A longitudinal-torsional composite ultrasonic vibration polishing system and method based on a milling and grinding machine tool

Abstract

The present application relates to optical element surface polishing system and method, specifically relates to a kind of longitudinal torsion compound ultrasonic vibration polishing system and method based on milling and grinding machine tool, solve the technical problem that it is difficult to guarantee the consistency and control precision of optical element surface material removal using milling and grinding machine tool to polish optical element.The present application integrates modular longitudinal torsion compound ultrasonic vibration tool holder in milling and grinding machine tool spindle, introduces longitudinal torsion compound ultrasonic vibration into the polishing process of milling and grinding machine tool, realizes the fine controllability of optical element surface material removal in polishing process by adjusting ultrasonic vibration parameters, improves the consistency and control precision of optical element surface material removal.Meanwhile, polishing tool is integrated on the modular longitudinal torsion compound ultrasonic vibration tool holder, without modifying the structure of milling and grinding machine tool, polishing of optical element with complex surface can be completed, so as to build the integrated process flow of milling and grinding machine tool from milling and grinding forming to longitudinal torsion compound ultrasonic vibration polishing continuous connection.

Description

TECHNICAL FIELD

[0001] The present application relates to an optical element surface polishing system and method, in particular to a longitudinal-torsional composite ultrasonic vibration polishing system and method based on a milling and grinding machine tool. BACKGROUND

[0002] With the increasing requirements of modern optical systems on performance and precision, optical elements with complex surfaces such as aspheric surfaces and free-form surfaces are widely used in aerospace, lasers and precision imaging systems. In order to achieve the required nanometer-level surface accuracy and nanometer-level surface roughness of optical elements, high-precision polishing technology must be further introduced after milling and grinding forming for finishing.

[0003] Traditional high-precision polishing technology usually relies on special equipment platforms such as numerical control polishing machine tools and magnetorheological polishing systems. Although these special equipment platforms have good polishing ability, they have problems such as complex structure, strong system independence, high procurement cost and difficulty in integrating with existing milling and grinding forming process chain, which limits their promotion and application in general milling and grinding forming environment. Especially in industrial production scenarios, it is difficult to ensure the process continuity from milling and grinding forming to polishing, increasing the risk of process conversion and clamping error.

[0004] In contrast, the milling and grinding machine tool, as a widely used basic machining platform, has good motion control precision and open control interface, and is an important carrier for realizing polishing function integration and process chain simplification. However, direct use of the milling and grinding machine tool for high-precision polishing of optical elements still faces certain challenges, such as high tool rigidity, insufficient flexible contact mechanism, different process algorithms for milling and grinding forming and polishing, etc., which limits the fine controllability of optical element surface material removal during polishing, especially in dealing with complex curvature variation regions such as free-form surfaces, there is still room for improvement in the consistency and control accuracy of optical element surface material removal. SUMMARY

[0005] The purpose of the present application is to solve the technical problem that the consistency and control accuracy of optical element surface material removal cannot be guaranteed when using a milling and grinding machine tool for polishing, and to provide a longitudinal-torsional composite ultrasonic vibration polishing system and method based on a milling and grinding machine tool.

[0006] To achieve the above purpose, the present application adopts the following technical solutions:

[0007] A longitudinal-torsional composite ultrasonic vibration polishing system based on a milling and grinding machine tool, characterized in that it comprises a milling and grinding machine tool, a modular longitudinal-torsional composite ultrasonic vibration tool holder integrated with the main shaft of the milling and grinding machine tool through a standard main shaft interface, a polishing tool installed on the modular longitudinal-torsional composite ultrasonic vibration tool holder, and an ultrasonic power supply, a vibration controller and a machine tool numerical control module.

[0008] The output end of the machine tool numerical control module is connected with the control end of the milling and grinding machine tool and the input end of the vibration controller respectively, for controlling the polishing track and the feeding speed of the milling and grinding machine tool spindle, and sending the ultrasonic vibration parameters to the vibration controller;

[0009] The power supply end of the vibration controller is connected with the output end of the ultrasonic power supply, and the output end is connected with the control end of the modular longitudinal-torsional composite ultrasonic vibration tool holder, for driving the modular longitudinal-torsional composite ultrasonic vibration tool holder to generate longitudinal-torsional composite ultrasonic vibration; the longitudinal-torsional composite ultrasonic vibration is composed of longitudinal ultrasonic vibration and torsional ultrasonic vibration; the polishing tool is used for polishing the optical element to be processed according to the polishing track and the feeding speed under the longitudinal-torsional composite ultrasonic vibration.

