both sides of the push cutter body and improve the machining accuracy of the slender push cutter.

Description

Technical Field

[0001] This invention relates to the field of push-cutting technology, specifically to a slender push-cutting tool and its processing technology for machining U-shaped openings. Background Technology

[0002] U-shaped openings are widely found in mechanical parts, typically seen in U-shaped wrenches and precision U-shaped blocks. Their U-shaped openings consist of two parallel planes and an arc surface. Currently, wire EDM is used to machine precision U-shaped openings in mechanical parts, but this method is inefficient and unsuitable for mass production. To improve production efficiency, precision U-shaped openings in mechanical parts can be machined using a broach (a type of broach). However, existing U-shaped opening broaches have drawbacks such as high cutting force and high vibration tolerance, which leads to a decrease in the machining quality of the U-shaped openings.

[0003] In addition, for narrow and deep U-shaped openings, the pusher is actually a slender pusher. The slender pusher itself also has manufacturing difficulties, such as the fact that the two flat and thin sides of the slender pusher are prone to bending and deformation. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a slender pusher for machining U-shaped openings and its machining process, aiming to provide a slender pusher with low pushing force, vibration resistance, high precision, and ease of manufacture, along with its corresponding machining process. The specific technical solution is as follows: A slender pusher for machining U-shaped openings includes an elongated pusher body. The elongated pusher body has a front guide section, a broaching section, a straightening section, and a rear clamping section arranged longitudinally. The broaching section has a number of cutting teeth spaced apart, and the straightening section has a number of straightening teeth spaced apart. Chip grooves are provided between adjacent cutting teeth and between adjacent straightening teeth. Viewed along the length parallel to the pusher body, the outer contours of the cutting teeth and straightening teeth are U-shaped with three cutting edges. The three cutting edges of the U-shaped outer contour include an arc-shaped cutting edge and a pair of parallel straight cutting edges connected to both ends of the arc-shaped cutting edge. A rectangular cross-section guide bar is arranged longitudinally on the back side of the elongated pusher body. A number of chip grooves are spaced apart on the three cutting edges of the cutting teeth. The chip grooves on adjacent cutting edges are staggered. The cutting edge contour plane formed by the arc-shaped cutting edge and the pair of straight cutting edges is inclined laterally relative to the elongated pusher body.

[0005] In the aforementioned slender pusher, after the U-shaped contour plane of its three cutting edges is tilted, both the arc segment cutting edge and the straight segment cutting edge become oblique lines. During the pusher process, the contact line between the cutting edge and the workpiece gradually increases. This design makes the cutting process lighter and smoother, and reduces vibration and noise during the machining process.

[0006] Preferably, the lateral tilt angle β of the contour plane formed by the arc-shaped cutting edge and the pair of straight cutting edges relative to the elongated pusher body is 10° to 15°.

[0007] Preferably, the end face of the front guide section is inclined at 4° to 6° relative to the lateral direction of the slender pusher, and its inclination direction is opposite to the inclination direction of the cutting edge contour plane.

[0008] Preferably, the rake angle of the cutting teeth and the straightening teeth is 11° to 13° and the clearance angle is 4° to 5°; the width of the chip groove is 0.5 to 0.7 mm and the depth is 0.3 to 0.5 mm.

[0009] Preferably, in order to facilitate the processing of slender push cutters, the two ends of the slender push cutter are provided with central holes.

[0010] Preferably, the slender pusher for machining U-shaped openings according to the present invention is further provided with a guide support block for preventing the slender pusher from moving laterally during cutting. The vibration-absorbing guide support block is provided with a groove for matching the rectangular cross-section guide strip on the slender pusher.

[0011] Preferably, the end center hole of the slender push cutter is a threaded center hole, and a longitudinal vibration damper is also provided to reduce the longitudinal vibration of the slender push cutter during cutting. The longitudinal vibration damper includes a sleeve for slidingly fitting on the outer circle of the thrust end of the slender push cutter. A butterfly spring assembly is provided inside the sleeve for elastically pressing the end face of the slender push cutter. The sleeve is elastically fitted onto the thrust end of the slender push cutter by a pre-tightening screw that passes through the center of the sleeve's bottom and the inner hole of the butterfly spring assembly and connects to the threaded center hole of the thrust end of the slender push cutter, thus achieving pre-tightening of the butterfly spring assembly. During operation, the chuck of the vertical push press clamps the sleeve and advances it longitudinally to achieve U-shaped cutting, and the longitudinal vibration of the slender push cutter is reduced by the butterfly spring assembly.

[0012] Preferably, the shape of the butterfly spring assembly is a rectangular shape that matches the end cross-sectional shape of the pusher, and it is formed by modifying the shape of a circular butterfly spring assembly through wire cutting.

[0013] A machining process for a slender pusher for machining U-shaped openings, characterized by comprising the following steps: (1) Preparation of the pusher blank: High-speed steel blank with a rectangular cross section is used as the pusher blank; (2) Push cutter planing: A layer of black skin is planed off the four sides and two ends of the push cutter blank; (3) Center hole machining: Drill center holes at both ends of the pusher; (4) Milling of each face of the pusher: The pusher is positioned by the center holes at both ends, and the face of each end of the pusher is milled by CNC milling; among them, the guide strip is milled on the back of the pusher, and the arc section of the pusher is milled into an arc surface on one side of the cutting edge. (5) Milling of chip grooves and cutting edges on push cutter: CNC milling of the tooth profiles of each chip groove, each cutting tooth and the correction tooth on the push cutter; (6) Heat treatment of pusher: The pusher is subjected to salt bath quenching and salt bath tempering heat treatment in succession. The heat treatment is carried out strictly in accordance with the process flow and the operation of each process is coordinated. Among them, the pusher is straightened during the cooling process after salt bath quenching in order to obtain good comprehensive mechanical properties and small workpiece deformation. (7) Cold treatment and aging treatment of pusher: Low temperature ice cooling technology is used to perform shaping treatment and aging treatment on pusher to remove heat treatment stress and cutting stress; (8) Grind the center hole of the pusher: Grind the center holes at both ends of the pusher; (9) Grinding of each face of the pusher: The pusher is positioned by the center holes at both ends, and the face of each end of the pusher is ground by CNC; among them, the guide strip is finely produced on the back of the pusher, and the cutting edge of the arc section of the pusher is finely ground into an arc surface; (10) Grinding of chip grooves and cutting edges of pusher: CNC grinding is used to process the tooth profile of each chip groove, each cutting tooth and the correction tooth on the pusher, and the chip groove is finely ground.

