Ultrasonic free track vibration cutting device for efficiently manufacturing complex microstructure of difficult-to-machine material

Abstract

The invention belongs to the related field of ultra-precision machining technology, and discloses an ultrasonic free track vibration cutting device for efficiently manufacturing a complex microstructure of a difficult-to-machine material, which comprises a signal generator, a power amplifier and an ultrasonic vibration cutting unit, wherein the signal generator is used for outputting three paths of independent initial driving signals of low-frequency bending vibration, low-frequency longitudinal vibration and high-frequency longitudinal vibration; the power amplifier is used for performing gain amplification on the three paths of electric signals and then inputting the electric signals into the ultrasonic vibration cutting unit; the ultrasonic vibration cutting unit is used for generating bending vibration in the cutting direction and longitudinal vibration after superposition in the cutting depth direction and correspondingly driving a tool to achieve cutting machining in a free track. According to the invention, a single bending vibration mode and a plurality of longitudinal vibration modes can be coupled, so that the vibration track is changed from a single elliptical track to any controllable complex curved surface track, and the method is particularly suitable for manufacturing the surface of a functional microstructure of a material difficult to machine.

Description

Technical Field

[0001] The present invention belongs to the field related to ultra-precision machining technology, and more specifically, relates to an ultrasonic free-trajectory vibration cutting device for efficient manufacturing of complex microstructures of difficult-to-machine materials. Background Art

[0002] Surfaces with special functional microstructures can make materials exhibit many excellent properties, such as hydrophobicity, optical function and tribological properties, etc. Processing functional microstructure surfaces on iron-based materials represented by pure iron, stainless steel, hydrogen-resistant steel, etc. has extremely wide applications in the manufacture of key components in the fields of national defense, optics, aerospace, etc.

[0003] With the rapid development of advanced manufacturing technology in high-end fields, existing processing technologies are difficult to meet the needs of efficient and high-precision manufacturing of complex microstructures, and the manufacturing technology of microstructures of difficult-to-process materials urgently needs further breakthroughs. Diamond cutting technology has the advantages of high processing freedom, high processing accuracy, and low sub-surface damage. It has been proven to be an effective means to prepare ultra-precision complex microstructures. In order to solve the problems of excessive tool wear and surface degradation of finished products caused by the easy thermochemical reaction between iron-based materials and tools, two-dimensional elliptical vibration cutting technology is currently mainly used to achieve ultra-precision diamond cutting of difficult-to-process materials. This technology can achieve periodic separation of the tool and the workpiece during the processing process, which is beneficial to tool cooling and inhibition of thermochemical reactions.

[0004] However, further research shows that the above-mentioned prior art still has the following defects or shortcomings, which are specifically manifested as follows: First, the vibration trajectories of the existing two-dimensional ultrasonic elliptical vibration cutting are all elliptical in shape, which are limited by the vibration trajectory under specific processing requirements, and the elliptical vibration trajectory will process a regular residual structure on the workpiece surface. Usually, the cutting speed is reduced to reduce the impact of this phenomenon. Therefore, there is a problem of low efficiency when using this method to manufacture microstructures of difficult-to-process materials; secondly, the existing two-dimensional ultrasonic elliptical vibration cutting device cannot use a single-cycle vibration trajectory to realize the processing of any single complex microstructure, and its processing efficiency still needs to be further improved. In addition, the dynamic stiffness of the device is low, which seriously restricts the manufacturing efficiency and manufacturing accuracy of the functional microstructure.

[0005] Accordingly, this field urgently needs further research and improvement in order to better meet the needs of creating free-form surfaces of difficult-to-machine materials. Summary of the invention

[0006] In response to one or more of the above defects or needs in the prior art, the present invention provides an ultrasonic free-trajectory vibration cutting device for the efficient manufacture of complex microstructures of difficult-to-process materials, wherein by re-studying and designing the composition structure and working mechanism of the cutting device, not only can a single bending vibration and multiple longitudinal vibration modes be coupled, so that the vibration trajectory is changed from a single elliptical trajectory to an adjustable arbitrarily complex curved surface trajectory, but also the tool and the workpiece are intermittently separated during the cutting process, which is beneficial to prolonging the tool life and inhibiting damage to the processed surface. Therefore, it is particularly suitable for efficient and high-precision processing of functional microstructure surfaces of various difficult-to-process materials.

