Large-range micro-nano structure array machining tool rest for vibration auxiliary imprinting and using method of large-range micro-nano structure array machining tool rest

Abstract

The invention discloses a large-range micro-nano structure array machining tool rest for vibration auxiliary imprinting and a using method thereof, and belongs to the field of tool rest design. The tool rest comprises a Z-axis stepping motor, a support, a piezoelectric displacement table, a flexible hinge base, a pre-tightening bolt, a first PZT actuator, a second PZT actuator, a tool base, a piezoelectric sensing unit and a diamond tool. The two PZT actuators are symmetrically installed in limiting grooves of the tool base, and the flexible hinge base and the tool base are connected through pre-tightening bolts; the piezoelectric sensing unit is provided with gaskets up and down and is fixed on the cutter base; the diamond cutter is fixed at the front end of the piezoelectric sensing unit; the two-dimensional elliptical vibration tool rest is fixed to the piezoelectric displacement table through bolts, and the two-dimensional elliptical vibration tool rest and the Z-axis stepping motor are connected through the support. The movement range of the piezoelectric displacement table can reach 100 microns, force signals of the piezoelectric sensing unit can be used as feedback, force feedback in the machining process is achieved, the machining depth is controlled in real time, and the step of precise aligning is avoided.

Description

Technical Field

[0001] The present invention belongs to the field of tool rest design, and particularly relates to a tool rest for machining a large-range micro-nano structure array by vibration-assisted imprinting and a using method thereof. Background Art

[0002] Micro-structure arrays are widely used in various fields such as aerospace, biomedicine, and optical engineering due to their hydrophilic / hydrophobic properties, friction and wear properties, biocompatibility, and optical properties. Currently, the main micro-structure array processing methods include optical and electron beam lithography, focused ion beam machining, LIGA, etc. However, most of them rely on expensive processing equipment, have a single processing material, and the manufacturing process is also very complex, which limits the development of domestic micro-structure array processing. Although traditional "macro" mechanical manufacturing technologies cannot meet the requirements of micro-structure array processing, the breakthrough of piezoelectric ceramic and sensor technologies has made "micro" mechanical manufacturing possible. Moreover, the processing materials of "micro" mechanical manufacturing are not restricted, and the processed structures are not limited to two-dimensional and quasi-three-dimensional forms, and three-dimensional complex curved surfaces can be processed. Therefore, "micro" mechanical manufacturing has great development potential.

[0003] "Micro" mechanical manufacturing is different from "macro" mechanical manufacturing. At the micro-nano scale, the clamping error of the workpiece and the rotational error of the spindle will seriously affect the processing consistency. Currently, it is mainly solved by manual fine-tuning, servo processing, and coordinate system conversion methods, which greatly limits the processing efficiency. Summary of the Invention

[0004] In order to solve the above problems existing in the background art, the present invention proposes a tool rest for machining a large-range micro-nano structure array by vibration-assisted imprinting and a using method thereof. The tool rest has functions of tool contact detection, real-time trajectory tracking, and large-range processing, supports the processing of indentation array structures, and has the advantages of high efficiency, low cost, flexible processing, and wide use. It has good interchangeability and can form a complete micro-nano structure array processing equipment when paired with a three-dimensional micro-nano displacement workbench.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A tool rest for machining a large-range micro-nano structure array by vibration-assisted imprinting, the mechanical structure components of the tool rest include a Z-axis stepper motor, a bracket, a piezoelectric displacement stage, and a two-dimensional elliptical vibration tool rest;

[0007] The two-dimensional elliptical vibration tool rest includes a flexible hinge base, a pre-tightening bolt, a PZT actuator I, a PZT actuator II, a tool base, a piezoelectric sensing unit, and a diamond tool;

[0008] First, assemble the two-dimensional elliptical vibration tool holder. Symmetrically install PZT actuator 1 and PZT actuator 2 in the limit slots of the tool base, and connect the flexible hinge base and the tool base through pre-tightening bolts; install gaskets above and below the circular piezoelectric sensing unit and fix it to the tool base through the conversion joint screw; fix the diamond tool to the front end of the piezoelectric sensing unit through the tail thread; fix the two-dimensional elliptical vibration tool holder to the piezoelectric displacement stage through bolts, and connect the two-dimensional elliptical vibration tool holder and the Z-axis stepper motor with a bracket.

[0009] A method for using the above tool holder, specifically:

[0010] Step 1: Perform vibration trajectory planning and contact force detection;

[0011] Step 2: Precisely adjust the following parameters during processing, the sample feed speed V sample , the driving voltages V1 and V2 of PZT actuator 1 and PZT actuator 2, the vibration frequency f and the phase difference . First, determine the sample feed speed V sample and the vibration frequency f. The indentation spacing d is calculated by the formula: , and by adjusting the phase difference the speed matching can be achieved. The present invention adopts a method combining simulation and experiment to achieve precise adjustment of the phase difference.