[0014] As a further improvement of the present invention, in step (6) heat treatment of the pusher, the pusher is straightened after heat treatment by using an online excitation synchronous straightening method to achieve automatic straightening of the pusher. The online excitation synchronous straightening method includes installing an online excitation synchronous straightening device on a CNC press, applying excitation energy to the pusher through the online excitation synchronous straightening device, so that the pusher is straightened by the pressure head on the CNC press under the excitation state, so as to release the internal stress caused by the pressure shaping to the maximum extent, reduce the deformation caused by the secondary release of internal stress during subsequent processing, thereby improving the accuracy and stability of the pusher after final processing.

[0015] Preferably, the online vibration synchronous straightening device includes a pair of vibrators for synchronously applying vibration force when the pusher is pressure-straightened. Each vibrator includes a servo telescoping device, an elastic element, a top pressure plate, and an ultrasonic transducer. The servo telescoping device is connected to the elastic element, the elastic element is connected to the top pressure plate, and the ultrasonic transducer is fixedly mounted on the top pressure plate and located on the same side of the top pressure plate as the elastic element. The other side of the top pressure plate is used to press against the side of the pusher.

[0016] The ultrasonic transducer is connected to the ultrasonic generator.

[0017] Preferably, the top pressure plate is a permanent magnet plate.

[0018] Preferably, the servo telescoping device is a servo cylinder, and the telescoping rod of the servo cylinder is connected to the elastic element.

[0019] The working mechanism of the vibrator in the above-mentioned online vibration synchronous straightening device is as follows: the servo telescoping device (such as a servo cylinder) pushes the top pressure plate (preferably a permanent magnet plate to increase adsorption reliability) against both sides of the pusher through the elastic element. The function of the elastic element (such as a helical spring, disc spring, or polyurethane pad) is to provide a flexible and constant clamping force and isolate the high-frequency vibration of the ultrasonic transducer to prevent it from being transmitted to the servo mechanism. The ultrasonic generator drives the ultrasonic transducer to generate high-frequency mechanical vibration, which is transmitted to the pusher body through the top pressure plate to realize online vibration stress relief during the straightening process; in particular, when the pressure head of the CNC press applies pressure to the pusher in the vibrating state, the material not only undergoes plastic deformation, but also its yield limit is temporarily reduced under high-frequency vibration (vibration plastic effect), making it easier to release stress and making the deformation more uniform and stable. The vibration energy promotes grain boundary movement and dislocation reorganization, so that the stress is released instantly during deformation, rather than being "locked" inside as in traditional straightening, which leads to new deformation due to stress redistribution during subsequent finishing.

[0020] As a further improvement of the present invention, the online excitation synchronous straightening device further includes an automatic pusher turning device and a pusher straightness detection device. The automatic pusher turning device includes a pair of pusher positioning seats located at both ends of the pusher's longitudinal direction, positioning grooves correspondingly disposed on the pair of pusher positioning seats for limiting the horizontal movement of the pusher's end, a servo lifter disposed on the pusher positioning seat, a servo angle motor disposed on the upper end of the lifting shaft of the servo lifter, and a servo finger cylinder disposed on the motor shaft of the servo angle motor for clamping the pusher during pusher turning; wherein, the pusher... The bottom surface of the positioning groove of the knife positioning seat is lower than the upper surface of the anvil on the moving worktable, and the upper end of the positioning groove of the push knife positioning seat is higher than the upper surface of the anvil; the push knife straightness detection device includes a horizontal guide rail installed on the moving worktable of the CNC press and located on the side of the straightening push knife and parallel to the push knife, and a detection arm movably set on the horizontal guide rail and moved on the horizontal guide rail by a servo linear drive mechanism. The detection arm extends upward and bends to a position above the push knife, and a laser range sensor aligned downward with the upper plane of the push knife is provided at the end of the extended end of the detection arm.

[0021] Preferably, the servo linear drive mechanism adopts a lead screw transmission device driven by a servo geared motor.

[0022] The servo telescopic device, ultrasonic generator, servo lifter, servo finger cylinder, servo linear drive mechanism and laser rangefinder are respectively connected to the control system of the CNC press.

[0023] Preferably, the horizontal guide rail is mounted on the movable workbench at a height lower than that of the anvil to prevent interference with the telescopic movement of the vibrator.

[0024] The steps for automatic straightening of the pusher using the online excitation synchronous straightening method are as follows: S1. Installation of pusher: Place the pusher that needs to be straightened on the anvil of the moving worktable of the CNC press; S2. Installation of the online vibration synchronous straightening device: At least N pairs of vibrators are fixedly installed on the CNC press using brackets. The N pairs of vibrators are arranged at intervals in the direction of movement parallel to the moving worktable. Each pair of vibrators is placed on both sides of the moving worktable of the CNC press, and the top pressure plate of each pair of vibrators is aligned with both sides of the push knife on the anvil. An automatic push knife turning device and a push knife straightness detection device are installed on the moving worktable. The automatic push knife turning device is placed on both ends of the push knife on the moving worktable, such that the ends of the push knife are located in the finger clamps of the servo finger cylinders but do not contact the finger clamps. The push knife straightness detection device is installed on one side of the push knife on the moving worktable. The guide rail of the push knife straightness detection device is parallel to the longitudinal direction of the push knife, and the laser rangefinder of the push knife straightness detection device is aligned downward with the upper end face of the push knife. S3. Determination of the pressure correction position for the pusher: The control system activates the pusher straightness detection device and drives the laser range sensor on the pusher straightness detection device to move in a direction parallel to the guide rail. The laser range sensor scans and detects the distance to the upper end face of the pusher along the longitudinal direction. After the control system collects the scanning distance data of the laser range sensor, it finds the bending error at various points along the longitudinal direction of the upper end face of the pusher and determines the part of the pusher that needs pressure correction. S4. Dynamic Pressure Shaping and Straightening: The control system drives the moving worktable to move the part of the pusher that needs pressure correction to the position directly below the pressure head of the CNC press. N pairs of vibrators are turned on, so that the top pressure plates of the N pairs of vibrators clamp the two sides of the pusher and apply excitation force to the pusher through ultrasonic transducers. Under the condition of excitation vibration of the pusher, the pressure head of the CNC press presses down on the part of the pusher that needs pressure correction and performs pressure shaping on the part. After pressure shaping, the pressure head of the CNC press rises and the top pressure plates of the N pairs of vibrators retract, so that the top pressure plates separate from the pusher, completing the online excitation synchronous straightening of the pusher. Repeat steps S3 to S4 above, cyclically applying pressure to each part of the straightening pusher where the straightness error exceeds the tolerance, until the straightness error of the pusher completely meets the specified requirements; In the determination of the pusher pressure correction position in S3, when the control system determines that the part to be straightened needs to be flipped and adjusted before it can be implemented, the control system drives the pusher automatic flipping device to operate. After the finger cylinder of the pusher automatic flipping device clamps the two ends of the pusher, the pusher is raised by the servo lifter. Then, the servo angle motor drives the finger cylinder to rotate 180 degrees around the motor shaft of the servo angle motor to realize the flipping and adjustment of the pusher. Then, the servo lifter lowers the pusher to reset, the finger cylinder is released, and the pusher is accurately positioned in its original position.

