A processing technology for deep core-pulling holes of an automobile bumper mold

Abstract

The present invention discloses a processing technology for deep core-pulling holes of an automobile bumper mold, which comprises the following steps: (1) clamping and positioning before five-axis machining; (2) machining of the inner hole of the core-pulling hole guiding part: using a five-axis machining center to mill a section of pre-positioning holes for outer machining from the outer end face of the mold towards the inner cavity direction of the mold, and then replacing the precision end mill with a deep hole drill bit, and drilling the inner hole of the guiding part of the deep core-pulling hole with the pre-positioning holes for outer machining as the reference; (3) pre-machining of the shaped holes of the core-pulling module installation part: using a five-axis machining center to pre-machine a section of shaped holes of the core-pulling module installation part from the inner cavity of the mold towards the outer end face direction of the mold in a milling manner, and a machining allowance is left for the pre-machined section of the shaped holes of the core-pulling module installation part; (4) clamping and positioning before CNC electric discharge machining; (5) formal machining of the shaped holes of the core-pulling module installation part; The present invention realizes high-quality and high-efficiency machining of the deep core-pulling holes of the automobile bumper mold.

Description

Technical Field

[0001] The present invention relates to the technical field of mold processing, and particularly relates to a processing technology for deep core-pulling holes of an automobile bumper mold. Background Art

[0002] As Figure 2 Deep core-pulling holes 30 are respectively arranged on both sides of the automobile bumper mold as shown. The deep core-pulling hole 30 includes a counterbore inner hole 1, a guiding inner hole 2, and a special-shaped hole 3 for the core-pulling module installation part that are connected in sequence. Among them, the special-shaped hole for the core-pulling module installation part has high processing accuracy requirements because the core-pulling module needs to be installed.

[0003] The conventional processing method for the special-shaped hole of the core-pulling module installation part is as follows: First, the counterbore inner hole 1 and the guiding inner hole 2 are processed on a five-axis machining center, and the bottom hole of the special-shaped hole of the core-pulling module installation part is pre-drilled. After processing, the mold is transferred to a CNC electric discharge machining machine. A lengthened special-shaped profiling electrode is used to pass through the guiding inner hole 2 and extend into the bottom hole of the special-shaped hole 3 of the core-pulling module installation part to perform CNC electric discharge machining on the special-shaped hole of the core-pulling module installation part.

[0004] The deficiencies of the above processing method are as follows: The length of the special-shaped profiling electrode is too long, resulting in vibration during electric discharge machining. On the one hand, the efficiency of electric discharge machining is reduced, and on the other hand, it is difficult to guarantee the accuracy of the special-shaped hole of the core module installation part. Summary of the Invention

[0005] In order to solve the above problems, the present invention proposes a processing technology for deep core-pulling holes of an automobile bumper mold, aiming to achieve high-quality processing of deep core-pulling holes of an automobile bumper mold and improve the processing efficiency. The specific technical solutions are as follows:

[0006] A processing technology for deep core-pulling holes of an automobile bumper mold includes the following steps:

[0007] (1) Clamping and positioning before five-axis machining: Clamp and position the mold on the workbench of the five-axis machining center. After aligning the position of the mold, fix the mold.

[0008] (2) Machining of the guiding inner hole of the core-pulling hole: Install a precision end mill on the spindle head of the five-axis machining center, mill a section of pre-positioning hole for outer-side machining from the outer end face of the mold towards the inner cavity direction of the mold, and then replace the precision end mill with a deep-hole drill bit. Taking the pre-positioning hole for outer-side machining as a reference, drill and machine the guiding inner hole of the deep core-pulling hole.

[0009] (3)Pre-machining of the special-shaped hole in the core-pulling module installation part: Replace the precision end mill on the spindle head of the five-axis machining center, turn the five-axis head of the five-axis machining center by 180 degrees, and pre-machine a section of the special-shaped hole in the core-pulling module installation part from the inner cavity of the mold towards the outer end face of the mold in a milling manner, and leave machining allowance for the pre-machined section of the special-shaped hole in the core-pulling module installation part;

[0010] (4)Clamping and positioning before CNC electrical discharge machining: Clamp and position the mold on the workbench of the CNC electrical discharge machining machine. After aligning the position of the mold, fix the mold;

[0011] (5)Formal machining of the special-shaped hole in the core-pulling module installation part: Install the special electrode on the spindle head of the CNC electrical discharge machining machine. Take the pre-machined section of the special-shaped hole in the core-pulling module installation part as the reference and align the zero position of the special electrode; then use the special electrode to perform CNC electrical discharge machining on the special-shaped hole in the core-pulling module installation part;

[0012] (6)Inspection of the size and position of the special-shaped hole in the core-pulling module installation part: Take the inner hole of the guiding part of the deep core-pulling hole of the mold as the reference to inspect the size and position of the special-shaped hole in the core-pulling module installation part.

