Bending-twisting composite ultrasonic elliptical vibration boring system and machining method thereof

Abstract

The invention provides a bending-twisting composite ultrasonic elliptical vibration boring system and a machining method thereof. The bending-twisting composite ultrasonic elliptical vibration boring system comprises a shell, an elliptical vibration unit is arranged in the shell, and the elliptical vibration unit is connected with a boring cutter; the elliptical vibration unit comprises four semicircular ring piezoelectric ceramics and two circular ring piezoelectric ceramics, the four semicircular ring piezoelectric ceramics are combined into two circular ring piezoelectric ceramic groups, the bending vibration mode of the vibration unit is excited based on axial polarization, and bending ultrasonic vibration is generated; the two circular ring piezoelectric ceramics excite the torsional vibration mode of the vibration unit based on tangential polarization, torsional ultrasonic vibration is generated, the elliptical vibration unit is made to present a bending-torsional composite vibration mode, and an elliptical vibration track is formed. The material machinability can be improved, cutting chatter is restrained, tool abrasion is reduced, and the small-aperture precision and ultra-precision machining bottleneck of difficult-to-machine materials is broken through.

Description

Technical Field

[0001] The invention relates to the field of vibration boring processing, and in particular to a bending-torsion composite ultrasonic elliptical vibration boring system and a processing method thereof. Background Art

[0002] Fields such as aerospace, automobile manufacturing, and electronic equipment have extremely high requirements for the precision processing level of materials. Moreover, related components usually need to have characteristics such as light weight, high strength, and high wear resistance. Therefore, difficult-to-process materials such as titanium alloys, high-temperature alloys, and hardened steel are often used. High temperatures are easily generated during the processing, tool wear is serious, and processing accuracy is difficult to guarantee. In particular, the precision and ultra-precision processing of small apertures of difficult-to-process materials, the problem of machining chatter has always troubled engineers and researchers, and is a key problem that needs to be solved in the manufacturing industry.

[0003] Ultrasonic vibration machining is to apply ultrasonic vibration to the tool or workpiece to achieve periodic intermittent machining, which can significantly improve the machinability of materials, reduce cutting forces and reduce tool wear. It is an effective method to suppress the chatter of small-diameter boring of difficult-to-machine materials. Among them, ultrasonic elliptical vibration machining shows more prominent advantages than one-dimensional ultrasonic vibration machining.

[0004] Based on the significant advantages of ultrasonic elliptical vibration machining, relevant researchers at home and abroad have developed a series of ultrasonic vibration machining equipment. For example, patents with announcement numbers CN109261475B and CN102049545A use ultrasonic vibration-assisted machining, which also mentions the conversion-type torsional ultrasonic vibration excitation form using the mode of "opening spiral grooves or inclined grooves on the horn". However, it lacks stability during the machining process and cannot be accurately adjusted and controlled: The splicing of multiple groups of semicircular piezoelectric ceramics will increase the dynamic resistance and heat generation. The conversion torsional ultrasonic vibration excitation mode of "opening spiral grooves or inclined grooves on the amplitude rod" is also inconvenient for precise adjustment and control, and lacks stability during the processing. As a result, the existing technology lacks precision and ultra-precision elliptical vibration processing systems for small apertures, and the problem of precision and ultra-precision processing of small apertures of difficult-to-process materials has not been effectively solved. Moreover, piezoelectric ceramics are consumable parts. In the prior art, they are directly fixed in the housing, and the housing is fixed to the machining center, which makes the piezoelectric ceramics inconvenient to operate during subsequent replacement and maintenance. Summary of the invention

[0005] The main purpose of the present invention is to provide a bending-torsion composite ultrasonic elliptical vibration boring system and a processing method thereof, so as to solve the problems of lack of stability, inability to accurately adjust and control in the existing ultrasonic vibration boring process.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A bending-torsion composite ultrasonic elliptical vibration boring system and a processing method thereof, comprising a shell, an elliptical vibration unit is arranged in the shell, the elliptical vibration unit is connected to a boring tool for boring, and the elliptical vibration unit is electrically connected to a dual-channel ultrasonic generator; The elliptical vibration unit includes four semi-circular piezoelectric ceramics and two circular piezoelectric ceramics. The four semi-circular piezoelectric ceramics are combined into two circular piezoelectric ceramic groups, and the bending vibration mode of the vibration unit is excited based on the axial polarization to generate bending ultrasonic vibration. The two circular piezoelectric ceramics excite the torsional vibration mode of the vibration unit based on the tangential polarization to generate torsional ultrasonic vibration, thereby making the elliptical vibration unit present a bending-torsion composite vibration mode, forming an elliptical vibration trajectory; The elliptical vibration unit also includes a horn, two first copper electrodes, two second copper electrodes, a middle cover plate, a rear cover plate, a center bolt and a threaded column; The central bolt passes through the rear cover plate, the annular piezoelectric ceramic and the second copper electrode and is threadedly connected with the middle cover plate; One end of the threaded column is connected to the middle cover plate, and the other end passes through the annular piezoelectric ceramic group and the first copper electrode and is threadedly connected to the amplitude transformer.