[0010] Further, the standard spindle interface is an HSK63A type taper quick-change interface.

[0011] Further, the polishing tool is a wheel type polishing tool, a spherical polishing tool or a semi-spherical polishing tool, and the material thereof is an elastic material.

[0012] Further, the radial constant load of the polishing tool is 10N-30N.

[0013] The application further provides a longitudinal-torsional composite ultrasonic vibration polishing method based on a milling and grinding machine tool, which adopts the above-mentioned longitudinal-torsional composite ultrasonic vibration polishing system based on a milling and grinding machine tool, and the speciality thereof lies in comprising the following steps:

[0014] Step 1, detecting the surface shape of the optical element to be processed to obtain the actual surface shape, then obtaining the surface shape error distribution between the actual surface shape and the target theoretical surface shape, and determining the two-dimensional removal amount distribution according to the surface shape error distribution;

[0015] Step 2, selecting a regular polishing path and determining the track density distribution of the regular polishing path based on the two-dimensional removal amount distribution and the process parameters of the milling and grinding machine tool to obtain the polishing path; then combining the path boundary constraint and the speed smoothing strategy to optimize the polishing path to obtain the polishing track;

[0016] Step 3, determining the ultrasonic vibration parameter boundary by adopting a stepwise parameter adjustment strategy based on the two-dimensional removal amount distribution; then determining the unit removal function under different ultrasonic vibration parameters under the constraint of the ultrasonic vibration parameter boundary;

[0017] Step 4, constructing an ultrasonic vibration parameter adjustment model to determine the ultrasonic vibration parameter grade corresponding to the surface shape error; then determining the ultrasonic vibration parameter distribution corresponding to the two-dimensional removal amount distribution according to the ultrasonic vibration parameter adjustment model under the constraint of the ultrasonic vibration parameter boundary;

[0018] Step 5: Based on the two-dimensional removal amount distribution, the unit removal function under different ultrasonic vibration parameters, and the ultrasonic vibration parameter distribution, the residence time distribution corresponding to the polishing trajectory is calculated by the pulse iteration method, and then the residence time distribution is converted into the feed rate distribution.

[0019] Step 6: Turn on the ultrasonic power supply, input the polishing trajectory, feed speed distribution and ultrasonic vibration parameter distribution into the machine tool CNC module for data conversion, and then the machine tool CNC module transmits the converted polishing trajectory and feed speed distribution to the milling machine tool, and transmits the converted ultrasonic vibration parameter distribution to the vibration controller;

[0020] Step 7: The milling machine tool controls the spindle to move according to the polishing trajectory and feed speed distribution, thereby driving the modular longitudinal torsion composite ultrasonic vibration tool holder to move. At the same time, the vibration controller controls the modular longitudinal torsion composite ultrasonic vibration tool holder to generate longitudinal torsion composite ultrasonic vibration with different ultrasonic vibration parameters according to the ultrasonic vibration parameter distribution, so that the polishing tool polishes the optical element to be processed according to the polishing trajectory and feed speed distribution under longitudinal torsion composite ultrasonic vibration with different ultrasonic vibration parameters.

[0021] Step 8: Perform surface shape detection on the polished optical element to be processed to obtain the actual surface shape after polishing. Obtain the surface shape error distribution between the actual surface shape after polishing and the target theoretical surface shape to obtain the residual surface shape error distribution. Determine whether the residual surface shape error distribution meets the preset accuracy requirements. If yes, the polishing of the optical element to be processed is completed; if not, determine the residual two-dimensional removal amount distribution based on the residual surface shape error distribution, and then use it as the two-dimensional removal amount distribution, and return to step 5.