[0013] Preferably, the processing technology of the deep core-pulling hole of the automobile bumper mold further includes the machining of the inner hole of the counterbore part of the deep core-pulling hole of the mold; the machining of the inner hole of the counterbore part is arranged after the pre-machining of the special-shaped hole in the core-pulling module installation part.

[0014] In the present invention, the special electrode includes an electrode shank part, an electrode profiling machining part, and a transition connection part connected between the electrode shank part and the electrode profiling machining part.

[0015] In the present invention, the transverse cross-sectional shape of the electrode profiling machining part of the special electrode is rectangular and rounded corners are provided at the corners of the rectangle; a reverse longitudinal inclined plane is provided on the electrode profiling machining part.

[0016] As a preferred solution for the inspection of the size and position of the special-shaped hole in the core-pulling module installation part in the present invention, in the inspection process of the size and position of the special-shaped hole in the core-pulling module installation part in step (6), a special inspection tool is used to inspect the special-shaped hole in the core-pulling module installation part; the special inspection tool includes a go gauge inspection tool and a no-go gauge inspection tool.

[0017] Preferably, the go gauge fixture includes a reference positioning shaft and a go gauge provided at one end of the reference positioning shaft; the no-go gauge fixture includes a reference positioning shaft and a no-go gauge provided at one end of the reference positioning shaft; wherein, the outer circle of the reference positioning shaft is adapted to the inner hole of the core-pulling hole guiding portion; the outer shapes of the go gauge and the no-go gauge are respectively consistent with the shape of the inner hole of the core-pulling hole guiding portion, and the outer dimension of the go gauge takes the lower limit value of the dimensional tolerance of the special-shaped hole of the core-pulling module mounting portion, and the outer dimension of the no-go gauge takes the upper limit value of the dimensional tolerance of the special-shaped hole of the core-pulling module mounting portion.

[0018] Preferably, the reference positioning shaft includes a pipe body and a pair of thin-walled rings arranged at intervals on the outer circle of the pipe body for adapting to the inner hole of the core-pulling hole guiding portion. The two ends of the thin-walled ring are integrally connected to the outer circle of the reference positioning shaft by welding. An annular groove is provided on the inner hole surface of the thin-walled ring, and a closed annular cavity is formed between the annular groove and the outer circle of the reference positioning shaft. The closed annular cavity is communicated with the inner hole of the pipe body through a hydraulic hole provided on the pipe body; one end of the pipe body is closed by connecting the go gauge or the no-go gauge, and the other end of the pipe body is closed by providing a cover plate. A hydraulic pipe communicating with the inner hole of the pipe body is provided on the cover plate, and the other end of the hydraulic pipe is connected to a hydraulic source.

[0019] Preferably, a pressure gauge is provided on the hydraulic pipe.

[0020] Preferably, the hydraulic pipe is a hydraulic hose.

[0021] The method for detecting the special-shaped hole of the core-pulling module mounting portion is as follows: Insert the reference positioning shaft of the go gauge fixture into the inner hole of the guiding portion for positioning, adjust the pressure in the hydraulic pipe to be moderate, so that the outer circle of the thin-walled ring on the reference positioning shaft expands outwards and contacts the inner hole of the guiding portion, and at the same time the thin-walled ring on the reference positioning shaft can slide axially. Check whether the go gauge at the front end of the reference positioning shaft can enter the special-shaped hole of the core-pulling module mounting portion and reach the axial position. After passing the inspection, then replace it with the no-go gauge fixture for inspection. If the no-go gauge at the front end of the reference positioning shaft cannot enter the special-shaped hole of the core-pulling module mounting portion, it indicates that the dimensional and positional inspection results of the special-shaped hole of the core-pulling module mounting portion are qualified. If either of the two inspections using the go gauge fixture and the no-go gauge fixture is unqualified, it indicates that the dimensional and positional inspection results of the special-shaped hole of the core-pulling module mounting portion are unqualified.

