Novel fixed abrasive polishing disc driven by non-Newtonian fluid

Abstract

The invention discloses a novel non-Newtonian fluid driven fixed abrasive polishing disc, and relates to the technical field of optical element polishing. The fixed abrasive polishing disc comprises an eccentric adjusting frame, a metal back plate, a caliber adjusting ring, a non-Newtonian fluid layer, a rubber sleeve, a fixing ring and a fixed abrasive polishing pad. The metal back plate is matched with the eccentric adjusting frame through the connecting shaft to achieve the adjustable eccentric distance, the caliber adjusting ring can be replaced with different calibers to meet different requirements, the rubber sleeve is filled with the non-Newtonian fluid layer, the fixed abrasive polishing pad is fixed with cerium oxide abrasive, and the size of the fixed abrasive polishing pad is slightly larger than that of the rubber sleeve. The dynamic stiffness characteristic of the non-Newtonian fluid layer is utilized to realize effective correction of full-band errors; the rigidity and efficiency are improved through the fixed grinding material, and hydration reaction is avoided; and multi-structure collaborative optimization of pressure transmission and fringe effect ensures process stability. Experiments show that the fixed abrasive polishing disk can reduce the intermediate frequency error of a fused quartz workpiece to 0.1 mu m and the Ra value to 1.6 nm, is suitable for diversified machining scenes and is high in practicability.

Description

Technical Field

[0001] This invention relates to the field of optical element polishing technology, and more specifically to a novel non-Newtonian fluid-driven bonded abrasive polishing disc for polishing planar and aspherical fused silica workpieces. Background Technology

[0002] In the precision polishing stage of aspherical optical components, the performance of the polishing tool directly determines the machining quality of the workpiece. Existing mainstream polishing tools are mainly divided into three categories: purely rigid tools, purely flexible tools, and semi-flexible tools. All have significant drawbacks: purely rigid tools cannot adapt to changes in the workpiece's curvature, affecting the correction of low-frequency errors; purely flexible tools can conform to the workpiece surface, but their efficiency in removing mid-to-high frequency errors is relatively low. Therefore, semi-flexible tools are considered for conformal and deterministic polishing to reduce errors across the entire frequency range.

[0003] In conformal polishing, traditional semi-flexible tools are generally large tools, such as stress disks (Yiliqi. Research on prestressed polishing method of off-axis aspherical silicon carbide thin plate and lightweight mirror [D]. Changchun: University of Chinese Academy of Sciences, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 2021) and airbags (Fu Zhenfeng, Wang Zhenzhong, Huang Xuepeng, et al. Research and analysis of airbag polishing of sapphire arc surface [J]. Aviation Manufacturing Technology, 2024, 67(15): 94-101, 119). These tools can ensure the accuracy of low-frequency surface shape and reduce high-frequency errors. However, due to high manufacturing costs and complex real-time control, they cannot completely remove mid-frequency errors below the TIF (tool influence function) scale. In deterministic polishing, small tools, such as asphalt disks, are generally used. However, asphalt is greatly affected by temperature, and the polishing efficiency of small tools is not high.

[0004] In summary, existing optical polishing tool heads have two major problems: first, large-sized tools have complex structures, are difficult to control, and struggle to naturally smooth out mid-frequency errors; second, small-sized tools can meet the requirements for mid-to-high frequency error correction, but their efficiency is low. Therefore, there is an urgent need to develop a new type of polishing tool that combines high adaptability and high efficiency. Summary of the Invention

[0005] The purpose of this invention is to address the problems of existing large-tool polishing discs, such as complex structure and control, and difficulty in removing mid-to-high frequency errors. It provides a novel non-Newtonian fluid-driven bonded abrasive polishing disc, which increases the stiffness of the polishing disc, improves processing efficiency, avoids the impact of hydration reactions on the physicochemical properties of optical components, optimizes polishing pressure transmission, reduces edge effects, and improves the consistency and process stability between actual and theoretical TIF. With the help of detachable components, the disc diameter and eccentricity are adjustable to meet different processing scenarios and process requirements, and can effectively reduce errors across the entire frequency band during conformal polishing.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A novel non-Newtonian fluid-driven bonded abrasive polishing disc includes an eccentric adjustment frame, a metal back plate, a diameter adjustment ring, a non-Newtonian fluid layer, a rubber sleeve, a fixing ring, and a bonded abrasive polishing pad.