[0025] To further improve the stress relief effect of vibration, in step S4, dynamic pressure shaping and straightening, after online vibration synchronous straightening is completed, the pusher is then subjected to independent enhanced vibration to further release the internal stress of the pusher; the steps for independent enhanced vibration of the pusher are as follows: A1. Slight lifting of the push knife: The control system drives the finger cylinder to clamp both ends of the push knife, and then drives the servo lifter to lift the push knife a slight distance, so that the push knife is no longer in contact with the anvil on the moving worktable. A2. Elastic clamping of push knife in mid-air: The control system drives the servo telescopic devices on N pairs of vibrators to move, so that the elastic top pressure plate of the vibrator presses against both sides of the push knife, and then the finger cylinder releases, forming an elastic clamping of the push knife in mid-air. A3. Independent Enhanced Vibration: The control system activates the ultrasonic transducers on N pairs of vibrators to apply vibration force to the push knife. The push knife is subjected to independent enhanced vibration force in the air environment, which further eliminates the pressure and shaping stress inside the push knife. After completion, the vibrator retracts its elastic clamping on the push knife, and the push knife falls back onto the anvil.

[0026] Preferably, in order to increase the reliability of the elastic clamping of the pusher when it is airborne, the top pressure plate of the vibrator is made of a permanent magnet plate; in addition, a support plate for supporting the lower end face of the two ends of the pusher is provided at the front of the lower end of the top pressure plate of the vibrator used to elastically hold the two ends of the pusher.

[0027] Considering that the chip groove of the pusher is a relatively weak part of the pusher, the heat effect of its grinding process will have an important impact on its grinding accuracy and stress deformation after grinding. Therefore, the following improved special grinding method is adopted: In the grinding of the chip groove and cutting edge of the pusher in step (10), the grinding of the chip groove adopts the grinding method of alternating back and forth moving grinding head, which reduces the temporal unevenness of the heat distribution on both sides of the pusher body; the alternating back and forth moving grinding head refers to the grinding head grinding each chip groove one by one. First, the first chip groove is ground clockwise along the U-shaped tool path, and then the second chip groove adjacent to it is ground counterclockwise along the U-shaped tool path. The chip grooves are ground alternately and cyclically in sequence, so that the heat transfer on both sides of the pusher is basically uniform in time, thereby reducing the uneven heat deformation during the grinding of the pusher.

[0028] The aforementioned alternating back-and-forth movement of the grinding head can be implemented through CNC grinding machine programming. To implement this method on a CNC tool grinder, the machining program needs to be planned accordingly. For example, assuming the initial entry point of the U-shaped tool path is A, the midpoint is B, and the final exit point is C, then for the 1st, 3rd, 5th... (odd-numbered) tooth grooves, the programming would cause the grinding head to enter from point A, pass through point B, and exit at point C (clockwise U-shaped path); for the 2nd, 4th, 6th... (even-numbered) tooth grooves, the programming would cause the grinding head to enter from point C, pass through point B, and exit at point A (counter-clockwise U-shaped path). This alternation of paths ensures that the heat and force on both sides of the pusher are statistically balanced.

[0029] The beneficial effects of this invention are: First, the present invention provides a slender pusher for machining U-shaped openings and a machining process thereof. The cutting edge profile plane of the slender pusher is set at an angle, forming a helical tooth structure. This allows the cutting edge to gradually enter the workpiece rather than simultaneously, effectively reducing peak cutting force and mitigating impact and vibration. In addition, the chip divider design splits wide chips into small fragments, which facilitates chip removal and reduces cutting resistance. The combination of these two features significantly improves cutting stability and the surface finish of the U-shaped opening.

[0030] Secondly, the present invention provides a slender pusher for processing U-shaped openings and a processing method thereof. The rectangular cross-section guide strip on the back of the slender pusher is precisely matched with the groove on the matching external guide support block, which provides strong lateral support for the slender pusher, effectively resists the lateral force generated during the cutting process, prevents the pusher from moving laterally and twisting, and ensures the dimensional and shape accuracy of the U-shaped opening.

[0031] Third, the present invention provides a slender pusher for machining U-shaped openings and a machining process, with a unique longitudinal vibration damper that elastically connects the pusher to the pusher chuck via a butterfly spring assembly. This damper can absorb and buffer the longitudinal vibrations generated during the cutting process, further ensuring the smoothness of the cutting process and extending the life of the pusher.

[0032] Fourth, this invention provides a slender pusher for machining U-shaped openings and its machining process. The slender pusher is machined using an online vibration synchronous straightening process, which offers high straightening accuracy and thorough stress relief. Traditional hot straightening or cold pressing straightening introduces new internal stresses, posing a risk of rebound deformation to the pusher. This invention's unique "online vibration synchronous straightening method" applies high-frequency vibration energy to the pusher via an ultrasonic transducer while applying correction pressure. This high-frequency vibration energy promotes dislocation slip and rearrangement within the material's internal lattice, allowing stress to be released and homogenized synchronously during plastic deformation. This achieves simultaneous "shaping" and "stress relief," significantly reducing deformation in subsequent machining, improving the straightness of the machined slender pusher, and substantially enhancing its dimensional stability and service life.

[0033] Fifth, the present invention provides a slender pusher for processing U-shaped openings and its processing technology. The online vibration synchronous straightening process includes a dedicated pusher straightness detection device and an automatic pusher turning device, integrated and installed on a CNC press and connected to the press's control system. This allows the pusher straightness detection device (laser range sensor) to automatically and accurately locate the bending point, and the automatic pusher turning device to automatically rotate the pusher 180° as needed, achieving intelligent straightening of complex bends (such as S-shaped bends) in slender pushers. The entire straightening process forms a closed loop through "positioning detection – correction – turning – re-correction," requiring no manual intervention, resulting in high efficiency and good consistency.

