Ultra-precision conformal polishing method and apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion

Abstract

An ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion is provided, the method utilizes an electrochemical gradient-thickening phase to induce electrochemical interfacial reactions that guide a directional motion of charged particles and control a particle aggregation effect of a suspension; and a flexible fluid abrasive tool is then used to generate a vibration-induced microdynamic force in a workpiece direction for efficient conformal material removal. An ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion includes a housing, a conformal polishing device, a power-supply auxiliary device, an electrochemical gradient-thickening polishing suspension conveying device, and a polishing auxiliary device. The present invention can machine a wide variety of workpieces, not only significantly improves surface form accuracy but also achieves polishing precision at the atomic and near-atomic scale.

Description

TECHNICAL FIELD

[0001] The present invention belongs to the field of ultra-precision lapping and polishing, in particular to an ultra-precision conformal polishing method and apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion. BACKGROUND TECHNOLOGY

[0002] A micro-structured surface is a tiny and structurally-defined surface arranged in a regular and periodic manner, and is capable of performing various specialized optical, physical, and biological functions. In recent years, due to the rapid advancements in industries such as fiber-optic communications and imaging technology, miniature components with micro-structured optical functional surfaces (also known as micro-structured optical functional elements) have been widely applied in miniaturized optoelectronic and communication products, biomedical devices, aerospace and intelligent guidance systems because of their compact size, light weight, and high levels of integration. For example, microprism structures, such as single-crystal silicon, silicon carbide, and other materials in spherical / aspherical lens commonly used in infrared optical systems, as well as micro-prism structures used in display backlight modules and infrared reflection systems for aircraft and satellites, all require nanometer-level surface roughness. However, owing to their extremely small structural dimensions, low stiffness, and stringent accuracy requirements, traditional polishing technologies often face significant limitations. Over the past few years, many researchers have continuously explored ultra-precision polishing methods suitable for micro-structured surfaces. To further improve the manufacturing efficiency of micro-structured array components and address the challenge of achieving uniform processing of micro-groove surfaces by an abrasive slurry in traditional abrasive-jet polishing, the present invention provides an ultra-precision conformal polishing method and apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion.

[0003] Electrochemical polishing is a surface treatment method that dissolves an anode of metal workpiece in specific electrochemical polishing solution environment, thereby reducing its surface roughness, increasing its brightness, and imparting a metallic luster. As a method of metal surface treatment, electrochemical polishing has the following advantages: 1) it can effectively reduce surface roughness, achieving excellent polishing results; 2) it exhibits high efficiency and has no direct relation to mechanical properties (such as hardness, toughness, strength) of the materials being treated; and 3) compared with mechanical polishing equipment, the equipment required for forming polished parts is simpler and more economical. During polishing, the workpiece does not contact the tool (cathode); therefore, no cutting force, heat generation, burrs, tool marks, or tool wear are produced.

[0004] Maintaining the rotational stability of impeller blades, rotors, bearings, and other components is a major challenge. Rotating components are prone to whirling due to internal structural factors or external disturbances, which may shorten service life or even cause structural damage. However, the present invention leverages this characteristic to implement micro-structured nano-scale polishing technology. By generating a vibration-induced microdynamic force through a smooth rotor structure toward a workpiece thereof, the induced vibration causes the rotor to form a whirling motion, thus enabling efficient and conformal material removal while effectively controlling surface form accuracy.

[0005] Published Chinese Patent CN117718551A discloses a multi-degree-of-freedom ultrasonic electrochemical-assisted polishing device and method for complex curved-surface parts. The device includes a machine bed, a five-axis linkage system, a spindle system, a measurement system, a chain-type tool magazine, a numerical control system and a polishing slurry circulation system mounted within the machine bed. A cutting tool, a workpiece, and the polishing slurry together form a closed electrochemical circuit, thereby constituting an electrochemical system. During processing, the ultrasonic transducer is activated, and the polishing slurry circulation system sprays the polishing slurry onto a machining area. The workpiece, acting as the anode, loses electrons. Through the coupled action of ultrasonic electrochemical mechanical grinding-polishing, surface material of the workpiece is removed, thereby achieving ultrasonic electrochemical-assisted polishing for complex curved-surface components, and obtaining the workpiece with improved surface quality and low surface roughness. The invention achieves fully automated machining through tool paths controlled by a numerical control system, and significantly improves the surface roughness and form accuracy of the machined parts compared with traditional mechanical grinding and polishing technology. However, the patent does not address the recovery or reutilization of the electrochemical polishing slurry.

[0006] Published Chinese Patent CN117584024A provides a high-efficiency polishing device and method using an ultrasonic vibration and electrochemical-assisted liquid-film shearing. The polishing device includes a polishing tank for holding a polishing slurry; a polishing plate is arranged at a bottom of the polishing tank and mounted on a drive shaft of the polishing plate; an ultrasonic generator disposed within the polishing tank below the polishing plate; a workpiece clamping and holding drive mechanism is disposed above the polishing tank for holding and driving the workpiece to rotate, and the workpiece clamping and holding drive mechanism is connected to an adjustment mechanism and is capable of moving up and down under the drive of the adjustment mechanism; the polishing tank is connected to a negative electrode of a pulse power supply, and the workpiece clamping and holding drive mechanism is connected to a positive electrode of the pulse power supply, forming a closed loop with the polishing slurry in the polishing tank during polishing. The polishing device of the invention combines ultrasonic vibration, electrochemical anodic oxidation, and liquid-film shearing polishing technology for polishing the workpiece, thereby improving the efficiency of material removal and machining uniformity. However, the patent cannot polish micro-scale structural components, and further improvements are expected in terms of component variety and performance.

