A dual-frequency vibration modulation turning device based on a combination of non-resonant and resonant working modes

Abstract

The present invention discloses a dual-frequency vibration modulation turning device based on a combination of non-resonant and resonant operating modes. The device comprises a non-resonant vibration device and a three-dimensional ultrasonic vibration device. The non-resonant vibration device comprises a compliance mechanism, a guide mechanism, and a motion platform. The guide mechanism constrains the motion platform to move along the Z-axis, and a piezoelectric ceramic stack applies an X-axis displacement to the compliance mechanism. The compliance mechanism amplifies the X-axis displacement into a Z-axis displacement and outputs it to the motion platform. The three-dimensional ultrasonic vibration device comprises an ultrasonic horn, with a tool mounted at the front end and an ultrasonic transducer mounted at the rear end. The ultrasonic transducer is fixed to the motion platform via a support. The present invention utilizes the non-resonant vibration device to generate low-frequency, large-amplitude vibration to achieve the creation of free-form surface contours, and utilizes the three-dimensional ultrasonic vibration device to generate ultrasonic elliptical vibration to improve the cutting performance of difficult-to-machine materials, thereby enabling high-precision machining of optical free-form surfaces on difficult-to-machine materials.

Description

Technical Field

[0001] The present invention relates to ultra-precision machining equipment, in particular to a dual-frequency vibration modulation turning device based on a non-resonant and resonant combined working mode. Background Art

[0002] Optical free-form surfaces can greatly enhance the performance of optical systems, such as suppressing optical system aberrations, anti-reflection and anti-friction, reducing the number of optical system components during the surface design process, and achieving simplification and integration of the system structure. In recent years, optical free-form surfaces have been increasingly used in aerospace, military, energy, semiconductor products, biomedicine and other fields. However, these free-form optical elements or the molds used to manufacture these free-form optical elements usually use some difficult-to-machine materials with poor machinability, such as optical glass, ferrous metals and cemented carbide. Although difficult-to-machine materials have more excellent physical, chemical and mechanical properties, these difficult-to-machine materials usually have high hardness, high brittleness and low fracture toughness, or are prone to chemical reactions with diamond tools. During the cutting process, they are very likely to produce high temperatures, tool wear, and crack proliferation and expansion, which not only reduces the service life of the tool, but also seriously affects the quality and efficiency of the processing.

[0003] Diamond turning technology based on fast tool servo is currently the most efficient freeform surface creation technology. However, due to severe tool wear when cutting difficult-to-machine materials, fast tool servo diamond turning technology has difficulty creating freeform surfaces on these materials.

[0004] The ultrasonic elliptical vibration cutting method superimposes a high-frequency vibration on the traditional main cutting motion direction and the cutting depth direction, achieving periodic separation between the tool and the workpiece. Research has shown that ultrasonic elliptical vibration cutting can significantly reduce cutting forces, improve process system stability, enhance workpiece surface quality, and improve tool life. It has been widely used in the cutting of various difficult-to-machine materials, such as high-performance alloys, composites, and hard and brittle materials. Although ultrasonic elliptical vibration cutting can achieve high-quality machining of some difficult-to-machine materials due to its excellent performance, it is difficult to directly create free-form surfaces. Vibration devices are divided into resonant and non-resonant vibration devices based on their operating principle. Generally speaking, vibration devices based on the resonant principle have a high operating frequency, but a small vibration amplitude and a fixed operating frequency, and are often used to improve the cutting performance of difficult-to-machine materials. Vibration devices based on the non-resonant principle have an adjustable vibration frequency and can simultaneously output multiple frequency components, making them suitable for machining complex microstructures. The scope of application of these two types of vibration devices shows that vibration devices with a single operating mode are not suitable for creating free-form surfaces in difficult-to-machine materials. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a dual-frequency vibration modulation turning device based on a combination of non-resonant and resonant working modes to address the problem that a vibration device with a single working mode is difficult to meet the needs of creating free-form surfaces of difficult-to-machine materials.