[0034] Sixth, the present invention provides a slender pusher for processing U-shaped openings and a processing technology thereof. The online excitation synchronous straightening process includes an "independent enhanced excitation" step. After online excitation synchronous straightening, the pusher is subjected to independent vibration aging treatment again in a "free-floating elastic clamping" state. This can further eliminate and homogenize the micro-stress accumulated in the previous process, which is a key step to ensure the long-term processing stability of the pusher.

[0035] Sixth, the present invention provides a slender pusher for machining U-shaped openings and a machining process thereof. In the machining process of the slender pusher, the grinding of its chip grooves adopts the "alternating back-and-forth grinding" method to effectively control thermal deformation: the method of alternating back-and-forth grinding along the U-shaped tool path can alternately change the grinding direction of adjacent chip grooves, so that the input sequence and time distribution of grinding heat on both sides of the pusher can be balanced. This machining method breaks the fixed direction heat flow and unilateral heat accumulation caused by traditional unidirectional sequential grinding, thereby significantly reducing the bending deformation caused by asymmetric thermal stress, which can improve the straightness (runout) of the slender pusher from 0.05mm to below 0.02mm, thus providing a key process guarantee for obtaining a slender pusher with high straightness.

[0036] Seventh, the present invention provides a slender pusher for processing U-shaped openings and a processing technology thereof. The online vibration synchronous straightening device (including a vibrator, a pusher straightness detection device, and a pusher automatic flipping device) integrated in the online vibration synchronous straightening process can adapt to the processing of slender parts of different specifications. It has good versatility and can therefore also be used for the automated and efficient straightening of other slender pushers (the straightening operation method is exactly the same), thus having good industrial application value.

[0037] Eighth, the present invention provides a slender pusher for processing U-shaped openings and a processing technology, and a specially designed exciter structure that can reduce the energy loss caused by the vibration energy of the exciter being transferred to the telescopic shaft, thereby improving the stress relief effect of excitation. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of a slender pusher for processing U-shaped openings according to the present invention; Figure 2 yes Figure 1 Top view; Figure 3 Yes, yes Figure 1 Longitudinal view of the cutting teeth and straightening teeth in the image; Figure 4 This is a schematic diagram of the connection between the guide support block and the longitudinal damper and the push knife; Figure 5 This is a schematic diagram (top view) of the online excitation synchronous straightening device. Figure 6 yes Figure 5 Front view of the automatic knife-turning device in the middle.

[0039] In the diagram: 1. Long strip-shaped pusher body; 2. Front guide section; 3. Broaching section; 4. Correction section; 5. Rear clamping section; 6. Cutting teeth; 7. Correction teeth; 8. Chip groove; 9. Three-sided cutting edge; 10. Arc-shaped cutting edge; 11. Straight-line cutting edge; 12. Rectangular cross-section guide bar; 13. Chip groove; 14. Center hole; 15. Guide support block; 16. Longitudinal vibration damper; 17. Sleeve; 18. Disc spring assembly; 19. Preload screw; 20. Vibrator. 1. Servo telescopic device; 22. Elastic element; 23. Top pressure plate; 24. Ultrasonic vibrator; 25. Automatic knife turning device; 26. Knife straightness detection device; 27. Servo lifter; 28. Knife positioning seat; 29. ​​Positioning groove; 30. Servo rotary motor; 31. Servo finger cylinder; 32. Moving worktable; 33. Horizontal guide rail; 34. Servo linear drive mechanism; 35. Detection arm; 36. Laser rangefinder sensor; 37. Bracket; 38. Anvil.

[0040] In the figure, β is the lateral tilt angle of the U-shaped profile plane of the three-sided cutting edge. Detailed Implementation

[0041] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention. Example 1:

[0042] like Figures 1 to 6The figure shows an embodiment of a slender pusher for machining U-shaped openings according to the present invention, comprising a long pusher body 1. The long pusher body 1 has a front guide section 2, a broaching section 3, a straightening section 4, and a rear clamping section 5 arranged longitudinally. A number of cutting teeth 6 are arranged at intervals on the broaching section 3, and a number of straightening teeth 7 are arranged at intervals on the straightening section 4. Chip grooves 8 are provided between adjacent cutting teeth 6 and between adjacent straightening teeth 7. Viewed along the length direction parallel to the pusher body 1, the outer contour shape of the cutting teeth 6 and the straightening teeth 7 is a U-shape with three cutting edges 9. The U-shaped outer contour has three cutting edges 9, including arc-shaped cutting edges 10 and a pair of straight cutting edges 11 connected to the two ends of the arc-shaped cutting edges 10 and parallel to each other; wherein, a rectangular cross-section guide bar 12 is arranged longitudinally on the back side of the elongated pusher body 1; a number of chip grooves 13 are arranged at intervals on the three cutting edges 9 of the cutting teeth 6, and the chip grooves 8 on two longitudinally adjacent cutting edges 9 are staggered; the cutting edge contour plane formed by the arc-shaped cutting edges 10 and the pair of straight cutting edges 11 is inclined laterally relative to the elongated pusher body 1.

[0043] In the aforementioned slender pusher, after the U-shaped contour plane of its three-sided cutting edge 9 is tilted, both the arc-shaped cutting edge 10 and the straight-line cutting edge 11 become oblique lines. During the pusher process, the contact line between the cutting edge and the workpiece gradually increases. This design makes the cutting process lighter and smoother, and reduces vibration and noise during the machining process.

[0044] Preferably, the lateral tilt angle β of the contour plane formed by the arc-shaped cutting edge 10 and the pair of straight cutting edges 11 relative to the elongated pusher body 1 is 10° to 15°.

[0045] Preferably, the end face of the front guide section 2 is inclined at 4° to 6° relative to the lateral direction of the slender pusher, and its inclination direction is opposite to the inclination direction of the cutting edge contour plane.

[0046] Preferably, the rake angle of the cutting tooth 6 and the straightening tooth 7 is 11° to 13° and the clearance angle is 4° to 5°; the width of the chip groove 13 is 0.5 to 0.7 mm and the depth is 0.3 to 0.5 mm.