[0007] In a preferred solution, the boring tool is connected to the head of the amplitude transformer by a fastening bolt; The two first copper electrodes are bonded to two annular piezoelectric ceramic groups, the two second copper electrodes are bonded to two annular piezoelectric ceramics, one channel of the dual-channel ultrasonic generator is connected to the first copper electrodes for exciting the semi-annular piezoelectric ceramics, and the other channel of the dual-channel ultrasonic generator is connected to the second copper electrodes for exciting the annular piezoelectric ceramics.

[0008] In a preferred embodiment, the surfaces of the central bolt and the threaded column are provided with an insulating layer; Epoxy resin glue is applied between the contact surfaces of the rear cover plate, the middle cover plate, the semicircular piezoelectric ceramic, the circular piezoelectric ceramic, the first copper electrode and the second copper electrode to increase the contact rate of the contact interface and reduce the loss of ultrasonic vibration energy transmission.

[0009] In the preferred embodiment, the boring tool has a diamond shape, a top angle of 75°-85°, a back angle of 6°-8°, a cutting edge length of 3.8-4.2 mm, and a thickness of 1.3-2 mm; The overall length of the elliptical vibration unit is three wavelengths of bending ultrasonic vibration and one wavelength of torsional ultrasonic vibration.

[0010] In a preferred solution, the horn is provided with a three-stage amplification structure for amplifying the elliptical vibration.

[0011] In the preferred scheme, two waterproof cable connectors are provided on the surface of the shell, and the waterproof cable connectors are connected to the dual-channel ultrasonic generator through cables. The first copper electrode is connected to one of the waterproof cable connectors, and the second copper electrode is connected to the other waterproof cable connector. The tail of the amplitude transformer and the rear cover plate are both provided with positioning grooves, and the side of the shell is threadedly connected with a first connecting bolt and a second connecting bolt, and the first connecting bolt and the second connecting bolt are against the inside of the positioning groove.

[0012] In the preferred solution, a connecting shaft is provided on the side of the housing away from the boring tool, two symmetrical clamping plates are provided on the side of the elliptical vibration unit, a positioning sleeve is provided inside the housing, the positioning sleeve is sleeved on the outside of the central bolt, a mounting hole is provided inside the housing, the mounting hole is a through hole, and is used for external equipment, a mounting sleeve is provided at one end of the housing, the mounting sleeve is sleeved on the outside of the amplitude transformer, the pin bolt passes through the mounting sleeve and is threadedly connected to the housing, and a plug-in column extending to the inside of the mounting sleeve is provided at one end of the clamping plate; Four power connection plates are provided inside one of the clamping plates, which are electrically connected to the first copper electrode and the second copper electrode. Two plug-in connectors are provided between the end of the clamping plate with the power connection plates and the shell. The two plug-in connectors are connected to two channels of the dual-channel ultrasonic generator through conductive slip rings, one of the plug-in connectors is connected to the first copper electrode through the power connection plate, and the other plug-in connector is connected to the second copper electrode through the power connection plate. The conductive slip ring is sleeved on the outside of the shell.

[0013] In a preferred solution, buffer pads are provided on the inner sides of the clamping plate, the positioning sleeve and the mounting sleeve. The buffer pads fit the elliptical vibration unit and extend to the inside of the positioning groove.

[0014] In a preferred embodiment, the elliptical vibration unit further includes a first connecting plate and a second connecting plate; The boring cutter is connected to the head of the horn by fastening bolts; The two first copper electrodes are bonded to the two annular piezoelectric ceramic groups, and the two second copper electrodes are bonded to the two annular piezoelectric ceramics; The central bolt passes through the two annular piezoelectric ceramics, the two second copper electrodes and the second connecting plate, and is threadedly connected to the second connecting plate. The central bolt, the two annular piezoelectric ceramics, the two second copper electrodes and the second connecting plate are combined into a torsional vibration group. The portion of the central bolt that exceeds the second connecting plate is threadedly connected to the inside of the middle cover plate. The threaded column passes through two annular piezoelectric ceramic groups, two first copper electrodes and a first connecting plate, and is threadedly connected to the first connecting plate. The middle cover plate, the two annular piezoelectric ceramic groups, the two first copper electrodes and the first connecting plate are combined into a bending vibration group. The portion of the threaded column that exceeds the first connecting plate is threadedly connected to the inside of the amplitude transformer.