[0022] Furthermore, in step 3, the ultrasonic vibration parameter boundary includes the ultrasonic vibration amplitude boundary;

[0023] In step 4, the ultrasonic vibration parameter adjustment model includes an ultrasonic vibration amplitude adjustment model, which is as follows:

[0024]

[0025]

[0026] Furthermore, the ultrasonic vibration amplitude satisfies the following condition:

[0027]

[0028]

[0029] in, , The amplitude distributions of longitudinal ultrasonic vibration and torsional ultrasonic vibration are represented respectively; x and y are the X-axis and Y-axis coordinates of the polishing point in the polishing trajectory, respectively. , respectively minimum amplitude, maximum amplitude of longitudinal ultrasonic vibration, , respectively minimum amplitude, maximum amplitude of torsional ultrasonic vibration; is a surface shape error distribution, is a maximum surface shape error; , respectively response sensitivity index of longitudinal ultrasonic vibration, torsional ultrasonic vibration, both of which are greater than 0.

[0030] Further, in step 5, the residence time distribution is calculated by the following formula:

[0031]

[0032] wherein, is a two-dimensional removal distribution, is a unit removal function, is a residence time distribution.

[0033] Further, in step 2, the regular polishing path is a grid type or spiral type trajectory.

[0034] Further, in step 3, the unit removal function is determined by a dot test method or a database matching method.

[0035] Further, in step 1, surface shape detection is performed by using a three-coordinate measuring device, a zygo laser interferometer or a luphoscan measuring device.

[0036] Compared with the prior art, the present application has the beneficial effects as follows:

[0037] 1. The longitudinal-torsional composite ultrasonic vibration polishing system based on a milling and grinding machine tool provided by the present application realizes fine and controllable removal of surface material of an optical element to be processed in a polishing process by integrating a modular longitudinal-torsional composite ultrasonic vibration tool holder into a main shaft of the milling and grinding machine tool, introducing longitudinal-torsional composite ultrasonic vibration into the polishing process of the milling and grinding machine tool, and adjusting ultrasonic vibration parameters, and improves consistency and control precision of surface material removal of the optical element to be processed.

[0038] 2. The longitudinal-torsional composite ultrasonic vibration polishing system based on a milling and grinding machine tool provided by the present application integrates a modular longitudinal-torsional composite ultrasonic vibration tool holder into a main shaft of the milling and grinding machine tool, and integrates a polishing tool on the modular longitudinal-torsional composite ultrasonic vibration tool holder, so that polishing of an optical element with nanoscale surface shape precision can be completed without modification of the structure of the milling and grinding machine tool, thereby constructing an integrated process flow of the milling and grinding machine tool from milling and grinding forming to longitudinal-torsional composite ultrasonic vibration polishing continuous connection, and giving consideration to system compatibility, machining precision and engineering implementability.

[0039] 3. The longitudinal-torsional composite ultrasonic vibration polishing system based on a milling and grinding machine tool according to the present application has a polishing tool radial constant load of 10N-30N, which can ensure that the polishing tool is in stable contact with the surface of the optical element to be processed within the polishing track range, so as to improve the consistency of the surface material removal of the optical element to be processed in the polishing process, thereby improving the polishing precision;

[0040] 4. The longitudinal-torsional composite ultrasonic vibration polishing method based on a milling and grinding machine tool according to the present application combines polishing path planning, pulse iteration method and feed speed distribution control strategy to realize the synergistic coupling of longitudinal-torsional composite ultrasonic vibration, polishing track and feed speed, so as to significantly improve the instantaneous material removal behavior, enhance the polishing track disturbance and spatial coverage ability, thereby improving the polishing efficiency and the surface shape precision and roughness control ability of the optical element to be processed, and the method can be applied to the precision polishing of hard and brittle optical elements with complex surfaces such as plane, aspherical surface and free-form surface.

[0041] 5. The longitudinal-torsional composite ultrasonic vibration polishing method based on a milling and grinding machine tool according to the present application adjusts the polishing track and feed speed of the polishing tool based on two-dimensional removal amount distribution, so as to improve the consistency of the surface material removal of the optical element to be processed and the processing precision, thereby improving the polishing precision.