[0047] Preferably, in order to facilitate the processing of the slender pusher, the two ends of the slender pusher are provided with central holes 14.

[0048] Preferably, in this embodiment, a slender pusher for processing U-shaped openings is also equipped with a guide support block 15 to prevent the slender pusher from moving laterally during cutting. The vibration-absorbing guide support block 15 is provided with a groove for matching the rectangular cross-section guide strip 12 on the slender pusher.

[0049] Preferably, the end center hole 14 of the slender push cutter is a threaded center hole, and a longitudinal vibration damper 16 is also provided to reduce the longitudinal vibration of the slender push cutter during cutting. The longitudinal vibration damper 16 includes a sleeve 17 for slidingly fitting on the outer circle of the thrust end of the slender push cutter. A butterfly spring assembly 18 is provided inside the sleeve 17 for elastically pressing the end face of the slender push cutter. The sleeve 17 is elastically fitted onto the thrust end of the slender push cutter by a pre-tightening screw 19 that passes through the center of the bottom of the sleeve 17 and the inner hole of the butterfly spring assembly 18 and connects to the threaded center hole of the thrust end of the slender push cutter. This achieves the pre-tightening of the butterfly spring assembly 18. During operation, the chuck of the vertical push press clamps the sleeve 17 for longitudinal advancement to achieve U-shaped cutting, and the longitudinal vibration of the slender push cutter is reduced by the butterfly spring assembly 18.

[0050] Preferably, the shape of the butterfly spring assembly 18 is a rectangular shape that matches the end cross-sectional shape of the pusher, and it is formed by modifying the shape of a circular butterfly spring assembly through wire cutting. Example 2:

[0051] A machining process for a slender pusher for machining U-shaped openings includes the following steps: (1) Preparation of the pusher blank: High-speed steel blank with a rectangular cross section is used as the pusher blank; (2) Push cutter planing: A layer of black skin is planed off the four sides and two ends of the push cutter blank; (3) Center hole machining: Drill center holes 14 at both ends of the pusher; (4) Milling of each face of the pusher: The pusher is positioned by the center holes 14 at both ends, and the end faces of the pusher are milled by CNC milling; among them, the guide strip 12 is milled on the back of the pusher, and the arc section cutting edge 10 of the pusher is milled into an arc surface on one side. (5) Milling of chip grooves 8 and cutting edges on pusher: CNC milling of the tooth profiles of each chip groove 8, each cutting tooth 6 and the correction tooth 7 on the pusher; (6) Heat treatment of pusher: The pusher is subjected to salt bath quenching and salt bath tempering heat treatment in succession. The heat treatment is carried out strictly in accordance with the process flow and the operation of each process is coordinated. Among them, the pusher is straightened during the cooling process after salt bath quenching in order to obtain good comprehensive mechanical properties and small workpiece deformation. (7) Cold treatment and aging treatment of pusher: Low temperature ice cooling technology is used to perform shaping treatment and aging treatment on pusher to remove heat treatment stress and cutting stress; (8) Grind the center hole of the pusher: Grind the center holes 14 at both ends of the pusher; (9) Grinding of each face of the pusher: The pusher is positioned by the center holes 14 at both ends, and each face of the pusher is ground by CNC grinding; among them, the guide strip 12 is finely produced on the back of the pusher, and the arc section cutting edge 10 of the pusher is finely ground into an arc surface on one side. (10) Chip grooves 8 and cutting edge grinding: CNC grinding is used to process the tooth profiles of each chip groove 8, each cutting tooth 6 and the correction tooth 7 on the pusher, and the chip groove 13 is finely ground.

[0052] As a further improvement of this embodiment, in step (6) heat treatment of the pusher, the pusher is straightened after heat treatment by using an online excitation synchronous straightening method to achieve automatic straightening of the pusher. The online excitation synchronous straightening method includes installing an online excitation synchronous straightening device on a CNC press, applying excitation energy to the pusher through the online excitation synchronous straightening device, so that the pusher is straightened by the pressure head on the CNC press under the excitation state, so as to release the internal stress caused by the pressure shaping to the maximum extent, reduce the deformation caused by the secondary release of internal stress during subsequent processing, thereby improving the accuracy and stability of the pusher after final processing.

[0053] Preferably, the online vibration synchronous straightening device includes a pair of vibrators 20 for synchronously applying vibration force when the pusher is pressure-straightened. Each vibrator 20 includes a servo telescopic device 21, an elastic element 22, a top pressure plate 23, and an ultrasonic transducer 24. The servo telescopic device 21 is connected to the elastic element 22, the elastic element 22 is connected to the top pressure plate 23, and the ultrasonic transducer 24 is fixedly installed on the top pressure plate 23 and located on the same side of the top pressure plate 23 together with the elastic element 22. The other side of the top pressure plate 23 is used to press against the side of the pusher.

[0054] The ultrasonic transducer 24 is connected to an ultrasonic generator.

[0055] Preferably, the top pressure plate 23 is a permanent magnet plate.

[0056] Preferably, the servo telescoping device 21 is a servo cylinder, and the telescoping rod of the servo cylinder is connected to the elastic element 22.

[0057] The working mechanism of the vibrator 20 in the above-mentioned online vibration synchronous straightening device is as follows: the servo telescopic device 21 (such as a servo cylinder) pushes the top pressure plate 23 (preferably a permanent magnet plate to increase adsorption reliability) against both sides of the pusher through the elastic element 22. The function of the elastic element 22 (such as a helical spring, disc spring, or polyurethane pad) is to provide a flexible and constant clamping force and isolate the high-frequency vibration of the ultrasonic transducer 24 to prevent it from being transmitted to the servo mechanism. The ultrasonic generator drives the ultrasonic transducer 24 to generate high-frequency mechanical vibration, which is transmitted to the pusher body through the top pressure plate 23 to realize online vibration stress relief during the straightening process; in particular, when the pressure head of the CNC press applies pressure to the pusher in the vibrating state, the material not only undergoes plastic deformation, but also its yield limit is temporarily reduced under high-frequency vibration (vibration plastic effect), making it easier to release stress and make the deformation more uniform and stable. Vibrational energy promotes grain boundary movement and dislocation reorganization, allowing stress to be released instantly during deformation, rather than being "locked" inside as in traditional straightening, which leads to new deformations during subsequent finishing due to stress redistribution.