[0012] Furthermore, in Step 2, determine the sample feed speed according to the indentation frequency and indentation spacing, establish a simulation model of elliptical vibration in finite element software, and obtain the reference values of the driving voltage and the phase difference.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1. As an alternative to the force sensor, the circular piezoelectric sensing unit has the characteristics of low cost, simple structure, miniaturization and light weight. Its mass is only 5.6 g, which does not affect the dynamic characteristics and vibration mode of the two-dimensional vibration tool holder. After the signal is amplified, it is calibrated. The measuring range is 10 N and the resolution is 0.01 N;

[0015] 2. Two PZT stacks drive the flexible hinge and the tool to vibrate along an elliptical trajectory. By controlling the waveform, amplitude and phase difference of the input voltage signal, the major axis and minor axis sizes of the elliptical trajectory can be controlled. In the case of 100 Hz and 30° phase difference, the major axis and minor axis of the elliptical trajectory are 9.8 μm and 4.5 μm respectively. Changing the sample feed speed and vibration frequency can adjust the period of the processed microstructure array;

[0016] 3. The processing system includes a piezoelectric displacement stage with a movement range of up to 100 μm. It can use the force signal of the piezoelectric sensing unit as feedback to achieve force feedback during the processing, control the processing depth in real time, and avoid the steps of precise alignment. It can reduce the machining depth difference caused by the clamping error of the sample and the spindle runout;

[0017] 4. During the processing of the indentation microstructure array, a relatively strict speed matching is required to avoid the trailing phenomenon. In the present invention, the vibration frequency of the tool and the feed speed of the sample are matched through simulation and theoretical calculation. After the matching is completed, the indenter structure can be perfectly reproduced on the surface of the sample, avoiding the trailing phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the vibration-assisted machining module device;

[0019] Figure 2 It is a diagram of the elliptical vibration trajectory of the tool;

[0020] Figure 3 It is a schematic diagram of force detection;

[0021] Figure 4 It is a schematic diagram of the large-range indentation array microstructure machining on a plane;

[0022] Figure 5 It is a schematic diagram of the large-range indentation array machining on a cylindrical surface;

[0023] Figure 6 It is a diagram of the vibration-assisted machining module;

[0024] Figure 7 It is the front view of the elliptical vibration-assisted machining module;

[0025] Figure 8 It is the top view of the elliptical vibration-assisted machining module;

[0026] Figure 9 It is the left view of the elliptical vibration-assisted machining module;

[0027] Figure 10 It is a schematic diagram of the tool base;

[0028] Figure 11 It is a schematic diagram of the processing system. DETAILED DESCRIPTION OF THE INVENTION

[0029] The technical solutions of the present invention will be further described below in conjunction with the drawings and embodiments, but it is not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention.

[0030] Embodiment 1

[0031] A tool holder for machining a large - scale micro - nano structure array by vibration - assisted imprinting, as Figure 1 shown, the mechanical structure components of the tool holder include a Z - axis stepper motor 1, a bracket 2, a piezoelectric displacement stage 3, and a two - dimensional elliptical vibration tool holder;

[0032] The two - dimensional elliptical vibration tool holder includes a flexible hinge base 4, a pre - tightening bolt 5, a PZT actuator 1 6, a PZT actuator 2 7, a tool base 8, a piezoelectric sensing unit 9, and a diamond tool 10;

[0033] First, assemble the two - dimensional elliptical vibration tool holder. Symmetrically install the PZT actuator 1 6 and the PZT actuator 2 7 in the limit slots of the tool base 8, and connect the flexible hinge base 4 and the tool base 8 through the pre - tightening bolt 5; The ring - shaped piezoelectric sensing unit 9 is installed with gaskets up and down and fixed to the tool base 8 through a conversion joint screw; The diamond tool 10 is fixed to the front end of the piezoelectric sensing unit 9 through a tail thread; The two - dimensional elliptical vibration tool holder is fixed to the piezoelectric displacement stage 3 through bolts, and the bracket 2 connects the two - dimensional elliptical vibration tool holder and the Z - axis stepper motor 1. As Figure 11 shown, the linear motor 1 13 and the linear motor 2 14 can respectively realize the feeding of the sample in the X and Y directions. When controlling the sample to contact the indenter, the turntable 12 rotates at a certain speed, and the cylindrical surface indentation array machining of the sample 11 can be realized. In Figure 11 , the label 15 represents the array machining tool holder.

