Ultra-smooth polishing method for large-aperture complex curved surface NiP composite material mirror
By planning polishing paths in different areas and using multi-stage cleaning processes, combined with robotic polishing equipment, the problems of uneven surface quality and contaminant residue in large-diameter, high-steep nickel-phosphorus alloy mirrors have been solved, achieving efficient and low-cost ultra-smooth processing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI INST OF OPTICS & FINE MECHANICS CHINESE ACAD OF SCI
- Filing Date
- 2026-03-26
- Publication Date
- 2026-06-12
AI Technical Summary
Existing technologies struggle to efficiently and cost-effectively process large-diameter, steeply curved nickel-phosphorus alloy mirrors, resulting in issues such as uneven surface quality, contaminant residue, and low processing efficiency.
By employing zoned polishing path planning, multi-stage polishing fluid control and cleaning processes, combined with robotic polishing equipment, we can achieve efficient zoned polishing and multi-stage cleaning, ensuring surface smoothness and uniform removal.
A super-smooth surface with a high-frequency roughness of less than 0.2 nm was achieved for a large-aperture, high-steep, complex curved nickel-phosphorus alloy mirror, meeting the high standards of extreme ultraviolet lithography and space optics, and reducing manufacturing costs and cycle time.
Smart Images
Figure CN121912264B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of ultra-precision machining technology of optical components, specifically relating to an ultra-smooth polishing method for large-diameter complex curved surface NiP composite material mirrors based on robotic polishing equipment. Background Technology
[0002] Large-aperture, ultra-smooth nickel-phosphorus alloy optical components are core foundational parts supporting scientific and technological projects such as space remote sensing, extreme ultraviolet lithography (EUVL), and laser nuclear fusion. In space telescope systems, their amorphous structure, excellent thermal stability, and lightweight composite properties make them ideal materials for achieving sub-nanometer surface accuracy and ultra-low surface roughness in meter-level primary mirrors. In the field of EUV lithography, nickel-phosphorus alloy coatings can serve as substrates for Mo / Si multilayer mirrors, meeting the stringent requirements of surface roughness below 0.1 nm RMS and extremely low defect density at a wavelength of 13.5 nm. In high-power laser systems, their high hardness, good thermal conductivity, and potential resistance to laser damage also demonstrate unique advantages.
[0003] However, with the development of cutting-edge fields such as laser nuclear fusion and space exploration, near-limit requirements have been placed on the aperture, surface complexity, and surface quality of optical components. Currently, the manufacturing of such components still faces multiple bottlenecks: during ultra-precision polishing, the special amorphous structure, high hardness, and significant elastic recovery of nickel-phosphorus alloys lead to complex removal mechanisms, poor compatibility of polishing slurries, and difficulty in controlling subsurface damage. Simultaneously, the synergistic suppression of surface shape errors across the entire frequency band (especially high-frequency roughness), efficient processing in ultra-clean environments, and the lack of dedicated equipment and integrated process chains severely restrict high-yield, short-cycle, and low-cost engineering applications, urgently requiring breakthroughs in the entire technology chain from materials to processes to equipment to testing. Near-meter-diameter, high-steep aspherical components have extremely high aspect ratios and rapidly changing curvatures, resulting in uneven material removal and affecting surface quality. Furthermore, due to the unique amorphous structure, soft chemical surface activity, and special surface energy characteristics of nickel-phosphorus alloys, polishing slurry residue easily remains on the surface, while the inherent characteristics of the ultra-smooth surface make it highly susceptible to adsorption of contaminants.