[0058] As a further improvement to this embodiment, the online vibration synchronous straightening device further includes an automatic pusher turning device 25 and a pusher straightness detection device 26. The automatic pusher turning device 25 includes a pair of pusher positioning seats 28 located at both ends of the pusher's longitudinal direction, positioning grooves 29 correspondingly disposed on the pair of pusher positioning seats 28 for limiting the horizontal movement of the pusher's end, a servo lifter 27 disposed on the pusher positioning seats 28, a servo angle motor 30 disposed on the upper end of the lifting shaft of the servo lifter 27, and a servo finger cylinder 31 disposed on the motor shaft of the servo angle motor 30 for clamping the pusher during pusher turning; wherein, the pusher positioning seat 28... The bottom surface of the positioning groove 29 of the 8 is lower than the upper surface of the anvil 38 on the movable worktable 32, and the upper end of the positioning groove 29 of the push knife positioning seat 28 is higher than the upper surface of the anvil 38; the push knife straightness detection device 26 includes a horizontal guide rail 33 installed on the movable worktable 32 of the CNC press and located on the side with the straightening push knife and parallel to the push knife, and a detection arm 35 movably arranged on the horizontal guide rail 33 and moved on the horizontal guide rail 33 by a servo linear drive mechanism 34. The detection arm 35 extends upward and bends to the position above the push knife, and a laser range sensor 36 is provided at the end of the extended end of the detection arm 35, which is aligned downward with the upper plane of the push knife.

[0059] Preferably, the servo linear drive mechanism 34 adopts a lead screw transmission device driven by a servo geared motor.

[0060] The servo telescopic device 21, ultrasonic generator, servo lifting device 27, servo finger cylinder 31, servo linear drive mechanism 34 and laser range sensor 36 are respectively connected to the control system of the CNC press.

[0061] Preferably, the horizontal guide rail 33 is installed on the movable worktable 32 at a height lower than the anvil 38 to prevent interference with the telescopic movement of the vibrator 20.

[0062] The steps for automatic straightening of the pusher using the online excitation synchronous straightening method are as follows: S1. Installation of pusher: Place the pusher that needs to be straightened on the anvil 38 of the moving worktable 32 of the CNC press; S2. Installation of the online vibration synchronous straightening device: At least N pairs of vibrators 20 are fixedly installed on the CNC press via brackets 37. The N pairs of vibrators 20 are arranged at intervals in the direction parallel to the movement of the moving worktable 32. Each pair of vibrators 20 is placed on both sides of the moving worktable 32 of the CNC press, and the top pressure plate 23 of each pair of vibrators 20 is aligned with both sides of the push knife on the anvil plate 38. The push knife automatic turning device 25 and the push knife straightness detection device are installed on the moving worktable 32 respectively. Device 26; wherein, the automatic flipping device 25 for the push knife is placed on the moving worktable 32 at both ends of the longitudinal direction of the push knife, and the ends of the push knife are respectively located in the finger clamping of the servo finger cylinder 31 but not in contact with the finger clamping; the push knife straightness detection device 26 is installed on one side of the push knife on the moving worktable 32, the guide rail 33 of the push knife straightness detection device 26 is parallel to the longitudinal direction of the push knife, and the laser range sensor 36 of the push knife straightness detection device 26 is aligned downward with the upper end face of the push knife; S3. Determination of the pressure correction position of the pusher: The control system activates the pusher straightness detection device 26 and drives the laser range sensor 36 on the pusher straightness detection device 26 to move in a direction parallel to the guide rail 33. The laser range sensor 36 scans and detects the distance of the upper end face of the pusher along the longitudinal direction. After the control system collects the scanning distance data of the laser range sensor 36, it finds the bending error of the upper end face of the pusher along the longitudinal direction and determines the part of the pusher that needs to be pressure corrected. S4. Dynamic Pressure Shaping and Straightening: The control system drives the moving worktable 32 to move the part of the pusher that needs pressure correction to the position directly below the pressure head of the CNC press. N pairs of vibrators 20 are turned on, so that the top pressure plates 23 of the N pairs of vibrators 20 clamp the two sides of the pusher respectively and apply excitation force to the pusher through the ultrasonic transducer 24. Under the condition of excitation vibration of the pusher, the pressure head of the CNC press presses down on the part of the pusher that needs pressure correction and performs pressure shaping on the part. After pressure shaping, the pressure head of the CNC press rises and the top pressure plates 23 of the N pairs of vibrators 20 retract, so that the top pressure plates 23 separate from the pusher, completing the online excitation synchronous straightening of the pusher. Repeat steps S3 to S4 above, cyclically applying pressure to each part of the straightening pusher where the straightness error exceeds the tolerance, until the straightness error of the pusher completely meets the specified requirements; In the determination of the pusher pressure correction position in S3, when the control system determines that the part to be straightened needs to be flipped and adjusted before it can be implemented, the control system drives the pusher automatic flipping device 25 to operate. After the finger cylinder 31 of the pusher automatic flipping device 25 clamps the two ends of the pusher, the pusher is raised by the servo lifter 27. Then, the servo angle motor 30 drives the finger cylinder 31 to rotate 180 degrees around the motor shaft of the servo angle motor 30 to realize the flipping and adjustment of the pusher. Then, the servo lifter 27 lowers the pusher to reset, the finger cylinder 31 is released, and the pusher is accurately positioned in its original position.

[0063] To further improve the stress relief effect of vibration, in step S4, dynamic pressure shaping and straightening, after online vibration synchronous straightening is completed, the pusher is then subjected to independent enhanced vibration to further release the internal stress of the pusher; the steps for independent enhanced vibration of the pusher are as follows: A1. Slight lifting of the push knife: The control system drives the finger cylinder 31 to clamp both ends of the push knife, and then drives the servo lifter 27 to lift the push knife a slight distance, so that the push knife is no longer in contact with the anvil 38 on the moving worktable 32. A2. Elastic clamping of push knife in mid-air: The control system drives the servo telescopic devices 21 on N pairs of vibrators 20 to move, so that the elastic top pressure plate 23 of the vibrator 20 presses against both sides of the push knife, and then the finger cylinder 31 releases, forming an elastic clamping of the push knife in mid-air. A3. Independent enhanced excitation: The control system activates the ultrasonic transducers 24 on the N pairs of vibrators 20 to apply excitation force to the push knife. The push knife is subjected to independent enhanced excitation force in the air environment, which further eliminates the pressure and shaping stress inside the push knife. After completion, the vibrator 20 retracts the elastic clamp on the push knife, and the push knife falls back onto the anvil 38.

