Engineering ceramic micro-machining method based on abrasive flexible constraint microjet

Abstract

The application discloses an engineering ceramic micro-machining method based on abrasive flexible constraint micro-jet, and relates to the technical field of engineering ceramic micro-machining, which comprises a precise powder feeding system, a shear thinning non-Newtonian fluid supply system, a two-stage nozzle system of solid abrasive particles and non-Newtonian fluid, a workbench control system, a waste liquid recovery system and the like. As a supply source of shear thinning fluid, the shear thinning fluid in a shear thinning fluid storage tank is connected to a shear thinning fluid nozzle through a peristaltic pump and a pulsation damper, and a shear thinning fluid flow beam is formed; an air source is connected to a gate valve, an adjusting valve and a gas-powder mixer, and is sprayed out through an abrasive nozzle to form a micro-abrasive gas jet beam. By reasonably arranging the shear thinning fluid flow beam around the micro-abrasive gas jet beam, the micro-abrasive gas jet beam is subjected to flexible constraint, and the active regulation of the impact stress field of the engineering ceramic material is realized, so that the near non-damage surface engineering ceramic microstructure machining can be realized.

Description

Technical Field

[0001] This invention relates to the field of microfabrication technology for engineering ceramic materials, specifically a method for microfabrication of engineering ceramics based on abrasive flexible constrained microjets. Background Technology

[0002] In the field of high-end equipment technology, engineering ceramics are widely used due to their high hardness, good chemical stability, and good biocompatibility, such as ceramic cutting tools, bioceramic components, ceramic bearings, ceramic sealing rings, and ceramic wear-resistant bushings. However, during the service life of engineering ceramic components, a large amount of wear debris generated by interfacial friction is difficult to remove, participating in and accelerating material wear as a third body between the contact surfaces. This not only affects the service life and reliability of engineering ceramic components, but also increases energy consumption, generates noise and vibration, and may even lead to serious safety accidents due to the sudden failure of engineering ceramic components. To significantly improve the service performance of engineering ceramic components, it is necessary to process spherical concave pits and straight / spiral groove microstructures with characteristic depths of 10–50 μm and characteristic widths of 50–200 μm on their surfaces. However, the high hardness and brittleness of engineering ceramic materials pose a severe challenge to the processing of high-performance microstructures, and the degree of microcrack damage on the surface of the microstructures directly affects the service performance of engineering ceramic components. Therefore, how to achieve near-destructive processing of engineering ceramic microstructures has become an urgent scientific problem to be solved by researchers.

[0003] Currently, the main processing methods for functional ceramic microstructures include micro-cutting technology, laser processing technology, electrical discharge machining technology, and abrasive jet processing technology.

[0004] Micro-machining technology refers to the process of micro-machining using cutting tools made of superhard materials with specific geometric cutting edges, such as micro-turning, micro-milling, micro-drilling, and micro-grinding. This method offers advantages such as low cost, high processing efficiency, and the ability to mass-produce. However, in practical applications, some key problems exist in micro-machining technology, such as severe tool wear, poor tool system rigidity, and easy tool breakage, which seriously restrict its widespread application in the machining of functional ceramic microstructures. Furthermore, the high hardness and brittleness of functional ceramic materials inevitably lead to surface / subsurface damage, including irregular cracks and material breakage, making functional ceramic components prone to failure under cyclic loads or vibrations.

[0005] Laser processing technology utilizes a high-power-density, uniform laser beam as a heat source. By integrating and focusing the laser beam onto the material surface, localized high temperatures are generated, reaching the material's melting or vaporization temperature, thus achieving material removal. Laser processing technology has attracted considerable attention due to its high efficiency and controllability, lack of cutting forces, absence of tool wear, and ability to process difficult-to-machine materials such as those with high hardness, high brittleness, and high melting points. However, the large amount of heat generated during laser processing can easily cause microcracks and oxide layers to form on the workpiece surface. Furthermore, the initial investment in lasers is substantial, and maintenance costs are high, all of which hinder the further development of laser processing technology in the processing of functional ceramic microstructures.

[0006] Electrical discharge machining (EDM) is a technique that uses electrical discharge between a tool electrode and a workpiece electrode to break down the insulating working fluid between the two electrodes, generating instantaneous high-temperature melting or even vaporization to remove material. However, due to the high conductivity requirements of the workpiece material, this method can only be used to process insulating functional ceramics with the aid of an auxiliary electrode. Similar to laser processing, the high heat generated on the processed surface can also lead to microcracks, reducing the performance of the functional ceramics.