[0008] The upper end of the metal backplate is provided with a connecting shaft, and the eccentric adjustment bracket has an oblong hole. The connecting shaft passes through the oblong hole and can slide along the oblong hole to adjust to the required eccentricity. After adjustment, it is locked by a threaded bolt to ensure the stability of the eccentricity. The diameter adjustment ring is connected to the lower end of the metal backplate. The diameter adjustment ring is conical and convex, and the boss is embedded in radial grooves to facilitate uniform pressure distribution. The non-Newtonian fluid layer is filled in a rubber sleeve. The rubber sleeve is used to wrap the non-Newtonian fluid layer and is connected to the metal backplate by a fixing ring to form an integrated structure. The bonded abrasive polishing pad is attached to the lower end face of the rubber sleeve.

[0009] Furthermore, the eccentric adjustment frame has a rectangular solid outline, and the metal back plate is as thin as possible while ensuring mechanical performance. Several through holes for bolt connection are evenly distributed along the edge of the metal back plate. Preferably, there are 8 through holes, and the edges of the diameter adjustment ring, the rubber sleeve, and the fixing ring are all provided with through holes corresponding to the 8 through holes. The bolts pass through the corresponding through holes of the fixing ring, the rubber sleeve, the diameter adjustment ring, and the metal back plate in sequence, locking the four together coaxially.

[0010] Furthermore, the caliber adjustment ring can be manufactured by 3D printing, and different caliber specifications can be replaced as needed.

[0011] Furthermore, the main material of the non-Newtonian fluid layer is silly-putty, uniformly mixed with micron-sized (30 / 100μm) acrylic microspheres of different particle sizes.

[0012] Furthermore, the rubber sleeve is made of nitrile rubber.

[0013] Furthermore, the bonded abrasive polishing pad can be made of polyurethane material with cerium oxide abrasive bonded to its surface. The bonded abrasive polishing pad has a certain number of ventilation holes distributed on it. The polishing pad is attached to the lower end of the rubber sleeve and is slightly larger than the rubber sleeve.

[0014] Compared with the prior art, the present invention has the following outstanding advantages and beneficial effects:

[0015] 1. The non-Newtonian fluid layer drives the polishing disc. Under low-frequency stress, the non-Newtonian fluid layer is flexible and can adapt to the curvature changes of the aspherical workpiece. Under high-frequency stress, the non-Newtonian fluid layer is rigid and can stably remove mid-to-high frequency errors. Experiments have verified that when using this polishing disc to process fused silica workpieces, the mid-frequency error of the PV value on the surface of fused silica, which is on the order of 12 μm, can be significantly reduced to 0.1 μm and the roughness Ra value can be reduced to 1.6 nm.

[0016] 2. The cerium oxide abrasive bonded to the polishing pad can increase the overall rigidity of the polishing disc, thereby improving processing efficiency; the workpiece is in an anhydrous environment during processing, which reduces the impact of hydration reaction on the physical and chemical properties of optical components and improves the utilization rate of abrasive grains, with an abrasive grain loss rate of less than 5%.

[0017] 3. The conical guide ring with groove structure for adjusting the diameter enhances the uniformity of the silly-putty filling; the non-Newtonian fluid layer is mixed with acrylic microparticles of different sizes to improve the uniformity of pressure distribution; the polishing pad, which is slightly larger than the rubber sleeve, can effectively improve the edge pressure change phenomenon of the polishing pad, so that the actual TIF and the theoretical TIF have better consistency and improve the stability of the polishing process.

[0018] 4. By replacing the diameter adjustment rings of different diameters, the diameter of the polishing disc can be quickly adjusted; by the cooperation between the waist-shaped elongated hole of the eccentric adjustment bracket and the connecting shaft, the eccentricity can be precisely adjusted, which can meet the processing needs of workpieces of different sizes and types and adapt to diverse processing scenarios. Attached Figure Description

[0019] Figure 1 This is a structural disassembly diagram of the present invention.

[0020] The markings in the figure are: 1-eccentric adjustment frame, 2-metal back plate, 3-diameter adjustment ring, 4-non-Newtonian fluid layer, 5-rubber sleeve, 6-fixing ring, 7-bonded abrasive polishing pad. Detailed Implementation

[0021] The following embodiments will further illustrate the present invention with reference to the accompanying drawings.