[0015] A processing method of a bending-torsion composite ultrasonic elliptical vibration boring system comprises the following steps: Step S1, start the dual-channel ultrasonic generator, and two ultrasonic signals act on the semi-circular piezoelectric ceramic and the circular piezoelectric ceramic respectively; Step S2, the semicircular piezoelectric ceramic is excited by an ultrasonic signal to generate bending ultrasonic vibration; The annular piezoelectric ceramic is excited by the ultrasonic signal to produce torsional ultrasonic vibration; Step S3, the elliptical vibration synthesized by the bending ultrasonic vibration and the torsional ultrasonic vibration acts on the horn; Step S4, adjusting the two ultrasonic signals so that the resonant frequency output by the elliptical vibration unit is 50-70 kHz and the amplitude is 10 μm-20 μm; Step S5: the elliptical vibration is amplified by the amplitude transformer and acts on the boring tool, and the boring tool performs bending-torsion composite ultrasonic elliptical vibration boring at the work station.

[0016] The present invention provides a bending-torsion composite ultrasonic elliptical vibration boring system and a processing method thereof. By adopting the above scheme, the following beneficial effects are achieved: 1. The bending-torsion composite ultrasonic elliptical vibration boring method can improve the material machinability, suppress cutting chatter and reduce tool wear, breaking through the bottleneck of precision and ultra-precision machining of small apertures of difficult-to-machine materials.

[0017] 2. The stability during boring processing is better, which ensures the processing accuracy and is convenient for precise adjustment and control. The precision and ultra-precision processing quality of small apertures of difficult-to-process materials is better.

[0018] 3. It is easy to replace and maintain the elliptical vibration unit, thereby increasing the efficiency of replacement and maintenance, so that the equipment can be quickly restored to use.

[0019] 4. The two groups of piezoelectric ceramics can be replaced separately, and there is no need to replace them as a whole. Not only is the replacement more convenient, the replacement efficiency is increased, but the normal piezoelectric ceramics will not be affected during replacement, thus reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a structural schematic diagram of the bending-torsion composite ultrasonic elliptical vibration boring system of the present invention.

[0021] Figure 2 It is a structural schematic diagram of the elliptical vibration unit of the present invention.

[0022] Figure 3 It is a schematic diagram of the polarization and excitation principle of the bending vibration and torsional vibration of the piezoelectric ceramics of the present invention; Figure 4 1 is an internal schematic diagram of a bending-torsion composite ultrasonic elliptical vibration boring system according to an embodiment of the present invention; Figure 5 It is an enlarged schematic diagram of the interior of a bending-torsion composite ultrasonic elliptical vibration boring system according to an embodiment of the present invention; Figure 6 is a schematic diagram of the structure of an embodiment of the elliptical vibration unit of the present invention; Figure 7 is a schematic structural diagram of an embodiment of the elliptical vibration unit of the present invention; Figure 8 yes Figure 5 Schematic diagram of the structure in which the semi-circular piezoelectric ceramics, middle cover, circular piezoelectric ceramics, rear cover and amplitude transformer are not installed.

[0023] In the figure: Fastening bolt 1, boring tool 2, amplitude transformer 3, semicircular piezoelectric ceramic 4, first copper electrode 51, second copper electrode 52, middle cover plate 6, positioning groove 61, circular piezoelectric ceramic 7, rear cover plate 8, center bolt 9, shell 10, first connecting bolt 11, second connecting bolt 12, waterproof cable connector 13, cable 14, dual-channel ultrasonic generator 15, conductive slip ring 16, connecting shaft 17, buffer pad 18, splint 101, positioning sleeve 102, mounting hole 103, mounting sleeve 104, pin bolt 105, plug-in connector 106, power connection sheet 107, plug-in column 108, first connecting plate 601, second connecting plate 602, threaded column 603. DETAILED DESCRIPTION

[0024] Embodiment 1: like Figure 1 , 2 , 3 and 7, a bending-torsion composite ultrasonic elliptical vibration boring system, comprising a housing 10, an elliptical vibration unit is arranged in the housing 10, the elliptical vibration unit is connected to a boring tool 2 for boring, and the elliptical vibration unit is electrically connected to a dual-channel ultrasonic generator 15; The elliptical vibration unit includes four semi-circular piezoelectric ceramics 4 and two circular piezoelectric ceramics 7. The models of the semi-circular piezoelectric ceramics 4 and the circular piezoelectric ceramics 7 are PZT-8. The four semi-circular piezoelectric ceramics 4 are combined into two circular piezoelectric ceramic groups, and the bending vibration mode of the vibration unit is excited based on the axial polarization to generate bending ultrasonic vibration. The two circular piezoelectric ceramics 7 excite the torsional vibration mode of the vibration unit based on the tangential polarization to generate torsional ultrasonic vibration, thereby making the elliptical vibration unit present a bending-torsion composite vibration mode, forming an elliptical vibration trajectory; The dual-channel ultrasonic generator 15 is used for excitation, and the elliptical vibration unit generates an elliptical vibration trajectory synthesized by bending ultrasonic vibration and torsional ultrasonic vibration, and outputs ultrasonic elliptical vibration on the boring tool 2, thereby improving the machinability of the material, suppressing cutting chatter and reducing tool wear, and breaking through the bottleneck of precision and ultra-precision machining of small apertures of difficult-to-machine materials.