[0022] As a further improvement of the present invention, in the formal machining process of the special-shaped hole of the core-pulling module mounting portion in step (5), there are an electric discharge rough machining step and an electric discharge finish machining step. In the electric discharge rough machining step, a certain machining allowance is left for the size of the special-shaped hole of the core-pulling module mounting portion, and in the electric discharge finish machining step, the size of the special-shaped hole of the core-pulling module mounting portion is machined to the finished size.

[0023] In the present invention, the number of the special-shaped holes in the core-pulling module installation part on the mold is a pair; in the formal machining process of the special-shaped holes in the core-pulling module installation part in step (5), the rough machining of the pair of special-shaped holes in the core-pulling module installation part is completed successively first, and then the finish machining of the pair of special-shaped holes in the core-pulling module installation part is completed successively.

[0024] As a further improvement of the present invention, an inner hole surface micro-stress elimination step for improving the accuracy of the special-shaped holes in the core-pulling module installation part after electric discharge finish machining is also provided between the electric discharge rough machining step and the electric discharge finish machining step. In the inner hole surface micro-stress elimination step, an inner hole surface micro-stress elimination tool is used to perform stress relief treatment on the surface layer of the special-shaped holes in the core-pulling module installation part; the inner hole surface micro-stress elimination tool includes a special-shaped thin-walled sleeve adapted to the special-shaped holes in the core-pulling module installation part, a conical expanding core installed in the inner hole of the special-shaped thin-walled sleeve and adapted to the inner hole of the special-shaped thin-walled sleeve, a plurality of opening slits respectively opened on the special-shaped thin-walled sleeve along both longitudinal ends towards the other end, a pressing plate arranged at the small head end of the conical expanding core, a tensioning bolt connecting the small head end of the conical expanding core and the pressing plate for expanding the special-shaped thin-walled sleeve, and an ultrasonic oscillator arranged at the large head end of the conical expanding core, and the ultrasonic oscillator is connected to an ultrasonic generator.

[0025] In order to make more ultrasonic energy concentrate on the surface layer part of the special-shaped holes in the core-pulling module installation part and improve the efficiency of stress relief on the surface layer of the special-shaped holes in the core-pulling module installation part, a further improvement scheme is: an elastic material layer is coated on the outer surface of the special-shaped thin-walled sleeve.

[0026] Preferably, the elastic material layer is rubber paint.

[0027] Preferably, the thickness of the rubber paint is 0.10 - 0.30 mm.

[0028] The working principle of the above inner hole surface micro-stress elimination tool is as follows:

[0029] Install the special-shaped thin-walled sleeve with the conical expanding core into the special-shaped holes in the core-pulling module installation part. Use the tensioning bolt to make the special-shaped thin-walled sleeve fit and tighten on the surface of the special-shaped holes in the core-pulling module installation part. Then turn on the ultrasonic generator. Under the action of the ultrasonic oscillator, ultrasonic energy is transmitted to the special-shaped holes in the core-pulling module installation part through the conical expanding core and the special-shaped thin-walled sleeve, and the ultrasonic energy received by the surface layer of the special-shaped holes in the core-pulling module installation part is the largest, so as to play a role in stress relief on the surface layer of the special-shaped holes in the core-pulling module installation part, and further improve the stress uniformity of the surface layer of the special-shaped holes in the core-pulling module installation part. After stress relief treatment, finish machining is performed on the special-shaped holes in the core-pulling module installation part, which can reduce the surface micro-deformation of the special-shaped holes in the core-pulling module installation part, thereby improving the accuracy of the finally machined special-shaped holes in the core-pulling module installation part.

[0030] The beneficial effects of the present invention are as follows:

[0031] First, for the processing technology of the deep core-pulling holes of an automotive bumper mold of the present invention, by formulating a reasonable process flow and processing method, precise centering processing of the special-shaped holes in the installation part of the core-pulling module is achieved using a short electrode, and the drawback that the vibration of electrical discharge machining caused by the excessive length of the electrode in the conventional processing method affects the machining accuracy is overcome. Thus, high-quality processing of the deep core-pulling holes of the automotive bumper mold is realized, and the processing efficiency is improved.

