Horn for single excitation three-dimensional ultrasonic vibration, auxiliary processing system and processing method thereof

Abstract

The present invention discloses a horn, auxiliary machining system, and machining method for single-excitation three-dimensional ultrasonic vibration. The horn comprises a horn body with a raised force-bearing end and an output end for mounting a tool bit. N inclined slots are provided between the force-bearing and output ends. A PC controls an ultrasonic generator to generate a high-frequency sinusoidal current, driving a piezoelectric ceramic stack to generate high-frequency vibrations, which in turn applies an excitation force to the horn. The horn converts the single excitation into spatial elliptical vibrations, causing the tool bit fixed to the output end to exhibit three-dimensional elliptical-like vibrations in space. This enables ultra-precision machining of complex free-form surfaces.

Description

Technical Field

[0001] The present invention relates to the field of vibration auxiliary technology, in particular to a horn for single-excitation three-dimensional ultrasonic vibration, an auxiliary processing system and a processing method thereof. Background Art

[0002] The main difference between ultrasonic vibration-assisted machining and traditional machining technology is that the tool and the workpiece are not in contact for a long time. Based on traditional machining, ultrasonic vibration-assisted machining applies an ultrasonic frequency excitation force to the tool under the original working state of the device, and the tool and the workpiece to be machined complete the cycle of contact, separation and re-contact in a certain period. Ultrasonic vibration-assisted machining has become an indispensable technology in precision and special machining due to its advantages such as low average cutting force, high machining efficiency and good surface machining quality. It can be used for some difficult-to-machine materials such as composite materials, hard and brittle materials, such as ceramics, glass, super-hard alloys, etc. At the same time, with the rapid development of the manufacturing industry towards precision and even ultra-precision, the workpiece is required to have a microstructure surface with a certain geometric shape and distribution pattern, which further expands the demand for ultrasonic vibration-assisted machining.

[0003] Vibration-assisted machining differs in the vibration mode. For example, in one-dimensional vibration-assisted machining, the cutter head 6 vibrates back and forth in one direction. Similarly, it can be divided into two-dimensional vibration-assisted machining and three-dimensional vibration-assisted machining. At the same time, the vibration sources of vibration-assisted machining include single excitation mode and multi-excitation mode. Since single excitation only requires one vibration source to apply vibration to the structure, while multi-excitation requires multiple vibration sources to apply vibration to the device, the single-excitation three-dimensional vibration device has the advantages of small size and simple structure. Among them, there are relatively mature single-excitation device designs in one-dimensional vibration-assisted machining and two-dimensional vibration-assisted machining, while the research on three-dimensional ultrasonic vibration-assisted machining systems at home and abroad focuses on multi-excitation devices, which are synthesized into three-dimensional vibrations through special structures. This often makes the traditional three-dimensional ultrasonic vibration-assisted machining device larger in size, and at the same time, it has high requirements for the coordination between multiple excitation sources. Therefore, it is very important to study the single-excitation three-dimensional ultrasonic vibration-assisted machining system device. At present, the research on single-excitation three-dimensional ultrasonic vibration-assisted machining is still insufficient, and there are many problems that need to be solved. Summary of the Invention

[0004] The purpose of the present invention is to provide a horn for single-excitation three-dimensional ultrasonic vibration to address the technical defects in the prior art.

[0005] Another object of the present invention is to provide a single-excitation three-dimensional ultrasonic vibration-assisted machining system based on the horn.

[0006] Another object of the present invention is to provide a processing method of the processing system.

[0007] The technical solution adopted to achieve the purpose of the present invention is:

[0008] A horn for single-excitation three-dimensional ultrasonic vibration comprises a horn body, wherein the horn body is provided with a protruding force-bearing end and an output end for assembling a cutter head, and N inclined grooves are provided between the force-bearing end and the output end.

[0009] In the above technical solution, the N inclined grooves have the same size and are parallel to each other, and the spacing between every two adjacent inclined grooves is the same. Preferably, N is 1 or 2 or 3, and more preferably, N is 3.

[0010] In the above technical solution, the angle between the inclined slot and the radial direction of the amplitude transformer body is 0-90°, preferably 30-70°, and most preferably 45°.

[0011] In the above technical solution, the three inclined grooves are between the force-bearing end and the output end, close to the output end, and the three inclined grooves are evenly distributed in parallel in a single row.