[0025] The housing 10 is provided with a mounting hole 103 , which is a through hole. When the boring cutter 2 is not required to rotate, bolts are directly used to pass through the mounting hole 103 to fix the housing 10 to the work station.

[0026] In the preferred scheme, the elliptical vibration unit also includes a variable amplitude rod 3, two first copper electrodes 51, two second copper electrodes 52, a middle cover plate 6, a rear cover plate 8, a center bolt 9 and a threaded column 603; wherein, the center bolt 9 passes through the rear cover plate 8, the annular piezoelectric ceramic 7 and the second copper electrode 52 and is threadedly connected to the middle cover plate 6; one end of the threaded column 603 is connected to the middle cover plate 6, and the other end passes through the annular piezoelectric ceramic group and the first copper electrode 51 and is threadedly connected to the variable amplitude rod 3, so that when the annular piezoelectric ceramic 7 needs to be replaced, it is only necessary to unscrew the center bolt 9, and when the annular piezoelectric ceramic group needs to be replaced, it is only necessary to unscrew the variable amplitude rod 3. The operation is simple and does not require overall disassembly, thereby avoiding affecting the intact piezoelectric ceramics during replacement.

[0027] The boring tool 2 is connected to the head of the horn 3 by the fastening bolt 1. The central bolt 9 and the threaded column 603 are subjected to a pre-tightening force of 120N when connected, and are subjected to thermal insulation and aging treatment to improve the stability of the overall structure. Four semi-circular piezoelectric ceramics 4 are combined into two circular piezoelectric ceramic groups, and based on the axial polarization, the bending vibration mode of the vibration unit is excited to generate bending ultrasonic vibration. The two circular piezoelectric ceramics 7 excite the torsional vibration mode of the vibration unit based on the tangential polarization to generate torsional ultrasonic vibration, thereby making the elliptical vibration unit present a bending-torsion composite vibration mode to form an elliptical vibration. The elliptical vibration is finally transmitted to the boring tool 2 through the amplitude transformer 3, and the boring tool 2 completes the ultrasonic elliptical vibration boring. The semi-circular piezoelectric ceramics 4 and the circular piezoelectric ceramics 7 are excited by starting the dual-channel ultrasonic generator 15. The torsional vibration in ultrasonic elliptical vibration boring is excited by the tangentially polarized annular piezoelectric ceramic 7, which can avoid the problems of increased dynamic resistance and increased heat generation caused by the splicing of semi-circular annular piezoelectric ceramics; at the same time, compared with the mode conversion type of torsional ultrasonic vibration excitation form of "opening spiral grooves or inclined grooves on the amplitude transformer", the tangentially polarized annular piezoelectric ceramic 7 can achieve precise adjustment of the torsional vibration amplitude, with higher adaptability and accuracy.

[0028] The elliptical vibration trajectory output by the tool is a combination of bending ultrasonic vibration and torsional ultrasonic vibration, and the two-phase ultrasonic vibration has a certain phase difference. The bending ultrasonic vibration is applied in the boring depth direction, which is beneficial to improve the processing efficiency; the torsional ultrasonic vibration acts in the boring speed direction, which is beneficial to enhance the rigidity of the boring system and reduce tool wear.

[0029] The two first copper electrodes 51 are bonded to two annular piezoelectric ceramic groups, and the two second copper electrodes 52 are bonded to two annular piezoelectric ceramics 7. One channel of the dual-channel ultrasonic generator 15 is connected to the first copper electrode 51 for exciting the semi-annular piezoelectric ceramic 4, and the other channel of the dual-channel ultrasonic generator 15 is connected to the second copper electrode 52 for exciting the annular piezoelectric ceramic 7. The dual-channel ultrasonic generator 15 generates two ultrasonic signals when it works. The two ultrasonic signals act on the first copper electrode 51 and the second copper electrode 52 respectively, and then respectively excite the semi-annular piezoelectric ceramic 4 and the annular piezoelectric ceramic 7.

[0030] In a preferred embodiment, the surfaces of the center bolt 9 and the threaded column 603 are provided with an insulating layer, and the insulating layer is preferably wound with insulating glue or sprayed with insulating paint to prevent the ultrasonic signal from being transmitted to the center bolt 9 and the threaded column 603, thereby preventing the ultrasonic signal of the first copper electrode 51 and the ultrasonic signal of the second copper electrode 52 from interfering with each other, thereby ensuring the stability of ultrasonic vibration boring; Epoxy resin glue is applied between the contact surfaces of the rear cover plate 8, the middle cover plate 6, the semicircular piezoelectric ceramic 4, the circular piezoelectric ceramic 7, the first copper electrode 51 and the second copper electrode 52 to increase the contact rate of the contact interface and reduce the loss of ultrasonic vibration energy transmission.

