An ultra-precision polishing method based on the thermal thickening effect

Abstract

A super-precision polishing method based on the thermo-thickening effect. Abrasives are added to a fluid with the thermo-thickening effect to prepare a thermo-thickening polishing fluid. During the polishing process, relative movement occurs between the workpiece and the thermo-thickening polishing fluid, and heat is generated by friction. The fluid with the thermo-thickening effect in the thermo-thickening polishing fluid is heated, and the side chains with lower critical solution temperature of different molecules will combine with each other to form multi-molecular polymers, resulting in the thermo-thickening phenomenon, and the viscosity of the thermo-thickening polishing fluid increases. The abrasives are wrapped in the multi-molecular polymers, and the holding ability of the fluid with the thermo-thickening effect on the abrasives increases, forming a flexible "fixed abrasive tool". Through the relative movement, the abrasives have a mechanical removal effect on the surface of the workpiece, realizing the polishing process. The polishing fluid with the thermo-rheological effect of the present invention can form a flexible "fixed abrasive tool" on complex curved surfaces with different curvatures, realizing the ultra-precision machining of complex curved surfaces, and having great economic and social effects.

Description

Technical Field

[0001] The present invention belongs to the field of ultra-precision machining, and relates to an ultra-precision polishing method based on the thermal thickening effect. By using a fluid with the thermal thickening effect to generate the thermal thickening effect when heated, the viscosity of the polishing liquid increases, the holding ability of the abrasive grains increases, and a flexible "fixed abrasive tool" is formed to mechanically remove the surface of the workpiece, realizing green, high-quality, and high-efficiency machining of complex curved surfaces. Background Art

[0002] With the development of technology, complex curved surface parts have been widely used in the fields of aerospace, national defense equipment, biomedicine, optical instruments, marine ships, etc. The blades of aircraft and rocket engines usually consist of blades with variable curvatures to improve energy utilization efficiency. In addition, the better the surface quality of the blade, the smaller the working resistance. Artificial alloy metal joints can be used as implants to replace human bone joints well. The rougher the surface of the alloy metal joint, the more serious the friction with the human bone, directly damaging the body. In an optical system, using a few complex curved surface elements to replace traditional multiple rotationally symmetric elements can greatly simplify the optical path structure, improve the system stability, and reduce the manufacturing cost.

[0003] At present, the industry has an increasing demand for complex curved surface parts, and at the same time, very high requirements are put forward for the surface quality of complex curved surfaces. As the last process of machining, polishing plays a decisive role in the surface quality and product performance of complex curved surface parts. In industrial production, the polishing of many complex curved surface parts is still completed by manual operation, which is not only inefficient but also has unstable machining quality. Currently, the main polishing technologies developed for complex curved surfaces include magnetorheological polishing, jet polishing, airbag polishing, and shear thickening polishing.

[0004] Magnetorheological polishing utilizes the rheological characteristics of magnetorheological polishing liquid in a magnetic field, and artificially controls the magnetic field to regulate the rheological characteristics, forming a flexible machining area to machine the surface of the workpiece. However, the magnetorheological polishing processing equipment is complex and the cost of using magnetorheological polishing liquid is high. Jet polishing uses a high-pressure pump to impact the surface of the workpiece with the polishing liquid and abrasive grains to achieve micro-cutting of the surface of the workpiece. However, jet polishing requires a high-power polishing liquid propulsion system, but the processing efficiency is very low. Airbag polishing uses an airbag controlled by a multi-axis robotic arm to flexibly contact the surface of the workpiece to achieve mechanical removal, and the airbag pressure adjustment realizes deterministic removal. However, airbag polishing has a high cost, is suitable for polishing large-sized and gradually changing curvature curved surfaces, and at the same time, the equipment cost of airbag polishing is very high. Shear thickening polishing utilizes the relative movement between the workpiece and the polishing liquid, and the polishing liquid in the contact area undergoes a shear thickening effect and the viscosity increases, forming a shear layer to produce a micro-cutting effect on the surface of the workpiece.

[0005] Existing invention patent: "A super-precision surface polishing method based on the shear thickening effect of non-Newtonian fluids", publication number CN102717325A, discloses a super-precision surface polishing method based on the shear thickening effect. Shear thickening polishing is restricted by the relative movement speed. Generally, the speed range where the shear thickening effect occurs in the polishing fluid is relatively narrow. For example, if the speed is lower or higher than a specific value, the shear thinning effect will occur, and effective control of the polishing parameters cannot be achieved. In addition, polyhydroxy polymers are usually used in shear thickening polishing fluids. During the polishing process, with the relative movement friction, the temperature of the polishing fluid increases, and the polyhydroxy polymers will deteriorate and lose the shear thickening effect, making it impossible to complete the polishing.