[0042] 6. The longitudinal-torsional composite ultrasonic vibration polishing method based on a milling and grinding machine tool according to the present application inputs the polishing track, feed speed distribution and ultrasonic vibration amplitude distribution into the machine tool numerical control module, and then transmits the ultrasonic vibration amplitude distribution to the vibration controller through the machine tool numerical control module, so as to realize the synergistic control of polishing track execution, feed speed and longitudinal-torsional composite ultrasonic vibration loading, and ensure the synergistic coupling of the polishing track, feed speed and longitudinal-torsional composite ultrasonic vibration in the polishing process. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 FIG. 1 is a structural schematic diagram of a longitudinal-torsional composite ultrasonic vibration polishing system based on a milling and grinding machine tool according to an embodiment of the present application;

[0044] Figure 2 FIG. 2 is a flowchart of a longitudinal-torsional composite ultrasonic vibration polishing method based on a milling and grinding machine tool according to an embodiment of the present application;

[0045] Figure 3 FIG. 3 is a surface shape error comparison diagram before and after polishing by using a traditional milling and grinding machine tool, wherein (a) is the surface shape error before polishing, and (b) is the surface shape error after polishing;

[0046] Figure 4 FIG. 4 is a surface shape error comparison diagram before and after polishing by using an embodiment of the present application, wherein (a) is the surface shape error before polishing, and (b) is the surface shape error after polishing. DETAILED DESCRIPTION

[0047] The longitudinal-torsional composite ultrasonic vibration polishing system and method based on a milling and grinding machine tool will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application, and are not intended to limit the protection scope of the present application.

[0048] A longitudinal-torsional composite ultrasonic vibration polishing system based on a milling and grinding machine tool, as shown in the accompanying drawings, comprises a milling and grinding machine tool, a modular longitudinal-torsional composite ultrasonic vibration tool holder integrated with the spindle of the milling and grinding machine tool through a standard spindle interface, a polishing tool mounted on the modular longitudinal-torsional composite ultrasonic vibration tool holder, and an ultrasonic power supply, a vibration controller and a machine tool numerical control module. Figure 1

[0049] The output end of the machine tool numerical control module is connected with the control end of the milling and grinding machine tool and the input end of the vibration controller, respectively, for controlling the polishing trajectory and the feed speed of the milling and grinding machine tool spindle and sending the ultrasonic vibration parameters to the vibration controller. The power supply end of the vibration controller is connected with the output end of the ultrasonic power supply, and the output end is connected with the control end of the modular longitudinal-torsional composite ultrasonic vibration tool holder, for driving the modular longitudinal-torsional composite ultrasonic vibration tool holder to generate longitudinal-torsional composite ultrasonic vibration, wherein the longitudinal-torsional composite ultrasonic vibration is composed of longitudinal ultrasonic vibration and torsional ultrasonic vibration. The polishing tool is used to polish the optical element to be processed according to the polishing trajectory and the feed speed under the longitudinal-torsional composite ultrasonic vibration.

[0050] The modular longitudinal-torsional composite ultrasonic vibration tool holder is a commercial integrated tool holder, which has independent longitudinal vibration channels and torsional vibration channels. The standard spindle interface is an HSK63A taper quick-change interface, which can realize high-rigidity and high-precision longitudinal-torsional composite ultrasonic vibration transmission. The polishing tool is a wheel-type polishing tool, a spherical polishing tool or a semi-spherical polishing tool, and the material thereof is an elastic material, and the radial constant load is 10N-30N.

[0051] The ultrasonic vibration assisted polishing technology can reduce the cutting resistance, improve the material response and enhance the material removal consistency. The longitudinal-torsional composite ultrasonic vibration adopted in the present embodiment can significantly improve the instantaneous contact state of the polishing tool and the optical element to be processed by introducing ultrasonic vibration in the longitudinal and torsional directions, form a high-frequency composite trajectory on the surface of the optical element to be processed, and improve the quality of the surface of the optical element to be processed and the material removal consistency. Meanwhile, the modular longitudinal-torsional composite ultrasonic vibration tool holder is integrated with the milling and grinding machine tool spindle through the standard spindle interface, without the need to change the original spindle structure, thereby ensuring the integrity and stability of the milling and grinding machine tool.

