Processing method of high-precision cycloolefin copolymer free-form surface lens

Abstract

The invention discloses a processing method of a high-precision cycloolefin copolymer free-form surface lens, the free-form surface lens comprises an upper end surface and a lower end surface, the upper end surface of the free-form surface lens comprises a free-form surface contour A surface and an outer circumferential surface a annularly arranged outside the free-form surface contour A surface; the lower end face of the free-form surface lens comprises a free-form surface contour surface B and an outer circumferential surface b annularly arranged outside the free-form surface contour surface B. The machining method comprises the steps of S1, tool rough machining, S2, lens blank rough machining, S3, inputting a digital-analog point cloud data file into ultra-precision equipment, S4, tool fine trimming, S5, lens blank plane fine trimming and S6, side wall vertical plane machining. S7, rough turning of the upper end face of the lens blank, S8, finish turning of the transition free-form surface outline A face, S9, turnover clamping, S10, rough turning of the lower end face of the lens blank and S11, finish turning of the transition free-form surface outline B face are conducted, and when ultra-precision equipment is used for machining in the steps S4, S5, S7, S8, S10 and S11, liquefied carbon dioxide is used for cooling.

Description

Technical Field

[0001] This invention relates to the field of freeform lens processing technology, and specifically to a method for processing high-precision cyclic olefin copolymer freeform lenses. Background Technology

[0002] Cyclic olefin copolymers (COCs) are high-performance thermoplastic polymers with advantages such as resistance to breakage and deformation, good cutting performance, excellent transparency, high refractive index, and low astigmatism. They can optimize light transmission and distribution, improving the optical quality of product surfaces. Therefore, they have been widely used in recent years to manufacture optical components, biomedical devices, and electronic components. In optical systems, freeform optical surfaces offer greater degrees of freedom compared to traditional spherical or aspherical surfaces, allowing for arbitrary control of the light emission angle and direction. This enables optical lenses to achieve a wider imaging range and higher image quality.

[0003] For mass production of COC freeform surface lenses, high-temperature injection molding is mainly used. While this method offers high production efficiency, it requires extremely high-precision freeform surface mold cores, and the mold manufacturing process is complex and expensive. For small-batch machining of COC freeform surface lenses, single-point diamond turning is often used. However, traditional single-point diamond turning for COC freeform surface lenses suffers from slow machining speed, high tool wear, and low yield. The main reason is that traditional single-point diamond turning requires continuous spraying of oily coolant onto the workpiece to reduce the heat generated by friction between the tool and the workpiece during cutting. Cycloolefin copolymers are not resistant to oily and aromatic solvents and are easily corroded by them. This makes it impossible to continuously spray oily coolant when machining cyclic olefin copolymers with single-point diamond turning. However, the high heat generated during machining cyclic olefin copolymer products will reduce the sharpness and life of the cutting tool. If the machining speed is not reduced and a targeted machining method is not designed, the wear of the cutting tool and the local expansion deformation of the workpiece surface will reduce the surface roughness and surface accuracy of the workpiece, thereby aggravating the severe tool marks on the surface of cyclic olefin copolymer workpieces. Therefore, there is a contradiction between machining speed, tool wear and yield. Targeted solutions are needed to improve the machining speed, reduce tool wear and improve the yield of COC freeform lenses using single-point diamond turning. Summary of the Invention

[0004] The purpose of this invention is to provide a method for processing high-precision freeform lenses made of cyclic olefin copolymers, in order to solve the problems of slow processing speed, high tool wear, and low yield mentioned in the background art.

[0005] The technical solution of this invention is implemented as follows:

[0006] A method for processing a high-precision freeform lens made of cyclic olefin copolymers, wherein the freeform lens includes an upper end face and a lower end face, the upper end face of the freeform lens includes a freeform contour A surface and an outer circumferential a surface surrounding the freeform contour A surface, and the lower end face of the freeform lens includes a freeform contour B surface and an outer circumferential b surface surrounding the freeform contour B surface. The processing method steps are as follows:

[0007] S1. Tooling rough machining: Use a CNC machine tool to rough machine the nylon material to obtain the first tooling and the first curved surface of the first tooling, and obtain the second tooling and the adsorption plane of the second tooling.

[0008] S2. Rough machining of lens blank: The cyclic olefin copolymer material is processed using a CNC machine tool to obtain the lens blank;

[0009] S3. Convert the digital models of the freeform surface profile A, the reverse concave surface corresponding to the freeform surface profile A, the outer circumference a, the freeform surface profile B, and the outer circumference b into corresponding point cloud data files and then input them into the ultra-precision equipment.

[0010] S4. Fixture finishing: Use ultra-precision equipment to load the point cloud data file of the reverse concave surface digital model to finish the first curved surface to obtain the first positioning surface, and use ultra-precision equipment to finish the plane of the adsorption plane to obtain the second positioning surface.

[0011] S5. Fine finishing of the lens blank: Use ultra-precision equipment to finely finish the upper and lower surfaces of the lens blank.

[0012] S6. Machining of the vertical plane of the side wall: Use a CNC machine tool to machine the outer side wall of the lens blank obtained in step S5 to obtain the vertical plane of the side wall.

[0013] S7. Rough turning of the upper end face of the lens blank: Install the second tooling in the ultra-precision equipment and load the lower end face of the lens blank onto the second positioning surface. Use the ultra-precision equipment to rough turn the upper end face of the lens blank to obtain the transition freeform surface profile A surface and the outer circumference a surface.

[0014] S8. Fine turning of the transition freeform surface profile A: Use ultra-precision equipment to load the point cloud data file of the freeform surface profile A digital model, and fine turn the transition freeform surface profile A to obtain the freeform surface profile A.

[0015] S9. Flipping and clamping: Replace the second tooling in the ultra-precision equipment with the first tooling, and load the free-form surface profile A of the lens blank onto the first positioning surface;

[0016] S10. Rough machining of the lower end face of the lens blank: Using ultra-precision equipment to load the point cloud data files of the digital model of the freeform surface profile B and the outer circumference b, the lower end face of the lens blank is rough machined to obtain the transition freeform surface profile B and the outer circumference b.