[0004] Currently used ultra-smooth polishing techniques include magnetorheological polishing, ion beam polishing, chemical mechanical polishing, and conventional mechanical polishing. These methods all have limitations in processing optical components with both large apertures and high steepness. Furthermore, existing polishing techniques for nickel-phosphorus alloy components largely focus on polishing slurry formulations or specific process improvements. Conformal polishing using composite abrasives is primarily aimed at small-aperture planar microstructures with gratings, but it does not solve the core macroscopic challenges of edge effects, pressure distribution uniformity, and maintaining surface finish for near-meter-diameter, high-steep aspherical surfaces. Other studies employ magnetorheological polishing, which can effectively correct surface shapes, but the equipment is complex and costly. Moreover, the stability of the magnetorheological fluid and the determinism of the removal function face serious challenges for such large-aperture workpieces. The main contaminants remaining after polishing nickel-phosphorus alloy components include nano-sized abrasives, polishing fluid additives, and metal ions. Surface cleaning of large-diameter, high-steepness nickel-phosphorus alloy components is still under development. Therefore, there is an urgent need for a high-efficiency, uniform, stable, and ultra-smooth processing technology that can handle large-diameter, high-steepness, complex curved surfaces of nickel-phosphorus alloy optical components. Summary of the Invention
[0005] The purpose of this invention is to overcome the aforementioned shortcomings of existing technologies and provide an ultra-smooth polishing method for large-diameter complex curved NiP composite material mirrors based on robotic polishing equipment. This method achieves ultra-smooth surfaces with a high-frequency roughness of 0.2 nm on 650 mm diameter, high-steep aspherical NiP composite materials by optimizing the polishing path to achieve segmented polishing, controlling the polishing fluid composition (concentration, pH, etc.), selecting polishing pads, and optimizing process parameters. By analyzing the influence of the geometric characteristics of large-diameter aspherical components on fluid dynamics and contaminant adhesion characteristics, a multi-stage progressive cleaning mode is adopted to comprehensively and thoroughly clean the processed surface, ensuring a high standard of surface finish.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] An ultra-smooth polishing method for large-diameter complex curved surface NiP composite material mirrors, characterized by the following steps:
[0008] Step 1: Plan the polishing path for large-diameter, steep, complex curved surface components. Divide the entire surface to be processed into multiple sub-regions, and plan a continuous polishing tool path in each sub-region. Make the direction of the polishing tool path follow the main curvature direction of the local surface in the sub-region, and generate a robot processing program file.
[0009] Step 2: According to the processing program file, the component is subjected to high-speed rough polishing using a first polishing pad and a first polishing liquid to remove turning marks;
[0010] Step 3: Using a second polishing pad and a second polishing liquid, perform nanoscale fine polishing on the component;
[0011] Step 4: Using a third polishing mold and a third polishing liquid, the component is subjected to an ultra-smooth polishing process with atomic-level removal.
[0012] Step 5: After completing the polishing operation in any of steps 2 to 4, a multi-stage progressive cleaning process is performed on the component to ensure surface cleanliness between each process.
[0013] Preferably, in step 1, the polishing path planning specifically includes: taking the geometric center of the component as the origin, uniformly dividing the entire surface to be processed into N radial fan-shaped sub-regions in the circumferential direction, where N ranges from 8 to 24; planning a continuous polishing tool path in each sub-region, and ensuring that the direction of the polishing tool path follows the principal curvature direction of the local surface in the sub-region; and using spline interpolation or circular arc transition at the boundary of each sub-region to perform smooth transition processing, so as to eliminate local removal abnormalities caused by abrupt path changes.
[0014] Preferably, in step 2, the first polishing pad is a polyurethane polishing pad with a hardness of Shore D 40-70, and the first polishing liquid is a cerium oxide polishing liquid with an average particle size of 0.1-1.2μm; the rough polishing process uses a polishing disc with a diameter of 30-80mm, controls the pressure at 3-8kg, the rotation speed at 300-800rpm, the polishing liquid flow rate at 15-30ml / min, and the processing time for each sub-area is 0.5-2 hours.
[0015] Preferably, the cerium oxide polishing solution is diluted with ultrapure water at a mass ratio of 5%-10% before use, and the pH is adjusted to 5-7 with citric acid.
[0016] Preferably, in step 3, the second polishing pad is a damping cloth polishing pad with a hardness of Shore A 50-80, and the second polishing liquid is a silica sol polishing liquid with an average particle size of 50-200nm; the fine polishing process uses a polishing disc with a diameter of 30-60mm, controls the pressure at 3-6kg, the rotation speed at 400-800rpm, the polishing liquid flow rate at 10-20ml / min, and the processing time for each sub-area is 1-2 hours.