[0012] In the above technical solution, the output end of the amplitude transformer is tilted upward, the angle between the side surface formed at the lower part and the lower bottom surface is 30-60 degrees, preferably 45 degrees, and an arc surface is formed on the upper part.

[0013] In the above technical solution, the top surfaces of the output end and the force-bearing end are both flat, and a screw hole is provided on the output end to assemble the cutter head.

[0014] Another aspect of the present invention is a single-excitation three-dimensional ultrasonic vibration auxiliary processing system, characterized in that it includes an ultrasonic generator, a piezoelectric ceramic stack, a horn according to any one of claims 1 to 6, and a tool head, wherein:

[0015] The ultrasonic generator is electrically connected to the piezoelectric ceramic stack, the piezoelectric ceramic stack is assembled with the force-bearing end through a fixing fixture, and the cutter head is fixed on the output end.

[0016] In the above technical solution, the auxiliary processing system for single-excitation three-dimensional ultrasonic vibration also includes a top plate, a middle plate and a base, the amplitude rod fixing plate is fixedly assembled on the base, the middle plate is assembled on the base, the top plate is assembled on the top of the middle plate, the top of the piezoelectric ceramic stack passes through the hole on the middle plate, and a stud is provided on the top plate. The bottom of the stud is in contact with the top of the piezoelectric ceramic stack, and the piezoelectric ceramic stack is fixed and a pre-tightening force is applied by screwing the stud.

[0017] In the above technical solution, the distance between two adjacent inclined slots is much smaller than the propagation wavelength of the longitudinal wave in the horn.

[0018] On the other hand, in the processing method of the auxiliary processing system, a PC controls an ultrasonic generator to generate a high-frequency sinusoidal current, selects the frequency of the second-order mode as the operating frequency, drives the piezoelectric ceramic stack to generate high-frequency vibration, and then applies an excitation force to the amplitude variable rod. The amplitude variable rod converts the single excitation into a spatial elliptical vibration, so that the tool head fixed on the output end exhibits a three-dimensional elliptical-like vibration in space.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention proposes a horn for single-excitation three-dimensional ultrasonic vibration. The horn has an oblique groove structure. By adjusting the appropriate angle and position of the oblique groove, the output end of the horn produces sinusoidal motion in three directions under single excitation, so that the tool head fixed at the output end exhibits three-dimensional elliptical vibration in space.

[0021] 2. The auxiliary processing system of the present invention can realize three-dimensional vibration by single excitation, and the operating frequency is within the ultrasonic range. Due to its small size, the auxiliary processing system can be applied to a variety of processing environments to achieve ultra-precision processing on complex free-form surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of the amplitude transformer, where (a) is the main view, (b) is the top view, and (c) is the front view.

[0023] Figure 2 It is a structural schematic diagram of a single-excitation three-dimensional ultrasonic vibration auxiliary processing system, wherein (a) is a main view, (b) is a partial structural main view, and (c) is a main view.

[0024] Figure 3 This is a schematic diagram of a single-excitation three-dimensional ultrasonic vibration auxiliary processing system.

[0025] Figure 4 This is the schematic diagram of the chute.

[0026] Figure 5 It is a decomposition diagram of spatial vibration.

[0027] Figure 6 is the first-order mode.

[0028] Figure 7 is the second-order mode.

[0029] Figure 8 is the vibration displacement curve.

[0030] Figure 9 Excerpt from Space Trajectory.

[0031] In the figure: 1-top plate, 2-middle plate, 3-base, 4-piezoelectric ceramic stack, 5-horn, 6-cutter head, 7-horn fixing plate;

[0032] 5-1 horn body, 5-2 load-bearing end, 5-3 output end, 5-4 chute;

[0033] 8-studs, 9-holes. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] Example 1 1.1

[0037] like Figure 1 As shown in (a), (b) and (c), a single-excitation three-dimensional ultrasonic vibration transformer 5 includes a transformer body 5-1, and the transformer body 5-1 is provided with a raised force-bearing end 5-2 and an output end 5-3 for assembling a cutter head 6. Three parallel and identically sized inclined grooves 5-4 are provided between the force-bearing end 5-2 and the output end 5-3, and the spacing between each two adjacent inclined grooves 5-4 is the same.