[0007] Published Chinese Patent CN115401534B provides a conformal polishing method for micro-array molds. The method involves fabricating a conformal polishing tool head that matches a surface form of the micro-array mold, and abrasive particles are added between the tool head and the mold surface. Using an XY two-dimensional electric translation stage, the mold or the tool head is driven to perform micro-vibration at a specified frequency and amplitude. The abrasive particles between the tool head and the mold surface generate micro-cutting action under their relative pressure and relative motion, thereby removing material and eliminating defects such as tool marks and scratches on the micro-mold surface. The method overcomes limitations of extremely small feature sizes in micro-array molds and enables simultaneous polishing of all feature points on the micro-array molds with high efficiency, without compromising the surface form accuracy of the micro-array molds. As a result, high surface form accuracy and excellent surface quality can be achieved. However, the patent does not involve electrochemical polishing, and there is still room for improvement in efficient polishing of workpieces. SUMMARY OF THE INVENTION

[0008] To overcome the shortcomings of the prior art and to address the problem of difficulty in achieving conformal processing for micro-structured components, the present invention provides an ultra-precision conformal polishing method and apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion, which can not only significantly improve the surface form accuracy, but also achieve polishing precision at the atomic and near-atomic scale.

[0009] A technical solution adopted by the present invention for solving the above technical problems is as follows:

[0010] an ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion is provided, the method utilizes an electrochemical gradient-thickening phase to induce electrochemical interfacial reactions that guide a directional motion of charged particles and control a particle aggregation effect of a suspension; and a flexible fluid abrasive tool is then used to generate a vibration-induced microdynamic force in a workpiece direction for efficient conformal material removal.

[0011] Further, the ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion includes the following steps:

[0012] (1) placing an anode workpiece on a polishing worktable, connecting an anode clamp to the anode workpiece, and connecting a cathode clamp to a flexible conformal component;

[0013] (2) activating a numerical control unit to control path and process parameters of the flexible conformal component, such that a starting point conforms to the surface of the anode workpiece;

[0014] (3) adding an electrochemical gradient-thickening polishing suspension containing nano-abrasive particles to a material storage tank, activating a hydraulic pump, and conveying the electrochemical gradient-thickening polishing suspension through a conveying pipe into the conformal polishing device;

[0015] (4) turning on a circuit controller and an electrochemical thickening generator, and inducing an electrochemical interface reaction by an electrochemical gradient-thickening phase that guides a directional motion of charged particles and controls a particle aggregation effect of the electrochemical gradient-thickening polishing suspension, such that the flexible conformal component exhibits real-time weak-rigidity rheological behavior in a fluid flow, thereby forming a flexible fluid abrasive tool; and

[0016] (5) activating a spindle housing, generating a vibration-induced microdynamic force in the workpiece direction on the rotating flexible fluid abrasive tool, and inducing the flexible fluid abrasive tool to generate a whirling motion by the vibration-induced microdynamic force, causing dynamic regulation mechanism for a vibration-induced micro-motion polishing slurry, and promoting micro-vibration of a flexible fluid to facilitate a dwell and dynamic trajectory behavior of the flexible fluid abrasive tool, achieving efficient conformal material removal and control of polished surface form accuracy in a region under the combined action of vibration-induced micro-motion.

[0017] Furthermore, in the step (1), a rotor is disposed within an inner cavity of the flexible conformal component, and a stator is disposed at an eccentric position of an outer cavity of the flexible conformal component, maintaining a predetermined degree of airtightness; the flexible conformal component deforms according to a shape of the anode workpiece, thereby closely conforming to a surface of the anode workpiece; when rotating with a rotating shaft, the flexible conformal component generates a vibration-induced microdynamic force in the workpiece direction; and the vibration-induced microdynamic force induces the flexible conformal component to form a whirling motion, thereby achieving efficient conformal material removal.

[0018] Furthermore, in the step (4), the electrochemical gradient-thickening phase is porous microsphere particles. When the porous microsphere particles are incorporated into the electrochemical gradient-thickening polishing suspension, they undergo a slow chemical reaction and thus generate negatively charged particles. These negatively charged particles subsequently induce an aggregation effect among positively charged metallic nano-abrasive particles.

[0019] Preferably, electrochemical gradient thickening or gradient dilution is achieved by adjusting a relative quantity ratio between the electrochemical gradient-thickening and the electrochemical gradient-thickening polishing suspension.

[0020] The electrochemical gradient-thickening phase is selected from carboxylates, carbonates, sulfites, amino acid salts, or the like.

[0021] In the step (3), the nano-abrasive particles include one or a mixture of two or more of nanodiamond, cubic boron oxide, boron carbide, silicon carbide, silicon nitride, silicon oxide, gallium oxide, iron oxide, magnesium oxide, lithium fluoride, graphite, or Al2O3.

[0022] In the step (3), the electrochemical gradient-thickening polishing suspension includes an acidic electrochemical polishing slurry, a neutral electrochemical polishing slurry, and an alkaline electrochemical polishing slurry; for polishing a silicon-based material or an alloy material, the acidic electrochemical polishing slurry is used, including an electrochemical polishing slurry based on phosphoric acid, sulfuric acid, perchloric acid, or a phosphoric-sulfuric acid system combined with various additives. The electrochemical gradient-thickening phase incorporates controlled-release physicochemical particles (i.e., fluid flow-property regulating particles) to regulate hydrophilic-hydrophobic properties of the polishing slurry that is in contact with a structural surface.