[0052] The present embodiment also provides a longitudinal-torsional composite ultrasonic vibration polishing method based on a milling and grinding machine tool, which adopts the above-mentioned longitudinal-torsional composite ultrasonic vibration polishing system based on a milling and grinding machine tool.​Figure 2 as shown, comprising the following steps:

[0053] Step 1, using a three-coordinate measuring device, a zygo laser interferometer or a luphoscan measuring device, the surface shape of the optical element to be processed is detected to obtain the actual surface shape; then the surface shape error distribution between the actual surface shape and the target theoretical surface shape is obtained, and the two-dimensional removal amount distribution is determined accordingly.

[0054] Step 2, based on the two-dimensional removal amount distribution and the process parameters of the milling and grinding machine tool, a regular polishing path is selected and its trajectory density distribution is determined to obtain the polishing path; then the polishing path is optimized by combining the path boundary constraint and the speed smoothing strategy to obtain the polishing trajectory. The regular polishing path is a grid type or a spiral type trajectory.

[0055] In step 2, the polishing path is optimized by using the path boundary constraint and the speed smoothing strategy, which can ensure the continuity and collision-free of the obtained polishing trajectory.

[0056] Step 3, based on the two-dimensional removal amount distribution, a stepwise parameter adjustment strategy is used to determine the ultrasonic vibration parameter boundary; then under the constraint of the ultrasonic vibration parameter boundary, the unit removal function under different ultrasonic vibration parameters is determined. The ultrasonic vibration parameters include ultrasonic vibration amplitude, frequency and phase. In this embodiment, the ultrasonic vibration parameters include ultrasonic vibration amplitude, and accordingly, the ultrasonic vibration amplitude boundary and the unit removal function under different ultrasonic vibration amplitudes are obtained.

[0057] In step 3, the unit removal function is determined by the dot test method or the database matching method, which can adapt to the removal characteristics under different materials and working conditions.

[0058] The dot test method specifically includes: under the set process parameters including speed, ultrasonic vibration amplitude, radial constant load, performing local dot test, measuring the removal depth of the material per unit time, and constructing a spatial removal response model of the polishing tool under the set process parameters to obtain the unit removal function.

[0059] The database matching method specifically includes: establishing a database of typical process parameters and corresponding removal functions, matching the closest removal function under different ultrasonic vibration amplitudes according to the process parameters of the milling and grinding machine tool to obtain the unit removal function. The database matching method can quickly realize the coupling of the process parameters and the unit removal function.

[0060] Step 4, constructing an ultrasonic vibration amplitude adjustment model to determine the ultrasonic vibration amplitude level corresponding to the surface shape error; then according to the ultrasonic vibration amplitude adjustment model, the ultrasonic vibration amplitude distribution corresponding to the two-dimensional removal amount distribution is determined under the constraint of the ultrasonic vibration amplitude boundary. The ultrasonic vibration amplitude adjustment model is:

[0061]

[0062]

[0063] And, when the ultrasonic vibration amplitude exceeds the maximum amplitude, take the maximum amplitude; when the ultrasonic vibration amplitude is lower than the minimum amplitude, take the minimum amplitude; when it is within the allowable range, keep the original value. That is, the ultrasonic vibration amplitude needs to meet the following conditions:

[0064]

[0065]

[0066] Wherein, , respectively are the amplitude distribution of longitudinal ultrasonic vibration, torsional ultrasonic vibration; x, y respectively are the X-axis, Y-axis coordinates of the polishing point in the polishing track; , respectively are the minimum amplitude, maximum amplitude of longitudinal ultrasonic vibration, , respectively are the minimum amplitude, maximum amplitude of torsional ultrasonic vibration; is the surface error distribution, is the maximum surface error; , respectively are the response sensitivity index of longitudinal ultrasonic vibration, torsional ultrasonic vibration, both of which are 1-2.

[0067] In this embodiment, = 6μm, = 6μm; =0.5μm, =0.5μm. Set the error threshold , when , let , , to avoid over-polishing in the low error area.

[0068] Step 5, based on the two-dimensional removal distribution, the unit removal function under different ultrasonic vibration amplitudes and the ultrasonic vibration amplitude distribution, the residence time distribution corresponding to the polishing track is calculated by pulse iteration method, and then the residence time distribution is converted into the feed speed distribution. Wherein, the residence time distribution is calculated by the following formula:

[0069]

[0070] Wherein, is the two-dimensional removal distribution, is the unit removal function, is the residence time distribution.