[0017] Preferably, in step 4, the third polishing mold is a soft damping cloth polishing mold with a hardness of Shore A 30-45, and the third polishing liquid is a silica sol polishing liquid with an average particle size of 50-200nm; the ultra-smooth polishing process uses a polishing disc with a diameter of 20-50mm, controls the pressure at 2-4kg, the rotation speed at 400-800rpm, the polishing liquid flow rate at 15-25ml / min, and the processing time for each sub-region is 3-6 hours.
[0018] Preferably, the silica sol polishing slurry is diluted with ultrapure water at a mass ratio of 10%-15% before use, and the pH is adjusted to 4-6 with hydrochloric acid, and the content of impurities with a particle size greater than 200nm in the polishing slurry is ≤0.01%.
[0019] Preferably, the multi-stage progressive cleaning process in step 5 includes the following sub-steps performed sequentially:
[0020] Pretreatment cleaning: Use a polishing mold with a hardness of Shore A 30-45, combined with high-purity deionized water with a pressure of 0.3-0.6MPa and a flow rate greater than 10L / min, to brush and remove residual polishing liquid, abrasive debris and soluble residues from the surface of the processed area.
[0021] Chemical cleaning: Immerse or spray the components in an alkaline cleaning agent with a pH of 9-11, control the temperature of the cleaning solution at 35-45℃, and clean for 40-60 minutes to remove organic contaminants and metal ion residues.
[0022] Precision rinsing: The components are rinsed in a stepped manner through at least 3 cleaning tanks. Each cleaning tank uses ultrapure water at 40-50℃, and the residence time in each rinsing tank is 15-20 minutes.
[0023] Drying and dehydration: Rinse with 50-60℃ hot ultrapure water, and then blow dry the residual moisture on the surface with dry nitrogen gas.
[0024] Preferably, the volume ratio of the alkaline cleaning agent used in the chemical cleaning is: sodium carbonate 2%-4%, surfactant 0.1%-0.5%, EDTA 0.08%-2%, benzotriazole 0.4%-0.8%, and the balance is ultrapure water.
[0025] Preferably, the rough polishing, fine polishing and ultra-smooth polishing processes in steps 2, 3 and 4 are all completed on the same robotic polishing equipment, without the need for multiple clamping and transfer. By clamping and processing the large-diameter, high-steep complex curved surface NiP composite material mirror in one go, an ultra-smooth surface with a high frequency roughness ≤0.2nm RMS is obtained.
[0026] Compared with the prior art, the present invention has the following advantages:
[0027] 1. This invention addresses the geometric features of large-aperture, steep, and complex curved optical elements. By designing a phased, regional, efficient, and controllable systematic solution, it achieves ultra-smooth processing at a high frequency of 0.2nm by using only robotic polishing equipment and precisely controlling the process parameters of each step. This method does not limit the complexity of the surface shape or the aperture size, and has the outstanding advantages of high efficiency and low cost. It also has strong versatility and practicality.
[0028] 2. The large-diameter curved surface is divided into radial fan-shaped sub-regions, so that the polishing path follows the direction of the local principal curvature and achieves a smooth transition at the boundary, which solves the problems of path adaptability and removal uniformity in polishing large-diameter, high-steep curved surfaces.
[0029] 3. Coarse polishing, fine polishing, and ultra-smooth polishing use polyurethane pads (hard), damping cloth (medium-soft), and soft damping cloth (soft) respectively, along with polishing liquids of corresponding particle sizes and decreasing pressure, to form a smooth transition from mechanical removal to chemical mechanical action, avoiding the accumulation of subsurface damage.
[0030] 4. Use a mild alkaline source as the main component, combined with surfactants and complexing agents to control the pH of the cleaning solution between 9 and 10. This can effectively remove surface contaminants while ensuring zero damage to the component surface. The cleaning method is progressive, and each step prevents secondary pollution.
[0031] 5. Cleaning is triggered immediately after each polishing process, and the cleaning process itself is divided into four progressive stages: pretreatment, chemical cleaning, precision rinsing, and drying. The chemical cleaning solution uses a synergistic formula of mild alkali source, surfactant, complexing agent and corrosion inhibitor to ensure zero residue and zero damage to the ultra-smooth surface.