[0006] Technical solution: The dual-frequency vibration modulation turning device based on the non-resonant and resonant combined working mode of the present invention includes a non-resonant vibration device and a three-dimensional ultrasonic vibration device;

[0007] The non-resonant vibration device includes a frame and a first pre-tightening screw. A compliance mechanism, a piezoelectric ceramic stack, a guide mechanism, and a motion platform are disposed within the frame. The compliance mechanism is connected at both ends to the motion platform and the frame, and the motion platform is connected at both ends to the frame via the guide mechanism. The piezoelectric ceramic stack is disposed within the compliance mechanism. The first pre-tightening screw passes through the frame and the compliance mechanism from the side and is connected to the threaded connection end of the piezoelectric ceramic stack. The guide mechanism is used to constrain the motion platform to move along the Z-axis. The piezoelectric ceramic stack is used to apply an X-axis displacement to the compliance mechanism, and the compliance mechanism is used to amplify the X-axis displacement into a Z-axis displacement and output it to the motion platform.

[0008] The three-dimensional ultrasonic vibration device includes an ultrasonic horn, a tool is installed at the front end of the ultrasonic horn, and an ultrasonic transducer is installed at the rear end; the ultrasonic transducer is fixed on the motion platform through a support seat.

[0009] Furthermore, the compliant mechanism includes two convex blocks arranged opposite to each other, and the piezoelectric ceramic stack is located between the two convex blocks; one end of the moving platform has a second boss, and the inner wall of the frame has a third boss, and the second and third bosses are opposite to each other; the two convex blocks are respectively connected to the second boss and the third boss through the deformation block; the first pre-tightening screw passes through the convex block.

[0010] The compliant mechanism in the non-resonant vibration device adopts a bridge structure, which can achieve a larger amplitude vibration output and realize the creation of large-depth free-form surfaces and microstructures. The bridge structure is driven by a piezoelectric ceramic stack, which is more stable under low-frequency vibration, helping to reduce instability and swing during the vibration process and improve the controllability and stability of the device.

[0011] Furthermore, the other end of the motion platform has a first boss, the guide mechanism adopts a flexible hinge structure, and both sides of the first boss and the second boss are connected to the inner wall of the frame through the flexible hinge structure.

[0012] The guide mechanism in the non-resonant vibration device adopts a flexible hinge structure with low longitudinal stiffness, high lateral stiffness and low stress concentration, which improves the ability of the non-resonant vibration device to suppress parasitic motion and other external interference.

[0013] Furthermore, the flexible hinge structure connected to the first boss is flush with the end surface of the first boss.

[0014] Furthermore, the frame is provided with bolt holes for connecting to the machine tool guide rails.

[0015] Furthermore, the frame, the compliance mechanism, the guide mechanism and the motion platform are an integrated structure.

[0016] The non-resonant vibration device adopts an integrated structural design and processing, which can reduce the error caused by assembly and improve the processing accuracy.

[0017] Furthermore, the ultrasonic transducer includes a longitudinal vibration piezoelectric ceramic, a first bending vibration piezoelectric ceramic group and a second bending vibration piezoelectric ceramic group. The longitudinal vibration piezoelectric ceramic is used to generate longitudinal vibration deformation in the Z-axis direction, the first bending vibration piezoelectric ceramic group is used to generate bending vibration deformation in the X-axis direction, and the second bending vibration piezoelectric ceramic group is used to generate bending vibration deformation in the Y-axis direction.

[0018] The three-dimensional ultrasonic vibration device used in the resonant device of the present invention generates vibrations in three directions by designing three groups of piezoelectric ceramics. It can realize the output of elliptical trajectories in any direction, modulate the direction of the elliptical trajectory according to the installation error, and reduce the influence of the installation error on the processing effect; and can realize the output of spatial ellipsoidal trajectory, further improving the cutting performance of difficult-to-process materials.