[0023] The controlled-release physicochemical particles are sodium polyacrylate, polyvinyl alcohol, polyurethane thickeners, and the like.

[0024] An ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion includes a housing, a conformal polishing device, a power-supply auxiliary device, an electrochemical gradient-thickening polishing suspension conveying device, and a polishing auxiliary device; the conformal polishing device is located in a center of the housing; the power-supply auxiliary device is located at a left end of the housing; the electrochemical gradient-thickening polishing suspension conveying device is located at a right end of the housing; and the polishing auxiliary device is located within the housing; and

[0025] the conformal polishing device includes, from top to bottom, a spindle housing, a spindle, an electrochemical gradient-thickening polishing suspension flow channel, a current delivery channel, an electrochemical thickening generator, a connecting shaft, a rotating shaft, a flexible conformal component, and a detector; an upper end of the spindle is connected to the spindle housing, and a lower end of the spindle is connected to the electrochemical thickening generator; the electrochemical gradient-thickening polishing suspension flow channel and the current delivery channel are formed at a position of the spindle; the connecting shaft is configured to connect the electrochemical thickening generator and the rotating shaft; and the flexible conformal component and the detector are mounted at a position of the rotating shaft.

[0026] Further, a rotor is disposed within an inner cavity of the flexible conformal component, and a stator is disposed at an eccentric position of an outer cavity of the flexible conformal component, maintaining a predetermined degree of airtightness.

[0027] The power-supply auxiliary device includes a high-voltage power supply, an anode clamp, a cathode clamp, a circuit protection device, a transformer, and a circuit controller; an anode of the power supply is connected to an anode workpiece via the circuit protection device, and a cathode of the power supply is connected to the flexible conformal component via the transformer; and the circuit controller is configured to control power supply and current of a circuit.

[0028] The electrochemical gradient-thickening polishing suspension conveying device includes a conveying pipe, a hydraulic pump, a material storage tank, and a recovery tank; and an electrochemical gradient-thickening polishing suspension flows sequentially through the hydraulic pump and the conformal polishing device through the conveying pipe, enters an inner cavity of the flexible conformal component, and then flows through a through hole of a polishing workbench into the recovery tank, thereby completing the delivery and recovery of an electrochemical polishing slurry.

[0029] The polishing auxiliary device includes a numerical control unit, a lifting frame, a movable frame, a slideway, an X-axis guide rail, a Y-axis guide rail, a Z-axis guide rail, an anode workpiece, a fixture, and a polishing workbench; the lifting frame, the movable frame, and the slideway are interconnected via the X-axis guide rail, the Y-axis guide rail, or the Z-axis guide rail, respectively; the numerical control unit controls their motions; the Z-axis guide rail on the slideway is connected to the conformal polishing device, a lower end of the conformal polishing device is provided with the polishing workbench; and the polishing workbench is provided with a fixture, and the anode workpiece is mounted at a position of the fixture.

[0030] The electrochemical thickening generator enables controllable gradient changes in a viscosity of the electrochemical gradient-thickening polishing suspension, allowing gradient thickening to achieve an optimal viscosity threshold, thereby effectively regulating the rheological behavior and maintaining real-time rigidity stability of the flexible fluid abrasive tool.

[0031] The numerical control unit not only adjusts a degree of freedom of the conformal polishing system, but also controls conformal polishing paths and processing parameters. It controllably adjusts a removal trajectory and dwell-state parameters, actively regulates surface conformity, and achieves deterministic material removal, thereby further improving the surface form accuracy of large-area micro-structured surfaces and ultimately ensuring conformal polishing performance.

[0032] The detector may track the material removal process in real time and provide immediate feedback when over-polishing or under-polishing occurs, preventing damage to microstructures caused by machining errors.

[0033] The polishing workbench is provided with a fixture to secure the anode workpiece. A through hole is formed on the polishing workbench, such that the electrochemical gradient-thickening polishing suspension, after processing, it flows into the recovery tank.

[0034] The spindle is provided with the electrochemical gradient-thickening polishing suspension flow channel and the current delivery channel. The electrochemical gradient-thickening polishing suspension flows into a conformal polishing system through the electrochemical gradient-thickening polishing suspension flow channel, and current is supplied to the flexible conformal component via the cathode clamp.

[0035] The anode workpiece includes spherical or aspherical lens substrate made of monocrystalline silicon or silicon carbide for infrared optical systems, miniature sensing components, stainless-steel micro-gear bolts and nuts, and the like.

[0036] The high-voltage power supply commonly used in electrochemical processing is a silicon rectifier power supply or a thyristor rectifier power supply. The circuit protection device is configured to effectively prevent damage caused by short circuits or excessive current load.The present invention has the following beneficial effects:

[0037] 1. A wide variety of workpieces machined. The apparatus of the present invention is capable of machining different types of workpieces, such as microarray components, miniature sensing elements, miniature gears, bolts, nuts, and basic components of microstructures.

[0038] 2. Vibration-induced micro-motion structures. A smooth rotor is disposed within the inner cavity of the polishing fluid abrasive tool, and an eccentric stator is disclosed within in the outer cavity. According to force analysis and dynamic distribution, a vibration-induced microdynamic force is generated on the smooth rotor mechanism in a workpiece direction; the vibration-induced microdynamic force induces a whirling motion of the rotor, causing dynamic regulation mechanism for a vibration-induced micro-motion polishing slurry, and promoting micro-vibration of a flexible fluid to facilitate a dwell and dynamic trajectory behavior of the flexible fluid abrasive tool, achieving efficient conformal material removal and control of polished surface form accuracy in a region under the combined action of vibration-induced micro-motion. An electrochemical gradient-thickening phase incorporates temperature-sensitive or controlled-release physicochemical particles (i.e., fluid flow-property regulating particles) to achieve hydrophilic-hydrophobic properties of the polishing slurry that is in contact with a structural surface.