[0064] Preferably, in order to increase the reliability of the elastic clamping of the pusher blade, the top pressure plate 23 of the vibrator 20 is made of a permanent magnet plate; in addition, the lower front part of the bottom pressure plate 23 of the vibrator 20, which is used to elastically hold the two ends of the pusher blade, is provided with a support plate for supporting the lower end face of the two ends of the pusher blade.

[0065] Considering that the chip groove 8 of the pusher is a relatively weak part of the pusher, the heat effect of its grinding process will have an important impact on its grinding accuracy and stress deformation after grinding. Therefore, the following improved special grinding method is adopted: In the grinding process of the chip groove 8 and the cutting edge of the pusher in step (10), the grinding process of the chip groove 8 adopts the grinding process of alternating back and forth moving grinding head, which reduces the temporal unevenness of the heat distribution on both sides of the pusher body; the alternating back and forth moving grinding head refers to the grinding head grinding each chip groove 8 one by one. First, the first chip groove 8 is ground clockwise along the U-shaped tool path, and then the second chip groove 8 adjacent to it is ground counterclockwise along the U-shaped tool path. The chip groove 8 is ground alternately and cyclically in sequence, so that the heat transfer on both sides of the pusher is basically uniform in time, thereby reducing the uneven heat deformation during the grinding of the pusher.

[0066] The aforementioned alternating back-and-forth movement of the grinding head can be implemented through CNC grinding machine programming. To implement this method on a CNC tool grinder, the machining program needs to be planned accordingly. For example, assuming the initial entry point of the U-shaped tool path is A, the midpoint is B, and the final exit point is C, then for the 1st, 3rd, 5th... (odd-numbered) tooth grooves, the programming would cause the grinding head to enter from point A, pass through point B, and exit at point C (clockwise U-shaped path); for the 2nd, 4th, 6th... (even-numbered) tooth grooves, the programming would cause the grinding head to enter from point C, pass through point B, and exit at point A (counter-clockwise U-shaped path). This alternation of paths ensures that the heat and force on both sides of the pusher are statistically balanced.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A machining process for machining an elongated push broach for a U-shaped opening, characterized in that, Includes the following steps: (1) Preparation of the pusher blank: High-speed steel blank with a rectangular cross section is used as the pusher blank; (2) Push cutter planing: A layer of black skin is planed off the four sides and two ends of the push cutter blank; (3) Center hole machining: Drill center holes at both ends of the pusher; (4) Milling of each face of the pusher: The pusher is positioned by the center holes at both ends, and the face of each end of the pusher is milled by CNC milling; among them, the guide strip is milled on the back of the pusher, and the arc section of the pusher is milled into an arc surface on one side of the cutting edge. (5) Milling of chip grooves and cutting edges on push cutter: CNC milling of the tooth profiles of each chip groove, each cutting tooth and the correction tooth on the push cutter; (6) Heat treatment of pusher: The pusher is subjected to salt bath quenching and salt bath tempering heat treatment in succession. The heat treatment is carried out strictly in accordance with the process flow and the operation of each process is coordinated. Among them, the pusher is straightened during the cooling process after salt bath quenching in order to obtain good comprehensive mechanical properties and small workpiece deformation. (7) Cold treatment and aging treatment of pusher: Low temperature ice cooling technology is used to perform shaping treatment and aging treatment on pusher to remove heat treatment stress and cutting stress; (8) Grind the center hole of the pusher: Grind the center holes at both ends of the pusher; (9) Grinding of each face of the pusher: The pusher is positioned by the center holes at both ends, and the face of each end of the pusher is ground by CNC; among them, the guide strip is finely produced on the back of the pusher, and the cutting edge of the arc section of the pusher is finely ground into an arc surface; (10) Grinding of chip grooves and cutting edges of pusher: CNC grinding of the tooth profile of each chip groove, each cutting tooth and the correction tooth on the pusher, and precision grinding of chip grooves; In step (6) heat treatment of the pusher, the pusher is straightened after heat treatment by using an online excitation synchronous straightening method to achieve automatic straightening of the pusher. The online excitation synchronous straightening method includes installing an online excitation synchronous straightening device on a CNC press, applying excitation energy to the pusher through the online excitation synchronous straightening device, so that the pusher is straightened by the pressure head on the CNC press under the excitation state, so as to release the internal stress caused by the pressure shaping to the maximum extent, reduce the deformation caused by the secondary release of internal stress during subsequent processing, thereby improving the accuracy and stability of the pusher after final processing. The online vibration synchronous straightening device includes a pair of vibrators for synchronously applying vibration force when the pusher is pressure-straightened. Each vibrator includes a servo telescoping device, an elastic element, a top pressure plate, and an ultrasonic transducer. The servo telescoping device is connected to the elastic element, the elastic element is connected to the top pressure plate, and the ultrasonic transducer is fixedly mounted on the top pressure plate and located on the same side of the top pressure plate together with the elastic element. The other side of the top pressure plate is used to press against the side of the pusher.

2. The machining process for a slender pusher for machining a U-shaped opening according to claim 1, characterized in that, The online vibration synchronous straightening device further includes an automatic pusher turning device and a pusher straightness detection device. The automatic pusher turning device includes a pair of pusher positioning seats located at both ends of the pusher's longitudinal direction, positioning grooves correspondingly disposed on the pair of pusher positioning seats to limit the horizontal movement of the pusher's end, a servo lifter disposed on the pusher positioning seat, a servo angle motor disposed on the upper end of the lifting shaft of the servo lifter, and a servo finger cylinder disposed on the motor shaft of the servo angle motor to clamp the pusher during pusher turning; wherein, the positioning of the pusher positioning seat... The bottom surface of the groove is lower than the upper surface of the anvil on the movable workbench, and the upper end of the positioning groove of the push knife positioning seat is higher than the upper surface of the anvil; the push knife straightness detection device includes a horizontal guide rail installed on the movable workbench of the CNC press and located on the side of the straightening push knife and parallel to the push knife, a detection arm movably set on the horizontal guide rail and moved on the horizontal guide rail by a servo linear drive mechanism, the detection arm extending upward and bending to the position above the push knife, and a laser range sensor aligned downward with the upper plane of the push knife is provided at the end of the extended end of the detection arm.