[0034] The three - view drawings of the vibration - assisted machining module are as Figures 6 - 9 shown to more detailedly display the design features of the device. When the piezoelectric actuator works, it needs to be pre - tightened, and use a wrench to adjust the Figure 1 pre - tightening bolt 5 in it. The piezoelectric sensing unit also needs to be pre - tightened. The piezoelectric sensing unit is connected to the tool base through bolts, and by adjusting the tightening force of the bolts, the pre - tightening force of the piezoelectric sensing unit can be adjusted. The indenter is connected to the piezoelectric sensing unit in a threaded manner, and different - shaped indenters can be conveniently replaced.

[0035] The working principle, design principles, and specific usage methods of the tool holder are introduced in detail as follows:

[0036] (a) Elliptical trajectory planning and measurement

[0037] The elliptical trajectory of the tool is obtained by the motion synthesis of two piezoelectric actuators, and its working principle is as Figure 2 shown. Changing the initial input Figure 2The voltage amplitudes E1 and E2 and the phase difference Δφ of PZT actuator 1 and PZT actuator 2 control the major and minor axes a and b of the elliptical trajectory. For an elliptical trajectory, it can be regarded as being synthesized by two simple harmonic vibrations with the same frequency and perpendicular vibration directions (the vibration directions are the x and y axes respectively). These two simple harmonic vibrations are described by equations (1) and (2):

[0038] (1)

[0039] (2)

[0040] where A x and A y are the output displacements of the two piezoelectric ceramic stacks respectively, is the phase difference between the two voltage signals, f is the vibration frequency, t is the time; the synthesized elliptical trajectory is described by equation (3):

[0041] (3)

[0042] In the formula, and are the standard vectors in the X and Y directions in the coordinate axes respectively, is the vector of the elliptical trajectory. Further simplification gives the equation of the elliptical trajectory:

[0043] (4)

[0044] Convert the elliptical trajectory into the form of the standard elliptical equation:

[0045] (5)

[0046] The general form of the standard elliptical equation is as follows:

[0047] (6)

[0048] In the formula, A, B, C, D, and E are the coefficients of each term respectively.

[0049] The center point coordinates (h, k) of the ellipse are:

[0050] (7)

[0051] The lengths of the major axis a and the minor axis b are:

[0052] (8)

[0053] (9)

[0054] In summary, by changing the amplitudes E1, E2 of the initial input simple harmonic vibrations and the phase difference Δφ, the major and minor axes a and b of the elliptical trajectory can be controlled. Measure the vibration trajectory of the tool, Figure 2 The vibration trajectory of the tool with Δφ = π / 6 is given.

[0055] (b) Contact force detection and feedback

[0056] Contact force detection is the core innovation of the two-dimensional elliptical vibration tool holder. The principle is based on the piezoelectric effect. When a force is applied to the PZT, a voltage will be generated. This voltage is very weak and can be used as a signal for the cutting depth and cutting force after passing through the voltage amplification module.

[0057] The principle of this function is as Figure 3 shown. When the indenter vibrates along an elliptical trajectory under no-load conditions, the piezoelectric sensing unit detects the vibration signal and outputs a weak voltage signal with a certain frequency f0 and amplitude A0. This voltage signal is input into an oscilloscope after passing through the voltage amplification module, and the vibration mode of the indenter can be detected in real time. At the same time, the stepping motor drives the processing sample closer to the indenter until the indenter contacts the workpiece. At the beginning of the contact, periodic contact occurs between the tip of the indenter and the surface of the sample. The period is related to the frequency of the elliptical vibration. The piezoelectric sensing unit will receive an additional pressure. After separating from the surface, it will return to the no-load vibration mode. Therefore, a series of "spikes" will appear in the signal waveform of the piezoelectric sensing unit. When spikes are observed in the oscilloscope, it indicates that the indenter has contacted the surface of the sample. The greater the protrusion amplitude of the spikes, the greater the cutting depth and contact force. By adjusting the amplification factor of the voltage amplification module, the sensitivity of contact force detection can be controlled, thereby achieving the minimum contact force between the indenter and the workpiece. This function is generally applied to the tool setting process before machining.

[0058] The process of signal acquisition and processing is as follows:

[0059] 1. Amplify the vibration signal of the piezoelectric ceramic and then collect it using a signal acquisition card (signal acquisition module);

[0060] 2. Write code to obtain the amplitude and average value of the vibration signal (signal processing module);

[0061] 3. Use the amplitude as the process variable for PID control, and the output of the PID control is the input voltage of the piezoelectric displacement stage (PID control module);

[0062] 4. After adjusting the PID parameters, the depth control of indentation machining can be achieved.