[0007] Abrasive jet machining is a non-traditional machining method that uses fluid to drive abrasive particles to be ejected onto the surface of a workpiece, achieving material removal in specific areas. Compared to the methods mentioned above, this technology offers advantages such as no tool wear, no heat-affected zone, high processing flexibility, and preservation of the physical and chemical integrity of the material surface. It is widely used in the processing of microstructures on the surfaces of hard and brittle materials. Furthermore, microstructures processed using abrasive jet machining have advantages such as chamfered boundaries and flat bottoms, which are highly beneficial for reducing contact stress in friction pairs and enhancing hydrodynamic effects.

[0008] In the process of micro abrasive air jet processing, the divergence effect of the micro abrasive air jet becomes more and more obvious as the jet distance increases. In order to reduce the impact of the divergence effect of the micro abrasive air jet on the processing resolution of microstructures, researchers have successively proposed mask-type, short-off distance (SOD) and air jet-assisted focusing methods.

[0009] For air-jet assisted focusing, the suppression of the divergence of the micro-abrasive air jet mainly relies on the action of the air jets on both sides. However, this method involves complex equipment, and the micro-abrasive air jet is easily disturbed by the air jets on both sides, leading to problems such as poor processing accuracy. For mask-based processing methods, the erosion wear of the mask material during erosion and the secondary erosion effect of the abrasive rebounding from the opening edge on the workpiece result in a mask opening size transfer error of up to 20%. Shortening the erosion distance to reduce the impact of the micro-abrasive air jet divergence effect on the microstructure processing resolution is an effective process method, but it is prone to producing W-shaped microstructures.

[0010] Furthermore, brittle peeling of powdered materials is the primary removal method for functional ceramic materials under high normal and low tangential impact forces, introducing microcracks on the surface / cross-section and significantly reducing the serviceability of functional ceramic components. This is the main reason currently hindering the widespread application of micro-abrasive air jet processing technology in the processing of high-performance microstructures of functional ceramics. Therefore, controlling microcracks is particularly important. To achieve near-damage-free processing of functional ceramic surface microstructures, researchers both domestically and internationally have been dedicated to studying plastic shear erosion processing techniques for functional ceramic materials under high tangential impact forces. Although the degree of microcrack damage on the processed surface / cross-section has been significantly improved, the material removal efficiency is low and the process space is small. Therefore, while ensuring processing efficiency, reducing the divergence of the micro-abrasive air jet and minimizing microcrack damage are scientific and technological challenges that must be addressed in the application of micro-abrasive air jet processing technology in the processing of high-performance microstructures of functional ceramics. Summary of the Invention

[0011] The purpose of this invention is to address the problems of severe jet divergence and poor surface finish in existing micro-abrasive gas jet processing methods for engineering ceramics, and to provide a micro-machining method for engineering ceramics based on flexible constrained abrasive jets to solve the above-mentioned technical problems.

[0012] The technical solution of this invention is:

[0013] A method for microfabrication of engineering ceramics based on abrasive flexible confined microjets, characterized in that it includes:

[0014] A precision powder feeding system, comprising a dry compressed air gate valve, a pressure regulating valve, an abrasive bin, and an air-powder mixer; the dry compressed air is sequentially regulated by the pressure regulating valve and effectively mixed with the gas-solid two-phase mixture of the air-powder mixer to obtain a certain pressure and a certain abrasive mass flow rate, and then the abrasive flow is fed into the abrasive nozzle.

[0015] A shear-thinning fluid supply system includes a shear-thinning fluid storage tank, a peristaltic pump, and a pulsation damper. The shear-thinning fluid is then stabilized by the peristaltic pump and the pulsation damper to obtain a stable shear-thinning fluid, which is then delivered into the shear-thinning fluid nozzle.

[0016] A two-stage nozzle system for solid abrasive particles and shear-thinning fluid is provided. This system includes a micro-abrasive gas jet nozzle, a second-layer flexible constraint system, and a first-layer flexible constraint system. Six shear-thinning fluid nozzles are uniformly arranged in the first and second-layer flexible constraint systems. The position angles β1 and β2 of adjacent shear-thinning fluid nozzles within the same layer are both 60°, while the position angle β3 of adjacent shear-thinning fluid nozzles in the first and second-layer flexible constraint systems is 30°. The first-layer flexible constraint system… In the system, the spray angle of the first-layer shear-thinning fluid nozzle is adjusted and fixed by the first-layer nozzle tightening device. The angle θ1 ranges from 15° to 30°, and the distance d1 between the focal point and the outlet end of the micro-abrasive gas jet nozzle ranges from 2 to 4 mm. In the second-layer flexible constraint system, the spray angle of the second-layer shear-thinning fluid nozzle is adjusted and fixed by the second-layer nozzle tightening device. The angle θ2 ranges from 45° to 60°, and the distance d2 between the focal point and the outlet end of the micro-abrasive gas jet nozzle ranges from 6 to 8 mm.