[0038] The force-bearing end 5-2 is a raised end surface provided on the horn body 5-1. The piezoelectric ceramic stack 4 applies an excitation force to the horn 5 via the force-bearing end 5-2. Based on the ultrasonic oblique incidence theory, when the longitudinal wave generated by the excitation force is transmitted to the position of the inclined groove 5-4, the sound wave is reflected at the contact surface between the inclined groove 5-4 and the air, generating a reflected longitudinal wave and a reflected transverse wave. Figure 4 As shown in the figure, the reflected longitudinal and transverse waves form a certain angle with the axial direction of the horn 5, generating two components in the axial and radial directions of the horn 5, respectively. The axial component causes the output end 5-3 to vibrate along the X-axis, while the radial component causes the output end 5-3 to vibrate along the Z-axis. At the same time, because the skewed slots 5-4 are parallel to each other and the spacing is much smaller than the wavelength of the longitudinal wave propagating in the horn 5, the waveforms reflected by the skewed slots 5-4 are superimposed on each other, resulting in vibration in both the X-axis and Z-axis directions at the output end 5-3 of the horn 5.

[0039] like Figure 5 As shown, the amplitude transformer 5 is excited in the Y-axis direction at the force point to generate displacements in the X and Y directions. The displacement in the X-axis direction is decomposed by the inclined slot 5-4 to obtain displacements in the X and Z directions, that is, at the output end 5-3, simple harmonic vibrations of the same frequency in three directions perpendicular to each other are exhibited, and the vibrations are respectively along the directions of the X-axis, Y-axis and Z-axis.

[0040] Finite element simulations were performed for 1, 2, 3, and 4 chute slots 5-4. As the number of chute slots 5-4 increased, the amplitude effect increased. However, when the number of chute slots 5-4 exceeded 3, the amplitude effect decreased. Because increasing the number of chute slots is detrimental to actual processing and excessive chute slots reduce the strength of the horn body 5-1, a 3-chute configuration was temporarily selected.

[0041] The size and spacing of the chute also have a certain impact. The length, width, and number of chute can be varied using finite element analysis to select the appropriate parameters.

[0042] Preferably, the total length of the amplitude converter 5 is L, the height is H, and the width is D. In order to achieve three-dimensional vibration output, a single row of three parallel and evenly distributed inclined grooves 5-4 are added near the output end 5-3 of the amplitude converter 5. The angle of the inclined groove 5-4 is α, the distance from the inclined groove 5-4 to the output end 5-3 is d, the length of the inclined groove 5-4 is L1, the width of the inclined groove 5-4 is W1, and the spacing between two adjacent inclined grooves 5-4 is W2.

[0043] Finite element simulation revealed that the chute angle α, length L1, and number of chute components have the greatest impact on the horn, while the chute width W1 and the distance d from the chute 5-4 to the output end 5-3 have less influence. A chute angle of 30 to 70 degrees is most effective, and a length L1 of 1 to 3 mm is sufficient. Excessive length will reduce structural rigidity. The chute width W1 ranges from 0.1 to 0.4 mm, with 0.4 mm selected for ease of fabrication. Finite element simulation determined the optimal value of d to be 0.5 mm. Changing d affects the amplitude ratio, z / x.

[0044] Preferably, the end of the amplitude transformer 5 where the output end 5 - 3 is located is tilted upward, the angle between the side surface formed at the lower part and the lower bottom surface is 45°, and an arc surface is formed at the top. 1.2

[0046] Synthesis of simple harmonic motion with the same frequency:

[0047] For simple harmonic vibrations of the same frequency in three mutually perpendicular directions, when the vibration directions are along the X-axis, Y-axis, and Z-axis respectively, the simple harmonic vibration equation is:

[0048]

[0049] Where: A1, A2, A3 are amplitudes (mm); ω is the circular frequency (rad); t is the time (s); α1, α2, α3 are the initial phases.

[0050] Eliminating t in the parameter formula (1-1), the vibration trajectory equation is obtained, and its trajectory equation in the OXYZ space is:

[0051]

[0052] Formula (1-2) can be further expressed as:

[0053]

[0054] From formula (1-3), it can be seen that the vibration trajectory is an ellipse centered at the origin, and the shape of the ellipse is affected by the phase difference and amplitude of simple harmonic vibrations in three directions.