[0063] During processing, this mechanism uses the force signal of the piezoelectric sensing unit as the displacement feedback of the piezoelectric displacement stage, which can avoid inconsistent processing depths caused by sample clamping errors and spindle runout. The specific implementation measures are as follows: Set the voltage of the sensing unit corresponding to the processing depth. When the processing depth increases, the voltage feedback by the sensing unit increases. When it exceeds the set value, the piezoelectric displacement stage moves in the Figure 4 negative X direction until the feedback voltage equals the set voltage. When the processing depth decreases, the feedback voltage is less than the set voltage, and the piezoelectric displacement stage moves in the Figure 4 positive X direction until the feedback voltage equals the set voltage, which can ensure the consistency of the processing depth.

[0064] (c) Machining of indentation microstructure arrays

[0065] The machining of indentation microstructure arrays is an application after the vibration trajectory planning and contact force detection are completed, and it is also a major feature of this invention. The speed matching principle is shown in the figure. When the indenter vibrates along an elliptical trajectory, its speed can be decomposed into V x parallel to the sample surface and V y perpendicular to the sample surface. The normal speed V y is responsible for completing the machining of the indentation, and the tangential speed V x ensures that the sample can be continuously fed at a certain speed. When the feeding speed of the sample is inconsistent with V x , it will cause the indenter to scratch on the sample surface, resulting in the damage of the processed structure. Therefore, several parameters need to be precisely adjusted during processing: the sample feeding speed V sample , the driving voltages V1 and V2 of PZT actuator 1 and PZT actuator 2, the vibration frequency f, and the phase difference . First, determine the sample feeding speed V sample and the vibration frequency f. The indentation spacing d is calculated by the formula:

[0066]

[0067] By adjusting the phase difference , speed matching can be achieved. This invention uses a combined method of simulation and experiment to achieve precise adjustment of the phase difference. First, determine the sample feeding speed according to the indentation frequency and indentation spacing. Establish a simulation model of elliptical vibration in finite element software to obtain the reference values of the driving voltage and phase difference. Taking the square pyramid indentation array with an indentation spacing of 40 μm as an example, set the sample speed V sample to 40 mm / s and the indentation frequency to 100 Hz. The simulation result is a driving phase difference of 30°. In the experiment, due to installation errors and other problems, after fine-tuning, the determined phase difference is 28.5°. This parameter can be used for large-scale machining of indentation arrays and can well avoid the appearance of trailing phenomena.

Claims

1. A tool holder for machining a large-range micro-nano structure array by vibration-assisted imprinting, characterized in that: The mechanical structure components of the tool rest include a Z-axis stepper motor (1), a bracket (2), a piezoelectric displacement stage (3), and a two-dimensional elliptical vibration tool rest; The two-dimensional elliptical vibration tool rest includes a flexible hinge base (4), a pre-tightening bolt (5), a PZT actuator I (6), a PZT actuator II (7), a tool base (8), a piezoelectric sensing unit (9), and a diamond tool (10); First, assemble the two-dimensional elliptical vibration tool rest. Symmetrically install the PZT actuator I (6) and the PZT actuator II (7) in the limit slots of the tool base (8), and connect the flexible hinge base (4) and the tool base (8) through the pre-tightening bolt (5); Install gaskets above and below the ring-shaped piezoelectric sensing unit (9), and fix it to the tool base (8) through the conversion joint screw; The diamond tool (10) is fixed to the front end of the piezoelectric sensing unit (9) through the tail thread; The two-dimensional elliptical vibration tool rest is fixed to the piezoelectric displacement stage (3) through bolts, and the bracket (2) connects the two-dimensional elliptical vibration tool rest and the Z-axis stepper motor (1).

2. A method for using the tool rest according to claim 1, characterized in that: The method is specifically as follows: Step 1: Perform vibration trajectory planning and contact force detection; Step 2: Precisely adjust the following parameters during processing: the sample feed rate V sample , the driving voltages V1 and V2 of PZT actuator 1 and PZT actuator 2, the vibration frequency f, and the phase difference ; First, determine the sample feed rate V sample and the vibration frequency f. The indentation spacing d is calculated by the formula: . By adjusting the phase difference , speed matching can be achieved. The present invention uses a combined method of simulation and experiment to achieve precise adjustment of the phase difference.

3. The method of use according to claim 2, wherein: In Step 2, determine the sample feed speed according to the indentation frequency and indentation spacing, establish a simulation model of elliptical vibration in finite element software, and obtain the reference values of the driving voltage and phase difference.

Images