3. The machining process for a slender pusher for machining a U-shaped opening according to claim 2, characterized in that, The steps for automatic straightening of the pusher using the online excitation synchronous straightening method are as follows: S1. Installation of pusher: Place the pusher that needs to be straightened on the anvil of the moving worktable of the CNC press; S2. Installation of the online vibration synchronous straightening device: At least N pairs of vibrators are fixedly installed on the CNC press using brackets. The N pairs of vibrators are arranged at intervals in the direction of movement parallel to the moving worktable. Each pair of vibrators is placed on both sides of the moving worktable of the CNC press, and the top pressure plate of each pair of vibrators is aligned with both sides of the push knife on the anvil. An automatic push knife turning device and a push knife straightness detection device are installed on the moving worktable. The automatic push knife turning device is placed on both ends of the push knife on the moving worktable, such that the ends of the push knife are located in the finger clamps of the servo finger cylinders but do not contact the finger clamps. The push knife straightness detection device is installed on one side of the push knife on the moving worktable. The guide rail of the push knife straightness detection device is parallel to the longitudinal direction of the push knife, and the laser rangefinder of the push knife straightness detection device is aligned downward with the upper end face of the push knife. S3. Determination of the pressure correction position for the pusher: The control system activates the pusher straightness detection device and drives the laser range sensor on the pusher straightness detection device to move in a direction parallel to the guide rail. The laser range sensor scans and detects the distance to the upper end face of the pusher along the longitudinal direction. After the control system collects the scanning distance data of the laser range sensor, it finds the bending error at various points along the longitudinal direction of the upper end face of the pusher and determines the part of the pusher that needs pressure correction. S4. Dynamic Pressure Shaping and Straightening: The control system drives the moving worktable to move the part of the pusher that needs pressure correction to the position directly below the pressure head of the CNC press. N pairs of vibrators are turned on, so that the top pressure plates of the N pairs of vibrators clamp the two sides of the pusher and apply excitation force to the pusher through ultrasonic transducers. Under the condition of excitation vibration of the pusher, the pressure head of the CNC press presses down on the part of the pusher that needs pressure correction and performs pressure shaping on the part. After pressure shaping, the pressure head of the CNC press rises and the top pressure plates of the N pairs of vibrators retract, so that the top pressure plates separate from the pusher, completing the online excitation synchronous straightening of the pusher. Repeat steps S3 to S4 above, cyclically applying pressure to each part of the straightening pusher where the straightness error exceeds the tolerance, until the straightness error of the pusher completely meets the specified requirements; In the determination of the pusher pressure correction position in S3, when the control system determines that the part to be straightened needs to be flipped and adjusted before it can be implemented, the control system drives the pusher automatic flipping device to operate. After the finger cylinder of the pusher automatic flipping device clamps the two ends of the pusher, the pusher is raised by the servo lifter. Then, the servo angle motor drives the finger cylinder to rotate 180 degrees around the motor shaft of the servo angle motor to realize the flipping and adjustment of the pusher. Then, the servo lifter lowers the pusher to reset, the finger cylinder is released, and the pusher is accurately positioned in its original position.

4. The machining process for a slender pusher for machining a U-shaped opening according to claim 3, characterized in that, In step S4, dynamic pressure shaping and straightening, after online vibration synchronous straightening is completed, the pusher is then subjected to independent enhanced vibration to further release the internal stress of the pusher; the steps for independent enhanced vibration of the pusher are as follows: A1. Slight lifting of the push knife: The control system drives the finger cylinder to clamp both ends of the push knife, and then drives the servo lifter to lift the push knife a slight distance, so that the push knife is no longer in contact with the anvil on the moving worktable. A2. Elastic clamping of push knife in mid-air: The control system drives the servo telescopic devices on N pairs of vibrators to move, so that the elastic top pressure plate of the vibrator presses against both sides of the push knife, and then the finger cylinder releases, forming an elastic clamping of the push knife in mid-air. A3. Independent enhanced excitation: The control system activates the ultrasonic transducers on N pairs of exciters to apply excitation force to the pusher. The pusher is subjected to independent enhanced excitation force in the air environment, which further eliminates the pressure and shaping stress inside the pusher. Once completed, the vibrator retracts its elastic clamp on the pusher, and the pusher falls back onto the anvil.

5. The machining process for a slender pusher for machining a U-shaped opening according to claim 1, characterized in that, In step (10) of grinding the chip groove and cutting edge of the pusher, the grinding of the chip groove adopts the grinding method of alternating back and forth moving the grinding head, which reduces the temporal unevenness of the heat distribution on both sides of the pusher body. The alternating back and forth moving grinding of the grinding head means that when the grinding head grinds each chip groove one by one, it first grinds the first chip groove by moving the grinding head clockwise along the U-shaped tool path, and then grinds the second chip groove adjacent to it by moving the grinding head counterclockwise along the U-shaped tool path. The chip grooves are ground alternately and cyclically in sequence, so that the heat transfer on both sides of the pusher is basically uniform in time, thereby reducing the uneven heat deformation during the grinding of the pusher.

6. The machining process for a slender pusher for machining a U-shaped opening according to claim 1, characterized in that, The slender pusher includes a long, narrow pusher body. The long, narrow pusher body has a front guide section, a broaching section, a correction section, and a rear clamping section arranged longitudinally. The broaching section has a number of cutting teeth spaced apart, and the correction section has a number of correction teeth spaced apart. Chip grooves are provided between adjacent cutting teeth and between adjacent correction teeth. Viewed along the length parallel to the pusher body, the outer contours of the cutting teeth and correction teeth are U-shaped with three cutting edges. The three cutting edges of the U-shaped outer contour include an arc-shaped cutting edge and a pair of parallel straight cutting edges connected to the two ends of the arc-shaped cutting edge. A rectangular cross-section guide bar is arranged longitudinally on the back side of the long, narrow pusher body. A number of chip grooves are spaced apart on the three cutting edges of the cutting teeth. The chip grooves on adjacent cutting edges are staggered. The cutting edge contour plane formed by the arc-shaped cutting edge and the pair of straight cutting edges is inclined laterally relative to the long, narrow pusher body.

7. The machining process for a slender pusher for machining a U-shaped opening according to claim 6, characterized in that, The profile plane formed by the arc-shaped cutting edge and a pair of straight cutting edges has a lateral tilt angle β of 10° to 15° relative to the elongated pusher body.

8. The machining process for a slender pusher for machining a U-shaped opening according to claim 6, characterized in that, It is also equipped with a guide support block to prevent the slender pusher from moving laterally during cutting. The guide support block is provided with a groove that is adapted to the rectangular cross-section guide strip on the slender pusher.

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