[0055] Example 2

[0056] A single-excitation three-dimensional ultrasonic vibration auxiliary processing system includes an ultrasonic generator, a piezoelectric ceramic stack 4, a horn 5 as described in Example 1, a horn fixing plate 7, and a tool head 6, wherein:

[0057] The ultrasonic generator drives the piezoelectric ceramic stack 4 to generate high-frequency vibration. The piezoelectric ceramic stack 4 is assembled with the force-bearing end 5-2 of the amplitude transformer 5 through a fixing fixture. The cutter head 6 is fixed on the output end 5-3, and the amplitude transformer 5 is fixed on the amplitude transformer fixing plate 7.

[0058] like Figure 3 As shown, in the system, the PC controls the ultrasonic generator to generate high-frequency sinusoidal current, driving the piezoelectric ceramic stack 4 to generate high-frequency vibration, thereby applying an excitation force to the horn 5, which converts the single excitation into spatial elliptical vibration.

[0059] Preferably, the auxiliary processing system also includes a top plate 1, a middle plate 2 and a base 3, the amplitude transformer fixing plate 7 is fixedly assembled on the base 3, the middle plate 2 is assembled on the base 3, the top plate 1 is assembled on the top of the middle plate 2, the top of the piezoelectric ceramic stack 4 passes through the hole 9 on the middle plate 2, and a stud 8 is provided on the top plate 1, the bottom of the stud 8 is in contact with the top of the piezoelectric ceramic stack 4, and the piezoelectric ceramic stack 4 is fixed and a pre-tightening force is applied by screwing the stud 8, and the amplitude transformer 5 and the amplitude transformer fixing plate 7 are located below the middle plate 2.

[0060] Example 3

[0061] This embodiment performs finite element verification on the devices of embodiment 1 and embodiment 2.

[0062] Since the primary focus is on the vibration effects of horn 5 under a single excitation, ABAQUS finite element software can be used to analyze only horn 5. Import the 3D model of horn 5 into ABAQUS, selecting aluminum alloy as the material. The specific material properties are shown in Table 1. Once all other conditions are set, finite element analysis can be performed. First, perform a modal analysis on the model to determine the natural frequency and corresponding mode shape. Then, perform transient dynamic analysis based on the selected frequency based on the mode shape to determine the output end vibration trajectory.

[0063] Table 1 Material parameters

[0064]

[0065] 3.1 Modal analysis

[0066] The theory of oblique ultrasonic incidence explains the principle of skew conversion. The skew angle α is the primary factor affecting the horn. To investigate the effect of the skew angle on the output vibration trajectory, this paper selected 0°, 30°, 45°, 60°, 70°, and 80° skew angles for finite element simulation. The numerical values ​​of the horn's structural parameters are shown in Table 2.

[0067] Table 2 Structural parameters of the horn

[0068]

[0069] Modal analysis can obtain the natural frequency and vibration mode of the horn 5. The results show that the vibration mode of the horn 5 at different angles in the first-order mode is mainly the longitudinal vibration of the output end 5-3. The vibration mode is as follows: Figure 6 The second-order mode vibration shape is mainly the lateral vibration of the output end 5-3, as shown in Figure 7 shown.

[0070] 3.2 Transient dynamics analysis

[0071] The modal analysis results show that while the first- and second-order modes meet the frequency requirements, the vibration shape of the second-order mode is more consistent with expectations. Therefore, the frequency of the second-order mode should be selected as the operating frequency of the horn. The relationship between the frequency and displacement excitation curve formula is shown in Table 3. ABAQUS simulation software was used to apply ultrasonic excitation force to the load points of the horn model for transient dynamic analysis.

[0072] Table 3 Excitation frequency and excitation curve formula

[0073]

[0074] Extract the spatial displacement curve of the output end 5-3 node, such as Figure 8 As shown in the figure, the output end of the horn amplifies the 1-micron excitation force. When the skew angle is zero, there is almost no Z-axis displacement. As the skew angle increases, the Z-axis amplitude increases, further demonstrating that the skew is key to generating Z-axis displacement. Furthermore, the motion trajectories of the model output in the X, Y, and Z directions all exhibit simple harmonic motion at the same frequency, but with a certain phase difference.