[0017] S11. Fine machining of the transition freeform surface profile B: Using ultra-precision equipment to load the point cloud data file of the freeform surface profile B digital model, the transition freeform surface profile B obtained in step S10 is finely machined to obtain the freeform surface profile B.

[0018] When using ultra-precision equipment for processing in steps S4, S5, S7, S8, S10, and S11, liquefied carbon dioxide is used for cooling.

[0019] A further technical solution is to supplement steps S1, S2, S4 to S11 as follows:

[0020] S1. Tooling rough machining: A cylindrical first tooling and a cylindrical second tooling made of nylon material are obtained by using a CNC machine tool. The first tooling includes a first through hole penetrating the upper and lower end faces of the first tooling, a first curved surface opened on the upper end face of the first tooling, a plurality of first annular grooves opened in the first curved surface, and a first connecting groove opened in the first curved surface to connect the first through hole and the plurality of first annular grooves. The second tooling includes a second through hole penetrating the upper and lower end faces of the second tooling, an adsorption plane opened on the upper end face of the second tooling, a plurality of second annular grooves opened in the adsorption plane, and a second connecting groove opened in the adsorption plane to connect the second through hole and the plurality of second annular grooves.

[0021] S2. Rough machining of lens blank: The cyclic olefin copolymer material is machined into a cylindrical lens blank using a CNC lathe. The lens blank has an upper end face and a lower end face. The diameter of the lens blank is 40±0.02mm and the thickness is 7.10±0.02mm.

[0022] S4. Fixture finishing: The lower end face of the first fixture is mounted on the spindle of an ultra-precision equipment with negative pressure function. Negative pressure assembly is used. A diamond tool with an arc radius of 0.5mm is used. The point cloud data file of the reverse concave surface digital model is used to perform digital model finishing on the first curved surface of the first fixture to form the first positioning surface. Then, the first fixture is removed and the lower end face of the second fixture is mounted on the spindle of an ultra-precision equipment with negative pressure function. Negative pressure assembly is used. A diamond tool with an arc radius of 0.5mm is used. The adsorption plane of the second fixture is finished to form the second positioning surface. The surface roughness Ra of the first positioning surface and the second positioning surface is <10nm, and the surface mating accuracy of the first positioning surface and the second positioning surface is <0.005mm.

[0023] S5. Lens blank plane finishing: The lower end face of the lens blank is mounted on the spindle of an ultra-precision equipment with negative pressure function. Negative pressure assembly is used, and a diamond tool with an arc radius of 0.5mm is used to finish the plane of the lens blank. The upper end face of the lens blank is mounted on the spindle of an ultra-precision equipment with negative pressure function. Negative pressure assembly is used, and a diamond tool with an arc radius of 0.5mm is used to finish the plane of the lens blank. The flatness of both the upper and lower end faces of the lens blank is <0.003mm, and the surface roughness is Ra<10nm.

[0024] S6. Machining of the vertical plane of the side wall: Use a CNC milling machine to machine the outer side wall of the lens blank obtained in step S5 to obtain the vertical plane of the side wall. The vertical plane of the side wall is perpendicular to the upper and lower end faces of the lens blank. The flatness requirement of the vertical plane of the side wall is ≤0.005mm.

[0025] S7. Rough turning of the upper end face of the lens blank: Install the lower end face of the second fixture on the spindle of the ultra-precision equipment with negative pressure function, attach the lower end face of the lens blank that was finely finished in step S5 to the second positioning surface, and turn on the negative pressure adsorption. Use a dial indicator to contact the outer wall of the second fixture and the outer wall of the lens blank to adjust so that the coaxiality of the second fixture, the lens blank and the ultra-precision lathe spindle is within 1um. Use the three-point circle method to calculate the approximate fitting contour surface A01 of the pre-machined freeform surface contour A surface. Use a diamond tool with an arc radius of 0.5mm and adopt XZ two-axis linkage machining to rough turn the upper end face of the lens blank to form the approximate fitting contour surface A01. Then use a dial indicator to contact the vertical plane of the side wall of the lens blank to adjust so that the straightness of the vertical plane of the side wall is ≤0.001mm. Finally, use XZC three-axis linkage slow tool servo machining to process the transition freeform surface contour A surface and the outer circumference a surface with a small amount of allowance.

[0026] S8. Fine turning of the transition freeform surface profile A: Using a diamond tool with an arc radius of 0.5mm in an ultra-precision device, and using a slow tool servo for fine machining, the point cloud data file of the freeform surface profile A is used to refine the transition freeform surface profile A obtained in step S7 to obtain the freeform surface profile A.

[0027] S9. Flipping and Clamping: Remove the lens blank and the second fixture that have been precision machined in step S8. Install the lower end face of the first fixture on the spindle of the ultra-precision equipment with negative pressure function. Install the freeform surface profile A onto the first positioning surface and turn on the negative pressure adsorption. Use a dial indicator to contact the outer wall of the first fixture and the outer wall of the lens blank to adjust so that the coaxiality of the first fixture, the lens blank and the ultra-precision lathe spindle is within 1µm. Use a dial indicator to contact the lower end face of the lens blank and pull horizontally to make horizontal adjustment so that the horizontal straightness is <0.003mm. Then rotate the first fixture and the lens blank 90°. Use a dial indicator to contact the lower end face of the lens blank and pull vertically to make vertical adjustment so that the vertical straightness is <0.003mm.

[0028] S10. Rough turning of the lower end face of the lens blank: Use a dial indicator to contact the vertical plane of the side wall of the lens blank to adjust it so that the straightness of the vertical plane of the side wall is ≤0.001mm. Use a diamond tool with an arc radius of 0.5mm and use XZC three-axis linkage slow tool servo machining. Use the point cloud data file of the digital model of the freeform surface profile B surface and the outer circumference b surface to perform digital model rough finishing on the lower end face of the lens blank to obtain the transition freeform surface profile B surface and the outer circumference b surface.