[0017] A processing system includes a four-axis moving platform and a base. An engineering ceramic workpiece is mounted on the four-axis moving platform. The processing of engineering ceramic microstructures is achieved by adjusting the relative positional relationship between the engineering ceramic workpiece and the micro-abrasive air jet nozzle.

[0018] A waste liquid recovery system, wherein the waste liquid recovery system collects waste liquid into a waste liquid storage tank by opening and closing a waste liquid gate valve, and after a certain period of settling, it is ready for subsequent use.

[0019] The shear-thinning fluid used in this invention can be either PEO aqueous solution or CMC aqueous solution, or other types of non-Newtonian fluids with shear-thinning properties.

[0020] The micromachining method for engineering ceramics based on abrasive flexible confined microjets of the present invention can be achieved through the following steps:

[0021] S1: Open the dry compressed air gate valve, pressure regulating valve and air-powder mixer in sequence, adjust the abrasive injection pressure and mass flow rate, and then close the dry compressed air gate valve.

[0022] S2: Fix the engineering ceramic workpiece on the four-axis moving platform and adjust its relative position with the micro abrasive air jet nozzle;

[0023] S3: Pour the prepared shear-thinning fluid into the non-Newtonian fluid storage tank and turn on the peristaltic pump. After the shear-thinning fluid gathers in the middle area between the engineering ceramic and solid abrasive particle nozzles, simultaneously turn on the drying compressed air gate valve and the four-axis moving platform program.

[0024] S4: After the four-axis moving platform program finishes running, turn off the peristaltic pump and the dry compressed air gate valve in sequence, take out the engineering ceramic workpiece, and complete the processing of its surface microstructure.

[0025] The processing system of the present invention has the following functions:

[0026] The relative positions of the shear-thinning fluid nozzle and the solid abrasive particle nozzle can be precisely adjusted as the research progresses; the rheological mass flow rate and the characteristics of the abrasive air jet can be accurately controlled by the peristaltic pump and the precision powder feeding system, respectively, to achieve flexible constraint of the micro abrasive air jet.

[0027] The advantages of this invention are:

[0028] On the one hand, because non-Newtonian fluids have low momentum / energy exchange with the surrounding still air medium during the jetting process, abrasive air jets do not suffer from problems such as poor processing accuracy due to disturbances in the air jets on both sides, as is the case with air jet-assisted focusing. On the other hand, due to the shear-thinning characteristics of non-Newtonian fluids, abrasive flexible constraint microjet processing does not form a distinct W-shaped surface profile due to the presence of a central stagnation zone, as is the case with micro-abrasive slurry jet processing.

[0029] The beneficial effects of this invention are:

[0030] On the one hand, it weakens the outward divergence of abrasive particles at the edge of the micro-abrasive air jet; on the other hand, it induces tangential erosion of the abrasive particle group at the impact interface under high impact angle conditions in the erosion processing area, thereby achieving the purpose of suppressing erosion cracks in the microstructure of functional ceramics.

[0031] This invention is rationally designed and economically effective, and has significant application value in the field of precision micro-machining of engineering ceramic microstructures. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the abrasive flexible confined microjet machining system of the present invention;

[0033] Figure 2 This is a schematic diagram of the nozzle layout in an abrasive flexible confined microjet machining system;

[0034] Figure 3 It is a comparison of the three-dimensional morphology and cross-sectional profile of the microporous structure of a quartz glass substrate.

[0035] In the diagram, 1-dry compressed air gate valve, 2-pressure regulating valve, 3-abrasive bin, 4-air-powder mixer, 5-precision powder feeding system, 6-two-stage nozzle system for solid abrasive particles and shear-thinning fluid, 7-micro abrasive air jet nozzle, 8-shear-thinning fluid nozzle, 9-engineering ceramic workpiece, 10-four-axis moving platform, 11-base, 12-machining system, 13-waste liquid gate valve, 14-waste liquid storage tank, 15-waste liquid recovery system, 16-shear-thinning fluid supply system, 17-shear-thinning fluid storage tank, 18-peristaltic pump, 19-pulse damper, 801-second-layer shear-thinning fluid nozzle, 802-second-layer nozzle tightening device, 803-first-layer shear-thinning fluid nozzle, 804-first-layer nozzle tightening device, 805-second-layer flexible constraint system, 806-first-layer flexible constraint system. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Similar solutions made by other people in the art are all within the protection scope of the present invention.