[0031] In the preferred embodiment, the boring tool 2 has a diamond shape, a top angle of 80°, a back angle of 7°, a cutting edge length of 4 mm, and a thickness of 1.5 mm; The overall length of the elliptical vibration unit is three wavelengths of bending ultrasonic vibration and one wavelength of torsional ultrasonic vibration. By solving the bending vibration equation and the torsional vibration equation in parallel, a common analytical solution is obtained to achieve frequency merging of the bending vibration mode and the torsional vibration mode, thereby improving the output stability of the elliptical vibration trajectory.

[0032] In the preferred scheme, the amplitude transformer 3 is provided with a three-stage amplification structure for amplifying the elliptical vibration, which can amplify the ultrasonic vibration excited by the semi-circular piezoelectric ceramic 4 and the circular piezoelectric ceramic 7 multiple times, which is not only beneficial to improving the vibration speed of the boring tool 2, but also can further exert the advantages of ultrasonic elliptical vibration boring.

[0033] In the preferred embodiment, two waterproof cable connectors 13 are provided on the surface of the shell 10, and the waterproof cable connectors 13 are connected to the dual-channel ultrasonic generator 15 through cables 14. The first copper electrode 51 is connected to one of the waterproof cable connectors 13, and the second copper electrode 52 is connected to the other waterproof cable connector 13. The tail of the amplitude transformer 3 and the rear cover plate 8 are both provided with positioning grooves 61, and the side of the shell 10 is threadedly connected with the first connecting bolt 11 and the second connecting bolt 12, and the first connecting bolt 11 and the second connecting bolt 12 are against the inside of the positioning groove 61.

[0034] Embodiment 2: Please refer to Figure 4 and 5 A connecting shaft 17 is provided on the side of the housing 10 away from the boring cutter 2, which is used for the boring system of the present application to connect the main shaft of the processing equipment. The connection method can be connected by a coupling in the prior art. Two symmetrical clamping plates 101 are provided on the side of the elliptical vibration unit. The clamping plates 101 extend to the inside of the positioning groove 61. A positioning sleeve 102 is provided inside the housing 10. The positioning sleeve 102 is sleeved on the outside of the center bolt 9. A mounting sleeve 104 is provided at one end of the housing 10. The mounting sleeve 104 is sleeved on the outside of the amplitude transformer 3. The pin bolt 105 passes through the mounting sleeve 104 and is threadedly connected to the housing 10. A plug-in column 108 extending to the inside of the mounting sleeve 104 is provided at one end of the clamping plate 101. Four electrical connection plates 107 are provided inside one of the clamping plates 101, and the electrical connection plates 107 are electrically connected to the first copper electrode 51 and the second copper electrode 52 in a contact manner. The material of the electrical connection plates 107 is preferably copper. Two plug-in connectors 106 are provided between the end of the clamping plate 101 provided with the electrical connection plates 107 and the housing 10. The two plug-in connectors 106 are connected to two channels of the dual-channel ultrasonic generator 15 through a conductive slip ring 16, one of the plug-in connectors 106 is connected to the first copper electrode 51 through the electrical connection plates 107, and the other plug-in connector 106 is connected to the second copper electrode 52 through the electrical connection plates 107. The conductive slip ring 16 is sleeved on the outside of the housing 10, and the input end of the conductive slip ring 16 is electrically connected to the dual-channel ultrasonic generator 15, and the output end of the conductive slip ring 16 is electrically connected to the plug-in connector 106.

[0035] When the first copper electrode 51 and the second copper electrode 52 need to be replaced, the pin bolt 105 is unscrewed, and then the mounting sleeve 104 is moved outward to make the mounting sleeve 104 away from the housing 10, and then the elliptical vibration unit is pulled outward. The force of the pull-out will drive the clamping plate 101 away from the housing 10. During this process, the plug-in connector 106 will be separated. When the elliptical vibration unit, the mounting sleeve 104 and the clamping plate 101 are all taken out, the clamping plate 101 is separated, and then the center bolt 9 is unscrewed. Finally, the first copper electrode 51 and the second copper electrode 52 can be replaced. Otherwise, the installation can be completed. The operation is simple and the efficiency is higher. In order to further increase the replacement efficiency, a plurality of elliptical vibration units are reserved. When replacing, the elliptical vibration unit can be directly replaced, which has higher replacement efficiency and simpler operation. The replaced elliptical vibration unit can be reserved after the first copper electrode 51 and the second copper electrode 52 are replaced.

