An ultra-precision machining method based on laser-assisted roll control

Abstract

The application discloses a kind of based on laser auxiliary roll control's ultra-precision machining method, comprising the following steps: first, according to workpiece material, determine expected modification layer crystal structure and thickness using simulation and system experiment method;Second, use laser auxiliary roll method to carry out traversal modification treatment to workpiece surface;Third, use ultra-precision machining method to the material after laser auxiliary roll modification is carried out ultra-precision forming processing;Fourth, use laser auxiliary roll method to the surface of ultra-precision machining is carried out finishing polishing processing.The ultra-precision machining method based on laser auxiliary roll control provided in the present application, in the front process of ultra-precision machining, based on laser auxiliary roll, the workability of workpiece material can be improved in advance, by controlling laser and roll parameters of laser auxiliary roll, the amorphous proportion of modification layer to be machined, the polycrystalline grain refinement scale and the modification layer thickness are flexibly regulated.

Description

Technical Field

[0001] This invention belongs to the field of surface modification treatment and ultra-precision machining and manufacturing technology, specifically relating to an ultra-precision machining method based on laser-assisted rolling control. Background Technology

[0002] Optical components have been widely used in consumer electronics, communications, remote sensing, and national defense in recent years, and ultra-precision machining is the main method for realizing the industrial production of optical components. However, due to the poor machinability of some difficult-to-machine materials, traditional ultra-precision machining methods cannot directly meet production requirements. For example, brittle materials such as polycrystalline zinc selenide are prone to fragmentation under mechanical forces, and the large differences in machinability between polycrystalline grains and the obvious grain boundary effect make it easy for grains on the machined surface to cleave and peel off during traditional ultra-precision cutting, and some grains are prone to local fragmentation, limiting the uniformity of the machined surface. On the other hand, even if plastic surface processing is achieved through ultra-precision cutting and other methods, the periodic tool marks introduced by machining still severely limit the functional surface properties. For example, soft metals such as pure lead have a strong tendency for plastic flow, resulting in obvious cutting side flow, and the built-up edge of the tool severely limits the quality of ultra-precision optical machining. While polishing can remove defects and eliminate periodic tool marks, achieving a uniform and flat optical surface, it inevitably affects processing efficiency and surface accuracy. Furthermore, for some micro / nano structures that cannot be polished, it directly limits the surface quality. Therefore, for difficult-to-machine materials where ideal surface quality is hard to achieve, it is necessary to explore new auxiliary processing techniques based on existing ultra-precision machining methods to further improve surface finish.

[0003] Laser-assisted rolling is an effective method for refining surface grains, locally modifying amorphous materials, and controlling surface stress. It utilizes laser heating of the rolling area to effectively excite dislocations within the material, achieving a more ideal rolling control effect and significantly improving the material's machinability. Currently, no researchers have systematically applied laser-assisted rolling to the modification and control of workpiece materials in ultra-precision machining. On the other hand, rolling is an ideal means of achieving a smooth finish on precision-machined workpieces, effectively eliminating cutting marks. Furthermore, some researchers have shown that cutting marks can be significantly eliminated after laser irradiation, but no studies have yet combined laser and rolling in the smoothing and polishing of ultra-precision machined surfaces. This patent analysis suggests that laser-assisted rolling can, on the one hand, control the machinability of difficult-to-machine materials, providing good pre-modification support for traditional ultra-precision machining; on the other hand, it also offers a new and effective solution for eliminating periodic tool marks on the surface of ultra-precision machining. In conclusion, there is an urgent need to develop an ultra-precision composite machining process based on laser-assisted rolling control to further improve the surface quality of difficult-to-machine materials. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems and provide an ultra-precision machining method based on laser-assisted rolling control that can effectively improve the surface quality and subsurface integrity of difficult-to-machine materials and eliminate or save time occupied by some polishing processes.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: an ultra-precision machining method based on laser-assisted rolling control, comprising the following steps:

[0006] S1. Determine the expected crystalline structure and thickness of the modified layer based on the workpiece material using simulation and system experimental methods;

[0007] S2. Use laser-assisted rolling to perform traverse modification treatment on the surface of the workpiece;

[0008] S3. Using ultra-precision machining methods to perform ultra-precision forming processing on materials modified by laser-assisted roll forming;

[0009] S4. Laser-assisted rolling is used to perform surface finishing and polishing on ultra-precision machined surfaces, which improves roughness, repairs defects in the machining damage layer, and enhances the integrity of the machined surface.