[0019] Furthermore, the longitudinal vibration piezoelectric ceramic is composed of two stacked piezoelectric ceramic rings, the first bending vibration piezoelectric ceramic group and the second bending vibration piezoelectric ceramic group are respectively composed of four semi-circular piezoelectric ceramics, the bending vibration piezoelectric ceramic is composed of two semi-circular rings with opposite polarization directions, and the arrangement of the first and second bending vibration piezoelectric ceramic groups differs by 90°.

[0020] Furthermore, the three-dimensional ultrasonic vibration device also includes a second pre-tightening screw, and the ultrasonic transducer also includes a flange plate and two partitions of unequal thickness. The second pre-tightening screw passes through the thicker partition, the second bending vibration piezoelectric ceramic group, the thinner partition, the first bending vibration piezoelectric ceramic group, the flange plate and the longitudinal vibration piezoelectric ceramic in sequence and is fixed to the rear end face of the ultrasonic amplitude transformer.

[0021] Furthermore, the support seat includes a base and a flange arranged on the base, the base is connected to the motion platform through bolts, and the flange is connected to the flange plate through bolts.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0023] (1) The dual-frequency vibration modulation turning device provided by the present invention can realize the advantages of combined processing using ultrasonic elliptical vibration cutting and fast tool servo diamond turning technology. In the process of dual-frequency vibration modulation diamond turning free-form surface processing, a non-resonant vibration device is used to generate low-frequency, large-amplitude vibration as a tool servo motion to achieve the creation of free-form surface contours. The ultrasonic elliptical vibration generated by a three-dimensional ultrasonic vibration device (resonant vibration device) is used to improve the cutting performance of difficult-to-process materials, thereby achieving high-precision processing of optical free-form surfaces on difficult-to-process materials.

[0024] (2) The present invention adopts a mode in which a non-resonant vibration device and a three-dimensional ultrasonic vibration device (resonant vibration device) are designed separately and work in combination, thereby solving the problems of low processing efficiency, poor processing accuracy and difficulty in driving and controlling when a single vibration device uses low / high frequency current drive coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a schematic structural diagram of a dual-frequency vibration modulation turning device based on a non-resonant and resonant combined working mode provided by an embodiment of the present invention;

[0026] Figure 2 2 is a schematic structural diagram of a non-resonant vibration device according to an embodiment of the present invention;

[0027] Figure 3 yes Figure 2 A top view of

[0028] Figure 4 This is a schematic structural diagram of a support base according to an embodiment of the present invention;

[0029] Figure 5 is a schematic structural diagram of a three-dimensional ultrasonic vibration device according to an embodiment of the present invention;

[0030] Figure 6 is a schematic diagram of the arrangement of three groups of piezoelectric ceramics in an embodiment of the present invention;

[0031] Figure 7 This is a schematic diagram of the bridge-type amplification principle of the compliant mechanism in an embodiment of the present invention;

[0032] Figure 8 Schematic diagram of tool trajectory with dual-frequency vibration modulation in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings.

[0034] Attachment Figures 1 to 8 The reference numerals in the figures are as follows:

[0035] 1, non-resonant vibration device; 11, convex block; 12, piezoelectric ceramic stack; 13, frame; 14, first pre-tightening screw; 15, guide mechanism; 16, motion platform; 17, bolt hole;

[0036] 2, support base; 21, base; 22, flange;

[0037] 3. Three-dimensional ultrasonic vibration device; 31. Ultrasonic horn; 32. Ultrasonic transducer; 321. Longitudinal vibration piezoelectric ceramic; 322. Flange plate; 323. First bending vibration piezoelectric ceramic group; 324. Second bending vibration piezoelectric ceramic group; 325. Spacer; 33. Second pre-tightening screw;

[0038] 4. Cutting tools.

[0039] like Figure 1 As shown, an embodiment of the present invention provides a dual-frequency vibration modulation turning device based on a non-resonant and resonant combined working mode, including a non-resonant vibration device 1, a support seat 2, a three-dimensional ultrasonic vibration device 3 and a tool 4.