[0032] 6. All processes are completed on the same robot platform, eliminating the need for multiple clamping operations, which greatly improves efficiency and stability, making it particularly suitable for the engineering production of large-diameter components. Attached Figure Description
[0033] Figure 1 This is a schematic diagram of the process for the ultra-smooth polishing method of a large-diameter complex curved surface NiP composite material mirror based on robotic polishing equipment according to the present invention.
[0034] Figure 2 This is a path planning diagram for a 650mm diameter, high-steep aspherical nickel-phosphorus alloy component in an embodiment of the present invention.
[0035] Figure 3 This is a high-frequency roughness test image (atomic force microscope, test field of view 5μm×5μm) of a 650mm diameter high-steep aspherical nickel-phosphorus alloy component before processing in an embodiment of the present invention.
[0036] Figure 4This is a high-frequency roughness test image (atomic force microscope, test field of view 5μm×5μm) of a 650mm diameter high-steep aspherical nickel-phosphorus alloy component after processing, according to an embodiment of the present invention.
[0037] Figure 5 This is a mid-frequency roughness test image (white light interferometer) of a 650mm diameter high-steepness aspherical nickel-phosphorus alloy component before processing, according to an embodiment of the present invention.
[0038] Figure 6 This is a mid-frequency roughness test image (white light interferometer) of a 650mm diameter high-steepness aspherical nickel-phosphorus alloy component after processing, according to an embodiment of the present invention. Detailed Implementation
[0039] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings. It should be understood that these embodiments are only some embodiments of the present invention and not all embodiments, and should not limit the scope of protection of the present invention. It should be noted that, in the absence of conflict, the technical features of these embodiments and possible embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.
[0040] This invention provides an ultra-smooth polishing method for large-diameter, complex curved NiP composite material mirrors based on robotic polishing equipment. Targeting the geometric characteristics of large-diameter, high-steep aspherical components, a regional path planning strategy is employed. A three-stage gradient process—rough polishing, fine polishing, and ultra-smooth polishing—achieves precise control over material removal. A multi-stage progressive cleaning process is introduced after each polishing step to ensure surface cleanliness. The entire process is integrated on a single robotic polishing platform, achieving high efficiency, high stability, and high-quality processing.
[0041] Please see Figure 1 , Figure 1 The flowchart shows the ultra-smooth polishing method for the large-diameter complex curved surface NIP composite material mirror of the present invention. Figure 1 As shown, an ultra-smooth polishing method for a large-diameter, complex curved surface NIP composite material mirror includes the following steps:
[0042] Step 1. Polishing path planning:
[0043] Using the geometric center of the large-diameter, steep, complex curved surface component as the origin, the entire surface to be processed is uniformly divided into N radial fan-shaped sub-regions along the circumference. The value of N is determined comprehensively based on the component diameter, the degree of curvature change, and processing efficiency requirements, and is usually an integer between 8 and 24. Within each sub-region, a continuous polishing tool path is planned, ensuring that the direction of the polishing tool path follows the principal curvature direction of the local surface within the sub-region to guarantee optimal contact between the polishing tool and the workpiece surface and uniform pressure distribution. At the boundaries of each sub-region, spline interpolation or circular arc transitions are used for smooth transition processing to avoid abnormal local removal amounts caused by abrupt path changes. After completing the path planning, a machining program file executable by the robot is generated.
[0044] Step 2. High-speed rough polishing stage (removing tool marks)
[0045] The aim is to quickly remove periodic tool marks and surface damage layers left by previous turning processes, thus initially improving surface accuracy. A polyurethane polishing pad with a Shore D hardness of 40-70 is used, its surface featuring irregularly distributed micropores, which facilitates the storage and uniform distribution of the polishing slurry. The polishing slurry uses cerium oxide with an average particle size of 0.1-1.2 μm, diluted with ultrapure water at a mass ratio of 5%-10% before use, and the pH is adjusted to a weakly acidic or neutral range of 5-7 with citric acid to stabilize the chemical activity of the polishing slurry.