[0037] like Figure 1-3 As shown.

[0038] A method for micromachining engineering ceramics based on abrasive flexible confined microjets includes: a dry compressed air gate valve 1, a pressure regulating valve 2, an abrasive bin 3, an air-powder mixer 4, a precision powder feeding system 5, a two-stage nozzle system of solid abrasive particles and shear-thinning fluid 6, a micro-abrasive air jet nozzle 7, a shear-thinning fluid nozzle 8, an engineering ceramic workpiece 9, a four-axis moving platform 10, a base 11, a machining system 12, a waste liquid gate valve 13, a waste liquid storage tank 14, a waste liquid recovery system 15, a shear-thinning fluid supply system 16, a shear-thinning fluid storage tank 17, a peristaltic pump 18, a pulsation damper 19, a second-layer shear-thinning fluid nozzle 801, a second-layer nozzle tightening device 802, a first-layer shear-thinning fluid nozzle 803, a first-layer nozzle tightening device 804, a second-layer flexible confining system 805, and a first-layer flexible confining system 806, etc. Figure 1-2As shown, dry compressed air is sequentially pressure-regulated by pressure regulating valve 2 and effectively mixed with the gas-solid two-phase mixture in gas-powder mixer 4 to obtain a certain pressure and a certain abrasive mass flow rate. The abrasive stream is then fed into the micro abrasive air jet nozzle 7. The shear-thinning fluid is thus stabilized by peristaltic pump 18 and pulsation damper 19 to obtain a stable shear-thinning fluid, which is then fed into the first layer shear-thinning fluid nozzle 803 and the second layer shear-thinning fluid nozzle 801. In the first and second layer flexible constraint systems, six shear-thinning fluid nozzles are evenly arranged. The position angles β1 and β2 of adjacent shear-thinning fluid nozzles within the same layer are both 60°, and the position angle β3 of adjacent shear-thinning fluid nozzles in the first and second layer flexible constraint systems is 30°. In the first layer flexible constraint system 806, the spray angle of the first layer shear-thinning fluid nozzle 803 is adjusted and fixed by the first layer nozzle tightening device 804. The angle θ1 ranges from 15° to 30°, and the distance d1 between its focal point and the outlet end of the micro-abrasive gas jet nozzle ranges from 1 to 2 mm. In the second layer flexible constraint system 805, the spray angle of the second layer shear-thinning fluid nozzle 801 is adjusted and fixed by the second layer nozzle tightening device 802. The angle θ2 ranges from 45° to 60°, and the distance d2 between its focal point and the outlet end of the micro-abrasive gas jet nozzle ranges from 2 to 6 mm. The engineering ceramic workpiece 9 is mounted on a four-axis moving platform 10. The microstructure processing of the engineering ceramic is achieved by adjusting the relative position of the engineering ceramic workpiece 9 and the micro-abrasive air jet nozzle. The waste liquid recovery system collects waste liquid into the waste liquid storage tank 14 through the opening and closing of the waste liquid gate valve 13. After a certain period of settling, the waste liquid is ready for subsequent use.

[0039] Example

[0040] Reference Figure 1 In this embodiment, abrasive flexible constraint microjet machining is performed by fixing the workpiece on a four-axis moving platform and adjusting its relative position to the micro-abrasive air jet nozzle (details are shown in the table below). During the machining process, the micro-hole machining of the workpiece is achieved by controlling the abrasive injection time. The abrasive injection pressure is regulated by the pressure regulating valve 2, and the shear-thinning fluid is driven by the peristaltic pump 18.

[0041] The shear-thinning fluid is an aqueous solution composed of 8 million PEO molecules and water.

[0042] The gas is dried compressed air.

[0043] Table 1 lists the process conditions for abrasive flexible confined microfluidic machining in this embodiment, with the workpiece being quartz glass:

[0044] Table 1. Process conditions for abrasive flexible confined microfluidic machining

[0045] Process conditions Value Processing distance (mm) 3 Machining angle (deg) 90 Processing time (s) 10 Injection pressure (MPa) 0.2 Abrasive type <![CDATA[Al2O3]]> Abrasive size 25μm PEO aqueous solution concentration (wt%) 0.8 PEO aqueous solution flow rate (kg / min) 10

[0046] After 10 seconds of processing, the hole diameter was reduced by 9% in abrasive flexible constraint microjet machining compared to microabrasive air jet machining.

[0047] As can be seen from the above embodiments, this abrasive flexible confined microjet processing method can effectively focus the micro-abrasive gas jet beam and reduce the divergence of the micro-abrasive gas jet beam.