[0040] Combine Figure 2 and Figure 3 The non-resonant vibration device 1 includes a rectangular frame 13 and a first pre-tightening screw 14. A compliance mechanism, a piezoelectric ceramic stack 12, a guide mechanism 15 and a motion platform 16 are arranged inside the frame 13. The compliance mechanism includes two convex blocks 11 arranged opposite to each other, and the piezoelectric ceramic stack 12 is located between the two convex blocks 11. The motion platform 16 has holes at the four corners and a square hole in the center. It has a second boss at one end and a first boss at the other end. The inner wall of the frame 13 has a third boss, and the second and third bosses are opposite to each other. The two convex blocks 11 are respectively connected to the second boss and the third boss through a deformation block. The guide mechanism 15 adopts a flexible hinge structure, and the first boss and the second boss are respectively connected to the inner wall of the frame 13 on both sides through a flexible hinge structure, wherein the flexible hinge structure connecting the first boss is flush with the end face of the first boss. The first pre-tightening screw 14 passes through the frame 13 and the convex block 11 from the side and is connected to the threaded connection end of the piezoelectric ceramic stack 12. One end of the piezoelectric ceramic stack 12 is pre-tightened by the first pre-tightening screw 14, and the other end abuts against the middle of the convex block 11.

[0041] In addition, bolt holes 17 for connecting to the machine tool guide rails are provided at the four corners of the frame 13. In this embodiment, the frame 13, the compliance mechanism, the guide mechanism 15 and the motion platform 16 are an integrated structure.

[0042] The flexible hinge structure has the characteristics of low longitudinal stiffness, high lateral stiffness and low stress concentration, which enables the guide mechanism 15 to improve the ability of the non-resonant vibration device to suppress parasitic motion and other external interference, thereby constraining the motion platform 16 to move along the Z axis. The piezoelectric ceramic stack 12 is driven by piezoelectricity, and the compliance mechanism adopts the bridge amplification principle. The principle is as follows Figure 7 As shown. By applying a low-frequency AC signal to the piezoelectric ceramic stack 12, the piezoelectric ceramic stack 12 symmetrically applies X-axis displacement to the two convex blocks 11. Through the bending deformation of the flexible hinge, the compliant mechanism amplifies the X-axis displacement into a Z-axis displacement, which is output to the motion platform 16. This non-resonant vibration device typically operates below its natural frequency, is suitable for low-frequency vibration requirements, and can ensure the device's motion accuracy. The bridge structure is more stable under low-frequency vibration, helping to reduce instability and oscillation during the vibration process, and improving the controllability and stability of the turning device.

[0043] Combine Figure 5 The three-dimensional ultrasonic vibration device 3 includes an ultrasonic horn 31 and a second pre-tightening screw 33. The ultrasonic horn 31 is arranged along the Z-axis, and the tool 4 is mounted at the front end of the ultrasonic horn 31. The ultrasonic transducer 32 includes a longitudinal vibration piezoelectric ceramic 321, a flange plate 322, a first bending vibration piezoelectric ceramic group 323, a second bending vibration piezoelectric ceramic group 324, and two partitions 325 of unequal thickness. The thickness of the partitions is determined by the installation position of the piezoelectric ceramic group. The flange plate 322 is provided with six bolt holes evenly distributed along the circumference. The second pre-tightening screw 33 passes through the thicker partition 325, the second bending vibration piezoelectric ceramic group 324, the thinner partition 325, the first bending vibration piezoelectric ceramic group 323, the flange plate 322, and the longitudinal vibration piezoelectric ceramic 321, securing it to the rear end face of the ultrasonic horn 31.