[0046] During processing, select a polishing disc with a diameter of 30-80mm (the specific size depends on the size of the sub-area), control the pressure at 3-8kg, the rotation speed at 300-800rpm, and the polishing slurry flow rate at 15-30ml / min. Process each sub-area sequentially, with the processing time set according to the initial surface quality, typically 0.5-2 hours. After processing, promptly use a large amount of deionized water with a Shore A35 hardness polishing mold to clean the surface of any remaining polishing slurry. Continue processing the remaining sub-areas sequentially using the same process until the entire diameter of the 650mm component is machined. This process effectively removes the periodic tool marks generated after turning.
[0047] Step 3. Nanoscale Fine Polishing Stage: Further reduce surface roughness to the nanoscale.
[0048] A damping cloth polishing pad with a Shore A hardness of 50-80 is used, which has moderate elasticity and microscopic chip space to achieve uniform material removal. A silica sol polishing slurry with an average particle size of 50-200 nm is selected, requiring that the content of impurities with a particle size greater than 200 nm be ≤0.01% to avoid large particles scratching the surface. Before use, the stock solution is diluted with ultrapure water at a mass ratio of 10%-15%, and the pH value is adjusted to a weakly acidic range of 4-6 with diluted hydrochloric acid (e.g., diluting the stock hydrochloric acid 10 times) to promote the chemical reaction between the silica sol and the nickel-phosphorus alloy surface, forming an easily removable softened layer.
[0049] During processing, a polishing disc with a diameter of 30-60mm is used, with a controlled pressure of 3-6kg, a rotation speed of 400-800rpm, and a polishing slurry flow rate of 10-20ml / min. The processing time for each sub-area is typically 1-2 hours. After processing, a large amount of deionized water is used to clean the surface of any remaining polishing slurry using a Shore A35 polishing mold. This process is repeated sequentially for the remaining sub-areas, using the same technique, until the entire 650mm diameter component is processed. This polishing process achieves nanoscale polishing results for high-frequency surface roughness.
[0050] Step 4. Atomic-level ultra-smooth polishing stage
[0051] A polishing mold with a hardness of Shore A30-45 is used to reduce mechanical forces and avoid creating new scratches or subsurface damage. The polishing slurry is still a high-purity silica sol polishing slurry with an average particle size of 50-200 nm, prepared in the same way as in step 3, but the impurity content must be strictly controlled to ensure that the impurity content is ≤0.1%.
[0052] During processing, a small polishing disc with a diameter of 20-50mm is used, with the pressure reduced to 2-4kg and the rotation speed maintained at 400-800rpm. The polishing slurry flow rate is 15-25ml / min. The processing time for each sub-region needs to be appropriately extended, typically 3-6 hours, to ensure atomic-level surface planarization. After processing, a large amount of deionized water is used to clean the surface of any remaining polishing slurry with a soft damping cloth. This process is repeated sequentially using the same technique for the remaining 15 sub-regions until the entire 650mm diameter component is processed. This process achieves a sub-nanometer-level ultra-smooth polishing result with high-frequency surface roughness. The 5µm field of view is measured using an atomic force microscope.
[0053] Step 5. Multi-stage progressive cleaning process
[0054] This invention regards cleaning as an equally important process as polishing, and adopts a four-stage progressive cleaning process of pretreatment, chemical cleaning, precision rinsing and drying. The cleaning process is forcibly triggered after each polishing process from step 2 to step 4 to ensure the surface cleanliness between each process.
[0055] Pre-treatment cleaning: Immediately after polishing, use a soft polishing mold with a Shore A hardness of 30-45, along with high-pressure (0.3-0.6MPa) and high-flow-rate (>10L / min) high-purity deionized water, to scrub the polishing area and quickly remove polishing liquid, abrasive debris, and most soluble residues adhering to the surface. This step effectively prevents residues from adhering firmly after drying.