[0036] In the preferred embodiment, Figure 5 and 8As shown, a buffer pad 18 is provided on the inner side of the splint 101, the positioning sleeve 102 and the mounting sleeve 104. The material of the buffer pad 18 is preferably PORON and rubber. The buffer pad 18 fits the elliptical vibration unit and extends to the inside of the positioning groove 61. By providing the buffer pad 18, the ultrasonic vibration generated by the elliptical vibration unit can be prevented from being transmitted to the shell 10, thereby not only reducing the capacity loss of the ultrasonic vibration, but also preventing the ultrasonic vibration from affecting the shell 10, thereby ensuring the stability of the operation of the ultrasonic elliptical vibration boring system of the present application.

[0037] Embodiment 3: Please refer to Figure 6 The elliptical vibration unit includes a horn 3 for connecting a boring tool 2. The boring tool 2 is connected to the head of the horn 3 by a fastening bolt 1. The tail of the horn 3 is provided with four semicircular piezoelectric ceramics 4, two circular piezoelectric ceramics 7, two first copper electrodes 51, two second copper electrodes 52, a middle cover plate 6, a rear cover plate 8, a center bolt 9, a first connecting plate 601, a second connecting plate 602 and a threaded column 603. The model of the semicircular piezoelectric ceramics 4 and the circular piezoelectric ceramics 7 is PZT-8. Four semi-circular piezoelectric ceramics 4 are combined into two circular piezoelectric ceramic groups, and based on the axial polarization, the bending vibration mode of the vibration unit is excited to generate bending ultrasonic vibration. The two circular piezoelectric ceramics 7 excite the torsional vibration mode of the vibration unit based on the tangential polarization to generate torsional ultrasonic vibration, thereby making the elliptical vibration unit present a bending-torsion composite vibration mode to form an elliptical vibration trajectory. The elliptical vibration is finally transmitted to the boring tool 2 through the amplitude transformer 3, and the boring tool 2 completes the ultrasonic elliptical vibration boring. The semi-circular piezoelectric ceramics 4 and the circular piezoelectric ceramics 7 are excited by starting the dual-channel ultrasonic generator 15. Two first copper electrodes 51 are attached to two annular piezoelectric ceramic groups, two second copper electrodes 52 are attached to two annular piezoelectric ceramics 7, one channel of the dual-channel ultrasonic generator 15 is connected to the first copper electrodes 51 for exciting the semi-annular piezoelectric ceramics 4, and the other channel of the dual-channel ultrasonic generator 15 is connected to the second copper electrodes 52 for exciting the annular piezoelectric ceramics 7; The central bolt 9 passes through the two annular piezoelectric ceramics 7, the two second copper electrodes 52 and the second connecting plate 602, and is threadedly connected to the second connecting plate 602. The central bolt 9, the two annular piezoelectric ceramics 7, the two second copper electrodes 52 and the second connecting plate 602 are combined into a torsional vibration group. The portion of the central bolt 9 that exceeds the second connecting plate 602 is threadedly connected to the inside of the middle cover plate 6. A threaded column 603 is fixed at one end of the middle cover plate 6 close to the amplitude transformer 3. The threaded column 603 passes through two annular piezoelectric ceramic groups, two first copper electrodes 51 and the first connecting plate 601, and is threadedly connected to the first connecting plate 601. The middle cover plate 6, the two annular piezoelectric ceramic groups, the two first copper electrodes 51 and the first connecting plate 601 are combined into a bending vibration group. The part of the threaded column 603 that exceeds the first connecting plate 601 is threadedly connected to the inside of the amplitude transformer 3.

[0038] Considering that the semi-circular piezoelectric ceramic 4 and the circular piezoelectric ceramic 7 will not be damaged at the same time, in this embodiment, the bending vibration is grouped into a bending vibration group, and the torsional vibration is grouped into a torsional vibration group, which are then combined to form an elliptical vibration unit. Therefore, during use, the torsional vibration group can be unscrewed by relatively rotating the center bolt 9 and the middle cover plate 6, and then the circular piezoelectric ceramic 7 can be disassembled and replaced after unscrewing the second connecting plate 602; the threaded column 603 can be unscrewed out of the horn 3 by relatively rotating the middle cover plate 6 and the horn 3, and then the first connecting plate 602 can be unscrewed. 1, the semi-circular ring piezoelectric ceramic 4 can be replaced; in summary, there is no need to disassemble the entire piezoelectric ceramic 4 or the circular piezoelectric ceramic 7 for replacement. The operation is simple and the replacement efficiency is higher. Moreover, the semi-circular ring piezoelectric ceramic 4 or the circular piezoelectric ceramic 7 that has not been replaced will not be affected during replacement. For example, when only the semi-circular ring piezoelectric ceramic 4 is replaced, the circular piezoelectric ceramic 7 will not be affected, thereby avoiding accidental damage to the normal semi-circular ring piezoelectric ceramic 4 or the circular piezoelectric ceramic 7 during replacement, and avoiding unnecessary losses.

[0039] Both the bending vibration group and the torsional vibration group can be preset, and no temporary assembly is required during replacement, thereby increasing the efficiency during replacement.