[0039] 3. Advantages of the numerical control unit. The polishing system can be controlled in the X, Y, and Z directions, and can be regulated for different sizes of components, greatly accommodating the machining of various types of components. In addition, it can control conformal polishing paths and processing parameters, controllably adjust a removal trajectory and dwell-state parameters, actively regulates surface conformity, and achieves deterministic material removal, thereby further improving the surface form accuracy of large-area micro-structured surfaces.

[0040] 4. Extremely high surface form accuracy. Under the action of the electrochemical thickening generator, a specific electrochemical gradient thickening effect is generated, and the “flexibility” of the fluid abrasive tool is further regulated. In the vibration-induced micro-motion region, the fluid abrasive tool exhibits a real-time weakly rigid rheological behavior, forming a flexible fluid abrasive tool. When the conformal polishing device controls the dynamic motion of the workpiece, and the flexible fluid abrasive (fluid abrasive tool) tool, hydrophilic-hydrophobic properties of the polishing slurry is regulated to facilitate large-area contact of micro-abrasives with the surface of the workpiece, enabling highly efficient material removal by fine abrasive particles.

[0041] 5. The present invention requires relatively low requirements for polishing equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG. 1 is a schematic diagram of an ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion.

[0043] FIG. 2 is a schematic diagram of a polishing method of an ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion.

[0044] FIG. 3 is a schematic diagram of a thickening mechanism for an electrochemical gradient-thickening polishing suspension.

[0045] FIG. 4 is a schematic diagram of a polishing auxiliary device of an ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion.

[0046] FIG. 5 is a schematic diagram of an anode workpiece, where (a) illustrates a silicon carbide microlens structure; (b) illustrates a silicon nitride microprism structure; (c) illustrates a cylindrical array microstructure; and (d) illustrates a tetrahedral array microstructure.

[0047] Reference numerals in the accompanying drawings: 1. housing; 2. circuit controller; 3. lift frame; 4. slideway; 5. Z-axis guide rail; 6. X-axis guide rail; 7. movable frame; 8. numerical control unit; 9. conveying pipe; 10. hydraulic pump; 11. material storage tank; 12. Y-axis guide rail; 13. recovery tank; 14. anode workpiece; 15. polishing workbench; 16. electrochemical thickening generator; 17. circuit protection device; 18. high-voltage power supply; 19. transformer; 20. spindle housing; 21. spindle; 22. electrochemical gradient-thickening polishing suspension flow channel; 23. current delivery channel; 24. connecting shaft; 25. rotating shaft; 26. flexible conformal component; 27. detector; 28. electrochemical gradient-thickening phase; 29. nano-abrasive particles; 30. stator; 31. rotor; 32. vibration; 33. aggregation effect; 34. whirling motion.DETAILED DESCRIPTIONS OF THE EMBODIMENTS

[0048] The present invention will be further described below with reference to the accompanying drawings.

[0049] Referring to FIGS. 1-5, an ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion is provided. The method utilizes an electrochemical gradient-thickening phase 28 to induce electrochemical interfacial reactions that guide a directional motion of charged particles and control a particle aggregation effect of a suspension; and a flexible fluid abrasive tool is then used to generate a vibration-induced microdynamic force in a workpiece direction for efficient conformal material removal. The method not only significantly improves surface form accuracy but also achieves polishing precision at the atomic and near-atomic scale.

[0050] An ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion is provided. The apparatus includes a housing 1, a conformal polishing device, a power-supply auxiliary device, an electrochemical gradient-thickening polishing suspension conveying device, and a polishing auxiliary device. The conformal polishing device includes, from top to bottom, a spindle housing 20, a spindle 21, an electrochemical gradient-thickening polishing suspension flow channel 22, a current delivery channel 23, an electrochemical thickening generator 16, a connecting shaft 24, a rotating shaft 25, a flexible conformal component 26, and a detector 27. The conformal polishing device is located in a center of the housing 1. The power-supply auxiliary device includes a high-voltage power supply 18, an anode clamp, a cathode clamp, a circuit protection device 17, a transformer 19, and a circuit controller 2. The power-supply auxiliary device is located at a left end of the housing 1. The electrochemical gradient-thickening polishing suspension conveying device includes a conveying pipe 9, a hydraulic pump 10, a material storage tank 11, and a recovery tank 13. The electrochemical gradient-thickening polishing suspension conveying device is located at a right end of the housing 1. The polishing auxiliary device includes a numerical control unit 8, a lifting frame 3, a movable frame 7, a slideway 4, an X-axis guide rail 6, a Y-axis guide rail 12, a Z-axis guide rail 5, an anode workpiece 14, a fixture, and a polishing workbench 15. The polishing auxiliary device is located within the housing 1.

[0051] In the conformal polishing device, an upper end of the spindle 21 is connected to the spindle housing 20, and a lower end of the spindle is connected to the electrochemical thickening generator 16. The electrochemical gradient-thickening polishing suspension flow channel 22 and the current delivery channel 23 are formed at a position of the spindle 21. The connecting shaft 24 is configured to connect the electrochemical thickening generator 16 and the rotating shaft 25. The flexible conformal component 26 and the detector 27 are mounted at a position of the rotating shaft 25.