[0032] Second, for the processing technology of the deep core-pulling holes of an automotive bumper mold of the present invention, an inner hole surface micro-stress elimination step for improving the accuracy of the special-shaped holes in the installation part of the core-pulling module after electrical discharge finishing is also provided between the electrical discharge roughing step and the electrical discharge finishing step. The surface layer of the special-shaped holes in the installation part of the core-pulling module is subjected to ultrasonic vibration stress relief using a specially designed inner hole surface micro-stress elimination tool. Its ultrasonic energy can be concentrated on the surface layer part of the hole, and the stress relief effect is good, thereby reducing the micro-deformation caused by the redistribution of the surface stress of the hole after electrical discharge finishing, and further improving the machining accuracy of the special-shaped holes in the installation part of the core-pulling module.

[0033] Third, for the processing technology of the deep core-pulling holes of an automotive bumper mold of the present invention, specially designed go gauges and no-go gauges can eliminate the gap between the reference positioning shaft and the inner hole of the guiding part during detection, thereby improving the detection accuracy and ensuring the machining quality of the special-shaped holes in the installation part of the core-pulling module. Brief Description of the Drawings

[0034] Figure 1 is a schematic flow chart of the processing technology of the deep core-pulling holes of an automotive bumper mold of the present invention;

[0035] Figure 2 is a schematic structural diagram of setting deep core-pulling holes on an automotive bumper mold;

[0036] Figure 3 is a schematic structural diagram of a special electrode for processing special-shaped holes in the installation part of the core-pulling module;

[0037] Figure 4 is a schematic structural diagram of go gauges and no-go gauges for detecting special-shaped holes in the installation part of the core-pulling module;

[0038] Figure 5 is a schematic diagram of stress relief treatment on the surface layer of the special-shaped holes in the installation part of the core-pulling module using an inner hole surface micro-stress elimination tool;

[0039] Figure 6 is Figure 5 a partial enlarged view of

[0040] In the figure: 1. Inner hole of counterbore part; 2. Inner hole of guiding part; 3. Special-shaped hole of core-pulling module installation part; 4. Electrode shank part; 5. Electrode profiling machining part; 6. Transition connection part; 7. Fillet; 8. Longitudinal inclined plane; 9. Datum positioning shaft; 10. Go gauge; 11. Not-go gauge; 12. Pipe body; 13. Annular groove; 14. Thin-walled ring; 15. Closed annular cavity; 16. Hydraulic hole; 17. Cover plate; 18. Hydraulic pipe; 19. Hydraulic source; 20. Pressure gauge; 21. Inner hole surface micro-stress elimination tool; 22. Special-shaped thin-walled sleeve; 23. Tapered core expander; 24. Open cut; 25. Pressure plate; 26. Tightening bolt; 27. Ultrasonic vibrator; 28. Ultrasonic generator; 29. Automobile bumper mold; 30. Deep core-pulling hole. Detailed implementation manners

[0041] The following combines the accompanying drawings and embodiments to further describe the detailed implementation manners of the present invention. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention. Embodiment 1:

[0042] As Figures 1 to 6 shown is an embodiment of the processing technology of the deep core-pulling hole of an automobile bumper mold of the present invention, including the following steps:

[0043] (1) Clamping and positioning before five-axis machining: Clamp and position the mold 29 on the workbench of the five-axis machining center. After aligning the position of the mold 29, fix the mold 29.

[0044] (2) Machining of the inner hole of the guiding part of the core-pulling hole: Install a precision end mill on the spindle head of the five-axis machining center, mill a section of the outer machining pre-positioning hole from the outer end face of the mold 29 towards the inner cavity direction of the mold 29, and then replace the precision end mill with a deep hole drill bit, and drill and machine the inner hole 2 of the guiding part of the deep core-pulling hole 30 with the outer machining pre-positioning hole as the reference.

[0045] (3) Pre-machining of the special-shaped hole of the core-pulling module installation part: Replace the precision end mill on the spindle head of the five-axis machining center, turn the five-axis head of the five-axis machining center by 180 degrees, and pre-machine a section of the special-shaped hole 3 of the core-pulling module installation part from the inner cavity of the mold 29 towards the outer end face direction of the mold 29 in a milling manner, and a machining allowance is left for the pre-machined section of the special-shaped hole 3 of the core-pulling module installation part.