[0007] To achieve the above object, according to one aspect of the present invention, there is provided an ultrasonic free-trajectory vibration cutting device for efficient manufacturing of complex microstructures of difficult-to-machine materials, characterized in that the device comprises a signal generator, a power amplifier and an ultrasonic vibration cutting unit, wherein:

[0008] The signal generator is used to output three independent high-frequency sinusoidal electrical signals, which are used as initial driving signals for low-frequency bending vibration, low-frequency longitudinal vibration, and high-frequency longitudinal vibration respectively;

[0009] The power amplifier is used to perform gain amplification on the three-way electrical signal output by the signal generator, and then input the signals into the ultrasonic vibration cutting unit;

[0010] The ultrasonic vibration cutting unit comprises a low-frequency bending vibration piezoelectric ceramic group, a low-frequency longitudinal vibration piezoelectric ceramic group, a high-frequency longitudinal vibration piezoelectric ceramic group, an ultrasonic amplitude transformer and a tool, wherein the low-frequency bending vibration piezoelectric ceramic group generates bending vibration in the cutting direction through the contraction and expansion of the piezoelectric ceramic inside thereof based on the received low-frequency bending vibration driving signal, thereby realizing the periodic separation between the tool and the workpiece; the low-frequency longitudinal vibration piezoelectric ceramic group and the high-frequency longitudinal vibration piezoelectric ceramic group each generate different longitudinal vibrations in the cutting depth direction through the contraction and expansion of the piezoelectric ceramic inside thereof based on the received low-frequency longitudinal vibration and high-frequency longitudinal vibration driving signals, and the two longitudinal vibrations are modally superimposed to become new longitudinal vibrations;

[0011] The ultrasonic amplitude transformer is used to amplify the bending vibration and longitudinal vibration generated by the piezoelectric ceramic group to perform particle displacement, and then concentrate them at its output end and drive the tool installed thereto to perform corresponding vibration cutting and realize free trajectory high-frequency vibration.

[0012] As a further preferred embodiment of the present invention, the low-frequency bending vibration piezoelectric ceramic group, the low-frequency longitudinal vibration piezoelectric ceramic group, and the high-frequency longitudinal vibration piezoelectric ceramic group preferably together constitute an ultrasonic transducer with a sandwich structure, and are equipped with end covers serving as the skeleton part of the ultrasonic transducer, and then pre-tightening bolts are used to apply a pre-tightening force to clamp the parts.

[0013] As a further preferred embodiment of the present invention, the ultrasonic horn preferably adopts a cone segment transition step shape, and the cone head end thereof as the output end is provided with a tool groove for installing the tool.

[0014] As a further preferred embodiment of the present invention, the end cap and the ultrasonic horn are each processed with standing wave nodes for fixing parts, and the stability of the entire system under high-frequency impact is improved by means of such double standing wave nodes.

[0015] As a further preferred embodiment of the present invention, the low-frequency bending vibration piezoelectric ceramic group is preferably composed of eight half-ring piezoelectric ceramics and installed in opposite directions of polarity; the low-frequency longitudinal vibration piezoelectric ceramic group and the high-frequency longitudinal vibration piezoelectric ceramic group are preferably each composed of two full-ring piezoelectric ceramics, and the operating frequency of the high-frequency longitudinal vibration piezoelectric ceramic group is three times that of the low-frequency longitudinal vibration piezoelectric ceramic group.

[0016] As a further preferred embodiment of the present invention, for the initial driving signals of the low-frequency bending vibration, the low-frequency longitudinal vibration, and the high-frequency longitudinal vibration, their amplitudes and phases can be freely adjusted according to the desired final cutting trajectory.

[0017] According to another aspect of the present invention, a corresponding ultrasonic free-trajectory vibration cutting method is also provided.

[0018] As a further preferred embodiment of the present invention, the driving signal finally obtained is an arbitrary smooth curve, and the frequency is in the 10,000 Hz level.