[0029] S11. Fine turning of the transition freeform surface profile B surface: Using a diamond tool with an arc radius of 0.5mm in an ultra-precision device, and using XZC three-axis linkage slow tool servo for fine machining, the point cloud data file of the freeform surface profile B surface digital model is used to refine the transition freeform surface profile B surface obtained in step S10 to obtain the freeform surface profile B surface.

[0030] When using ultra-precision equipment for processing in steps S4, S5, S7, S8, S10, and S11, liquefied carbon dioxide is used to cool the diamond cutting tool and the lens blank.

[0031] A further technical solution is that the first tooling in step S1 includes a lower cylinder and a convex cylinder located at the top of the lower cylinder. The lower cylinder and the convex cylinder are integrally machined from nylon material using a CNC lathe. The first tooling also includes an upper annular cylinder, which is machined from nylon material using a CNC lathe. A first through hole is drilled along the central axis of the lower cylinder and the convex cylinder using a drilling machine. Subsequently, a concave first curved surface is machined from the upper end face of the convex cylinder using a CNC milling machine. Three holes are then milled from the center of the first curved surface outwards using a CNC milling machine. The first annular groove is set concentrically. A first connecting groove is opened in the first curved surface using a CNC milling machine to connect the first through hole and the three first annular grooves. The bottom surface of the upper annular cylinder is fixedly installed on the top surface of the lower cylinder. The outer diameter of the lower annular cylinder is the same as that of the lower cylinder. The lower annular cylinder is sleeved on the outside of the convex cylinder. The top surface of the lower annular cylinder is higher than the first curved surface, thus forming a height difference. The inner wall of the lower annular cylinder is not fitted to the outer wall of the convex cylinder. The inner wall of the lower annular cylinder is also provided with a straight wall for fitting and fitting the vertical plane of the side wall for limiting the position.

[0032] A further technical solution is that, in step S1, the second tooling is first processed by a CNC lathe to obtain a cylindrical second tooling from the nylon material, and then processed by a CNC milling machine to obtain an adsorption plane. Five concentric annular second annular grooves are opened from the center of the adsorption plane outward by a CNC milling machine. A second connecting groove is opened in the adsorption plane to connect the five second annular grooves and pass through the center of the adsorption plane. Finally, two second through holes are opened in the adsorption plane by a drilling machine. The two second through holes are symmetrically arranged with the center of the adsorption plane as the symmetrical point.

[0033] A further technical solution is that the three-point circle drawing method is as follows:

[0034] Take three points (x1, y1), (x2, y2), and (x3, y3) on the freeform surface profile A and substitute them into the general equation of a circle. We obtain three equations, and solve them using the elimination method to find D, E, and F, where the center of the circle is (- ,- ), radius is The XZ axis linkage machining of the contour surface A01 is performed with radius r to approximate the fit.

[0035] A further technical solution is that, in step S7, the process parameters for XZ two-axis linkage machining are: spindle speed 500 rpm / min, cutting amount 0.02 mm / time, and feed rate 15 mm / min; the process parameters for XZC three-axis linkage slow tool servo machining are: spindle speed 60 rpm / min, cutting amount 0.01 mm / time, and step distance 0.1 mm.

[0036] A further technical solution is that, in step S8, the main process parameters for slow-tool servo finishing are a spindle speed of 42 rpm / min, a cutting amount of 0.003 mm / cut, and a step distance of 0.005 mm.

[0037] A further technical solution is that, in step S10, the process parameters for slow-speed servo machining of the XZC three-axis linkage are: spindle speed 60 rpm / min, cutting amount 0.02 mm / cut, and step distance 0.1 mm.

[0038] A further technical solution is that, in step S11, the main process parameters for the slow-tool servo finishing of the XZC three-axis linkage are: spindle speed 42 rpm / min, cutting amount 0.003 mm / cut, and step distance 0.005 mm.

[0039] The beneficial effects of this invention are as follows:

[0040] 1. By using liquefied carbon dioxide as a cooling medium to cool single-point diamond tools and lens blanks, the excellent gas shielding properties of cyclic olefin copolymers, which can block gases such as CO2, ensure that the cooling medium does not affect the COC material. This reduces the temperature of the tool during machining, improves the tool's sharpness and service life, effectively increases machining speed, alleviates the phenomenon of local expansion and deformation of the machined surface, improves the surface roughness and surface accuracy of the workpiece, and reduces the tool marks caused by tool wear and excessive heat.

[0041] 2. By designing the first and second toolings and performing single-point diamond turning on the contact surfaces of the first and second toolings and the lens blank, the fitting accuracy and adsorption stability of the lens blank with the first and second positioning surfaces of the first and second toolings can be effectively improved, thereby improving the surface accuracy of the workpiece and reducing the phenomenon of severe tool marks caused by vibration, thus improving the yield rate.

[0042] 3. When processing the freeform surface profile A with a large curvature, first use the three-point circle drawing method in conjunction with XZ two-axis linkage for roughing, then use XZC three-axis linkage for roughing, and finally use digital model for fine finishing. This can save a lot of production time and cost, and at the same time obtain a cyclic olefin copolymer freeform surface lens with good surface quality and surface shape PV≤5um.

[0043] 4. By designing annular grooves and connecting grooves, the tooling can evenly adsorb the lens blank surface when adsorbing it, which can avoid deformation problems caused by concentrated adsorption force. Attached Figure Description

[0044] Figure 1 This is a three-dimensional schematic diagram of the first tooling;

[0045] Figure 2This is a partial structural sectional view of the first tooling;

[0046] Figure 3 This is a schematic diagram of the first tooling from another perspective;

[0047] Figure 4 This is a three-dimensional schematic diagram of the second tooling;

[0048] Figure 5 This is a schematic diagram of the second tooling from another perspective;

[0049] Figure 6 This is a top view of a freeform lens;

[0050] Figure 7 For the Figure 6 A sectional view of the DD line;

[0051] Figure 8 This is a flowchart of the processing method.