[0048] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention. While this paper frequently uses terms such as dry compressed air gate valve 1, pressure regulating valve 2, abrasive bin 3, air-powder mixer 4, precision powder feeding system 5, two-stage nozzle system for solid abrasive particles and shear-thinning fluid 6, micro abrasive air jet nozzle 7, shear-thinning fluid nozzle 8, engineering ceramic workpiece 9, four-axis moving platform 10, base 11, processing system 12, waste liquid gate valve 13, waste liquid storage tank 14, waste liquid recovery system 15, shear-thinning fluid supply system 16, shear-thinning fluid storage tank 17, peristaltic pump 18, pulsation damper 19, second-layer shear-thinning fluid nozzle 801, second-layer nozzle tightening device 802, first-layer shear-thinning fluid nozzle 803, first-layer nozzle tightening device 804, second-layer flexible constraint system 805, and first-layer flexible constraint system 806, the possibility of using other terms is not excluded. The use of these terms is merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

[0049] This embodiment is just one example of the present invention, and any technical solution that adopts a similar structure is within the protection scope of the present invention.

[0050] The parts not covered in this invention are the same as or can be implemented using existing technologies.

Claims

1. A method for microfabrication of engineering ceramics based on abrasive flexible confined microjets, characterized in that... It includes: Dry compressed air gate valve (1), pressure regulating valve (2), abrasive bin (3), air-powder mixer (4), precision powder feeding system (5), two-stage nozzle system for solid abrasive particles and shear-thinning fluid (6), micro abrasive air jet nozzle (7), shear-thinning fluid nozzle (8), engineering ceramic workpiece (9), four-axis moving platform (10), base (11), processing system (12), waste liquid gate valve (13), waste liquid storage tank (14), waste liquid recovery system (15), shear-thinning fluid supply system (16), shear-thinning fluid storage tank (17), peristaltic pump (18), pulsation damper (19), second-layer shear-thinning fluid nozzle (801), second-layer nozzle tightening device (802), first-layer shear-thinning fluid nozzle (803), first-layer nozzle tightening device (804), second-layer flexible constraint system (805), first-layer flexible constraint system (806).

2. The method for microfabrication of engineering ceramics based on abrasive flexible confined microjets according to claim 1, characterized in that: The two-stage nozzle system for solid abrasive particles and shear-thinning fluid includes: In the first and second layer flexible constraint systems, six shear-thinning fluid nozzles are uniformly arranged at the axial position of the micro-abrasive gas jet nozzle (7); among them, the position angles β1 and β2 of adjacent shear-thinning fluid nozzles in the same layer are both 60°, and the position angle β3 of adjacent shear-thinning fluid nozzles in the first and second layer flexible constraint systems is 30°.

3. The method for microfabrication of engineering ceramics based on abrasive flexible confined microjets according to claim 2, characterized in that: The first and second layer flexible restraint systems include: In the first layer flexible constraint system (806), the spray angle of the first layer shear thinning fluid nozzle (803) is adjusted and fixed by the first layer nozzle tightening device (804). The angle θ1 ranges from 15° to 30°, and the distance d1 between the focal point and the outlet end of the micro abrasive gas jet nozzle (7) ranges from 1 to 2 mm. In the second layer flexible constraint system (805), the injection angle of the second layer shear-thinning fluid nozzle (801) is adjusted and fixed by the second layer nozzle tightening device (802). The angle θ2 ranges from 45° to 60°, and the distance d2 between the focal point and the outlet end of the micro-abrasive gas jet nozzle (7) ranges from 2 to 6 mm.

4. The method for microfabrication of engineering ceramics based on abrasive flexible confined microjets according to claim 1, characterized in that, Includes the following steps: S1: Open the dry compressed air gate valve (1), pressure regulating valve (2) and air-powder mixer (4) in sequence, adjust the abrasive injection pressure and mass flow rate, and then close the dry compressed air gate valve (1); S2: Fix the engineering ceramic workpiece (9) on the four-axis moving platform (10) and adjust its relative position with the micro abrasive air jet nozzle (7); S3: Pour the prepared shear thinning fluid into the shear thinning fluid storage tank (17) and turn on the peristaltic pump (18). After the shear thinning fluid gathers in the middle area between the engineering ceramic workpiece and the micro abrasive air jet nozzle (7), simultaneously open the drying compressed air gate valve (1) and the four-axis moving platform (10) control program. S4: After the control program of the four-axis moving platform (10) is completed, turn off the peristaltic pump (18) and the dry compressed air gate valve (1) in sequence, take out the engineering ceramic workpiece (9), and complete the processing of its surface microstructure.

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