[0019] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0020] 1. The ultrasonic free-trajectory vibration cutting scheme provided by the present invention couples a single bending vibration and multiple longitudinal vibration modes, and can realize free regulation of the vibration trajectory by changing the amplitude and phase of multiple channels, so that the vibration trajectory is changed from a single elliptical trajectory to an adjustable arbitrarily complex curved trajectory, which can better meet the requirements of high efficiency and high quality in the processing of complex microstructures of difficult-to-process materials;

[0021] 2. Compared with the fast tool servo technology, the ultrasonic free trajectory vibration cutting solution provided by the present invention adds bending vibration on the basis of longitudinal vibration, so that the tool and the workpiece are intermittently separated during the cutting process, which is beneficial to prolong the tool life, inhibit the damage of the machining surface, and has good cutting performance for difficult-to-machine materials;

[0022] 3. The ultrasonic vibration cutting system provided by the present invention can operate at a high-frequency resonant frequency, and the vibration frequency is significantly higher than that of the fast tool servo technology, which is conducive to the efficient and flexible processing of complex microstructures; in addition, since double-stationary point support can be adopted, it has better rigidity than a single-stationary point fixed device, which is conducive to improving the stability of the device under high-frequency vibration impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the main structural components of the ultrasonic free trajectory vibration cutting device according to the present invention;

[0024] Figure 2 is a schematic structural diagram of an ultrasonic vibration cutting unit according to a preferred embodiment of the present invention;

[0025] Figure 3 is a schematic diagram for exemplarily showing the generation of a desired composite vibration trajectory through vibration trajectory control according to the present invention;

[0026] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0027] 1- tool; 2- ultrasonic amplitude transformer; 3- low frequency bending vibration piezoelectric ceramic group; 41- low frequency longitudinal vibration piezoelectric ceramic group; 42- high frequency longitudinal vibration piezoelectric ceramic group; 5- end cover. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Figure 1 The main structural components of the ultrasonic free trajectory vibration cutting device according to the present invention are shown in FIG. Figure 1 To explain the present invention in more detail.

[0030] like Figure 1 As shown, the ultrasonic free trajectory vibration cutting device of the present invention mainly includes components such as a signal generator, a power amplifier and an ultrasonic vibration cutting unit, and through the redesign of these components and their working mechanisms, it breaks through the limitations of traditional elliptical trajectories, and makes the vibration trajectory evolve from an ellipse to an arbitrary smooth curve, thereby realizing efficient and high-precision manufacturing of microstructures of difficult-to-process materials.

[0031] The signal generator is used to output three independent high-frequency sinusoidal electrical signals, which are used as initial driving signals for low-frequency bending vibration, low-frequency longitudinal vibration, and high-frequency longitudinal vibration respectively; wherein the amplitude and phase of each initial driving signal can be freely adjusted according to the required trajectory.

[0032] The power amplifier is used to perform gain amplification on the three-way electrical signal output by the signal generator, and then input the three-way electrical signal into the ultrasonic vibration cutting unit.

[0033] As one of the key improvements of the present invention, the ultrasonic vibration cutting unit includes a low-frequency bending vibration piezoelectric ceramic group 3, a low-frequency longitudinal vibration piezoelectric ceramic group 41, a high-frequency longitudinal vibration piezoelectric ceramic group 42, an ultrasonic amplitude transformer 2 and a tool 1, wherein the low-frequency bending vibration piezoelectric ceramic group 3 generates bending vibration in the cutting direction based on the received low-frequency bending vibration driving signal through the contraction and expansion of the piezoelectric ceramics inside it, thereby realizing the periodic separation between the tool and the workpiece; the low-frequency longitudinal vibration piezoelectric ceramic group 41 and the high-frequency longitudinal vibration piezoelectric ceramic group 42 each generate different longitudinal vibrations in the cutting depth direction through the contraction and expansion of the piezoelectric ceramics inside them based on the received low-frequency longitudinal vibration and high-frequency longitudinal vibration driving signals, and these two longitudinal vibrations are modally superimposed to become new longitudinal vibrations; in addition, the ultrasonic amplitude transformer 2 is used to perform particle displacement amplification on the bending vibration and longitudinal vibration generated by the above-mentioned piezoelectric ceramic group, and then concentrate them at its output end and drive the tool 1 installed thereon to perform corresponding vibration cutting, and realize free trajectory high-frequency vibration.