[0056] Chemical cleaning: Immerse or spray the components in an alkaline cleaning agent with a pH of 9-11. Maintain the cleaning solution temperature at 35-45℃ and clean for 40-60 minutes. The preferred volume ratio of this alkaline cleaning solution is: sodium carbonate 2%-4% (as a mild alkali source), surfactant 0.1%-0.5% (to reduce surface tension and improve wettability and detergency), EDTA 0.08%-2% (to complex metal ions and prevent secondary deposition), benzotriazole 0.4%-0.8% (as a copper / nickel corrosion inhibitor to protect the substrate), and the balance being ultrapure water. This formulation effectively removes organic contaminants and metal ions while ensuring zero damage to the substrate.
[0057] Precision rinsing: Components are sequentially rinsed through at least three rinsing tanks in a stepped rinsing process. Each tank uses ultrapure water at 40-50°C, gradually reducing the concentration of contaminants to achieve residue-free rinsing. The residence time in each rinsing tank is typically 15-20 minutes.
[0058] Drying and dehydration: The components are finally rinsed with hot ultrapure water at 50-60℃, and then immediately dried with high-purity dry nitrogen (purity ≥99.999%) to obtain a dry, clean, and ultra-smooth surface.
[0059] Example
[0060] This embodiment uses a 650mm diameter aluminum-based nickel-phosphorus alloy composite aspherical mirror as the processing object to illustrate the implementation process and effects of the method of the present invention.
[0061] S1: Polishing Path Planning
[0062] Please see the appendix Figure 2Using the geometric center of the component as the origin, the entire aspherical surface is uniformly divided into 16 radial fan-shaped sub-regions along the circumference. Within each sub-region, a continuous spiral or grating-style polishing path is planned, ensuring that the path direction follows the principal curvature direction (i.e., the direction of maximum slope) of the local surface of the sub-region as closely as possible. At the boundaries of each sub-region, a circular arc transition is used to smoothly connect the paths, generating the robot machining program.
[0063] S2: High-speed coarse polishing
[0064] Polishing pad: Polyurethane polishing pad, hardness Shore D 57;
[0065] Polishing solution: Cerium oxide polishing solution with an average particle size of 0.3μm, stock solution concentration of 25wt%, pH 9-10; when using, dilute ultrapure water and polishing solution stock solution at a mass ratio of 3:1, and adjust the pH to 6 with citric acid;
[0066] Process parameters: polishing disc diameter 60mm, pressure 5kg, rotation speed 500rpm, polishing fluid flow rate 20ml / min;
[0067] Processing method: Process in the order of sub-regions, with each sub-region taking 1 hour to process;
[0068] Cleaning: After each sub-area is completed, immediately clean the surface with plenty of deionized water and a soft polishing brush with a hardness of Shore A 35 to remove residue.
[0069] After full-diameter machining, the turning marks are basically removed, and the surface becomes more uniform.
[0070] S3: Nanoscale Precision Polishing
[0071] Polishing pad: Damping cloth polishing pad, hardness Shore A 64;
[0072] Polishing slurry: Silica sol polishing slurry with an average particle size of 120nm, stock concentration of 25%, pH 9-10, of which the content of impurities larger than 120nm is ≤0.1%; when using, dilute ultrapure water and polishing slurry stock at a mass ratio of 3:1, and adjust the pH to 5 with hydrochloric acid diluted 10 times.
[0073] Process parameters: polishing disc diameter 40mm, pressure 5kg, rotation speed 500rpm, polishing fluid flow rate 15ml / min; processing method: processing in sub-area sequence, each sub-area processing for 1 hour;
[0074] Cleaning: After each sub-area is completed, immediately clean the surface with plenty of deionized water using a soft polishing brush with a hardness of Shore A 35.
[0075] S4: Atomic-level ultra-smooth polishing
[0076] Polishing mold: Soft damping cloth polishing mold, hardness Shore A 35;
[0077] Polishing slurry: The same silica sol polishing slurry as in step 3, prepared in the same manner;
[0078] Process parameters: polishing disc diameter 40mm, pressure reduced to 3kg, rotation speed 500rpm, polishing fluid flow rate 20ml / min;
[0079] Processing method: Process in sub-region sequence, with each sub-region taking 4 hours to process;
[0080] Cleaning: After each sub-area is completed, immediately perform the complete step 5 cleaning process (see below).