[0010] Furthermore, the simulation software used in step S1 is molecular dynamics and finite element analysis software, which are used to analyze the cutting performance of different crystalline modified layers and the laser heating temperature field, respectively.

[0011] Furthermore, the systematic experimental methods in step S1 include high-temperature nanoindentation and high-temperature nano-scratch tests that can obtain the thermodynamic characteristics of materials, and nano-oblique cutting and ultra-precision machining tests that evaluate the machinability of materials.

[0012] Furthermore, the modified layer crystalline structure in step S1 includes the size of the refined grain feature size and the proportion of amorphous state.

[0013] Furthermore, in step S1, the thickness of the modified layer is greater than the removal depth of the ultra-precision machining.

[0014] Furthermore, the laser-assisted rolling method in steps S2 and S4 refers to the method of using a laser beam to heat the rolling area online in situ while rolling the workpiece, so as to further improve the rolling effect. Specifically, it includes a laser source, a rolling cutter body, and a workpiece. The rolling cutter body performs rolling operations on the workpiece, while the laser source emits a laser beam, which is guided to enter the rolling cutter body from the incident surface of the rolling cutter body, pass through the cutter body material with good light transmittance, and exit from a designated position on the contact surface of the cutter body. It continuously irradiates and heats the contact area between the rolling cutter body and the workpiece, realizing the online in-situ heating effect. Under the in-situ laser heating and the mechanical action of the rolling cutter body, the material achieves pre-modification or surface finishing and polishing effects.

[0015] Furthermore, the laser-assisted rolling method in step S2 includes the following steps:

[0016] S21. Clamping and debugging preparation;

[0017] S22, In-situ surface shape measurement;

[0018] S23, laser-assisted rolling modification.

[0019] Furthermore, step S3 includes the following sub-steps.

[0020] S31, Ultra-precision machining and forming;

[0021] S32. In-situ surface shape measurement;

[0022] S33. Determine the surface accuracy. If the surface accuracy is not up to standard, return to step S23.

[0023] Furthermore, the ultra-precision machining method in step S3 includes ultra-precision cutting, ultra-precision grinding, and ultra-precision polishing.

[0024] Furthermore, in step S4, the finishing and polishing process includes the following sub-steps.

[0025] S41, Laser-assisted roll polishing;

[0026] S42. Disassemble the workpiece and conduct a comprehensive quality evaluation of the workpiece according to the laser-assisted rolling polishing acceptance standard;

[0027] S43. Determine the surface quality. If the surface quality is unqualified, return to step S21. If the surface quality is qualified, the process ends.

[0028] Furthermore, the laser-assisted rolling polishing acceptance criteria include three inspection indicators: surface roughness, surface three-dimensional morphology power spectral density analysis, and surface stress state. Only when all three indicators are met can the surface quality be judged as qualified. The process ends when the surface quality is qualified. If any one of the three indicators fails to meet the requirements, the process returns to step S21.

[0029] Furthermore, in step S4, laser-assisted rolling polishing refers to a method that reduces surface roughness, repairs defects in the processing damage layer, and improves the integrity of the processed surface by combining the recrystallization of the micro-melting zone on the surface of the workpiece during the laser-assisted rolling process with the mechanical action of the rolling head.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention provides an ultra-precision machining method based on laser-assisted rolling control. In the preceding steps of ultra-precision machining, laser-assisted rolling can pre-improve the machinability of the workpiece material. By controlling the laser and rolling parameters, the amorphous proportion, polycrystalline grain refinement scale, and modified layer thickness of the modified layer can be flexibly adjusted. For difficult-to-machine brittle materials, increasing the amorphous proportion of the modified layer can effectively reduce material hardness, improve material plasticity, and suppress the generation of brittle cracks during machining. Grain refinement and stress control within the material can suppress grain cleavage and shedding. For difficult-to-machine metallic materials, surface grain refinement can effectively suppress grain boundary effects, increase surface hardness, and improve cutting side flow, grain boundary steps, and tool build-up, etc. The formation of a gradient crystal structure on the workpiece surface will help improve the final performance of the device.