[0052] In the figure, 1 is the lower cylinder, 101 is the convex cylinder, 2 is the upper annular cylinder, 3 is the first curved surface, 4 is the first through hole, 5 is the first annular groove, 6 is the first connecting groove, 7 is the straight wall, 8 is the second tooling, 9 is the adsorption plane, 10 is the second through hole, 11 is the second annular groove, 12 is the second connecting groove, 13 is the vertical plane of the side wall, 14 is the freeform surface profile A surface, 15 is the outer circumference a surface, 16 is the freeform surface profile B surface, and 17 is the outer circumference b surface. Detailed Implementation

[0053] To better understand the technical content of this invention, specific embodiments are provided below, and the invention will be further described in conjunction with the accompanying drawings.

[0054] The machining method disclosed herein requires the use of CNC machine tools, including lathes, milling machines, drilling machines, etc. The ultra-precision grinding equipment used is the Precitech Nanoform 250 ultra-precision five-axis machining center.

[0055] See Figures 1 to 8 A high-precision freeform lens made of cyclic olefin copolymers includes an upper end face and a lower end face. The upper end face of the freeform lens includes a freeform contour A surface 14 and an outer circumferential a surface 15 surrounding the freeform contour A surface 14. The lower end face of the freeform lens includes a freeform contour B surface 16 and an outer circumferential b surface 17 surrounding the freeform contour B surface 16. Its manufacturing method is characterized by the following steps:

[0056] S1. Tooling rough machining: A cylindrical first tooling and a cylindrical second tooling 8 made of nylon material are obtained by CNC machine tool machining. The first tooling includes a first through hole 4 penetrating the upper and lower end faces of the first tooling, a first curved surface 3 opened on the upper end face of the first tooling, a plurality of first annular grooves 5 opened in the first curved surface 3, and a first connecting groove 6 opened in the first curved surface 3 to connect the first through hole 4 and the plurality of first annular grooves 5. The second tooling 8 includes a second through hole 10 penetrating the upper and lower end faces of the second tooling 8, an adsorption plane 9 opened on the upper end face of the second tooling 8, a plurality of second annular grooves 11 opened in the adsorption plane 9, and a second connecting groove 12 opened in the adsorption plane 9 to connect the second through hole 10 and the plurality of second annular grooves 11.

[0057] S2. Rough machining of lens blank: The cyclic olefin copolymer material is machined into a cylindrical lens blank using a CNC lathe. The lens blank has an upper end face and a lower end face. The diameter of the lens blank is 40±0.02mm and the thickness is 7.10±0.02mm.

[0058] S3. Convert the digital models of freeform surface profile A surface 14, the reverse concave surface digital model corresponding to freeform surface profile A surface 14, the digital model of outer circumference a surface 15, the digital model of freeform surface profile B surface 16, and the digital model of outer circumference b surface 17 into corresponding point cloud data files and then input them into the ultra-precision equipment.

[0059] S4. Fixture finishing: The lower end face of the first fixture is mounted on the spindle of an ultra-precision equipment with negative pressure function. Negative pressure assembly is used, and a diamond tool with an arc radius of 0.5mm is used. The point cloud data file of the reverse concave surface digital model is used to perform digital model finishing on the first curved surface 3 of the first fixture to form the first positioning surface. Then, the first fixture is removed and the lower end face of the second fixture 8 is mounted on the spindle of an ultra-precision equipment with negative pressure function. Negative pressure assembly is used, and a diamond tool with an arc radius of 0.5mm is used to perform plane finishing on the adsorption plane 9 of the second fixture 8 to form the second positioning surface. The surface roughness Ra of the first positioning surface and the second positioning surface is <10nm, and the surface mating accuracy of the first positioning surface and the second positioning surface is <0.005mm.

[0060] S5. Lens blank plane finishing: Mount the lower end face of the lens blank on the spindle of an ultra-precision equipment with negative pressure function, use negative pressure assembly, and use a diamond tool with an arc radius of 0.5mm to finish the plane of the lens blank. Mount the upper end face of the lens blank on the spindle of an ultra-precision equipment with negative pressure function, use negative pressure assembly, and use a diamond tool with an arc radius of 0.5mm to finish the plane of the lens blank. The flatness of both the upper and lower end faces of the lens blank is <0.003mm, and the surface roughness is Ra<10nm.

[0061] S6. Machining of the sidewall vertical plane 13: Use a CNC milling machine to machine the outer sidewall of the lens blank obtained in step S5 to obtain the sidewall vertical plane 13. The sidewall vertical plane 13 is perpendicular to the upper and lower end faces of the lens blank. The flatness requirement of the sidewall vertical plane 13 is ≤0.005mm. In the subsequent C-axis adjustment, the sidewall vertical plane 13 is used as the adjustment reference to set the C-axis angle reference. When machining the sidewall vertical plane 13, another plane symmetrical to the sidewall vertical plane 13 can also be machined simultaneously to improve dynamic balance, but this symmetrical plane does not have flatness requirements and is not used as the reference for subsequent C-axis adjustment.

[0062] S7. Rough turning of the upper end face of the lens blank: Install the lower end face of the second fixture 8 on the spindle of the ultra-precision equipment with negative pressure function, attach the lower end face of the lens blank that was finely finished in step S5 to the second positioning surface, and turn on the negative pressure adsorption. Use a dial indicator to contact the outer wall of the second fixture 8 and the outer wall of the lens blank to adjust so that the coaxiality of the second fixture 8, the lens blank and the ultra-precision lathe spindle is within 1um. Use the three-point circle method to calculate the approximate fitting contour surface A01 of the pre-machined freeform surface contour A surface 14. Use a diamond tool with an arc radius of 0.5mm and adopt XZ two-axis linkage machining to rough turn the upper end face of the lens blank to form the approximate fitting contour surface A01. Then use a dial indicator to contact the vertical plane 13 of the side wall of the lens blank to adjust so that the straightness of the vertical plane 13 of the side wall is ≤0.001mm. Finally, use XZC three-axis linkage slow tool servo to machine the transition freeform surface contour A surface and the outer circumference a surface 15 with a small amount of remaining material.