[0006] Therefore, there is an urgent need to develop a polishing method with high efficiency, high quality, and low cost for the ultra-precision machining of complex parts. Summary of the Invention

[0007] In order to overcome the problems of high shear speed requirements in shear thickening polishing and the invalidation of the polishing fluid caused by temperature rise during the processing, the present invention uses a fluid with a thermal thickening effect, and utilizes the heat generated by friction during the polishing process to generate the thickening effect of the fluid, improve the holding ability of abrasive grains, form a flexible "fixed abrasive tool" in the polishing contact area, and achieve the polishing of complex curved surface workpieces.

[0008] The technical solution adopted by the present invention to solve its technical problems is:

[0009] A super-precision polishing method based on the thermal thickening effect, adding abrasive grains to a fluid with a thermal thickening effect to prepare a thermal thickening polishing fluid; wherein, the fluid with a thermal thickening effect accounts for 50%-98% of the mass fraction of the thermal thickening polishing fluid, the abrasive grains account for 2%-50% of the mass fraction of the thermal thickening polishing fluid, and the particle size range of the abrasive grains is 0.01-100μm;

[0010] During the polishing process, the workpiece and the thermal thickening polishing fluid move relatively, and friction generates heat; the fluid with a thermal thickening effect in the thermal thickening polishing fluid is heated to generate a thermal thickening effect, the viscosity of the polishing fluid increases, the holding ability of the abrasive grains dispersed in the polishing fluid increases, a flexible "fixed abrasive tool" is formed, and the abrasive grains have a mechanical removal effect on the surface of the workpiece.

[0011] Furthermore, a single molecule of the fluid with a thermal thickening effect is composed of a main chain and multiple side chains with a lower critical solution temperature. When the temperature in the polishing area exceeds the critical value, the side chains with a lower critical solution temperature in the thermal thickening fluid molecules will combine with each other to form multi-molecular polymers, and the abrasive grains dispersed in the polishing fluid are wrapped in the formed polymers. The multi-molecular polymers have a good holding effect on the abrasive grains, and the abrasive grains have a polishing effect and a mechanical removal effect on the surface material of the workpiece, thereby realizing the polishing of the workpiece surface.

[0012] Furthermore, the fluid with a heat thickening effect includes, but is not limited to, PAA-G-PPO or PAA-co-PANa-g-PPO. The molecular structure of the fluid with a heat thickening effect can be constructed with different main chains and side chains with a lower critical solution temperature according to the polishing requirements of different workpieces, so as to achieve the ideal critical thickening temperature and ideal thickening viscosity required for polishing.

[0013] Furthermore, the abrasive grains are one or a combination of two or more of single crystal diamond, polycrystalline diamond, iron oxide, aluminum trioxide, silicon oxide, zirconium dioxide, molybdenum oxide, titanium dioxide, cerium dioxide, chromium oxide, calcined silicon dioxide, copper oxide, and colloidal silicon dioxide, etc.

[0014] Preferably, the heat thickening polishing liquid further includes a dispersant and an active agent. The dispersant can evenly distribute the abrasive grains in the fluid with a heat thickening effect. The dispersant is one or a combination of two or more of sodium polyacrylate, polyvinyl alcohol, citric acid, sodium hexametaphosphate, diethylenetriamine, pyridine, sodium dodecylbenzenesulfonate, polyvinylpyrrolidone, and isopropanolamine; the active agent can increase the repulsive force between abrasive grain particles, reduce abrasive grain agglomeration, play a certain lubricating role during mechanical removal, make the force on the surface of the polished workpiece more uniform, and improve the polishing quality of the workpiece. The active agent is one or a combination of two or more of polyamine-based polymers, fatty alcohol polyoxyethylene ethers, polyoxyethylene alkylphenol ethers, coconut oil amide propyl betaine, and alkyl polyglycosides.

[0015] More preferably, the heat thickening polishing liquid further includes a pH buffer and a pH regulator, including but not limited to sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium carbonate, potassium hydrogen phosphate, potassium dihydrogen phosphate, one or a combination of two or more; the pH regulator adjusts the heat thickening polishing liquid to the optimal pH value according to the characteristics of different workpieces, and the pH buffer can improve the pH stability of the heat thickening polishing liquid.

[0016] Furthermore, the relative movement between the workpiece and the heat thickening polishing liquid is one or a combination of linear movement and curvilinear movement.

[0017] The beneficial effects of the present invention are mainly manifested in:

[0018] 1) The thermorheological properties of the thermorheological polishing liquid not only ensure that the flexible fixed abrasive tool formed by it can adapt to complex curved surfaces with different curvatures, but also ensure that it has sufficient mechanical force to perform micro-cutting on surface micro-protrusions, realizing ultra-precision and high-efficiency polishing of complex curved surfaces.