[0032] 2. In the subsequent process of ultra-precision machining, laser-assisted rolling can be used to improve the surface integrity of ultra-precision machined workpieces. The method described in this invention works by simultaneously forming a micro-melting zone on the surface through laser heating and pressing with a large-sized rolling head. On the one hand, the regular cutting marks and machining residual height introduced by machining can be effectively smoothed, achieving a polishing effect on the surface of the workpiece. On the other hand, the recrystallization process of the micro-melting zone is conducive to repairing the crystal structure of the machining-affected layer, while improving the surface roughness and subsurface integrity of the workpiece. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of laser-assisted rolling in an ultra-precision machining method based on laser-assisted rolling control according to the present invention.

[0034] Figure 2 This is a diagram of the laser-assisted rolling composite integrated processing system of the present invention.

[0035] Explanation of reference numerals in the attached drawings: 001, Laser in-situ rolling modification system; 002, Turning tool holder; 003, In-situ measuring device; 004, Workpiece. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0037] like Figure 1 and Figure 2As shown, the present invention provides an ultra-precision machining method based on laser-assisted rolling control, comprising the following steps:

[0038] S1. Based on the workpiece material, the expected crystalline structure and thickness of the modified layer are determined using simulation and system experimental methods.

[0039] The simulation software used in step S1 is molecular dynamics and finite element analysis software, which are used to analyze the cutting performance of modified layers with different crystalline states and the laser heating temperature field, respectively. The systematic experimental methods in step S1 include high-temperature nanoindentation and high-temperature nano-scraping tests to obtain the thermodynamic characteristics of the material, and nano-oblique cutting and ultra-precision machining experiments to evaluate the material's machinability. The crystalline structure of the modified layer in step S1 includes the characteristic size of the refined grains and the proportion of amorphous material. The thickness of the modified layer in step S1 is greater than the removal depth of the ultra-precision machining.

[0040] S2. Use laser-assisted rolling to perform traverse modification treatment on the surface of the workpiece.

[0041] The laser-assisted rolling method in step S2 refers to the method of using a laser beam to heat the rolling area online in situ while rolling the workpiece, in order to further improve the rolling effect. Specifically, it includes a laser source, a rolling cutter, and a workpiece. The rolling cutter performs the rolling operation on the workpiece, while the laser source emits a laser beam, guiding the laser beam from the incident surface of the rolling cutter into the cutter, passing through the cutter material with good light transmittance, and exiting from a designated position on the contact surface of the cutter. This continuously irradiates and heats the contact area between the rolling cutter and the workpiece, achieving an online in-situ heating effect. Under the in-situ laser heating and the mechanical action of the rolling cutter, the material achieves pre-modification or surface finishing and polishing effects on the workpiece.

[0042] The laser-assisted rolling method in step S2 includes the following sub-steps:

[0043] S21. Clamping and debugging preparation.

[0044] S22, In-situ surface shape measurement.

[0045] S23, laser-assisted rolling modification.

[0046] S3. Use ultra-precision machining methods to perform ultra-precision forming on materials modified by laser-assisted rolling.

[0047] The ultra-precision machining methods in step S3 include ultra-precision cutting, ultra-precision grinding, and ultra-precision polishing. Step S3 also includes the following sub-steps:

[0048] S31, ultra-precision machining and forming.

[0049] S32, In-situ surface shape measurement.

[0050] S33, determining the surface profile accuracy, and returning to step S23 if the surface profile accuracy is unqualified.

[0051] S4, performing finishing polishing on an ultra-precision machined surface by a laser-assisted rolling method to repair machining damage layer defects and improve machined surface integrity while improving roughness.

[0052] In step S4, the finishing polishing treatment comprises the following sub-steps

[0053] S41, laser-assisted rolling polishing.

[0054] S42, detaching a workpiece, and performing comprehensive quality evaluation on the workpiece according to the acceptance standard for laser-assisted rolling polishing.

[0055] S43, determining the surface quality, returning to step S21 if the surface quality is unqualified, and ending the process if the surface quality is qualified.

[0056] Comprehensive surface quality evaluation is performed according to the acceptance standard for laser-assisted rolling polishing, wherein the acceptance standard for laser-assisted rolling polishing comprises three inspection indicators: surface roughness, power spectral density analysis of three-dimensional surface topography, and surface stress state. The surface quality can only be determined as qualified when all three indicators meet the requirements simultaneously. In this embodiment, the acceptance standard for laser-assisted rolling polishing requires that the surface roughness Sa is less than 5 nm; for the power spectral density analysis results before and after polishing, the main frequency peak intensity is reduced by at least 70%, and the surface stress after polishing is in a compressive stress state with a stress value less than 20 MPa. The process ends when the surface quality is qualified, and the process returns to step S21 when any one of the three indicators is unqualified.