[0063] S8. Fine turning of the transition freeform surface profile A: Using a diamond tool with an arc radius of 0.5mm in an ultra-precision device, and using a slow tool servo for fine machining, the point cloud data file of the freeform surface profile A14 digital model is used to refine the transition freeform surface profile A14 obtained in step S7 to obtain the freeform surface profile A14.

[0064] S9. Flipping and Clamping: Remove the lens blank and the second fixture 8 that have been precision machined in step S8. Install the lower end face of the first fixture on the spindle of the ultra-precision equipment with negative pressure function. Install the freeform surface profile A surface 14 onto the first positioning surface and turn on the negative pressure adsorption. Use a dial indicator to contact the outer wall of the first fixture and the outer wall of the lens blank to adjust so that the coaxiality of the first fixture, the lens blank and the ultra-precision lathe spindle is within 1µm. Use a dial indicator to contact the lower end face of the lens blank and pull it horizontally to make horizontal adjustment so that the horizontal straightness is <0.003mm. Then rotate the first fixture and the lens blank 90° and use a dial indicator to contact the lower end face of the lens blank and pull it vertically to make vertical adjustment so that the vertical straightness is <0.003mm.

[0065] S10. Rough turning of the lower end face of the lens blank: Use a dial indicator to contact the vertical plane 13 of the side wall of the lens blank to adjust it so that the straightness of the vertical plane 13 of the side wall is ≤0.001mm. Use a diamond tool with an arc radius of 0.5mm and XZC three-axis linkage slow tool servo machining. Use the point cloud data files of the digital model of the freeform surface profile B surface 16 and the outer circumference b surface 17 to perform digital model rough finishing on the lower end face of the lens blank to obtain the transition freeform surface profile B surface and the outer circumference b surface 17.

[0066] S11. Fine turning of the transition freeform surface profile B surface: Using a diamond tool with an arc radius of 0.5mm in an ultra-precision device, and using XZC three-axis linkage slow tool servo for fine machining, the point cloud data file of the freeform surface profile B surface 16 digital model is used to refine the transition freeform surface profile B surface obtained in step S10 to obtain the freeform surface profile B surface 16.

[0067] When using ultra-precision equipment for machining in steps S4, S5, S7, S8, S10, and S11 above, liquefied carbon dioxide is used to cool the diamond cutting tool and the lens blank.

[0068] When using the above method, because cyclic olefin copolymers are easily corroded by oily and aromatic solvents, oily solvents cannot be used for cooling during single-point diamond machining of cyclic olefin copolymers. This leads to a large accumulation of heat during the cutting process, which exacerbates tool wear and surface deformation, resulting in poor workpiece surface accuracy and severe tool marks. Using liquefied carbon dioxide instead of traditional oily solvents to cool cyclic olefin copolymers is beneficial because cyclic olefin copolymers have good gas shielding properties that can block gases such as CO2. At the same time, the liquefied carbon dioxide released at room temperature will quickly vaporize and absorb the large amount of heat generated by friction between the diamond tool and the cyclic olefin copolymer workpiece during cutting. Therefore, it can improve the sharpness and service life of the tool, alleviate the phenomenon of local expansion and deformation of the machined surface, improve the surface roughness and surface accuracy of the workpiece, and reduce the tool marks caused by tool wear and large amounts of heat.

[0069] By performing single-point diamond turning finishing on the first fixture, the second fixture, and the lens blank, machining quality issues can be resolved. Without finishing the blank or fixture, excessive surface roughness and low surface accuracy will lead to poor fit accuracy of the positioning surfaces. During single-point diamond turning, poor fit accuracy between the fixture and the blank's positioning surfaces results in poor adsorption stability during negative pressure adsorption, causing slight vibrations during machining. These vibrations reduce the workpiece's surface accuracy and cause severe tool marks. The single-point diamond turning finishing process described above significantly improves the fit accuracy and adsorption stability between the lens blank and the first and second positioning surfaces of the first and second fixtures 8, thereby improving the workpiece's surface accuracy and reducing severe tool marks caused by vibration.

[0070] Since the freeform surface profile A surface 14 is a freeform surface, it is usually machined using XZC three-axis linkage slow-tool servo. However, XZC three-axis linkage slow-tool servo machining has a low rotation speed and long processing time. If used for roughing the freeform surface profile A surface 14, the machining allowance is large and the efficiency is low, resulting in a large time cost. Therefore, the three-point circle method and XZ two-axis linkage machining are used instead of XZC three-axis linkage slow-tool servo machining to rough the freeform surface profile A surface 1401, obtaining an approximate fitting profile surface A01. Since XZ two-axis linkage machining takes less time than XZC three-axis linkage slow-tool servo machining, for roughing freeform surface profiles with large allowances, XZ two-axis linkage approximate fitting profile surface machining will greatly improve the roughing efficiency of freeform surfaces and save a lot of production time costs.

[0071] Therefore, for small-batch processing of cyclic olefin copolymer freeform lenses, the above steps for ultra-precision single-point diamond machining can obtain cyclic olefin copolymer freeform lenses with good surface quality and surface shape PV≤5um while saving a lot of production time and costs.