[0019] 2) The polishing speed and the heat generated during the polishing process will not have an adverse effect on the polishing liquid.

[0020] 3) Thicken the polishing by using the heat generated by friction during the polishing process. The processing equipment is simple and the polishing cost is low. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the mechanism of the polishing process of the present invention;

[0022] Figure 2 It is a schematic diagram of the thermorheological mechanism of the present invention;

[0023] Figure 3 It is a schematic diagram of the perspective structure of the use state of the embodiment of the present invention; Detailed Embodiments

[0024] The present invention will be further described below with reference to the drawings.

[0025] Refer to Figures 1 to 3 , a super-precision polishing method based on the heat thickening effect. The workpiece 2 is fixedly installed on the polishing tool 8. The heat thickening polishing liquid 1 includes a fluid 3 with a heat thickening effect and abrasive grains 4. The polishing tank 6 is fixedly installed on the polishing machine 7, and the heat thickening polishing liquid 1 is placed in the polishing tank 6;

[0026] Abrasive grains 4 are added to the fluid 3 with a heat thickening effect to prepare the heat thickening polishing liquid 1. Among them, the fluid 3 with a heat thickening effect accounts for 50%-98% of the mass fraction of the heat thickening polishing liquid 1, and the abrasive grains 4 account for 2%-50% of the mass fraction of the heat thickening polishing liquid 1. The particle size range of the abrasive grains 4 is 0.01-100 μm;

[0027] During the polishing process, the workpiece 2 and the heat thickening polishing liquid 1 move relative to each other. Heat is generated by the friction between the workpiece 2 and the heat thickening polishing liquid 1 at the relative movement position. The fluid 3 with a heat thickening effect in the heat thickening polishing liquid 1 will generate a heat thickening effect when heated. The viscosity of the polishing liquid 1 increases, and the holding ability of the abrasive grains 4 dispersed in the polishing liquid increases, forming a flexible "fixed abrasive tool", which has a mechanical removal effect on the surface of the workpiece.

[0028] A single molecule of the fluid 3 with a heat thickening effect is composed of a main chain 3.1 and multiple side chains 3.2 with a lower critical solution temperature. When the polishing area exceeds the critical value, the side chains 3.2 with a lower critical solution temperature in the heat thickening fluid molecules will combine with each other 5 to form a multi-molecular polymer. The abrasive grains 4 dispersed in the polishing liquid are wrapped in the formed polymer. The multi-molecular polymer has a good holding effect on the abrasive grains. The abrasive grains 4 have a polishing effect and have a mechanical removal effect on the surface material of the workpiece 2, thereby realizing the polishing of the surface of the workpiece 2.

[0029] The molecular structure of the fluid 3 with a heat thickening effect is constructed with different main chains 3.1 and side chains 3.2 with a lower critical solution temperature according to the polishing requirements of different workpieces 2, so as to achieve the ideal critical thickening temperature and ideal thickening viscosity required for polishing.

[0030] The abrasive grains 4 described above are selected from one or a combination of two or more of single crystal diamond, polycrystalline diamond, iron oxide, aluminum trioxide, silicon oxide, zirconium dioxide, molybdenum oxide, titanium dioxide, cerium dioxide, chromium oxide, calcined silicon dioxide, copper oxide, and colloidal silicon dioxide, etc., according to the polishing materials and hardness of different workpieces.

[0031] Furthermore, a dispersant and an active agent are added to the heat thickening polishing liquid 1. The dispersant can evenly distribute the abrasive grains 4 in the fluid with a heat thickening effect. The dispersant is one or a combination of two or more of sodium polyacrylate, polyvinyl alcohol, citric acid, sodium hexametaphosphate, diethylenetriamine, pyridine, sodium dodecylbenzenesulfonate, polyvinylpyrrolidone, isopropanolamine, etc.; the active agent increases the repulsive force between the abrasive grains, reduces the agglomeration of the abrasive grains, plays a certain lubricating role during mechanical removal, makes the force on the surface of the polished workpiece 2 more uniform, and improves the polishing quality of the workpiece 2. The active agent is one or a combination of two or more of polyamine-based polymers, fatty alcohol polyoxyethylene ethers, polyoxyethylene alkylphenol ethers, cocamidopropyl betaine, alkyl polyglycosides, etc.

[0032] Even further, the heat thickening polishing liquid 1 also includes a pH buffer and a pH regulator, including but not limited to sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium carbonate, potassium hydrogen phosphate, potassium dihydrogen phosphate, one or a combination of two or more. The pH regulator adjusts the heat thickening polishing liquid to the optimal pH value according to the characteristics of the workpiece 2, and the pH buffer improves the pH stability of the heat thickening polishing liquid.