[0081] S5: Multi-stage progressive cleaning
[0082] Pre-treatment cleaning: Use a soft polishing mold with a hardness of Shore A 35, along with 0.4MPa high-pressure deionized water to clean the processed area;
[0083] Chemical cleaning: Immerse the components in an alkaline cleaning solution with pH 9 (ratio: sodium carbonate 2.5%, surfactant 0.2%, EDTA 0.08%, benzotriazole 0.5%, balance ultrapure water), at a cleaning solution temperature of 35℃, for 40 minutes;
[0084] Precision rinsing: The components are passed through three cleaning tanks in sequence, each containing 40°C ultrapure water, and each tank is left for 15 minutes.
[0085] Drying and dehydration: Rinse with 55°C hot ultrapure water for the final step, and then dry with high-purity drying nitrogen.
[0086] Processing result testing
[0087] High-frequency roughness: measured using atomic force microscopy (AFM) with a 5μm × 5μm field of view. Before processing (e.g.) Figure 3 The high-frequency roughness (as shown) is 2.14 nanometers; after processing (attached) Figure 4 The high-frequency roughness is reduced to 0.15nm RMS, reaching a sub-nanometer level of ultra-smoothness.
[0088] Mid-frequency roughness: measured using a white light interferometer. (Before processing - see attached image) Figure 5 There is a significant mid-frequency error; after processing (attached) Figure 6 The mid-frequency error is significantly suppressed.
[0089] The above test results show that the method of the present invention has successfully achieved an ultra-smooth surface with a full-diameter high-frequency roughness of less than 0.2 nm on a 650 mm diameter high-steep aspherical NiP composite material element, with good surface shape consistency, high surface cleanliness, and no scratches or residues.
[0090] This invention achieves a sub-nanometer surface roughness of 0.2 nm RMS, meeting the extreme surface quality requirements of fields such as extreme ultraviolet lithography and space optics. Regional path planning combined with gradient processes effectively solves the edge effects and uneven removal problems in the processing of large-diameter, steep curved surfaces. A progressive cleaning process, coupled with end-to-end cleaning control, thoroughly removes various contaminants, resulting in a high-standard smooth surface. The entire process is integrated on a single robotic platform, eliminating the need for expensive specialized equipment and multiple clamping operations, thus reducing manufacturing costs and cycle time. It can be widely applied to the ultra-smooth processing of various complex curved optical components.
[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of patent protection of the present invention. Any modifications, equivalent substitutions, or improvements made by those skilled in the art within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A method for super-smooth polishing of a large-aperture complex-curved NiP composite mirror, characterized in that, Includes the following steps: Step 1: Plan the polishing path for large-diameter, steep, and complex curved surface components. Divide the entire surface to be processed into multiple sub-regions, plan a continuous polishing tool path in each sub-region, and make the direction of the polishing path follow the main curvature direction of the local surface in the sub-region to generate a robot processing program file. Step 2: According to the processing program file, the component is subjected to high-speed rough polishing using a first polishing pad and a first polishing liquid to remove turning marks; Step 3: Using a second polishing pad and a second polishing liquid, perform nanoscale fine polishing on the component; Step 4: Using a third polishing mold and a third polishing liquid, the component is subjected to an ultra-smooth polishing process with atomic-level removal. Step 5: After completing the polishing operation in any of the steps 2 to 4, a multi-stage progressive cleaning process is performed on the component to ensure the surface cleanliness between each process. The multi-stage progressive cleaning process in step 5 includes the following sub-steps performed sequentially: Pretreatment cleaning: Use a polishing mold with a hardness of Shore A 30-45, combined with high-purity deionized water with a pressure of 0.3-0.6MPa and a flow rate greater than 10L / min, to brush and remove residual polishing liquid, abrasive debris and soluble residues from the surface of the processed area. Chemical cleaning: Immerse or spray the components in an alkaline cleaning agent with a pH of 9-11, control the temperature of the cleaning solution at 35-45℃, and clean for 40-60 minutes to remove organic contaminants and metal ion residues. Precision rinsing: The components are rinsed in a stepped manner through at least 3 cleaning tanks. Each cleaning tank uses ultrapure water at 40-50℃, and the residence time in each rinsing tank is 15-20 minutes. Drying and dehydration: Rinse with 50-60℃ hot ultrapure water, and then blow dry the residual moisture on the surface with dry nitrogen gas.