[0072] Specifically, the first tooling in step S1 includes a lower cylinder 1 and a convex cylinder 101 located on top of the lower cylinder 1. The lower cylinder 1 and the convex cylinder 101 are integrally machined from nylon material using a CNC lathe. The first tooling also includes an upper annular cylinder 2, which is machined from nylon material using a CNC lathe. A first through hole 4 is drilled along the central axis of the lower cylinder 1 and the convex cylinder 101 using a drilling machine. Subsequently, a concave first curved surface 3 is machined from the upper end face of the convex cylinder 101 using a CNC milling machine. Three concentric holes are then milled from the center of the first curved surface 3 outwards using a CNC milling machine. The first annular groove 5 is arranged in a circular shape. A first connecting groove 6 is opened in the first curved surface 3 using a CNC milling machine to connect the first through hole 4 with the three first annular grooves 5. The bottom surface of the upper circular cylinder 2 is fixedly installed on the top surface of the lower cylinder 1. The outer diameter of the lower circular cylinder is the same as the outer diameter of the lower cylinder 1. The lower circular cylinder is sleeved on the outside of the convex cylinder 101. The top surface of the lower circular cylinder is higher than the first curved surface 3, thus forming a height difference. The inner wall of the lower circular cylinder is not fitted to the outer wall of the convex cylinder 101. The inner wall of the lower circular cylinder is also provided with a straight wall 7 for fitting and fitting the vertical plane 13 of the side wall for limiting the position.

[0073] The first through hole 4 and the first annular groove 5 on the first tooling are used for negative pressure adsorption. The first tooling is installed on the spindle disk of the ultra-precision equipment. The ultra-precision equipment spindle has a built-in negative pressure function. When the negative pressure switch is turned on, negative pressure can be generated. The lens blank is adsorbed through the first through hole 4 of the first tooling. The first annular groove 5 can allow the negative pressure to be evenly adsorbed on the surface of the lens blank, which can avoid the deformation problem caused by the concentration of adsorption force.

[0074] Specifically, in step S1, the second tooling 8 is first processed by a CNC lathe to obtain a cylindrical second tooling 8 from the nylon material, and then processed by a CNC milling machine to obtain an adsorption plane 9. Five concentric annular second annular grooves 11 are opened from the center of the adsorption plane 9 outward using a CNC milling machine. A second connecting groove 12 is opened in the adsorption plane 9 to connect the five second annular grooves 11 and pass through the center of the adsorption plane 9. Finally, two second through holes 10 are opened in the adsorption plane 9 using a drilling machine. The two second through holes 10 are symmetrically arranged with the center of the adsorption plane 9 as the symmetrical point.

[0075] The second through hole 10 and the second annular groove 11 on the second tooling 8 are used for negative pressure adsorption. The second tooling 8 is installed on the spindle disk of the ultra-precision equipment. The ultra-precision equipment spindle has a built-in negative pressure function. When the negative pressure switch is turned on, negative pressure can be generated. The lens blank is adsorbed through the second through hole 10 on the second tooling 8. The second annular groove 11 can allow the negative pressure to adsorb evenly on the surface of the lens blank, which can avoid the deformation problem caused by the concentration of adsorption force.

[0076] It should be noted that the lower end faces of the first tooling and the second tooling 8 are also provided with some non-penetrating holes for mounting on ultra-precision equipment. This is a common technical means for negative pressure adsorption mounting of tooling on ultra-precision equipment in the prior art. Therefore, these holes will not be described in detail here, and these holes should be used as the default prior art means on the first tooling and the second tooling 8.

[0077] It should be noted that the digital model finishing method and the planar finishing method are commonly used conventional machining methods in ultra-precision equipment. Therefore, the specific settings of the digital model finishing method and the planar finishing method will not be described in detail in this disclosure.

[0078] Specifically, the three-point circle drawing method is as follows:

[0079] Take three points (x1, y1), (x2, y2), and (x3, y3) on the freeform surface profile A14 and substitute them into the general equation of a circle. We obtain three equations, and solve them using the elimination method to find D, E, and F, where the center of the circle is (- ,- ), radius is The XZ axis linkage machining of the contour surface A01 is performed with radius r to approximate the fit.

[0080] Taking the section DD in the attached diagram as an example, a coordinate system is established with the intersection point of the single-dot dashed line and the freeform surface profile A14 of the lens blank as the origin. The coordinates of this point are (0,0). Then, two points are selected at the leftmost and rightmost ends of the freeform surface profile A14. The coordinates of the leftmost end are (-18.850, 2.885), and the coordinates of the rightmost end are (18.850, 2.885). Substituting the coordinates of these three points into the general equation of a circle... We can obtain:

[0081] F=0

[0082] -18.850D + 2.885E = -363.645

[0083] 18.850D + 2.885E = −363.645

[0084] By combining the equations, we can obtain D=O and E. , = 64.67.

[0085] Specifically, in step S7, the process parameters for XZ two-axis linkage machining are: spindle speed 500 rpm / min, cutting amount 0.02 mm / cut, and feed rate 15 mm / min; the process parameters for XZC three-axis linkage slow tool servo machining are: spindle speed 60 rpm / min, cutting amount 0.01 mm / cut, and step distance 0.1 mm.

[0086] Specifically, in step S8, the main process parameters for slow-tool servo finishing are: spindle speed 42 rpm / min, cutting depth 0.003 mm / cut, and step distance 0.005 mm.

[0087] Specifically, in step S10, the process parameters for slow-speed servo machining of the XZC three-axis linkage are: spindle speed 60 rpm / min, cutting amount 0.02 mm / cut, and step distance 0.1 mm.