[0057] In practical application, the processing object of the present invention is difficult-to-machine materials, wherein the difficult-to-machine materials comprise two categories: brittle materials and metallic materials. The brittle materials comprise polycrystalline tungsten carbide, polycrystalline silicon carbide, single-crystal silicon carbide, polycrystalline zinc sulfide, polycrystalline zinc selenide, monocrystalline silicon, monocrystalline germanium, sapphire, quartz glass, glass-ceramic, calcium fluoride crystal, and barium fluoride crystal; the metallic materials refer to pure copper, pure tin, pure lead, stainless steel, invar, and tungsten alloy. Laser-assisted rolling polishing refers to a method that achieves reduction of surface roughness, repair of machining damage layer defects and improvement of machined surface integrity through recrystallization of a laser surface micro-melting zone combined with the mechanical action of a rolling head.

[0058] In practical application, step S4 can be omitted when the ultra-precision machining quality has met the requirements.

[0059] In this embodiment, the material being processed is polycrystalline tungsten carbide. First, the thermodynamic characteristics of the material are obtained using high-temperature nanoindentation testing, and the average grain size is measured using electron backscatter diffraction pattern characterization. Orthogonal cutting models with different modified layer crystal structures are established through molecular dynamics or finite element simulation analysis. Combined with single-point diamond cutting experiments, an evaluation model for the nano-cutting performance of the modified layer is constructed based on the surface quality of the test cuts and tool life, determining the optimal modified layer crystal structure and the corresponding laser-assisted rolling modification parameters.

[0060] Workpiece 004 is clamped and fixed on the spindle of an ultra-precision machine tool, rotating with the C-axis, which is the machine tool's rotating axis. To improve overall processing efficiency, in this embodiment, the in-situ measuring device 003, the laser in-situ rolling modification system 001, and the turning tool holder 002 are all mounted on the B-axis table of the machine tool, where the B-axis table refers to the rotary table on the ultra-precision machine tool perpendicular to the C-axis. In actual use, only the B-axis needs to be rotated to flexibly achieve different process requirements on-machine, such as... Figure 2 As shown. In this embodiment, in-situ surface shape measurement refers to measuring the surface contour of the workpiece through the center using a contact probe. The in-situ measurement device 003 includes a standard radius probe, a height fine-tuning device, and a signal processing unit. The probe radius is used to accurately calculate the surface contour of the workpiece. The height fine-tuning device moves the measuring probe up and down through a differential screw to ensure that the center of the measuring probe and the center of the workpiece are at the same horizontal level. The information processing unit is used to transmit, process, and save the probe signal.

[0061] After obtaining the surface profile of the clamped workpiece 004 using the in-situ measuring device 003, the curvature radius R of the contact surface of the rolling tool body and the cutting edge radius of the diamond tool is determined. tool Along the workpiece contact point P C Loss of direction Compensate the tool body geometry profile and calculate the control point P for rolling and ultra-precision cutting. L Trajectory:

[0062]

[0063] By using the optimal process parameters obtained from theoretical and experimental research, laser-assisted rolling modification is performed on the workpiece to produce a modified layer with ideal crystalline state and thickness on the workpiece surface, effectively improving the material's machinability.

[0064] Modified polycrystalline tungsten carbide workpieces are processed by subtractive forming using ultra-precision cutting methods. The surface accuracy is then evaluated using an in-situ surface shape measurement device. If the surface accuracy PV (Peak-valley) value is successfully controlled within 1 μm, subsequent processing steps continue; otherwise, surface laser-assisted roll forming modification is performed followed by another cutting process. Figure 1 As shown.