[0033] Furthermore, the relative movement between the workpiece 2 and the heat thickening polishing liquid 1 is selected from one or a combination of two of linear motion or curvilinear motion.

[0034] Refer to Figure 3 , using PAA-co-PANa-g-PPO as the fluid 1 with a heat thickening effect and alumina as the abrasive grains, prepare the heat thickening polishing liquid 1 and place it in the polishing tank 6. The polishing tank 6 is installed on the polishing machine 7 and rotates with the polishing machine 7, driving the heat thickening polishing liquid 1 to rotate. The polished workpiece 2 is a TC4 titanium alloy semi-ring, and the TC4 titanium alloy semi-ring is fixedly installed on the polishing fixture 8. The polishing fixture 8 drives the TC4 titanium alloy semi-ring to make a self-rotation motion. After polishing for 20 minutes, the surface roughness of the workpiece drops from R a 243nm to R a7.3 nm. It can be seen that the thermal thickening polishing method can meet the requirements of high-efficiency and high-quality polishing of complex surfaces.

[0035] Those of ordinary skill in the art will realize that the embodiments described herein are to assist the reader in understanding the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations without departing from the essence of the present invention based on these technical revelations disclosed in the present invention, and these deformations and combinations are still within the scope of protection of the present invention.

Claims

1. An ultra-precision polishing method based on the thermal thickening effect, characterized in that, Abrasive particles are added to a fluid with a thermal thickening effect to prepare a thermally thickened polishing liquid; wherein, the fluid with a thermal thickening effect accounts for 50%-98% of the mass fraction of the thermally thickened polishing liquid, the abrasive particles account for 2%-50% of the mass fraction of the thermally thickened polishing liquid, and the particle size range of the abrasive particles is 0.01-100 μm; During the polishing process, the workpiece and the thermally thickened polishing liquid move relative to each other, and heat is generated by friction. The fluid with a thermal thickening effect in the thermally thickened polishing liquid will produce a thermal thickening effect when heated, the viscosity of the polishing liquid increases, and the holding ability of the abrasive particles dispersed in the polishing liquid increases, forming a flexible "fixed abrasive tool", and the abrasive particles have a mechanical removal effect on the surface of the workpiece; A single molecule of the fluid with a thermal thickening effect is composed of a main chain and multiple side chains with a lower critical solution temperature; when the temperature in the polishing area exceeds the critical value, the side chains with a lower critical solution temperature in the thermally thickened fluid molecules will combine with each other to form a multi-molecular polymer; the abrasive particles dispersed in the polishing liquid are wrapped in the formed polymer, and the multi-molecular polymer has a good holding effect on the abrasive particles. The abrasive particles have a polishing effect and have a mechanical removal effect on the surface material of the workpiece, thereby realizing the polishing of the workpiece surface; The fluid with a thermal thickening effect is PAA-G-PPO or PAA-co-PANa-g-PPO; The abrasive particles are one or a combination of two or more of single crystal diamond, polycrystalline diamond, iron oxide, aluminum trioxide, silicon oxide, zirconium dioxide, molybdenum dioxide, titanium dioxide, cerium dioxide, chromium oxide, calcined silicon dioxide, copper oxide, and colloidal silicon dioxide; The thermally thickened polishing liquid further includes a dispersant and an active agent. The dispersant can evenly distribute the abrasive particles in the fluid with a thermal thickening effect. The dispersant is one or a combination of two or more of sodium polyacrylate, polyvinyl alcohol, citric acid, sodium hexametaphosphate, diethylenetriamine, pyridine, sodium dodecylbenzenesulfonate, polyvinylpyrrolidone, and isopropanolamine; the active agent can increase the repulsive force between the abrasive particles, reduce the agglomeration of the abrasive particles, play a lubricating role during mechanical removal, make the force on the surface of the polished workpiece more uniform, and improve the polishing quality of the workpiece; the active agent is one or a combination of two or more of polyamine-based polymers, fatty alcohol polyoxyethylene ethers, polyoxyethylene alkylphenol ethers, coconut oil amide propyl betaine, and alkyl polyglycosides; The thermally thickened polishing liquid further includes a pH buffer and a pH regulator. The pH buffer or pH regulator is one or a combination of two or more of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium carbonate, potassium hydrogen phosphate, and potassium dihydrogen phosphate.

2. The ultra-precision polishing method based on the thermal thickening effect according to claim 1, wherein The relative movement between the workpiece and the thermally thickened polishing liquid is one or a combination of linear motion and curvilinear motion.

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