[0088] Specifically, in step S11, the main process parameters for the slow-tool servo finishing of the XZC three-axis linkage are: spindle speed 42 rpm / min, cutting amount 0.003 mm / cut, and step distance 0.005 mm.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for processing a high-precision freeform lens made of cyclic olefin copolymers, wherein the freeform lens includes an upper end face and a lower end face, the upper end face of the freeform lens includes a freeform contour A surface and an outer circumferential a surface surrounding the freeform contour A surface, and the lower end face of the freeform lens includes a freeform contour B surface and an outer circumferential b surface surrounding the freeform contour B surface, characterized in that: The processing steps are as follows: S1. Tooling rough machining: Use a CNC machine tool to rough machine the nylon material to obtain the first tooling and the first curved surface of the first tooling, and obtain the second tooling and the adsorption plane of the second tooling. S2. Rough machining of lens blank: The cyclic olefin copolymer material is processed using a CNC machine tool to obtain the lens blank; S3. Convert the digital models of the freeform surface profile A, the reverse concave surface corresponding to the freeform surface profile A, the outer circumference a, the freeform surface profile B, and the outer circumference b into corresponding point cloud data files and then input them into the ultra-precision equipment. S4. Fixture finishing: Use ultra-precision equipment to load the point cloud data file of the reverse concave surface digital model to finish the first curved surface to obtain the first positioning surface, and use ultra-precision equipment to finish the plane of the adsorption plane to obtain the second positioning surface. S5. Fine finishing of the lens blank: Use ultra-precision equipment to finely finish the upper and lower surfaces of the lens blank. S6. Machining of the vertical plane of the side wall: Use a CNC machine tool to machine the outer side wall of the lens blank obtained in step S5 to obtain the vertical plane of the side wall. S7. Rough turning of the upper end face of the lens blank: Install the second tooling in the ultra-precision equipment and load the lower end face of the lens blank onto the second positioning surface. Use the ultra-precision equipment to rough turn the upper end face of the lens blank to obtain the transition freeform surface profile A surface and the outer circumference a surface. S8. Fine turning of the transition freeform surface profile A: Use ultra-precision equipment to load the point cloud data file of the freeform surface profile A digital model, and fine turn the transition freeform surface profile A to obtain the freeform surface profile A. S9. Flipping and clamping: Replace the second tooling in the ultra-precision equipment with the first tooling, and load the free-form surface profile A of the lens blank onto the first positioning surface; S10. Rough machining of the lower end face of the lens blank: Using ultra-precision equipment to load the point cloud data files of the digital model of the freeform surface profile B and the outer circumference b, the lower end face of the lens blank is rough machined to obtain the transition freeform surface profile B and the outer circumference b. S11. Fine machining of the transition freeform surface profile B: Using ultra-precision equipment to load the point cloud data file of the freeform surface profile B digital model, the transition freeform surface profile B obtained in step S10 is finely machined to obtain the freeform surface profile B. When using ultra-precision equipment for processing in steps S4, S5, S7, S8, S10, and S11, liquefied carbon dioxide is used for cooling.

2. The processing method of a high-precision cyclic olefin copolymer freeform lens according to claim 1, characterized in that: The following additions are made to steps S1, S2, S4 to S11: S1. Tooling rough machining: A cylindrical first tooling and a cylindrical second tooling made of nylon material are obtained by using a CNC machine tool. The first tooling includes a first through hole penetrating the upper and lower end faces of the first tooling, a first curved surface opened on the upper end face of the first tooling, a plurality of first annular grooves opened in the first curved surface, and a first connecting groove opened in the first curved surface to connect the first through hole and the plurality of first annular grooves. The second tooling includes a second through hole penetrating the upper and lower end faces of the second tooling, an adsorption plane opened on the upper end face of the second tooling, a plurality of second annular grooves opened in the adsorption plane, and a second connecting groove opened in the adsorption plane to connect the second through hole and the plurality of second annular grooves. S2. Rough machining of lens blank: The cyclic olefin copolymer material is machined into a cylindrical lens blank using a CNC lathe. The lens blank has an upper end face and a lower end face. The diameter of the lens blank is 40±0.02mm and the thickness is 7.10±0.02mm. S4. Fixture finishing: The lower end face of the first fixture is mounted on the spindle of an ultra-precision equipment with negative pressure function. Negative pressure assembly is used. A diamond tool with an arc radius of 0.5mm is used. The point cloud data file of the reverse concave surface digital model is used to perform digital model finishing on the first curved surface of the first fixture to form the first positioning surface. Then, the first fixture is removed and the lower end face of the second fixture is mounted on the spindle of an ultra-precision equipment with negative pressure function. Negative pressure assembly is used. A diamond tool with an arc radius of 0.5mm is used. The adsorption plane of the second fixture is finished to form the second positioning surface. The surface roughness Ra of the first positioning surface and the second positioning surface is <10nm, and the surface mating accuracy of the first positioning surface and the second positioning surface is <0.005mm. S5. Lens blank plane finishing: The lower end face of the lens blank is mounted on the spindle of an ultra-precision equipment with negative pressure function. Negative pressure assembly is used, and a diamond tool with an arc radius of 0.5mm is used to finish the plane of the lens blank. The upper end face of the lens blank is mounted on the spindle of an ultra-precision equipment with negative pressure function. Negative pressure assembly is used, and a diamond tool with an arc radius of 0.5mm is used to finish the plane of the lens blank. The flatness of both the upper and lower end faces of the lens blank is <0.003mm, and the surface roughness is Ra<10nm. S6. Machining of the vertical plane of the side wall: Use a CNC milling machine to machine the outer side wall of the lens blank obtained in step S5 to obtain the vertical plane of the side wall. The vertical plane of the side wall is perpendicular to the upper and lower end faces of the lens blank. The flatness requirement of the vertical plane of the side wall is ≤0.005mm. S7. Rough turning of the upper end face of the lens blank: Install the lower end face of the second fixture on the spindle of the ultra-precision equipment with negative pressure function, attach the lower end face of the lens blank that was finely finished in step S5 to the second positioning surface, and turn on the negative pressure adsorption. Use a dial indicator to contact the outer wall of the second fixture and the outer wall of the lens blank to adjust so that the coaxiality of the second fixture, the lens blank and the ultra-precision lathe spindle is within 1um. Use the three-point circle method to calculate the approximate fitting contour surface A01 of the pre-machined freeform surface contour A surface. Use a diamond tool with an arc radius of 0.5mm and adopt XZ two-axis linkage machining to rough turn the upper end face of the lens blank to form the approximate fitting contour surface A01. Then use a dial indicator to contact the vertical plane of the side wall of the lens blank to adjust so that the straightness of the vertical plane of the side wall is ≤0.001mm. Finally, use XZC three-axis linkage slow tool servo machining to process the transition freeform surface contour A surface and the outer circumference a surface with a small amount of allowance. S8. Fine turning of the transition freeform surface profile A: Using a diamond tool with an arc radius of 0.5mm in an ultra-precision device, and using a slow tool servo for fine machining, the point cloud data file of the freeform surface profile A is used to refine the transition freeform surface profile A obtained in step S7 to obtain the freeform surface profile A. S9. Flipping and Clamping: Remove the lens blank and the second fixture that have been precision machined in step S8. Install the lower end face of the first fixture on the spindle of the ultra-precision equipment with negative pressure function. Install the freeform surface profile A onto the first positioning surface and turn on the negative pressure adsorption. Use a dial indicator to contact the outer wall of the first fixture and the outer wall of the lens blank to adjust so that the coaxiality of the first fixture, the lens blank and the ultra-precision lathe spindle is within 1µm. Use a dial indicator to contact the lower end face of the lens blank and pull horizontally to make horizontal adjustment so that the horizontal straightness is <0.003mm. Then rotate the first fixture and the lens blank 90°. Use a dial indicator to contact the lower end face of the lens blank and pull vertically to make vertical adjustment so that the vertical straightness is <0.003mm. S10. Rough turning of the lower end face of the lens blank: Use a dial indicator to contact the vertical plane of the side wall of the lens blank to adjust it so that the straightness of the vertical plane of the side wall is ≤0.001mm. Use a diamond tool with an arc radius of 0.5mm and use XZC three-axis linkage slow tool servo machining. Use the point cloud data file of the digital model of the freeform surface profile B surface and the outer circumference b surface to perform digital model rough finishing on the lower end face of the lens blank to obtain the transition freeform surface profile B surface and the outer circumference b surface. S11. Fine turning of the transition freeform surface profile B surface: Using a diamond tool with an arc radius of 0.5mm in an ultra-precision device, and using XZC three-axis linkage slow tool servo for fine machining, the point cloud data file of the freeform surface profile B surface digital model is used to refine the transition freeform surface profile B surface obtained in step S10 to obtain the freeform surface profile B surface. When using ultra-precision equipment for processing in steps S4, S5, S7, S8, S10, and S11, liquefied carbon dioxide is used to cool the diamond cutting tool and the lens blank.