[0046] (4) Clamping and positioning before CNC electric discharge machining: Clamp and position the mold 29 on the workbench of the CNC electric discharge machining machine. After aligning the position of the mold 29, fix the mold 29.

[0047] (5)Formal machining of the special-shaped hole of the core-pulling module installation part: Install a special electrode on the spindle head of the CNC electric discharge machining machine tool. Align the zero position of the special electrode with a section of the pre-machined special-shaped hole 3 of the core-pulling module installation part as the reference. Then, use the special electrode to perform CNC electric discharge machining on the special-shaped hole 3 of the core-pulling module installation part.

[0048] (6)Inspection of the size and position of the special-shaped hole of the core-pulling module installation part: Take the inner hole 2 of the guiding part of the deep core-pulling hole 30 of the mold as the reference to inspect the size and position of the special-shaped hole 3 of the core-pulling module installation part.

[0049] Preferably, the machining process of the deep core-pulling hole of the automobile bumper mold further includes machining the inner hole 1 of the counterbore part of the deep core-pulling hole 30 of the mold. The machining of the inner hole 1 of the counterbore part is arranged after the pre-machining of the special-shaped hole 3 of the core-pulling module installation part.

[0050] In the present invention, the special electrode includes an electrode shank part 4, an electrode profiling machining part 5, and a transition connection part 6 connected between the electrode shank part 4 and the electrode profiling machining part 5.

[0051] In the present invention, the transverse cross-sectional shape of the electrode profiling machining part 5 of the special electrode is rectangular, and fillets 7 are provided at the corners of the rectangle; a reverse longitudinal inclined surface 8 is provided on the electrode profiling machining part.

[0052] As a preferred solution for inspecting the size and position of the special-shaped hole of the core-pulling module installation part in the present invention, in the inspection process of the size and position of the special-shaped hole of the core-pulling module installation part in step (6), a special inspection tool is used to inspect the special-shaped hole 3 of the core-pulling module installation part; the special inspection tool includes a go gauge inspection tool and a no-go gauge inspection tool.

[0053] Preferably, the go gauge inspection tool includes a reference positioning shaft 9 and a go gauge 10 provided at one end of the reference positioning shaft 9; the no-go gauge inspection tool includes a reference positioning shaft 9 and a no-go gauge 11 provided at one end of the reference positioning shaft 9; wherein, the outer diameter of the reference positioning shaft 9 is adapted to the inner hole 2 of the core-pulling hole guiding part; the outer shapes of the go gauge 10 and the no-go gauge 11 are respectively consistent with the shape of the inner hole 2 of the core-pulling hole guiding part, and the outer dimension of the go gauge 10 takes the lower limit value of the dimensional tolerance of the special-shaped hole 3 of the core-pulling module installation part, and the outer dimension of the no-go gauge 11 takes the upper limit value of the dimensional tolerance of the special-shaped hole 3 of the core-pulling module installation part.

[0054] Preferably, the reference positioning shaft 9 includes a tube body 12 and a pair of thin-walled rings 14 arranged at intervals on the outer circumference of the tube body 12 and adapted to the inner hole 3 of the core-pulling hole guiding portion. Both ends of the thin-walled ring 14 are integrally connected to the outer circumference of the reference positioning shaft 9 by welding. An annular groove 13 is provided on the inner hole surface of the thin-walled ring 14, and a closed annular cavity is formed between the annular groove 13 and the outer circumference of the reference positioning shaft 9. The closed annular cavity is communicated with the inner hole of the tube body 12 through a hydraulic hole 16 provided on the tube body 12. One end of the tube body 12 is closed by connecting the go gauge 10 or the no-go gauge 11, and the other end of the tube body 12 is closed by providing a cover plate 17. A hydraulic pipe 18 communicating with the inner hole of the tube body 12 is provided on the cover plate 17, and the other end of the hydraulic pipe 18 is connected to a hydraulic source 19.

[0055] Preferably, a pressure gauge 20 is provided on the hydraulic pipe 18.

[0056] Preferably, the hydraulic pipe 18 is a hydraulic hose.