[0022] like Figure 1 As shown in the figure, a novel non-Newtonian fluid-driven bonded abrasive polishing disc according to an embodiment of the present invention includes an eccentric adjustment frame 1, a metal back plate 2, a diameter adjustment ring 3, a non-Newtonian fluid layer 4, a rubber sleeve 5, a fixing ring 6, and a bonded abrasive polishing pad 7. The connection relationship and specific structure of each component are as follows:

[0023] Eccentric adjustment bracket 1: The overall shape is a rectangular solid. An elongated, waist-shaped hole is provided on the eccentric adjustment bracket 1. A connecting shaft is integrally formed on the metal back plate 2. The connecting shaft passes through the elongated, waist-shaped hole and can slide along it to adjust to the required eccentricity. After adjustment, it is locked in place by fine-threaded bolts to ensure stable eccentricity. In this embodiment, the distance between the centers of the two ends of the elongated, waist-shaped hole is 30mm, and its width is 10.5mm. The eccentricity can be adjusted within the range of 0 to 15mm.

[0024] Metal back plate 2: While ensuring that the mechanical properties meet the requirements during the polishing process, the thickness is minimized to reduce the overall weight; the metal material is 304 stainless steel, and in this embodiment, the thinnest part of the metal back plate can be 5mm; the edge of the metal back plate 2 is evenly distributed with 8 through holes, and the edges of the diameter adjustment ring 3, the rubber sleeve 5 and the fixing ring 6 are all provided with through holes corresponding to the 8 through holes; fine thread bolts (in this embodiment, standard fine thread M10 is used) pass through the corresponding through holes of the fixing ring 6, the rubber sleeve 5, the diameter adjustment ring 3 and the metal back plate 2 in sequence, and lock the four together coaxially.

[0025] Diameter adjustment ring 3: Connected to the lower part of the metal back plate 2, the diameter adjustment ring 3 has a conical protrusion on its inner side, and radial grooves are embedded in the protrusion. This structure is conducive to the uniform distribution of polishing pressure. In this embodiment, the structure has a taper of 110°, 8 grooves, a curvature r=15mm, and a depth and width of 0.5mm. The diameter adjustment ring 3 can be selected according to different diameter specifications according to processing requirements and is manufactured by 3D printing process for easy and quick replacement.

[0026] Non-Newtonian fluid layer 4: Filled inside the rubber sleeve 5, the main material of the non-Newtonian fluid layer 4 is silly-putty; to optimize pressure transmission, micron-sized acrylic microspheres of different particle sizes are uniformly mixed into the non-Newtonian fluid layer 4. In this embodiment, the microsphere particle sizes are 30μm and 100μm, respectively, with 30μm microspheres having a mass fraction of 3% and 100μm microspheres having a mass fraction of 5%. The silly-putty is a commercially available product, a silicon-based polymer material that combines viscosity, elasticity, and plasticity.

[0027] Rubber sleeve 5 and fixing ring 6: The rubber sleeve 5 is made of nitrile rubber and its function is to wrap the non-Newtonian fluid layer 4. The rubber sleeve 5 is connected to the metal back plate 2 through the fixing ring 6, so that the fixing ring 6, the rubber sleeve 5, the non-Newtonian fluid layer 4, the diameter adjustment ring 3 and the metal back plate 2 form an integrated structure to ensure the structural stability during the processing.

[0028] The bonded abrasive polishing pad 7 is made of polyurethane with cerium oxide abrasive bonded to its surface. The bonded abrasive polishing pad 7 has a number of vent holes to discharge debris and heat generated during polishing. The bonded abrasive polishing pad 7 is fitted and fixed to the lower end face of the rubber sleeve 5, and its size is slightly larger than the rubber sleeve 5 to improve the problem of sudden changes in edge pressure. In this embodiment, the polishing pad substrate can be an LP66 polyurethane polishing pad with a pore density of approximately 10. 5 - 10 7 The number of pores per cm³ corresponds to an average pore diameter of approximately 10-80 μm.