[0065] After the polycrystalline tungsten carbide workpiece meets the surface accuracy requirements using ultra-precision cutting, a rolling path is regenerated based on the surface measurement data from the previous step. Laser-assisted rolling parameters are then adjusted to polish the workpiece throughout its surface. Offline atomic force microscopy is used to comprehensively evaluate the surface quality of the workpiece after rolling polishing. If the surface cutting lines are essentially eliminated and the surface roughness is stable within the range of Sa < 5 nm, the workpiece is considered to be of acceptable quality. Otherwise, the surface shape is remeasured, and modification, cutting, and polishing are performed again. Simultaneously, a sample of processed workpieces is randomly inspected, and their final subsurface quality is systematically characterized using transmission electron microscopy. Comparison with samples that have not undergone laser-assisted rolling polishing reveals that the formation of micro-melting zones during laser-assisted rolling polishing, followed by recrystallization of these zones to form a repair layer, significantly improves the subsurface machining damage layer. In summary, the ultra-precision machining method based on laser-assisted rolling proposed in this invention can effectively improve the machinability of materials, achieving uniform optical surface processing, and also effectively enhance the integrity of the processed surface, thus ensuring the final performance of the device.

[0066] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for ultra-precision machining based on laser-assisted rolling control, characterized in that, Includes the following steps: S1. Determine the expected crystalline structure and thickness of the modified layer based on the workpiece material using simulation and system experimental methods; In step S1, the thickness of the modified layer is greater than the removal depth of the ultra-precision machining. S2. Use laser-assisted rolling to perform traverse modification treatment on the surface of the workpiece; The laser-assisted rolling method in step S2 includes the following sub-steps: S21. Clamping and debugging preparation; S22, In-situ surface shape measurement; S23, Laser-assisted rolling modification; S3. Using ultra-precision machining methods to perform ultra-precision forming processing on materials modified by laser-assisted roll forming; Step S3 includes the following sub-steps: S31, Ultra-precision machining and forming; S32. In-situ surface shape measurement; S33. Check the surface accuracy. If the surface accuracy is not up to standard, return to step S23. S4. Laser-assisted rolling is used to perform surface finishing and polishing on ultra-precision machined surfaces, which improves roughness, repairs defects in the machining damage layer, and improves the integrity of the machined surface. The laser-assisted rolling method in steps S2 and S4 uses the same laser in-situ rolling system; In step S4, the finishing and polishing process includes the following sub-steps: S41, Laser-assisted roll polishing; S42. Disassemble the workpiece and conduct a comprehensive quality evaluation of the workpiece according to the laser-assisted rolling polishing acceptance standard; S43. Determine the surface quality. If the surface quality is unqualified, return to step S21. If the surface quality is qualified, the process ends.

2. The ultra-precision machining method based on laser-assisted rolling control according to claim 1, characterized in that, The simulation software used in step S1 is molecular dynamics and finite element analysis software, which are used to analyze the cutting performance of different crystalline modified layers and the laser heating temperature field, respectively.

3. The ultra-precision machining method based on laser-assisted rolling control according to claim 1, characterized in that, The systematic experimental methods in step S1 include high-temperature nanoindentation and high-temperature nano-scratch tests to obtain the thermodynamic characteristics of materials, and nano-oblique cutting and ultra-precision machining tests to evaluate the machinability of materials.

4. The ultra-precision machining method based on laser-assisted rolling control according to claim 1, characterized in that: The modified layer crystalline structure in step S1 includes the size of the refined grain feature size and the proportion of amorphous state.

5. The ultra-precision machining method based on laser-assisted rolling control according to claim 1, characterized in that: The laser-assisted rolling method in steps S2 and S4 refers to the method of using a laser beam to heat the rolling area online in situ while rolling the workpiece, so as to further improve the rolling effect. Specifically, it includes a laser source, a rolling cutter body, and a workpiece. The rolling cutter body performs rolling operations on the workpiece, while the laser source emits a laser beam, which is guided to enter the rolling cutter body from the incident surface of the rolling cutter body, pass through the cutter body material with good light transmittance, and exit from a designated position on the contact surface of the cutter body. It continuously irradiates and heats the contact area between the rolling cutter body and the workpiece, realizing the online in-situ heating effect. Under the in-situ laser heating and the mechanical action of the rolling cutter body, the material achieves pre-modification or surface finishing and polishing effects.

6. The method according to claim 1, wherein the method is a laser-assisted roll-pressing based ultra-precision machining method. In step S4, laser-assisted rolling polishing refers to a method that reduces surface roughness, repairs defects in the processing layer, and improves the integrity of the processed surface by combining the recrystallization of the micro-melting zone on the surface of the workpiece during the laser-assisted rolling process with the mechanical action of the rolling head.

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