[0057] The method for detecting the irregular-shaped hole 3 of the core-pulling module installation part is as follows: Insert the reference positioning shaft 9 of the go gauge into the inner hole of the guiding portion for positioning, adjust the pressure in the hydraulic pipe 18 to be moderate, so that the outer circumference of the thin-walled ring 14 on the reference positioning shaft 9 expands outward and contacts the inner hole 2 of the guiding portion, and at the same time, the thin-walled ring 14 on the reference positioning shaft 9 can slide axially. Check whether the go gauge 10 at the front end of the reference positioning shaft 9 can enter the irregular-shaped hole 3 of the core-pulling module installation part and reach the axial position. After passing the inspection, replace it with the no-go gauge for inspection. If the no-go gauge at the front end of the reference positioning shaft 9 cannot enter the irregular-shaped hole 3 of the core-pulling module installation part, it indicates that the size and position detection result of the irregular-shaped hole 3 of the core-pulling module installation part is qualified. If either of the two inspections using the go gauge and the no-go gauge is unqualified, it indicates that the size and position detection result of the irregular-shaped hole 3 of the core-pulling module installation part is unqualified.

[0058] As a further improvement of the present invention, in the formal processing procedure of the irregular-shaped hole of the core-pulling module installation part in step (5), there are an electric discharge roughing step and an electric discharge finishing step. In the electric discharge roughing step, a certain machining allowance is left for the size of the irregular-shaped hole 3 of the core-pulling module installation part, and in the electric discharge finishing step, the size of the irregular-shaped hole 3 of the core-pulling module installation part is precisely machined to the required size.

[0059] In the present invention, the number of the irregular-shaped holes 3 of the core-pulling module installation part on the mold is a pair; in the formal processing procedure of the irregular-shaped holes of the core-pulling module installation part in step (5), the rough machining of a pair of irregular-shaped holes 3 of the core-pulling module installation part is completed in sequence first, and then the finish machining of a pair of irregular-shaped holes 3 of the core-pulling module installation part is completed in sequence.

[0060] As a further improvement of the present invention, an inner hole surface micro-stress elimination step is also provided between the rough electrical discharge machining step and the finish electrical discharge machining step, which is used to improve the accuracy of the special-shaped hole 3 of the core-pulling module mounting part after finish electrical discharge machining. In the inner hole surface micro-stress elimination step, an inner hole surface micro-stress elimination tool 21 is used to perform stress relief treatment on the surface of the special-shaped hole 3 of the core-pulling module mounting part; the inner hole surface micro-stress elimination tool 21 includes a special-shaped thin-walled sleeve 22 adapted to the special-shaped hole 3 of the core-pulling module mounting part, a tapered expanding core 23 installed in the inner hole of the special-shaped thin-walled sleeve 22 and adapted to the inner hole of the special-shaped thin-walled sleeve 22, a plurality of opening slits 24 respectively opened on the special-shaped thin-walled sleeve 22 along both longitudinal ends towards the other end, a pressing plate 25 arranged at the small head end of the tapered expanding core 23, a tightening bolt 26 connected between the small head end of the tapered expanding core 23 and the pressing plate 25 for expanding the special-shaped thin-walled sleeve 22, and an ultrasonic oscillator 27 arranged at the large head end of the tapered expanding core 23, and the ultrasonic oscillator 27 is connected to an ultrasonic generator 28.

[0061] In order to make more ultrasonic energy concentrate on the surface part of the special-shaped hole 3 of the core-pulling module mounting part and improve the efficiency of stress relief on the surface of the special-shaped hole 3 of the core-pulling module mounting part, a further improvement scheme is: an elastic material layer is coated on the outer surface of the special-shaped thin-walled sleeve 22.

[0062] Preferably, the elastic material layer is rubber paint.

[0063] Preferably, the thickness of the rubber paint is 0.10 - 0.30 mm.

[0064] The working principle of the above-mentioned inner hole surface micro-stress elimination tool 21 is as follows:

[0065] The special-shaped thin-walled sleeve 22 with the tapered expanding core 23 is installed into the special-shaped hole 3 of the core-pulling module mounting part. The tightening bolt 26 is used to make the special-shaped thin-walled sleeve 22 fit and tighten on the surface of the special-shaped hole 3 of the core-pulling module mounting part. Then, the ultrasonic generator 28 is turned on. Under the action of the ultrasonic oscillator 27, the ultrasonic energy is transmitted to the special-shaped hole 3 part of the core-pulling module mounting part through the tapered expanding core 23 and the special-shaped thin-walled sleeve 22, and the ultrasonic energy received by the surface of the special-shaped hole 3 of the core-pulling module mounting part is the largest, so as to play a role in stress relief on the surface of the special-shaped hole 3 of the core-pulling module mounting part, and further improve the stress uniformity of the surface of the special-shaped hole 3 of the core-pulling module mounting part. After stress relief treatment, finish machining is carried out on the special-shaped hole 3 of the core-pulling module mounting part, which can reduce the surface micro-deformation of the special-shaped hole of the core-pulling module mounting part (the surface micro-deformation is a micro-deformation below 0.02 mm), thereby improving the accuracy of the special-shaped hole 3 of the core-pulling module mounting part in the final machining. Example 2:

[0066] The deep core-pulling hole 30 of the automotive bumper mold is machined using the processing technology of Embodiment 1. The following two processing schemes are adopted for the special-shaped hole 3 of the core-pulling module installation part:

[0067] Scheme 1: Use a special electrode to carry out rough electrical discharge machining and finish electrical discharge machining on the special-shaped hole 3 of the core-pulling module installation part in sequence, and no stress relief treatment is arranged between the rough electrical discharge machining and the finish electrical discharge machining; after machining, the maximum error value of the surface of the special-shaped hole 3 of the core-pulling module installation part relative to the ideal surface is detected on a coordinate measuring machine to be 0.02 mm;

[0068] Scheme 2: Use a special electrode to carry out rough electrical discharge machining and finish electrical discharge machining on the special-shaped hole 3 of the core-pulling module installation part in sequence, and use the inner hole surface micro-stress elimination tool 21 to carry out stress relief treatment on the surface of the special-shaped hole 3 of the core-pulling module installation part between the rough electrical discharge machining and the finish electrical discharge machining, and the treatment time is 1 hour; after machining, the maximum error value of the surface of the special-shaped hole 3 of the core-pulling module installation part relative to the ideal surface is detected on a coordinate measuring machine to be 0.012 mm.

[0069] By comparing Scheme 1 and Scheme 2, it can be seen that the machining accuracy of Scheme 2 has been greatly improved compared with Scheme 1.

[0070] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A processing technology for deep core-pulling holes of an automobile bumper mold, characterized in that, The method includes the following steps: (1) Clamping and positioning before five-axis machining: Clamp and position the mold on the workbench of the five-axis machining center. After aligning the position of the mold, fix the mold; (2) Machining the inner hole of the core-pulling hole guiding part: Install a precision end mill on the spindle head of the five-axis machining center. Milling a section of pre-positioning hole for outer machining from the outer end face of the mold towards the inner cavity of the mold. Then replace the precision end mill with a deep hole drill bit, and drill the inner hole of the guiding part of the deep core-pulling hole with the pre-positioning hole for outer machining as the reference; (3) Pre-machining the special-shaped hole of the core-pulling module installation part: Replace the precision end mill on the spindle head of the five-axis machining center. Turn the five-axis head of the five-axis machining center by 180 degrees, and pre-machine a section of the special-shaped hole of the core-pulling module installation part in a milling manner from the inner cavity of the mold towards the outer end face of the mold, and a machining allowance is left for the pre-machined section of the special-shaped hole of the core-pulling module installation part; (4) Clamping and positioning before CNC electrical discharge machining: Clamp and position the mold on the workbench of the CNC electrical discharge machining machine. After aligning the position of the mold, fix the mold; (5) Formal machining of the special-shaped hole of the core-pulling module installation part: Install a special electrode on the spindle head of the CNC electrical discharge machining machine. Align the zero position of the special electrode with the pre-machined section of the special-shaped hole of the core-pulling module installation part as the reference; Then use the special electrode to perform CNC electrical discharge machining on the special-shaped hole of the core-pulling module installation part; wherein, the special electrode includes an electrode shank part, an electrode profiling machining part, and a transition connection part connected between the electrode shank part and the electrode profiling machining part; (6) Inspection of the size and position of the special-shaped hole of the core-pulling module installation part: Take the inner hole of the guiding part of the deep core-pulling hole of the mold as the reference to inspect the size and position of the special-shaped hole of the core-pulling module installation part; The transverse cross-sectional shape of the electrode profiling machining part of the special electrode is rectangular and rounded corners are provided at the corners of the rectangle; a longitudinal inclined surface is provided on the electrode profiling machining part; In the formal machining process of the special-shaped hole of the core-pulling module installation part in step (5), an electrical discharge rough machining step and an electrical discharge finish machining step are provided. A certain machining allowance is left for the size of the special-shaped hole of the core-pulling module installation part in the electrical discharge rough machining step, and the size of the special-shaped hole of the core-pulling module installation part is machined to the finished size in the electrical discharge finish machining step; An inner hole surface micro-stress elimination step for improving the precision of the special-shaped holes in the core-pulling module mounting part after finish EDM is also provided between the rough EDM step and the finish EDM step. In the inner hole surface micro-stress elimination step, an inner hole surface micro-stress elimination tool is used to relieve the stress on the surface of the special-shaped holes in the core-pulling module mounting part; the inner hole surface micro-stress elimination tool includes a special-shaped thin-walled sleeve adapted to the special-shaped holes in the core-pulling module mounting part, a conical expanding core installed in the inner hole of the special-shaped thin-walled sleeve and adapted to the inner hole of the special-shaped thin-walled sleeve, a plurality of opening slits respectively opened on the special-shaped thin-walled sleeve along both longitudinal ends towards the other end, a pressing plate arranged at the small end of the conical expanding core, a tensioning bolt connecting the small end of the conical expanding core and the pressing plate for expanding the special-shaped thin-walled sleeve, and an ultrasonic oscillator arranged at the large end of the conical expanding core, and the ultrasonic oscillator is connected to an ultrasonic generator; wherein, an elastic material layer is coated on the outer surface of the special-shaped thin-walled sleeve.