[0029] The following are the preparation and assembly steps of this invention:

[0030] 1. Preparation of bonded abrasive polishing pad 7: Weigh 65% of 2μm cerium oxide, 12.5% ​​of phenolic resin and 22.5% of deionized water by mass fraction, mix the three ingredients evenly to form an abrasive mixture; apply the abrasive mixture evenly to the surface of the polyurethane base polishing pad, place it in a sintering furnace and sinter at 130℃ for 5 min to complete the bonded molding and obtain the bonded abrasive polishing pad 7.

[0031] 2. Polishing disc body assembly: Insert the non-Newtonian fluid layer 4 into the rubber sleeve 5, and place the metal back plate 2, the diameter adjustment ring 3, the rubber sleeve 5, and the fixing ring 6 coaxially in sequence, so that the eight through holes of the four are aligned one by one; insert the bolts into each through hole in sequence and lock them to complete the assembly of the disc body; after the assembly is completed, attach and fix the bonded abrasive polishing pad 7 prepared in step 1 to the bottom of the disc body.

[0032] 3. Connection with machine tool: Insert the connecting shaft on the metal back plate 2 into the waist-shaped elongated hole of the eccentric adjustment frame 1, adjust it to the specified eccentricity, and then lock it with fine thread bolts; insert the spring clip into the upper connecting hole of the eccentric adjustment frame 1, and connect it to the machine tool spindle through the spring clip to complete the overall assembly.

[0033] This invention achieves full-frequency error correction based on the synergistic effect of the dynamic stiffness characteristics of non-Newtonian fluids and the efficient cutting characteristics of bonded abrasives. The specific working principle is as follows:

[0034] 1. Power transmission and stiffness self-adaptation: The machine tool spindle drives the eccentric adjustment frame 1 to rotate through the spring clip. The eccentric adjustment frame 1 drives the metal back plate 2 and the integrated disk to move synchronously. During the polishing process, the non-Newtonian fluid layer 4 exhibits differentiated stiffness under different frequency stresses. Under low frequency stress (corresponding to the large curvature change area of ​​the workpiece), it is flexible and conforms to the workpiece surface with the rubber sleeve 5 to achieve conformal polishing. Under high frequency stress (corresponding to the fine error area of ​​the workpiece surface), it is rigid and drives the solidified abrasive polishing pad 7 to stabilize the high frequency error in the cutting process.

[0035] 2. Pressure homogenization mechanism: The conical convex surface of the diameter adjustment ring 3 guides the non-Newtonian fluid layer 4 to flow uniformly towards the edge, and the radial grooves further disperse the pressure to avoid local pressure concentration; the mixed structure of 30μm and 100μm acrylic microspheres in the non-Newtonian fluid layer 4 further improves the uniformity of pressure transmission and ensures that the actual TIF is highly consistent with the theoretical TIF.

[0036] 3. Waterless polishing and high-efficiency processing: The bonded abrasive polishing pad 7 adopts a cerium oxide abrasive bonded structure, which can achieve cutting without the need for the water environment of traditional polishing, avoiding damage to the fused silica workpiece by hydration reaction; at the same time, the overall stiffness of the bonded abrasive is higher than that of loose abrasive, and combined with the eccentric movement of the eccentric adjustment frame 1, it significantly improves polishing efficiency and reduces abrasive wear.

[0037] The following describes the usage process and effect verification of this invention:

[0038] 1. Preparation and filling of non-Newtonian fluid layer 4: Silly-putty is used as a substrate, and acrylic microparticles with particle sizes of 30μm and 100μm are uniformly filled into it. The substrate is repeatedly kneaded for 5 minutes until there is no obvious stratification in the cross section, and a uniformly mixed non-Newtonian fluid layer 4 is obtained; it is then installed in a rubber sleeve 5.

[0039] 2. Process parameter settings: After the overall assembly of the polishing disc is completed, the eccentricity of the eccentric adjustment frame 1 is adjusted to 5mm, the machine tool spindle speed is set to 75r / min and the polishing pressure to 75Kpa. Using the fused silica workpiece as the processing object, a fixed-point spotting experiment is carried out to verify the stability of TIF.

[0040] 3. Full-band error correction experiment: Under the above-mentioned optimal process parameters, the optical element is uniformly polished on the whole surface using a grating path, and a full-band error correction experiment is carried out in combination with the dwell time algorithm.