[0052] The electrochemical thickening generator 16 enables controllable gradient changes in a viscosity of the electrochemical gradient-thickening polishing suspension, allowing gradient thickening to achieve an optimal viscosity threshold, thereby effectively regulating the rheological behavior and maintaining real-time rigidity stability of the flexible fluid abrasive tool.

[0053] A rotor 31 is disposed within an inner cavity of the flexible conformal component 26, and a stator 30 is disposed at an eccentric position of an outer cavity of the same, maintaining a predetermined degree of airtightness. The flexible conformal component 26 may deform according to a shape of the anode workpiece 14, thereby closely conforming to a surface of the anode workpiece 14. When the flexible conformal component 26 rotates with the rotating shaft 25, the flexible conformal component 26 generates a vibration-induced microdynamic force in a workpiece direction. The vibration-induced microdynamic force induces the flexible conformal component 26 to form a whirling motion, thereby achieving efficient conformal material removal.

[0054] The detector 27 may track the material removal process in real time and provide immediate feedback when over-polishing or under-polishing occurs, preventing damage to microstructures caused by machining errors.

[0055] The spindle 21 is provided with the electrochemical gradient-thickening polishing suspension flow channel 22 and the current delivery channel 23. The electrochemical gradient-thickening polishing suspension flows into the conformal polishing device through the electrochemical gradient-thickening polishing suspension flow channel 22, and current is supplied to the flexible conformal component 26 via the current delivery channel.

[0056] In the power-supply auxiliary device, the power-supply auxiliary device is located at a left end of the housing 1; and anode of the power supply is connected to an anode workpiece 14 via the circuit protection device 17, and a cathode of the power supply is connected to the flexible conformal component 26 via the transformer 19. The circuit controller 2 is configured to control power supply and current of a circuit.

[0057] The high-voltage power supply 18 is a silicon rectifier power supply or a thyristor rectifier power supply. The circuit protection device 17 is configured to effectively prevent damage caused by short circuits or excessive current load.

[0058] In the electrochemical gradient-thickening polishing-suspension conveying device, the electrochemical gradient-thickening polishing suspension flows sequentially through the hydraulic pump 10 and the conformal polishing device through the conveying pipe 9, enters an inner cavity of the flexible conformal component 26, and then flows through a through hole of a polishing workbench 15 into the recovery tank 13, thereby completing the delivery and recovery of an electrochemical polishing slurry.

[0059] In the present invention, the electrochemical gradient-thickening polishing suspension contains nano-abrasive particles 29. The nano-abrasive particles 29 include one or more of nanodiamond, cubic boron oxide, boron carbide, silicon carbide, silicon nitride, silicon oxide, gallium oxide, iron oxide, magnesium oxide, lithium fluoride, graphite, and Al2O3.

[0060] The electrochemical gradient-thickening polishing suspension typically includes an acidic electrochemical polishing slurry, a neutral electrochemical polishing slurry, and an alkaline electrochemical polishing slurry. For polishing a silicon-based material or an alloy material, the acidic electrochemical polishing slurry is primarily used, including an electrochemical polishing slurry based on phosphoric acid, sulfuric acid, perchloric acid, or a phosphoric-sulfuric acid system combined with various additives. An electrochemical gradient-thickening phase incorporates controlled-release physicochemical particles (i.e., fluid flow-property regulating particles) to regulate hydrophilic-hydrophobic properties of the polishing slurry that is in contact with a structural surface. The controlled-release physicochemical particles are typically sodium polyacrylate, polyvinyl alcohol, polyurethane thickeners, etc.

[0061] The electrochemical gradient-thickening polishing suspension in the present invention includes the following components in mass percentage: nano-abrasive particles, a pH-adjusting agent, controlled-release physicochemical particles, an oxidizing agent, and an electrochemical gradient-thickening phase (such as ferrous sulfate or sodium sulfite) are added to ultrapure water at 25°C to prepare the electrochemical gradient-thickening polishing suspension. Specifically, a mass fraction of the nano-abrasive particles is 7%-20%, a mass fraction of the pH-adjusting agent is 0.05%-1.0%, a mass fraction of the controlled-release physicochemical particles is 0.05%-1.0%, a mass fraction of the oxidizing agent is 0.05%-0.1%, and a mass fraction of the electrochemical gradient-thickening phase is 1%-10%.

[0062] The polishing auxiliary device includes a numerical control unit 8, a lifting frame 3, a movable frame 7, a slideway 4, an X-axis guide rail 6, a Y-axis guide rail 12, a Z-axis guide rail 5, an anode workpiece 14, a fixture, and a polishing workbench 15. The polishing auxiliary device is located within the housing 1. The lifting frame 3, the movable frame 7, and the slideway 4 are interconnected via the X-axis guide rail 6, the Y-axis guide rail 12, or the Z-axis guide rail 5, respectively. The numerical control unit 8 controls their motions. The Z-axis guide rail 5 on the slideway 4 is connected to the conformal polishing device, a lower end of the conformal polishing device is provided with the polishing workbench 15. The polishing workbench 15 is provided with a fixture, and the anode workpiece 14 is mounted at a position of the fixture.

[0063] The numerical control unit 8 not only adjusts a degree of freedom of the conformal polishing system, but also controls conformal polishing paths and processing parameters. It controllably adjusts a removal trajectory and dwell-state parameters, actively regulates surface conformity, and achieves deterministic material removal, thereby further improving the surface form accuracy of large-area micro-structured surfaces and ultimately ensuring conformal polishing performance.

[0064] The polishing workbench 15 is provided with a fixture to secure the anode workpiece 14. A through hole is formed on the polishing workbench 15, such that the electrochemical gradient-thickening polishing suspension, after processing, flows into the recovery tank 13.