[0040] Embodiment 4: A processing method of a bending-torsion composite ultrasonic elliptical vibration boring system comprises the following steps: Step S1, start the dual-channel ultrasonic generator 15, and two ultrasonic signals act on the semi-circular piezoelectric ceramic 4 and the circular piezoelectric ceramic 7 respectively; Step S2, the semicircular piezoelectric ceramic 4 is excited by the ultrasonic signal to generate bending ultrasonic vibration; The annular piezoelectric ceramic 7 is excited by the ultrasonic signal to generate torsional ultrasonic vibration; Step S3, the elliptical vibration synthesized by the bending ultrasonic vibration and the torsional ultrasonic vibration acts on the horn 3; Step S4, adjusting the two ultrasonic signals so that the resonant frequency output by the elliptical vibration unit is 60 kHz and the amplitude is 15 μm, which can be used to process difficult-to-process materials, such as an inner hole of TC4 titanium alloy material with a diameter of 4.5 mm; Step S5, the elliptical vibration is amplified by the horn 3 and acts on the boring tool 2, and the boring tool 2 performs bending-torsion composite ultrasonic elliptical vibration boring at the work station; The boring process is performed in the above-mentioned manner.

[0041] Through the method of the present application, bending-torsion composite ultrasonic elliptical vibration boring is used during processing, which can improve the machinability of the material, suppress cutting chatter and reduce tool wear, and has better overall stability, breaking through the bottleneck of precision and ultra-precision processing of small apertures of difficult-to-process materials and ensuring processing accuracy.

[0042] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A bending-torsion composite ultrasonic elliptical vibration boring system, characterized by: It comprises a housing (10), an elliptical vibration unit is arranged in the housing (10), the elliptical vibration unit is connected to a boring tool (2) for boring, and the elliptical vibration unit is electrically connected to a dual-channel ultrasonic generator (15); The elliptical vibration unit comprises four semi-circular piezoelectric ceramics (4) and two circular piezoelectric ceramics (7). The four semi-circular piezoelectric ceramics (4) are combined into two circular piezoelectric ceramic groups, and based on the axial polarization, the bending vibration mode of the vibration unit is excited to generate bending ultrasonic vibration. Based on the tangential polarization, the two circular piezoelectric ceramics (7) excite the torsional vibration mode of the vibration unit to generate torsional ultrasonic vibration, so that the elliptical vibration unit presents a bending-torsion composite vibration mode, forming an elliptical vibration trajectory. The elliptical vibration unit also includes a horn (3), two first copper electrodes (51), two second copper electrodes (52), a middle cover plate (6), a rear cover plate (8), a central bolt (9) and a threaded column (603); The central bolt (9) passes through the rear cover plate (8), the annular piezoelectric ceramic (7) and the second copper electrode (52) and is threadedly connected to the middle cover plate (6); One end of the threaded column (603) is connected to the middle cover plate (6), and the other end passes through the annular piezoelectric ceramic group and the first copper electrode (51) and is threadedly connected to the amplitude transformer (3).

2. According to claim 1, a bending-torsion composite ultrasonic elliptical vibration boring system, characterized in that: The boring tool (2) is connected to the head of the amplitude transformer (3) via a fastening bolt (1); Two first copper electrodes (51) are bonded to two annular piezoelectric ceramic groups, two second copper electrodes (52) are bonded to two annular piezoelectric ceramics (7), one channel of a dual-channel ultrasonic generator (15) is connected to the first copper electrodes (51) for exciting the semi-annular piezoelectric ceramics (4), and the other channel of the dual-channel ultrasonic generator (15) is connected to the second copper electrodes (52) for exciting the annular piezoelectric ceramics (7).

3. The bending-torsion composite ultrasonic elliptical vibration boring system according to claim 1, characterized in that: An insulating layer is provided on the surfaces of the central bolt (9) and the threaded column (603); Epoxy resin glue is applied between the contact surfaces of the rear cover plate (8), the middle cover plate (6), the semi-circular piezoelectric ceramic (4), the circular piezoelectric ceramic (7), the first copper electrode (51) and the second copper electrode (52) to increase the contact rate of the contact interface and reduce the loss of ultrasonic vibration energy transmission.

4. The bending-torsion composite ultrasonic elliptical vibration boring system according to claim 1, characterized in that: The boring tool (2) has a diamond shape, a top angle of 75°-85°, a back angle of 6°-8°, a cutting edge length of 3.8-4.2 mm, and a thickness of 1.3-2 mm; The overall length of the elliptical vibration unit is three wavelengths of bending ultrasonic vibration and one wavelength of torsional ultrasonic vibration.

5. The bending-torsion composite ultrasonic elliptical vibration boring system according to claim 1, characterized in that: The horn (3) is provided with a three-stage amplification structure for amplifying the elliptical vibration.