2. The method for super-smooth polishing of large-aperture complex curved NiP composite mirror according to claim 1, wherein, The polishing path planning in step 1 specifically includes: taking the geometric center of the component as the origin, uniformly dividing the entire surface to be processed into N radial fan-shaped sub-regions in the circumferential direction, where N ranges from 8 to 24; planning a continuous polishing path in each sub-region, and ensuring that the direction of the polishing path follows the principal curvature direction of the local surface in the sub-region; and using spline interpolation or circular arc transition at the boundary of each sub-region to perform smooth transition processing, so as to eliminate local removal abnormalities caused by abrupt path changes.
3. The method of claim 1, wherein the method is used for polishing a large aperture complex curved NiP composite mirror. In step 2, the first polishing pad is a polyurethane polishing pad with a hardness of Shore D 40-70, and the first polishing liquid is a cerium oxide polishing liquid with an average particle size of 0.1-1.2μm. The rough polishing process uses a polishing disc with a diameter of 30-80mm, controls the pressure at 3-8kg, the rotation speed at 300-800rpm, the polishing liquid flow rate at 15-30ml / min, and the processing time for each sub-area is 0.5-2 hours.
4. The method of claim 3, wherein the method is used for polishing a large aperture complex curved NiP composite mirror. Before use, the cerium oxide polishing solution is diluted with ultrapure water at a mass ratio of 5%-10%, and the pH is adjusted to 5-7 with citric acid.
5. The method of claim 1, wherein the method is used for polishing a large aperture complex curved NiP composite mirror. In step 3, the second polishing pad is a damping cloth polishing pad with a hardness of Shore A 50-80, and the second polishing liquid is a silica sol polishing liquid with an average particle size of 50-200nm. The fine polishing process uses a polishing disc with a diameter of 30-60mm, controls the pressure at 3-6kg, the rotation speed at 400-800rpm, the polishing liquid flow rate at 10-20ml / min, and the processing time for each sub-area is 1-2 hours.
6. The method of claim 1, wherein the method is used for polishing a large aperture complex curved NiP composite mirror. In step 4, the third polishing mold is a soft damping cloth polishing mold with a hardness of Shore A 30-45, and the third polishing liquid is a silica sol polishing liquid with an average particle size of 50-200nm. The ultra-smooth polishing process uses a polishing disc with a diameter of 20-50mm, controls the pressure at 2-4kg, the rotation speed at 400-800rpm, the polishing liquid flow rate at 15-25ml / min, and the processing time for each sub-region is 3-6 hours.
7. The ultra-smooth polishing method for large-aperture complex curved surface NiP composite material mirrors according to claim 5 or 6, characterized in that, Before use, the silica sol polishing slurry is diluted with ultrapure water at a mass ratio of 10%-15%, and the pH is adjusted to 4-6 with hydrochloric acid. The content of impurities with a particle size greater than 200nm in the polishing slurry is ≤0.01%.
8. The ultra-smooth polishing method for a large-aperture complex curved surface NiP composite material mirror according to claim 1, characterized in that, The volume ratio of the alkaline cleaning agent used in the chemical cleaning is as follows: sodium carbonate 2%-4%, surfactant 0.1%-0.5%, EDTA 0.08%-2%, benzotriazole 0.4%-0.8%, and the balance is ultrapure water.
9. The ultra-smooth polishing method for a large-aperture complex curved surface NiP composite material mirror according to claim 1, characterized in that, The rough polishing, fine polishing, and ultra-smooth polishing processes in steps 2, 3, and 4 are all completed on the same robotic polishing equipment, without the need for multiple clamping and transfers. By clamping and processing the large-diameter complex curved surface NiP composite material mirror in one go, an ultra-smooth surface with a high-frequency roughness ≤0.2nm RMS is obtained.