2. The processing technology for deep core-pulling holes of an automobile bumper mold according to claim 1, characterized in that, In the inspection process of the dimensions and positions of the special-shaped holes in the core-pulling module mounting part in step (6), a special inspection tool is used to inspect the special-shaped holes in the core-pulling module mounting part; the special inspection tool includes a go-gauge inspection tool and a no-go-gauge inspection tool.

3. The processing technology for deep core-pulling holes of an automobile bumper mold according to claim 2, characterized in that, The go-gauge inspection tool includes a reference positioning shaft and a go-gauge arranged at one end of the reference positioning shaft; the no-go-gauge inspection tool includes a reference positioning shaft and a no-go-gauge arranged at one end of the reference positioning shaft; wherein, the outer circle of the reference positioning shaft is adapted to the inner hole of the core-pulling hole guiding part; the outer shapes of the go-gauge and the no-go-gauge are respectively consistent with the shape of the inner hole of the core-pulling hole guiding part, and the outer dimension of the go-gauge takes the lower limit value of the dimensional tolerance of the special-shaped holes in the core-pulling module mounting part, and the outer dimension of the no-go-gauge takes the upper limit value of the dimensional tolerance of the special-shaped holes in the core-pulling module mounting part.

4. The processing technology for deep core-pulling holes of an automobile bumper mold according to claim 3, characterized in that, The reference positioning shaft includes a pipe body and a pair of spaced thin-walled rings arranged on the outer circle of the pipe body and adapted to the inner hole of the core-pulling hole guiding part. Both ends of the thin-walled ring are integrally connected to the outer circle of the reference positioning shaft by welding. An annular groove is opened on the inner hole surface of the thin-walled ring, and a closed annular cavity is formed between the annular groove and the outer circle of the reference positioning shaft. The closed annular cavity is communicated with the inner hole of the pipe body through a hydraulic hole arranged on the pipe body; one end of the pipe body is closed by connecting the go-gauge or the no-go-gauge, and the other end of the pipe body is closed by setting a cover plate. A hydraulic pipe communicating with the inner hole of the pipe body is arranged on the cover plate, and the other end of the hydraulic pipe is connected to a hydraulic source.

5. The processing technology for deep core-pulling holes of an automobile bumper mold according to claim 4, characterized in that, A pressure gauge is arranged on the hydraulic pipe.

6. The processing technology for deep core-pulling holes of an automobile bumper mold according to claim 1, characterized in that, The number of the special-shaped holes in the core-pulling module mounting part on the mold is a pair; in the formal machining process of the special-shaped holes in the core-pulling module mounting part in step (5), the rough machining of a pair of special-shaped holes in the core-pulling module mounting part is completed in sequence first, and then the finish machining of a pair of special-shaped holes in the core-pulling module mounting part is completed in sequence.

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