[0071] Step 6, turn on the ultrasonic power supply, input the polishing trajectory, feed speed distribution and ultrasonic vibration amplitude distribution into the machine tool numerical control module for data conversion, then the machine tool numerical control module transmits the converted polishing trajectory and feed speed distribution to the milling and grinding machine, and transmits the converted ultrasonic vibration amplitude distribution to the vibration controller.

[0072] Step 7, the milling and grinding machine control spindle moves according to the polishing trajectory and feed speed distribution, thereby driving the modular longitudinal-torsional composite ultrasonic vibration tool holder to move, at the same time, the vibration controller controls the modular longitudinal-torsional composite ultrasonic vibration tool holder to generate longitudinal-torsional composite ultrasonic vibration with different ultrasonic vibration amplitudes according to the ultrasonic vibration amplitude distribution, so that the polishing tool polishes the optical element to be processed according to the polishing trajectory and feed speed distribution under the longitudinal-torsional composite ultrasonic vibration with different ultrasonic vibration amplitudes.

[0073] Step 8, the surface shape of the polished optical element to be processed is detected to obtain the actual surface shape after polishing, the surface shape error distribution between the actual surface shape after polishing and the target theoretical surface shape is obtained, the residual surface shape error distribution is obtained, and it is judged whether the residual surface shape error distribution meets the preset accuracy requirement. If yes, the polishing of the optical element to be processed is completed; if no, the residual two-dimensional removal amount distribution is determined according to the residual surface shape error distribution, which is then taken as the two-dimensional removal amount distribution, and the step 5 is returned.

[0074] In this embodiment, the ultrasonic vibration amplitude is dynamically adjusted according to the two-dimensional removal amount distribution or the polishing stage, which can improve the ultrasonic vibration energy coupling efficiency and polishing adaptability.

[0075] In this embodiment, the modular longitudinal-torsional composite ultrasonic vibration tool holder is directly integrated into the milling and grinding machine spindle through the standard spindle interface, without the need to modify the original equipment structure, so that the function of the milling and grinding machine can be expanded. By introducing longitudinal-torsional composite ultrasonic vibration, in-situ polishing of the optical element to be processed after milling and grinding forming is realized, and combined with the path planning and feed speed control strategy, the polishing of the optical element with complex surface to nanometer level surface shape precision can be completed, taking into account the system compatibility, machining precision and engineering implementability. This embodiment can polish planar optical elements and optical elements with complex surfaces such as aspheric surfaces and free-form surfaces, and can polish optical elements of hard and brittle materials such as fused quartz and sapphire.

[0076] In order to verify the beneficial effects of this embodiment, a fused quartz planar optical test piece with a diameter of 40 mm and a thickness of 10 mm is selected as the optical element to be processed, and the milling and grinding machine used is AGM1600 numerical control milling and grinding machine.

[0077] Firstly, the AGM1600 numerical control milling and grinding machine is used to polish the optical element to be processed, as shown in FIG. 6. Figure 3As shown in the figure, the surface error of the optical element to be processed before and after polishing, wherein the polishing time is about 60 min, the surface error RMS (Root Mean Square Roughness) is reduced from 94.5 nm to 10.5 nm, and the convergence rate is about 88.9%.

[0078] Then, according to the longitudinal-torsional composite ultrasonic vibration polishing system based on the milling and grinding machine provided in the embodiment, through the HSK63A taper quick-change interface, the modular longitudinal-torsional composite ultrasonic vibration tool holder is integrated on the spindle of the AGM1600 numerical control milling and grinding machine, and the longitudinal and torsional ultrasonic transducers are integrated in the modular longitudinal-torsional composite ultrasonic vibration tool holder, wherein the frequency of the longitudinal ultrasonic vibration is 20 kHz, and the frequency of the torsional ultrasonic vibration is 20 kHz. The polishing tool adopts an elastic wheel type polishing head, the material is damping cloth, and the rotating speed of the polishing tool is set to 75 rpm and the pressure depth is 0.06 mm. The optical element to be processed is polished by using the longitudinal-torsional composite ultrasonic vibration polishing method based on the milling and grinding machine provided in the embodiment, as shown in the figure Figure 4 As shown in the figure, the surface error of the optical element to be processed before and after polishing, wherein the polishing time is about 60 min, the surface error RMS (Root Mean Square Roughness) is reduced from 94.5 nm to 10.5 nm, and the convergence rate is about 88.9%.