[0034] Also see Figure 2 According to a preferred embodiment of the present invention, the low-frequency bending vibration piezoelectric ceramic 3, the low-frequency longitudinal vibration piezoelectric ceramic group 41, and the high-frequency longitudinal vibration piezoelectric ceramic group 42 preferably together constitute a sandwich-structured ultrasonic transducer, and are equipped with an end cover 5 as the skeleton of the ultrasonic transducer, and then the pre-tightening bolts are used to apply the pre-tightening force to clamp the parts. The end cover 5 can be, for example, a hollow cylindrical structure, and the hollow design provides space for the pre-tightening bolts to pass through.

[0035] According to another preferred embodiment of the present invention, the ultrasonic horn 2 preferably adopts a cone segment transition step shape, and its cone head end as the output end is provided with a knife groove for installing the knife. In addition, the end cap 5 and the ultrasonic horn 2 are each processed with a standing wave node for fixing parts, and the stability of the entire system under high-frequency impact is improved by means of this double standing wave node.

[0036] Through the above design, the sandwich-structured ultrasonic vibration cutting unit has the advantages of compact structure, easy processing and high energy conversion efficiency. The ultrasonic horn adopts a stepped horn with a cone section transition, which is more suitable for concentrating the energy generated by the piezoelectric ceramic at the output end for output. The output end can be fixed with a set bolt to the diamond tool, and the rear end is processed with a threaded hole for connection with the pre-tightening bolt. Both the piezoelectric ceramic and the end cover adopt a hollow cylindrical structure. The pre-tightening bolt passes through each ultrasonic vibration cutting part and is connected to the threaded hole of the ultrasonic horn. The required pre-tightening force is applied by a torque wrench to firmly connect the parts.

[0037] like Figure 2 As shown in the figure, the low-frequency bending vibration piezoelectric ceramic group 3 is preferably composed of eight half-ring piezoelectric ceramics, and is installed in opposite directions of polarity, so as to generate bending vibration in the cutting direction through the contraction and expansion of the piezoelectric ceramics; the bending vibration is mainly used to achieve periodic separation of the tool and the workpiece, and accordingly give play to the advantages of ultrasonic vibration in cutting difficult-to-cut materials.

[0038] like Figure 2 As shown in , the low-frequency longitudinal vibration piezoelectric ceramic group 41 and the high-frequency longitudinal vibration piezoelectric ceramic group 42 are preferably each composed of two full-ring piezoelectric ceramics, and the operating frequency of the high-frequency longitudinal vibration piezoelectric ceramic group 42 is three times that of the low-frequency longitudinal vibration piezoelectric ceramic group 41. In this way, the contraction and expansion of the piezoelectric ceramics generate longitudinal vibrations in the cutting depth direction; the new longitudinal vibration is formed by the superposition of the two excited longitudinal vibration modes, and the longitudinal vibration trajectory can be adjusted by adjusting the amplitude and phase difference of the high-frequency and low-frequency longitudinal vibration input signals; the longitudinal vibration is mainly used to change the cutting trajectory, thereby realizing high-flexibility processing of complex microstructures.

[0039] Through the above design, the ultrasonic transducer is used to generate high-frequency vibrations of the desired trajectory according to the functional microstructure profile of the target; the final high-frequency vibration is obtained by coupling a bending vibration mode and two longitudinal vibration modes as described above, and multiple vibration modes are generated by an excitation device and superimposed together, ultimately driving the diamond tool to generate high-frequency vibrations of the desired trajectory.

[0040] The following will be combined Figure 3 A specific embodiment of the present invention is given to better explain the present invention.