[0044] The working principle of the piezoelectric ceramic in the ultrasonic transducer 32 is based on the inverse piezoelectric effect, that is, when an external electric field is applied, the material will undergo mechanical deformation. Figure 6 The longitudinal vibration piezoelectric ceramic 321 is composed of two stacked piezoelectric ceramic rings. The longitudinal vibration of the ultrasonic transducer 32 is generated by the longitudinal expansion and contraction deformation of the longitudinal vibration piezoelectric ceramic 321. The first bending vibration piezoelectric ceramic group 323 and the second bending vibration piezoelectric ceramic group 324 are each composed of four semi-circular piezoelectric ceramic rings. The bending vibration piezoelectric ceramic consists of two semi-circular rings with opposite polarization directions. When a high-frequency signal is applied to the piezoelectric ceramic, one semi-circular ring stretches and the other semi-circular ring compresses, causing the piezoelectric ceramic to generate a bending moment, thereby generating bending vibration of the ultrasonic transducer 32. The first and second bending vibration piezoelectric ceramic groups are arranged 90 degrees apart.

[0045] The three-dimensional ultrasonic vibration device 3 is set in the O-XYZ coordinate system, and the Y axis and the Z axis are as follows: Figure 6As shown, the X-axis is determined according to the right-hand rule. The longitudinal vibration piezoelectric ceramic 321 can generate longitudinal vibration deformation in the Z-axis direction, the first bending vibration piezoelectric ceramic group 323 can generate bending vibration deformation in the X-axis direction, and the second bending vibration piezoelectric ceramic group 324 can generate bending vibration deformation in the Y-axis direction. During the freeform surface machining process, the tool 4 contacts the workpiece to remove material.

[0046] Combine Figure 4 The support seat 2 includes a base 21 and a flange 22 arranged on the base 21. The base 21 has holes at four corners and is connected to the motion platform 16 by bolts. The flange 22 is connected to the flange plate 322 by bolts.

[0047] When in use, the tool 4 is driven by the ultrasonic vibration frequency f1 with a certain phase difference in the three directions generated by the three-dimensional ultrasonic vibration device 3 in the X, Y and Z directions, which can form a complex ellipsoid trajectory in three-dimensional space. In addition, the tool 4 is affected by the low-frequency vibration f2 with a large amplitude generated by the non-resonant vibration device 3 in the Z-axis direction. By coupling the high-frequency three-dimensional ultrasonic vibration with the low-frequency vibration, the dual-frequency vibration modulation of the tool 4 relative to the workpiece is achieved, and the trajectory of the tool 4 is as follows: Figure 8 shown.

[0048] In the dual-frequency vibration modulation turning process, the present invention utilizes a non-resonant vibration device to generate low-frequency vibration to achieve the creation of free-form surface contours, and utilizes a three-dimensional ultrasonic vibration device (resonant vibration device) to generate ultrasonic elliptical vibration to improve the cutting performance of difficult-to-process materials, thereby achieving high-precision processing of optical free-form surfaces on difficult-to-process materials.

Claims

1. A dual-frequency vibration modulation turning device based on a combination of non-resonant and resonant working modes, characterized in that: It includes a non-resonant vibration device (1) and a three-dimensional ultrasonic vibration device (3); The non-resonant vibration device (1) includes a frame (13) and a first pre-tightening screw (14); a compliance mechanism, a piezoelectric ceramic stack (12), a guide mechanism (15) and a motion platform (16) are arranged inside the frame (13); two ends of the compliance mechanism are respectively connected to the motion platform (16) and the frame (13), and two ends of the motion platform (16) are connected to the frame (13) through the guide mechanism (15); the piezoelectric ceramic stack (12) is arranged inside the compliance mechanism, the first pre-tightening screw (14) passes through the frame (13) and the compliance mechanism from the side and is connected to the threaded connection end of the piezoelectric ceramic stack (12); the guide mechanism (15) is used to constrain the motion platform (16) to move along the Z-axis direction; the piezoelectric ceramic stack (12) is used to apply an X-axis displacement to the compliance mechanism, and the compliance mechanism is used to amplify the X-axis displacement into a Z-axis displacement and output it to the motion platform (16); The three-dimensional ultrasonic vibration device (3) includes an ultrasonic amplitude transformer (31), a tool (4) is installed at the front end of the ultrasonic amplitude transformer (31), and an ultrasonic transducer (32) is installed at the rear end; the ultrasonic transducer (32) is fixed on the motion platform (16) through a support base (2); The compliant mechanism comprises two convex blocks (11) arranged opposite to each other, a piezoelectric ceramic stack (12) being located between the two convex blocks (11); a second boss being provided at one end of the motion platform (16), a third boss being provided on the inner wall of the frame (13), the second and third bosses being opposite to each other; the two convex blocks (11) being connected to the second boss and the third boss respectively through a deformation block; and a first pre-tightening screw (14) passing through the convex block (11); The other end of the motion platform (16) has a first boss, the guide mechanism (15) adopts a flexible hinge structure, and both sides of the first boss and the second boss are connected to the inner wall of the frame (13) through the flexible hinge structure.