6. The bending-torsion composite ultrasonic elliptical vibration boring system according to claim 1, characterized in that: Two waterproof cable connectors (13) are provided on the surface of the housing (10); the waterproof cable connectors (13) are connected to the dual-channel ultrasonic generator (15) via cables (14); the first copper electrode (51) is connected to one of the waterproof cable connectors (13); the second copper electrode (52) is connected to the other waterproof cable connector (13); the tail of the horn (3) and the rear cover plate (8) are both provided with positioning grooves (61); the side surface of the housing (10) is threadedly connected with a first connecting bolt (11) and a second connecting bolt (12); the first connecting bolt (11) and the second connecting bolt (12) are abutted against the inside of the positioning groove (61).

7. The bending-torsion composite ultrasonic elliptical vibration boring system according to claim 1, characterized in that: A connecting shaft (17) is provided on the side of the housing (10) away from the boring cutter (2), two symmetrical clamping plates (101) are provided on the side of the elliptical vibration unit, a positioning sleeve (102) is provided inside the housing (10), the positioning sleeve (102) is sleeved on the outside of the central bolt (9), a mounting hole (103) is provided inside the housing (10), the mounting hole (103) is a through hole for connecting an external device, a mounting sleeve (104) is provided at one end of the housing (10), the mounting sleeve (104) is sleeved on the outside of the amplitude transformer (3), a pin bolt (105) passes through the mounting sleeve (104) and is threadedly connected to the housing (10), and a plug-in column (108) is provided at one end of the clamping plate (101) and extends to the inside of the mounting sleeve (104); Four electrical connection sheets (107) are provided inside one of the clamping plates (101); the electrical connection sheets (107) are electrically connected to the first copper electrode (51) and the second copper electrode (52); two plug-in connectors (106) are provided between the end of the clamping plate (101) provided with the electrical connection sheets (107) and the housing (10); the two plug-in connectors (106) are connected to two channels of a dual-channel ultrasonic generator (15) via a conductive slip ring (16); one of the plug-in connectors (106) is connected to the first copper electrode (51) via the electrical connection sheets (107); the other plug-in connector (106) is connected to the second copper electrode (52) via the electrical connection sheets (107); and the conductive slip ring (16) is sleeved on the outside of the housing (10).

8. The bending-torsion composite ultrasonic elliptical vibration boring system according to claim 7, characterized in that: A buffer pad (18) is provided on the inner sides of the clamping plate (101), the positioning sleeve (102) and the mounting sleeve (104); the buffer pad (18) fits the elliptical vibration unit and extends to the interior of the positioning groove (61).

9. A bending-torsion composite ultrasonic elliptical vibration boring system according to any one of claims 3 to 8, characterized in that: The elliptical vibration unit further includes a first connecting plate (601) and a second connecting plate (602); The boring tool (2) is connected to the head of the amplitude transformer (3) via a fastening bolt (1); The two first copper electrodes (51) are bonded to two annular piezoelectric ceramic groups, and the two second copper electrodes (52) are bonded to two annular piezoelectric ceramics (7); The central bolt (9) passes through the two annular piezoelectric ceramics (7), the two second copper electrodes (52) and the second connecting plate (602), and is threadedly connected to the second connecting plate (602); the central bolt (9), the two annular piezoelectric ceramics (7), the two second copper electrodes (52) and the second connecting plate (602) are combined to form a torsional vibration group; the portion of the central bolt (9) that exceeds the second connecting plate (602) is threadedly connected to the inside of the middle cover plate (6); The threaded column (603) passes through two annular piezoelectric ceramic groups, two first copper electrodes (51) and a first connecting plate (601), and is threadedly connected to the first connecting plate (601); the middle cover plate (6), the two annular piezoelectric ceramic groups, the two first copper electrodes (51) and the first connecting plate (601) are combined into a bending vibration group; the portion of the threaded column (603) that exceeds the first connecting plate (601) is threadedly connected to the interior of the amplitude transformer (3).

10. A processing method of the bending-torsion composite ultrasonic elliptical vibration boring system according to any one of claims 1 to 9, characterized in that The steps include: Step S1, starting a dual-channel ultrasonic generator (15), wherein two ultrasonic signals act on the semicircular piezoelectric ceramic (4) and the circular piezoelectric ceramic (7) respectively; Step S2, the semicircular piezoelectric ceramic (4) is excited by an ultrasonic signal to generate bending ultrasonic vibration; The annular piezoelectric ceramic (7) is excited by the ultrasonic signal to generate torsional ultrasonic vibration; Step S3, the elliptical vibration synthesized by the bending ultrasonic vibration and the torsional ultrasonic vibration acts on the horn (3); Step S4, adjusting the two ultrasonic signals so that the resonant frequency output by the elliptical vibration unit is 50-70 kHz and the amplitude is 10 μm-20 μm; Step S5: the elliptical vibration is amplified by the amplitude transformer (3) and acts on the boring tool (2), and the boring tool (2) performs bending-torsion composite ultrasonic elliptical vibration boring at the work station.

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