3. The processing method of a high-precision cyclic olefin copolymer freeform lens according to claim 2, characterized in that: The first tooling in step S1 includes a lower cylinder and a convex cylinder at the top of the lower cylinder. The lower cylinder and convex cylinder are integrally machined from nylon material using a CNC lathe. The first tooling also includes an upper annular cylinder, which is machined from nylon material using a CNC lathe. A first through hole is drilled along the central axis of the lower cylinder and convex cylinder using a drilling machine. Subsequently, a concave first curved surface is machined from the upper end face of the convex cylinder using a CNC milling machine. Three concentrically arranged... The first annular groove is formed by using a CNC milling machine to open a first connecting groove in the first curved surface to connect the first through hole and the three first annular grooves. The bottom surface of the upper annular cylinder is fixedly installed on the top surface of the lower cylinder. The outer diameter of the lower annular cylinder is the same as that of the lower cylinder. The lower annular cylinder is sleeved on the outside of the convex cylinder. The top surface of the lower annular cylinder is higher than the first curved surface, thus forming a height difference. The inner wall of the lower annular cylinder is not fitted to the outer wall of the convex cylinder. The inner wall of the lower annular cylinder is also provided with a straight wall for fitting and fitting the vertical plane of the side wall for limiting the position.

4. The processing method of a high-precision cyclic olefin copolymer freeform lens according to claim 3, characterized in that: In step S1, the second tooling is first machined into a cylindrical shape using a CNC lathe on the nylon material, and then machined into an adsorption plane using a CNC milling machine. Five concentric annular grooves are then opened from the center of the adsorption plane outwards using a CNC milling machine. A second connecting groove is then opened in the adsorption plane to connect the five annular grooves and pass through the center of the adsorption plane. Finally, two second through holes are opened in the adsorption plane using a drilling machine. The two second through holes are symmetrically arranged with the center of the adsorption plane as the symmetrical point.

5. A method for processing a high-precision cyclic olefin copolymer freeform lens according to any one of claims 2-4, characterized in that: The three-point circle drawing method is as follows: Take three points (x1, y1), (x2, y2), and (x3, y3) on the freeform surface profile A and substitute them into the general equation of a circle. We obtain three equations, and solve them using the elimination method to find D, E, and F, where the center of the circle is (- ,- ), radius is The XZ axis linkage machining of the contour surface A01 is performed with radius r to approximate the fit.

6. The processing method of a high-precision cyclic olefin copolymer freeform lens according to claim 5, characterized in that: In step S7, the process parameters for XZ two-axis linkage machining are: spindle speed 500 rpm / min, cutting amount 0.02 mm / cut, and feed rate 15 mm / min; the process parameters for XZC three-axis linkage slow tool servo machining are: spindle speed 60 rpm / min, cutting amount 0.01 mm / cut, and step distance 0.1 mm.

7. The processing method of a high-precision cyclic olefin copolymer freeform lens according to claim 6, characterized in that: In step S8, the main process parameters for slow-tool servo finishing are: spindle speed 42 rpm / min, cutting amount 0.003 mm / cut, and step distance 0.005 mm.

8. The processing method of a high-precision cyclic olefin copolymer freeform lens according to claim 7, characterized in that: In step S10, the process parameters for slow-speed servo machining of the XZC three-axis linkage are: spindle speed 60 rpm / min, cutting amount 0.02 mm / cut, and step distance 0.1 mm.

9. The processing method of a high-precision cyclic olefin copolymer freeform lens according to claim 8, characterized in that: In step S11, the main process parameters for the slow-tool servo finishing of the XZC three-axis linkage are: spindle speed 42 rpm / min, cutting amount 0.003 mm / cut, and step distance 0.005 mm.

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