[0079] Therefore, the embodiment not only realizes better surface precision and higher convergence rate, but also effectively shortens the polishing time, has significant advantages in improving material removal efficiency and surface error suppression ability, can realize higher surface material removal consistency and control precision, and has good engineering application prospect.

[0080] The longitudinal-torsional composite ultrasonic vibration polishing system and method based on the milling and grinding machine provided in the embodiment make full use of the modular longitudinal-torsional composite ultrasonic vibration tool holder, integrate the longitudinal-torsional composite ultrasonic vibration into the traditional milling and grinding machine, realize efficient and flexible micro material removal control without changing the structure of the milling and grinding machine. At the same time, through the pulse iteration method combined with the feed speed control strategy, the polishing process has higher trajectory uniformity and surface error convergence ability. Tests show that compared with the traditional milling and grinding machine polishing, the embodiment can effectively shorten the processing time while ensuring higher surface precision, has significant efficiency advantages and application value, provides a reliable technical path for high-quality, low-cost and high-adaptability polishing of hard and brittle optical elements, realizes in-situ composite machining of milling and polishing processes, saves equipment resources, has good popularization prospect and engineering practicability.

Claims

1. A longitudinal-torsional composite ultrasonic vibration polishing method based on a milling machine tool, characterized in that, Includes the following steps: Step 1: Perform surface shape detection on the optical element to be processed to obtain the actual surface shape; then obtain the surface shape error distribution between the actual surface shape and the target theoretical surface shape, and determine the two-dimensional removal amount distribution accordingly; Step 2: Based on the two-dimensional removal amount distribution and the process parameters of the milling machine, select a regular polishing path and determine its trajectory density distribution to obtain the polishing path; then, combine the path boundary constraints and speed smoothing strategy to optimize the polishing path and obtain the polishing trajectory. Step 3: Based on the two-dimensional removal amount distribution, a step-by-step parameter adjustment strategy is adopted to determine the ultrasonic vibration parameter boundary; then, under the constraint of the ultrasonic vibration parameter boundary, the unit removal function under different ultrasonic vibration parameters is determined; the ultrasonic vibration parameter boundary includes the ultrasonic vibration amplitude boundary. Step 4: Construct an ultrasonic vibration parameter adjustment model to determine the ultrasonic vibration parameter level corresponding to the surface shape error; then, based on the ultrasonic vibration parameter adjustment model, determine the ultrasonic vibration parameter distribution corresponding to the two-dimensional removal amount distribution under the boundary constraints of the ultrasonic vibration parameters. The ultrasonic vibration parameter adjustment model includes an ultrasonic vibration amplitude adjustment model, which is as follows: Furthermore, the ultrasonic vibration amplitude satisfies the following condition: Among them, A z(x,y) A t(x,y) The amplitude distributions of longitudinal ultrasonic vibration and torsional ultrasonic vibration are represented respectively; x and y are the X-axis and Y-axis coordinates of the polishing point in the polishing trajectory, respectively. These represent the minimum and maximum amplitudes of longitudinal ultrasonic vibration, respectively. These represent the minimum and maximum amplitudes of the torsional ultrasonic vibration, respectively; E(x,y) is the surface shape error distribution, E max The maximum surface shape error; alpha z alpha t These are the response sensitivity indices for longitudinal ultrasonic vibration and torsional ultrasonic vibration, respectively, both of which have values ​​greater than 0. Step 5: Based on the two-dimensional removal amount distribution, the unit removal function under different ultrasonic vibration parameters, and the ultrasonic vibration parameter distribution, the residence time distribution corresponding to the polishing trajectory is calculated using the pulse iteration method. Then, the residence time distribution is converted into a feed rate distribution. The residence time distribution is calculated using the following formula: R(x,y)=H(x,y)*T(x,y) Where R(x,y) is the two-dimensional removal amount distribution, H(x,y) is the unit removal function, and T(x,y) is the residence time distribution; Step 6: Turn on the ultrasonic power supply, input the polishing trajectory, feed speed distribution and ultrasonic vibration parameter distribution into the machine tool CNC module for data conversion, and then the machine tool CNC module transmits the converted polishing trajectory and feed speed distribution to the milling machine tool, and transmits the converted ultrasonic vibration parameter distribution to the vibration controller; Step 7: The milling machine tool controls the spindle to move according to the polishing trajectory and feed speed distribution, thereby driving the modular longitudinal torsion composite ultrasonic vibration tool holder to move. At the same time, the vibration controller controls the modular longitudinal torsion composite ultrasonic vibration tool holder to generate longitudinal torsion composite ultrasonic vibration with different ultrasonic vibration parameters according to the ultrasonic vibration parameter distribution, so that the polishing tool polishes the optical element to be processed according to the polishing trajectory and feed speed distribution under longitudinal torsion composite ultrasonic vibration with different ultrasonic vibration parameters. Step 8: Perform surface shape detection on the polished optical element to be processed to obtain the actual surface shape after polishing. Obtain the surface shape error distribution between the actual surface shape after polishing and the target theoretical surface shape to obtain the residual surface shape error distribution. Determine whether the residual surface shape error distribution meets the preset accuracy requirements. If yes, the polishing of the optical element to be processed is completed; if not, determine the residual two-dimensional removal amount distribution based on the residual surface shape error distribution, and then use it as the two-dimensional removal amount distribution, and return to step 5.