[0041] Example 1

[0042] In this embodiment, the signal generator is used to generate three independent sinusoidal electrical signals. The resonant frequency of the required vibration mode is analyzed by frequency sweeping to determine that the device can operate stably at the resonant frequency and that the resonant frequency of the fourth-order longitudinal vibration is three times the frequency of the second-order longitudinal vibration. The resonant frequency is used as the operating frequency to excite the device to generate high-frequency vibrations with a larger amplitude.

[0043] The signal generator inputs the initial driving signal into the power amplifier, which amplifies the initial driving signal through internal electronic circuits and finally outputs an electrical signal sufficient to drive the piezoelectric ceramic to vibrate at high frequency.

[0044] Under the excitation of the driving signal output by the power amplifier, the ultrasonic vibration cutting device generates high-frequency vibration with controllable trajectory. Through the vibration mode coupling of second-order longitudinal vibration, fourth-order longitudinal vibration, and fourth-order bending vibration, the diamond tool generates high-frequency vibration of the required trajectory on the plane composed of the cutting and cutting depth directions.

[0045] More specifically, the bending vibration piezoelectric ceramic group includes 8 half-ring piezoelectric ceramics, which are driven by a bending vibration sinusoidal signal. When the upper piezoelectric ceramic contracts or expands, the lower piezoelectric ceramic will produce opposite movement, thereby generating bending vibration at the output end of the ultrasonic horn. The longitudinal vibration piezoelectric ceramic group includes 2 groups of high-frequency longitudinal vibration and low-frequency longitudinal vibration, each with 2 full-ring piezoelectric ceramics, which are driven by two longitudinal vibration sinusoidal signals. The working frequency of the high-frequency longitudinal vibration is three times the frequency of the low-frequency longitudinal vibration. The vibration trajectories generated by the two groups of longitudinal vibration piezoelectric ceramics are superimposed together, thereby generating longitudinal vibration at the output end of the ultrasonic horn. The above longitudinal vibration and bending vibration are applied to the diamond tool at the same time to achieve free trajectory high-frequency vibration.

[0046] The working principle of the present invention is: by superimposing two longitudinal vibration trajectories, the sinusoidal longitudinal vibration trajectory in the existing longitudinal-bending composite ultrasonic elliptical vibration cutting technology is changed into an adjustable free curve, and the three vibration modes excited can all be expressed as harmonic curves. Perform simulation. Figure 3 As shown in the demonstration, the special longitudinal vibration trajectory obtained by superimposing the two longitudinal vibration trajectories and the excited sinusoidal bending vibration trajectory act on the output end of the ultrasonic amplitude transformer at the same time, thereby generating the required composite vibration trajectory. This vibration trajectory breaks through the trajectory limitation of traditional elliptical vibration cutting and obtains the actual cutting trajectory at a certain cutting speed, which meets the processing requirements of the target special functional microstructure.

[0047] The specific operation method of the present invention is: according to the longitudinal vibration and bending vibration trajectories required for the target microstructure contour analysis, the longitudinal vibration trajectory is regulated by adjusting the amplitude and phase difference of the two longitudinal vibration input signals, and after obtaining the required longitudinal vibration trajectory, the phase difference between the longitudinal vibration and bending vibration input signals is adjusted to finally obtain the target two-dimensional vibration trajectory, thereby directly processing a single microstructure contour in each vibration cycle.

[0048] In summary, the ultrasonic free trajectory vibration cutting scheme according to the present invention can not only couple a single bending vibration and multiple longitudinal vibration modes, so that the vibration trajectory is changed from a single elliptical trajectory to an adjustable arbitrarily complex curved surface trajectory, but also the tool and the workpiece are intermittently separated during the cutting process, which is beneficial to prolong the tool life and inhibit damage to the machining surface. Therefore, it is particularly suitable for high-efficiency and high-precision machining of functional microstructure surfaces of various difficult-to-machine materials, and has good practical value and application prospects.