[0075] In order to measure the effect of different angle bevels on the Z-axis of the amplitude transformer, the ratio of the Z-axis amplitude to the X-axis amplitude at the output end is used to characterize the bevel conversion efficiency, that is, the amplitude ratio. The values ​​of X, Y, and Z at the maximum amplitude of the curve are taken respectively, and the amplitude ratio is calculated, as shown in Table 4. From the bevel angle of 0° to 60°, the amplitude ratio increases continuously with the increase of the angle. When the bevel angle is 60°, the amplitude ratio reaches about 1.8. When the bevel angle increases to 70°, the amplitude ratio decreases to about 0.93. It can be seen that there is a specific angle that makes the amplitude ratio the highest. This is mainly because an excessively large bevel angle will cause part of the longitudinal wave to be reflected back to the input end of the waveguide, reducing the reflection efficiency.

[0076] Table 4 Maximum amplitude and amplitude ratio of nodes

[0077]

[0078] The displacement data of the output node is extracted in the ABAQUS simulation software, and the partial spatial trajectory curve of the node is drawn using the ORIGIN data processing software. Figure 9 As shown in the figure, the spatial trajectory of the output end of the horn is elliptical, with sharp ends and a wider center. When the chute angle is 45°, the width of the middle portion of the trajectory is higher, and the three-dimensional vibration effect is more obvious. Therefore, the spatial trajectory curve of the output end of the horn can be influenced by changing the chute angle, and there is a certain regularity.

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A single excitation three-dimensional ultrasonic vibration auxiliary processing system, characterized in that: The invention comprises an ultrasonic generator, a piezoelectric ceramic stack, a horn and a cutter head, wherein: The ultrasonic generator is electrically connected to the piezoelectric ceramic stack, the piezoelectric ceramic stack is assembled with the force-bearing end through a fixing fixture, and the cutter head is fixed on the output end; The auxiliary processing system further includes a top plate, a middle plate, and a base, wherein the amplitude transformer fixing plate is fixedly mounted on the base, the middle plate is mounted on the base, and the top plate is mounted on the top of the middle plate. The top of the piezoelectric ceramic stack passes through the hole in the middle plate. A stud is provided on the top plate, and the bottom of the stud contacts the top of the piezoelectric ceramic stack. The piezoelectric ceramic stack is fixed and a pre-tightening force is applied by screwing the stud. The horn includes a horn body, the horn body is provided with a protruding force-bearing end and an output end for assembling a cutter head, and N inclined grooves are provided between the force-bearing end and the output end; The PC controls the ultrasonic generator to generate high-frequency sinusoidal current, selects the frequency of the second-order mode as the operating frequency, drives the piezoelectric ceramic stack to generate high-frequency vibration, and then applies an excitation force to the amplitude transformer. The amplitude transformer converts the single excitation into a spatial elliptical vibration, so that the cutter head fixed on the output end exhibits a three-dimensional elliptical vibration in space.

2. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 1, characterized in that: The N inclined slots have the same size and are parallel to each other, and the distance between every two adjacent inclined slots is the same.

3. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 2, characterized in that: N is 1 or 2 or 3.

4. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 2, characterized in that: N is 3.

5. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 1, characterized in that: The angle between the inclined slot and the radial direction of the amplitude transformer body is 0-90°.

6. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 1, characterized in that: The angle between the inclined groove and the radial direction of the amplitude transformer body is 30-70 degrees.

7. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 1, characterized in that: The included angle between the inclined slot and the radial direction of the amplitude transformer body is 45°.

8. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 1, characterized in that: The three inclined grooves are between the force-bearing end and the output end, close to the output end, and are evenly distributed in a single row and in parallel.

9. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 1, characterized in that: The end of the amplitude transformer where the output end is located is tilted upward, the angle between the side surface formed at the lower part and the lower bottom surface is 30-60 degrees, and an arc surface is formed at the top.

10. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 1, characterized in that: The end of the amplitude transformer where the output end is located is tilted upward, and the angle between the side surface formed at the lower part and the lower bottom surface is 45 degrees.

11. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 1, characterized in that: The top surfaces of the output end and the force-bearing end are both flat surfaces, and a screw hole is provided on the output end to assemble a cutter head.

12. The single excitation three-dimensional ultrasonic vibration auxiliary processing system according to claim 1, characterized in that: The distance between two adjacent bevel grooves is 0.2mm.

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