[0065] The anode workpiece 14 includes spherical or aspherical lens substrate made of monocrystalline silicon or silicon carbide for infrared optical systems, miniature sensing components, stainless-steel micro-gear bolts and nuts, and the like.

[0066] An ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion includes the following steps:

[0067] (1) placing an anode workpiece 14 on a polishing worktable 15, connecting an anode clamp to the anode workpiece 14, and connecting a cathode clamp to a flexible conformal component 26;

[0068] (2) activating a numerical control unit 8 to control path and process parameters of the flexible conformal component 26, such that a starting point conforms to the surface of the anode workpiece 14;

[0069] (3) adding an electrochemical gradient-thickening polishing suspension containing nano-abrasive particles 29 to a material storage tank 11, activating a hydraulic pump 10, and conveying the electrochemical gradient-thickening polishing suspension through a conveying pipe 9 into a conformal polishing device;

[0070] (4) turning on a circuit controller 2 and the electrochemical thickening generator 16, and inducing an electrochemical interface reaction by an electrochemical gradient-thickening phase 28 that guides a directional motion of charged particles and controls a particle aggregation effect of the electrochemical gradient-thickening polishing suspension, such that the flexible conformal component 26 exhibits real-time weak-rigidity rheological behavior in a fluid flow, thereby forming a flexible fluid abrasive tool; and

[0071] (5) activating a spindle housing 20, generating a vibration-induced microdynamic force in the workpiece direction on the rotating flexible fluid abrasive tool, and inducing the flexible fluid abrasive tool to generate a whirling motion by the vibration-induced microdynamic force, causing dynamic regulation mechanism for a vibration-induced micro-motion polishing slurry, and promoting micro-vibration of a flexible fluid to facilitate a dwell and dynamic trajectory behavior of the flexible fluid abrasive tool, achieving efficient conformal material removal and control of polished surface form accuracy in a region under the combined action of vibration-induced micro-motion, thereby implementing the novel ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion.Embodiment 1

[0072] This embodiment is applied to the machining of a silicon carbide microlens structure with a designed microlens processing structure period of 1.5 mm and a designed height of 0.5 mm (FIG. 5(a)). By employing the method and apparatus, a surface roughness of the silicon carbide microlens structure may reach Ra < 2 nm, and a form accuracy is maintained at PV < 200 nm.

[0073] The ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion comprises the following steps:

[0074] (1) placing a microlens workpiece on a polishing worktable 15, connecting an anode clamp to the microlens workpiece, and connecting a cathode clamp to a flexible conformal component 26;

[0075] (2) activating a numerical control unit 8 to control path and process parameters of the flexible conformal component 26, ensuring that a starting point conforms to a surface of the microlens workpiece;

[0076] (3) adding an electrochemical gradient-thickening polishing suspension containing nano-abrasive particles 29 to a material storage tank 11, activating a hydraulic pump 10, and conveying the electrochemical gradient-thickening polishing suspension through a conveying pipe 9 into a conformal polishing device;

[0077] (4) turning on a circuit controller 2 and the electrochemical thickening generator 16, and inducing an electrochemical interface reaction by an electrochemical gradient-thickening phase 28 to guide a directional motion of charged particles and control a particle aggregation effect of the electrochemical gradient-thickening polishing suspension, such that the flexible conformal component 26 exhibits real-time weak-rigidity rheological behavior in a fluid flow, thereby forming a flexible fluid abrasive tool; and

[0078] (5) activating a spindle housing 20, generating a vibration-induced microdynamic force in the workpiece direction on the rotating flexible fluid abrasive tool, and inducing the flexible fluid abrasive tool to generate a whirling motion by the vibration-induced microdynamic force, causing dynamic regulation mechanism for a vibration-induced micro-motion polishing slurry, and promoting micro-vibration of a flexible fluid to facilitate a dwell and dynamic trajectory behavior of the flexible fluid abrasive tool, achieving efficient conformal material removal and control of polished surface form accuracy in a region under the combined action of vibration-induced micro-motion, thereby implementing the novel ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion.Embodiment 2

[0079] This embodiment is applied to the machining of a silicon nitride microprism structure with a designed microlens processing structure period of 2 mm and a designed height of 0.6 mm (FIG. 5(b)). By employing the method and apparatus, a surface roughness of the silicon nitride microprism structure may reach Ra < 2.5 nm, and a form accuracy is maintained at PV < 200 nm.

[0080] The ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion comprises the following steps:

[0081] (1) placing a microprism workpiece on a polishing worktable 15, connecting an anode clamp to the microprism workpiece, and connecting a cathode clamp to a flexible conformal component 26;

[0082] (2) activating a numerical control unit 8 to control path and process parameters of the flexible conformal component 26, ensuring that a starting point conforms to a surface of the microprism workpiece;

[0083] (3) adding an electrochemical gradient-thickening polishing suspension containing nano-abrasive particles 29 to a material storage tank 11, activating a hydraulic pump 10, and conveying the electrochemical gradient-thickening polishing suspension through a conveying pipe 9 into a conformal polishing device;

[0084] (4) turning on a circuit controller 2 and the electrochemical thickening generator 16, and inducing an electrochemical interface reaction by an electrochemical gradient-thickening phase 28 guide a directional motion of charged particles and control a particle aggregation effect of the electrochemical gradient-thickening polishing suspension, such that the flexible conformal component 26 exhibits real-time weak-rigidity rheological behavior in a fluid flow, thereby forming a flexible fluid abrasive tool; and