[0041] Experimental results show that the polishing disc of this invention has strong low-frequency conformal properties, with the changes in PV and RMS values ​​of the workpiece before and after processing not exceeding 10%. The mid-frequency error is corrected to Rq=2.471nm, and the lowest high-frequency surface roughness can reach Ra=1.6nm, demonstrating excellent error control across the entire frequency band. Under process parameters of 75kPa and 63rpm, it can be used continuously for 1000 minutes, with slight variations in lifespan depending on different operating conditions.

[0042] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. For example, parameters such as the particle size combination of acrylic microspheres in the non-Newtonian fluid layer and the pore distribution density of the polishing pad can be adaptively adjusted according to actual processing requirements; the material of the diameter adjustment ring can also be selected from other suitable materials besides 3D printing consumables, provided that processing performance is met.

Claims

1. A novel non-Newtonian fluid-driven bonded abrasive polishing disc, characterized in that, It includes an eccentric adjustment frame, a metal back plate, a diameter adjustment ring, a non-Newtonian fluid layer, a rubber sleeve, a fixing ring, and a bonded abrasive polishing pad; The upper end of the metal backplate is provided with a connecting shaft, and the eccentric adjustment bracket has an oblong hole. The connecting shaft passes through the oblong hole and can slide along the oblong hole to adjust to the required eccentricity. After adjustment, it is locked by threaded bolts to ensure the stability of the eccentricity. The diameter adjustment ring is provided at the lower end of the metal backplate. The diameter adjustment ring is conical and convex, and the boss is embedded in radial grooves to facilitate uniform pressure distribution. The non-Newtonian fluid layer is filled in the rubber sleeve. The rubber sleeve is used to wrap the non-Newtonian fluid layer and is fixedly connected to the metal backplate by a fixing ring. The bonded abrasive polishing pad is attached to the lower end face of the rubber sleeve.

2. The novel non-Newtonian fluid-driven bonded abrasive polishing disc according to claim 1, characterized in that, The eccentric adjustment frame has a rectangular solid outline; several through holes for bolt connection are evenly distributed along the edge of the metal back plate, and corresponding through holes are opened on the edge of the diameter adjustment ring, the rubber sleeve, and the fixing ring; the bolt passes through the corresponding through holes of the fixing ring, the rubber sleeve, the diameter adjustment ring, and the metal back plate in sequence, and locks the four together coaxially.

3. A novel non-Newtonian fluid-driven bonded abrasive polishing disc according to claim 1, characterized in that, The caliber adjustment ring is made by 3D printing and can be replaced with different caliber specifications as needed.

4. A novel non-Newtonian fluid-driven bonded abrasive polishing disc according to claim 1, characterized in that, The non-Newtonian fluid layer is made of silly-putty material and uniformly mixed with micron-sized acrylic microspheres of different particle sizes.

5. A novel non-Newtonian fluid-driven bonded abrasive polishing disc according to claim 4, characterized in that, The micron-sized acrylic microspheres of different particle sizes are acrylic microparticles with particle sizes of 30μm and 100μm.

6. A novel non-Newtonian fluid-driven bonded abrasive polishing disc according to claim 1, characterized in that, The bonded abrasive polishing pad is made of polyurethane and has cerium oxide abrasive bonded to its surface. Ventilation holes are distributed on the bonded abrasive polishing pad.

7. A novel non-Newtonian fluid-driven bonded abrasive polishing disc according to claim 1, characterized in that, The solidified abrasive polishing pad is prepared by the following method: 65% by mass of 2μm cerium oxide, 12.5% ​​by mass of phenolic resin and 22.5% by mass of deionized water are mixed to form an abrasive mixture, which is then coated and sintered at 130°C for 5 minutes to solidify.

8. A novel non-Newtonian fluid-driven bonded abrasive polishing disc according to claim 1, characterized in that, The non-Newtonian fluid layer is flexible under low-frequency stress to adapt to the curvature of the workpiece, and rigid under high-frequency stress to eliminate mid-to-high frequency errors, thereby achieving full-band error reduction.

9. A novel non-Newtonian fluid-driven bonded abrasive polishing disc according to claim 1, characterized in that, The structure design of the bonded abrasive polishing pad combined with the non-Newtonian fluid layer enables the bonded abrasive polishing disc to polish in a waterless environment with an abrasive wear rate of less than 5%.

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