2. The dual-frequency vibration modulation turning device based on the non-resonant and resonant combined working mode according to claim 1 is characterized in that: The flexible hinge structure connected to the first boss is flush with the end surface of the first boss.

3. The dual-frequency vibration modulation turning device based on the non-resonant and resonant combined working mode according to claim 1 is characterized in that: The frame (13) is provided with bolt holes (17) for connecting to the machine tool guide rails.

4. The dual-frequency vibration modulation turning device based on a non-resonant and resonant combined working mode according to any one of claims 1 to 3, characterized in that: The frame (13), the compliant mechanism, the guide mechanism (15) and the motion platform (16) are an integrated structure.

5. The dual-frequency vibration modulation turning device based on the non-resonant and resonant combined working mode according to claim 1 is characterized in that: The ultrasonic transducer (32) comprises a longitudinal vibration piezoelectric ceramic (321), a first bending vibration piezoelectric ceramic group (323) and a second bending vibration piezoelectric ceramic group (324), wherein the longitudinal vibration piezoelectric ceramic (321) is used to generate longitudinal vibration deformation in the Z-axis direction, the first bending vibration piezoelectric ceramic group (323) is used to generate bending vibration deformation in the X-axis direction, and the second bending vibration piezoelectric ceramic group (324) is used to generate bending vibration deformation in the Y-axis direction.

6. The dual-frequency vibration modulation turning device based on the non-resonant and resonant combined working mode according to claim 5 is characterized in that: The longitudinal vibration piezoelectric ceramic (321) is composed of two stacked piezoelectric ceramic rings, the first bending vibration piezoelectric ceramic group (323) and the second bending vibration piezoelectric ceramic group (324) are respectively composed of four semi-circular piezoelectric ceramics, the bending vibration piezoelectric ceramic is composed of two semi-circular rings with opposite polarization directions, and the first and second bending vibration piezoelectric ceramic groups are arranged 90 degrees apart.

7. The dual-frequency vibration modulation turning device based on the non-resonant and resonant combined working mode according to claim 5 or 6, characterized in that: The three-dimensional ultrasonic vibration device (3) further includes a second pre-tightening screw (33), and the ultrasonic transducer (32) further includes a flange plate (322) and two partitions (325) of unequal thickness. The second pre-tightening screw (33) sequentially passes through the thicker partition (325), the second bending vibration piezoelectric ceramic group (324), the thinner partition (325), the first bending vibration piezoelectric ceramic group (323), the flange plate (322) and the longitudinal vibration piezoelectric ceramic (321) and is fixed to the rear end face of the ultrasonic amplitude transformer (31).

8. The dual-frequency vibration modulation turning device based on the non-resonant and resonant combined working mode according to claim 7 is characterized in that: The support seat (2) includes a base (21) and a flange (22) arranged on the base (21). The base (21) is connected to the motion platform (16) by bolts, and the flange (22) is connected to the flange plate (322) by bolts.

Images