[0085] (5) activating a spindle housing 20, generating a vibration-induced microdynamic force in the workpiece direction on the rotating flexible fluid abrasive tool, and inducing the flexible fluid abrasive tool to generate a whirling motion by the vibration-induced microdynamic force, causing dynamic regulation mechanism for a vibration-induced micro-motion polishing slurry, and promoting micro-vibration of a flexible fluid to facilitate a dwell and dynamic trajectory behavior of the flexible fluid abrasive tool, achieving efficient conformal material removal and control of polished surface form accuracy in a region under the combined action of vibration-induced micro-motion, thereby implementing the novel ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion.Embodiment 3

[0086] This embodiment is applied to the machining of a monocrystalline silicon cylindrical array microstructure with a designed microlens processing structure period of 1.8 mm and a designed height of 0.4 mm (FIG. 5(c)). By employing the method and apparatus, a surface roughness of the monocrystalline silicon cylindrical array microstructure may reach Ra < 2.3 nm, and a form accuracy is maintained at PV < 200 nm.

[0087] The ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion comprises the following steps:

[0088] (1) placing a cylindrical array microstructure workpiece on a polishing worktable 15, connecting an anode clamp to the cylindrical array microstructure workpiece, and connecting a cathode clamp to a flexible conformal component 26;

[0089] (2) activating a numerical control unit 8 to control path and process parameters of the flexible conformal component 26, ensuring that a starting point conforms to a surface of the cylindrical array microstructure workpiece;

[0090] (3) adding an electrochemical gradient-thickening polishing suspension containing nano-abrasive particles 29 to a material storage tank 11, activating a hydraulic pump 10, and conveying the electrochemical gradient-thickening polishing suspension through a conveying pipe 9 into a conformal polishing device;

[0091] (4) turning on a circuit controller 2 and the electrochemical thickening generator 16, and inducing an electrochemical interface reaction by an electrochemical gradient-thickening phase 28 guide a directional motion of charged particles and control a particle aggregation effect of the electrochemical gradient-thickening polishing suspension, such that the flexible conformal component 26 exhibits real-time weak-rigidity rheological behavior in a fluid flow, thereby forming a flexible fluid abrasive tool; and

[0092] (5) activating a spindle housing 20, generating a vibration-induced microdynamic force in the workpiece direction on the rotating flexible fluid abrasive tool, and inducing the flexible fluid abrasive tool to generate a whirling motion by the vibration-induced microdynamic force, causing dynamic regulation mechanism for a vibration-induced micro-motion polishing slurry, and promoting micro-vibration of a flexible fluid to facilitate a dwell and dynamic trajectory behavior of the flexible fluid abrasive tool, achieving efficient conformal material removal and control of polished surface form accuracy in a region under the combined action of vibration-induced micro-motion, thereby implementing the novel ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion.

[0093] It should be noted that the embodiments described herein are merely illustrative examples of the implementation of the inventive concept and are intended for explanation purposes only. The scope of protection of the present invention should not be construed as limited to the specific forms described in the embodiments. The scope of protection of the present invention also extends to equivalent technical solutions that those skilled in the art can conceive based on the inventive concept of the present invention.

Claims

1. An ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion, wherein the method utilizes an electrochemical gradient-thickening phase to induce electrochemical interfacial reactions that guide a directional motion of charged particles and control a particle aggregation effect of a suspension; and a flexible fluid abrasive tool is then used to generate a vibration-induced microdynamic force in a workpiece direction for efficient conformal material removal; and the ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion comprises the following steps: (1) placing an anode workpiece on a polishing worktable, connecting an anode clamp to the anode workpiece, and connecting a cathode clamp to a flexible conformal component of a conformal polishing device; wherein a rotor is disposed within an inner cavity of the flexible conformal component, and a stator is disposed at an eccentric position of an outer cavity of the flexible conformal component, thereby maintaining a predetermined degree of airtightness; the flexible conformal component deforms according to a shape of the anode workpiece, thereby closely conforming to a surface of the anode workpiece; when the flexible conformal component rotates with a rotating shaft, the flexible conformal component generates a vibration-induced microdynamic force in the workpiece direction; and the vibration-induced microdynamic force induces the flexible conformal component to form a whirling motion, thereby achieving efficient conformal material removal;(2) activating a numerical control unit to control path and process parameters of the flexible conformal component, such that a starting point conforms to the surface of the anode workpiece;(3) adding an electrochemical gradient-thickening polishing suspension containing nano-abrasive particles to a material storage tank, activating a hydraulic pump, and conveying the electrochemical gradient-thickening polishing suspension through a conveying pipe into the conformal polishing device;(4) turning on a circuit controller and an electrochemical thickening generator, and inducing an electrochemical interface reaction by an electrochemical gradient-thickening phase that guides a directional motion of charged particles and controls a particle aggregation effect of the electrochemical gradient-thickening polishing suspension, such that the flexible conformal component exhibits real-time weak-rigidity rheological behavior in a fluid flow, thereby forming a flexible fluid abrasive tool; and(5) activating a spindle housing, generating the vibration-induced microdynamic force in the workpiece direction on the rotating flexible fluid abrasive tool, and inducing the flexible fluid abrasive tool to generate a whirling motion by the vibration-induced microdynamic force, causing dynamic regulation mechanism for a vibration-induced micro-motion polishing slurry, and promoting micro-vibration of a flexible fluid to facilitate a dwell and dynamic trajectory behavior of the flexible fluid abrasive tool, achieving efficient conformal material removal and control of polished surface form accuracy in a region under the combined action of vibration-induced micro-motion.