2. The longitudinal-torsional composite ultrasonic vibration polishing method based on a milling machine tool according to claim 1, characterized in that: In step 2, the regular polishing path is a grid-type or spiral trajectory.

3. The longitudinal-torsional composite ultrasonic vibration polishing method based on a milling machine tool according to claim 2, characterized in that: In step 3, the unit removal function is determined by a dot-matrix test method or a database matching method.

4. The longitudinal-torsional composite ultrasonic vibration polishing method based on a milling machine tool according to claim 3, characterized in that: In step 1, a coordinate measuring machine, a Zygo laser interferometer, or a Luphoscan measuring machine is used for surface shape detection.

5. A longitudinal-torsional composite ultrasonic vibration polishing method based on a milling machine tool according to any one of claims 1-4, characterized in that: The polishing system used includes a milling machine, a modular longitudinal-torsional composite ultrasonic vibration tool holder integrated into the spindle of the milling machine through a standard spindle interface, a polishing tool mounted on the modular longitudinal-torsional composite ultrasonic vibration tool holder, as well as an ultrasonic power supply, a vibration controller and a machine tool CNC module. The output end of the CNC module of the machine tool is connected to the control end of the milling machine tool and the input end of the vibration controller, respectively, and is used to control the polishing trajectory and feed speed of the milling machine tool spindle, as well as send ultrasonic vibration parameters to the vibration controller; The power supply terminal of the vibration controller is connected to the output terminal of the ultrasonic power supply, and the output terminal is connected to the control terminal of the modular longitudinal-torsional composite ultrasonic vibration tool holder, which is used to drive the modular longitudinal-torsional composite ultrasonic vibration tool holder to generate longitudinal-torsional composite ultrasonic vibration; the longitudinal-torsional composite ultrasonic vibration is composed of longitudinal ultrasonic vibration and torsional ultrasonic vibration. The polishing tool is used to polish the optical components to be processed according to the polishing trajectory and feed speed under longitudinal-torsional combined ultrasonic vibration.

6. The longitudinal-torsional composite ultrasonic vibration polishing method based on a milling machine tool according to claim 5, characterized in that: The standard spindle interface is an HSK63A type tapered quick-change interface.

7. The longitudinal-torsional composite ultrasonic vibration polishing method based on a milling machine tool according to claim 6, characterized in that: The polishing tool is a wheel polishing tool, a spherical polishing tool, or a hemispherical polishing tool, and its material is an elastic material.

8. The longitudinal-torsional composite ultrasonic vibration polishing method based on a milling machine tool according to claim 7, characterized in that: The radial constant load of the polishing tool is 10N-30N.

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