[0049] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultrasonic free-trajectory vibration cutting device for efficient manufacturing of complex microstructures of difficult-to-process materials, characterized in that: The device comprises a signal generator, a power amplifier and an ultrasonic vibration cutting unit, wherein: The signal generator is used to output three independent high-frequency sinusoidal electrical signals, which are used as initial driving signals for low-frequency bending vibration, low-frequency longitudinal vibration, and high-frequency longitudinal vibration respectively; The power amplifier is used to perform gain amplification on the three-way electrical signal output by the signal generator, and then input the signals into the ultrasonic vibration cutting unit; The ultrasonic vibration cutting unit comprises a low-frequency bending vibration piezoelectric ceramic group (3), a low-frequency longitudinal vibration piezoelectric ceramic group (41), a high-frequency longitudinal vibration piezoelectric ceramic group (42), an ultrasonic amplitude transformer (2) and a tool (1), wherein the low-frequency bending vibration piezoelectric ceramic group (3) generates bending vibration in the cutting direction based on the received low-frequency bending vibration driving signal through the contraction and expansion of the piezoelectric ceramic inside thereof, thereby achieving periodic separation between the tool and the workpiece; the low-frequency longitudinal vibration piezoelectric ceramic group (41) and the high-frequency longitudinal vibration piezoelectric ceramic group (42) each generate different longitudinal vibrations in the cutting depth direction through the contraction and expansion of the piezoelectric ceramic inside thereof based on the received low-frequency longitudinal vibration and high-frequency longitudinal vibration driving signals, and the two longitudinal vibrations are modally superimposed to become new longitudinal vibrations; The ultrasonic amplitude transformer (2) is used to amplify the bending vibration and longitudinal vibration generated by the piezoelectric ceramic group to perform particle displacement, and then concentrate them at its output end and drive the tool (1) installed thereto to perform corresponding vibration cutting and realize free trajectory high-frequency vibration.

2. The ultrasonic free-trajectory vibration cutting device according to claim 1, characterized in that: The low-frequency bending vibration piezoelectric ceramic group (3), the low-frequency longitudinal vibration piezoelectric ceramic group (41), and the high-frequency longitudinal vibration piezoelectric ceramic group (42) preferably together constitute an ultrasonic transducer with a sandwich structure, and are equipped with an end cover (5) serving as the skeleton part of the ultrasonic transducer, and then a pre-tightening bolt is used to apply a pre-tightening force to clamp the various parts.

3. The ultrasonic free-trajectory vibration cutting device according to claim 2, characterized in that: The ultrasonic horn (2) preferably adopts a cone segment transition step shape, and its cone head end as the output end is provided with a tool groove for installing the tool.

4. The ultrasonic free-trajectory vibration cutting device according to claim 3, characterized in that: The end cover (5) and the ultrasonic horn (2) are each processed with a standing wave node for fixing parts, and the stability of the entire system under high-frequency impact is improved by means of the double standing wave node.

5. The ultrasonic free-trajectory vibration cutting device according to any one of claims 1 to 4, characterized in that: The low-frequency bending vibration piezoelectric ceramic group (3) is preferably composed of eight half-ring piezoelectric ceramics and installed in opposite polarity directions; the low-frequency longitudinal vibration piezoelectric ceramic group (41) and the high-frequency longitudinal vibration piezoelectric ceramic group (42) are preferably each composed of two full-ring piezoelectric ceramics, and the operating frequency of the high-frequency longitudinal vibration piezoelectric ceramic group (42) is three times that of the low-frequency longitudinal vibration piezoelectric ceramic group (41).

6. The ultrasonic free-trajectory vibration cutting device according to any one of claims 1 to 5, characterized in that: For the initial driving signals of the low-frequency bending vibration, the low-frequency longitudinal vibration, and the high-frequency longitudinal vibration, the amplitude and phase thereof can be freely adjusted according to the desired final cutting trajectory.

7. An ultrasonic free-trajectory vibration cutting method, characterized in that: The method is implemented by using the system as described in any one of claims 1 to 6.

8. The ultrasonic free trajectory vibration cutting method according to claim 7, characterized in that: The method is preferably used for manufacturing functional microstructure surfaces of difficult-to-process materials.

9. The ultrasonic free-trajectory vibration cutting method according to claim 8, characterized in that: The driving signal finally obtained is an arbitrary smooth curve, and the frequency is in the 10,000 Hz level.

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