2. The ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion according to claim 1, wherein in the step (4), the electrochemical gradient-thickening phase is porous microsphere particles; when being incorporated into the electrochemical gradient-thickening polishing suspension, the porous microsphere particles undergo a slow chemical reaction and generate negatively charged particles, and these negatively charged particles induce an aggregation effect among positively charged metallic nano-abrasive particles.

3. The ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion according to claim 1, wherein in the step (3), the nano-abrasive particles comprise one or a mixture of two or more of nanodiamond, cubic boron oxide, boron carbide, silicon carbide, silicon nitride, silicon oxide, gallium oxide, iron oxide, magnesium oxide, lithium fluoride, graphite, or Al2O3.

4. The ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion according to claim 1, wherein in the step (3), the electrochemical gradient-thickening polishing suspension comprises an acidic electrochemical polishing slurry, a neutral electrochemical polishing slurry, and an alkaline electrochemical polishing slurry; for polishing a silicon-based material or an alloy material, the acidic electrochemical polishing slurry is used, comprising an electrochemical polishing slurry based on phosphoric acid, sulfuric acid, perchloric acid, or a phosphoric-sulfuric acid system combined with various additives; and the electrochemical gradient-thickening phase incorporates controlled-release physicochemical particles, that is, fluid flow-property regulating particles, to regulate hydrophilic-hydrophobic properties of the polishing slurry that is in contact with a structural surface.

5. An ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion for implementing the ultra-precision conformal polishing method based on electrochemical gradient-thickening and vibration-induced micro-motion of claim 1, comprising a housing, a conformal polishing device, a power-supply auxiliary device, an electrochemical gradient-thickening polishing suspension conveying device, and a polishing auxiliary device; wherein the conformal polishing device is located in a center of the housing; the power-supply auxiliary device is located at a left end of the housing; the electrochemical gradient-thickening polishing suspension conveying device is located at a right end of the housing; and the polishing auxiliary device is located within the housing;the conformal polishing device comprises, from top to bottom, a spindle housing, a spindle, an electrochemical gradient-thickening polishing suspension flow channel, a current delivery channel, an electrochemical thickening generator, a connecting shaft, a rotating shaft, a flexible conformal component, and a detector; wherein an upper end of the spindle is connected to the spindle housing, and a lower end of the spindle is connected to the electrochemical thickening generator; the electrochemical gradient-thickening polishing suspension flow channel and the current delivery channel are formed at a position of the spindle; the connecting shaft is configured to connect the electrochemical thickening generator and the rotating shaft; and the flexible conformal component and the detector are mounted at a position of the rotating shaft.

6. The ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion according to claim 5, wherein the power-supply auxiliary device comprises a high-voltage power supply, an anode clamp, a cathode clamp, a circuit protection device, a transformer, and a circuit controller; an anode of the power supply is connected to an anode workpiece via the circuit protection device, and a cathode of the power supply is connected to the flexible conformal component via the transformer; and the circuit controller is configured to control power supply and current of a circuit.

7. The ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion according to claim 5, wherein the electrochemical gradient-thickening polishing suspension conveying device comprises a conveying pipe, a hydraulic pump, a material storage tank, and a recovery tank; and an electrochemical gradient-thickening polishing suspension flows sequentially through the hydraulic pump and the conformal polishing device through the conveying pipe, and enters an inner cavity of the flexible conformal component, then flows through a through hole of a polishing workbench into the recovery tank, thereby completing the delivery and recovery of an electrochemical polishing slurry.

8. The ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion according to claim 5, wherein the polishing auxiliary device comprises a numerical control unit, a lifting frame, a movable frame, a slideway, an X-axis guide rail, a Y-axis guide rail, a Z-axis guide rail, an anode workpiece, a fixture, and a polishing workbench; the lifting frame, the movable frame, and the slideway are interconnected via the X-axis guide rail, the Y-axis guide rail, or the Z-axis guide rail, respectively; the numerical control unit controls motions of the lifting frame, the movable frame, and the slideway; the Z-axis guide rail on the slideway is connected to the conformal polishing device, a lower end of the conformal polishing device is provided with the polishing workbench; and the polishing workbench is provided with a fixture, and the anode workpiece is mounted at a position of the fixture.

9. The ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion according to claim 6, wherein the electrochemical gradient-thickening polishing suspension conveying device comprises a conveying pipe, a hydraulic pump, a material storage tank, and a recovery tank; and an electrochemical gradient-thickening polishing suspension flows sequentially through the hydraulic pump and the conformal polishing device through the conveying pipe, and enters an inner cavity of the flexible conformal component, then flows through a through hole of a polishing workbench into the recovery tank, thereby completing the delivery and recovery of an electrochemical polishing slurry.

10. The ultra-precision conformal polishing apparatus based on electrochemical gradient-thickening and vibration-induced micro-motion according to claim 6, wherein the polishing auxiliary device comprises a numerical control unit, a lifting frame, a movable frame, a slideway, an X-axis guide rail, a Y-axis guide rail, a Z-axis guide rail, an anode workpiece, a fixture, and a polishing workbench; the lifting frame, the movable frame, and the slideway are interconnected via the X-axis guide rail, the Y-axis guide rail, or the Z-axis guide rail, respectively; the numerical control unit controls motions of the lifting frame, the movable frame, and the slideway; the Z-axis guide rail on the slideway is connected to the conformal polishing device, a lower end of the conformal polishing device is provided with the polishing workbench; and the polishing workbench is provided with a fixture, and the anode workpiece is mounted at a position of the fixture.

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