A method for ultra-precision grinding with controllable ductile domain machining dimensions

Abstract

The present invention discloses an ultra-precision grinding method with controllable ductile domain processing scale, wherein the controllable ductile domain processing scale is to modify silicon carbide, calcium fluoride and other workpieces through plasma, generate a modified layer on its surface, greatly reduce the hardness and brittleness of the modified layer, and make the plasma flow act evenly on the modified area through magnetron homogenization, so that the modified area and thickness are controllable, and then use a porous diamond grinding wheel to ultra-precision grind the workpiece surface, the grinding depth is not greater than the thickness of the modified layer plus the sum of the ductile domain removal depth of the material itself, and the multi-blade micro-cutting of the porous abrasive can significantly reduce the grinding damage. The present invention can not only realize the low-damage processing of the ductile domain processing scale of silicon carbide and calcium fluoride workpieces with controllable controllable ductile domain processing scale through the efficient coordinated magnetron homogenization plasma modification of the porous diamond grinding wheel, but also the modification and grinding can be carried out simultaneously, with high processing efficiency, meeting the requirements of industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of high-efficiency and low-damage grinding processing, and specifically relates to an ultra-precision grinding method with controllable processing scale in a ductile domain. Background Art

[0002] Workpieces such as silicon carbide and calcium fluoride generally go through three stages: "blank forming-grinding-polishing". In order to efficiently remove the geometric errors and processing damage of blank forming, minimize the scratches and damage layers caused by the process itself, reduce the burden of the polishing link, and improve processing efficiency, the intermediate ultra-precision grinding process must achieve high-efficiency and low-damage processing requirements. According to existing literature reports, the intermediate processes of workpieces such as silicon carbide and calcium fluoride can adopt single-point diamond turning, grinding and ultra-precision grinding. Single-point diamond turning has been widely used in the surface processing of free-cutting materials and soft and brittle crystal materials, but this technology is based on the characteristics of the rotating axis of the parts, so it is difficult to deal with complex structure strong light workpieces such as large-aperture strong laser wedge lenses and off-axis aspheric lenses. Surface grinding technology is difficult to directly process blanks to obtain complex surfaces with high geometric accuracy, and the processing efficiency is low. Ultra-precision grinding technology using conventional abrasives and grinding tools can achieve higher surface accuracy and processing efficiency, but there is a more serious problem of surface / subsurface damage. In order to reduce the damaged layer, only fine-grained abrasives can be used, but the grinding tool (grinding wheel) wears quickly and is easily clogged, requiring frequent dressing, which reduces the processing efficiency and does not effectively solve the problem of the damaged layer on the processing surface.

[0003] Therefore, in order to meet the processing needs of workpieces such as silicon carbide and calcium fluoride, it is urgent to develop a new processing method with high efficiency and low damage, which is of great significance for improving the processing quality. Summary of the invention

[0004] In order to solve the problems of large machining surface damage and low efficiency in the grinding of workpieces such as silicon carbide and calcium fluoride, the present invention proposes an ultra-precision grinding method with controllable machining scale in the ductile domain.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] An ultra-precision grinding method with controllable processing scale in a ductile domain, characterized in that the grinding method with controllable processing scale in a ductile domain involves a plasma generator, a magnetron homogenizing device, a grinding device and a workpiece, wherein the plasma generator is composed of a radio frequency generator, a matcher, oxygen, a flow control valve, water vapor, a constant temperature box, and a plasma torch, wherein the oxygen and water vapor are connected to the plasma torch through a flow control valve, wherein the water vapor is connected to the constant temperature box to ensure the supply of water vapor, and the magnetron homogenizing device is composed of a frequency conversion controller, a magnetic pole, an outer sleeve, The inner sleeve is installed at the end of the plasma torch through the inner sleeve, the magnetic poles are composed of an iron core, a copper coil, and a joint, the copper coil is wound on the iron core, the iron core is installed on the inner sleeve and the outer sleeve, the joint is connected to the frequency conversion controller, and the frequency conversion controller controls the current to control the magnitude and frequency of the magnetic field. The grinding device is composed of a grinding wheel made of porous abrasive particles, a control unit, and a workbench, wherein the control unit can be configured according to performance requirements to control the grinding wheel processing process parameters. The grinding method with controllable ductility domain processing scale is as follows:

[0007] 1) The plasma generated by the plasma generator contains hydroxyl radicals (OH - ), oxygen ions (O - ), can react with the material on the workpiece surface at a relatively low temperature to form a modified layer, reducing the hard, brittle and difficult-to-process characteristics of the workpiece material, while the magnetron homogenization device evenly expands the concentrated beam plasma ejected from the plasma torch, on the one hand reducing the concentrated plasma temperature, on the other hand expanding the modified area, thereby firstly realizing the controllable modification of the workpiece surface modification depth and modification area;

[0008] 2) The grinding wheel prepared with porous abrasive grains is used to grind the workpiece surface, and the grinding depth is not greater than the sum of the thickness of the modified layer and the plastic removal thickness of the workpiece material, that is, ultra-precision grinding is ensured within the ductile region of the workpiece material;

[0009] 3) Plasma modification and ultra-precision grinding are carried out simultaneously, that is, the two work together effectively to achieve high-efficiency and low-damage grinding of the workpiece.

[0010] The magnetic poles in the magnetically controlled homogenizing device surround the inner sleeve, that is, 3 to 10 magnetic poles are evenly distributed in the circumferential direction, and the intensity of the generated magnetic field is regulated by a frequency conversion controller.

[0011] If the workpiece is calcium fluoride, a calcium hydroxide and calcium oxide modified layer will be generated on the surface of the workpiece. If it is silicon carbide, a silicon dioxide modified layer will be generated on the surface of the workpiece. The thickness of the modified layer is 0.1-10 μm.

[0012] The porous abrasive grains are porous diamond abrasive grains made by a thermochemical etching method or an oxidation-reduction method. The diameter of the porous abrasive grains and the diameter of the etching holes need to be determined and selected in combination with the workpiece material and the thickness of the modified layer.

[0013] Compared with the prior art, the invention has the following advantages and significant effects:

[0014] (1) The processing scale of the ductile domain is greatly improved, and existing precision machine tools can be used to achieve low-damage processing of workpieces. On the one hand, the surface of the workpiece is modified by magnetron plasma to form a modified layer. The hardness and brittleness of the modified layer material are greatly reduced, increasing the processable scale of the ductile domain. On the other hand, the multi-edge and micro-edge of porous diamond are used to replace the conventional large single-edge cutting of diamond to further reduce processing damage, thereby realizing a new method of ultra-precision composite grinding processing with controllable ductile domain scale and using existing precision equipment.

[0015] (2) Plasma modification and porous grinding wheel grinding can be carried out simultaneously to achieve efficient processing of workpieces. The chemical modification liquid and solidification reaction agent used in existing chemical mechanical composite processing such as mechanical chemical grinding have low catalytic modification efficiency, making it difficult to achieve high-efficiency processing. The present invention adopts plasma modification, and the modification efficiency can match the ultra-precision grinding efficiency, which can be carried out simultaneously. At the same time, the multi-blade and micro-blade cutting of the porous grinding wheel is adopted to avoid the problem of frequent dressing of fine-grained diamond grinding wheels, thereby achieving high-efficiency processing.

[0016] (3) The processing method meets the requirements of green environmental protection production. The present invention adopts oxygen and water vapor plasma modification, does not contain substances harmful to the environment, and has low cost, which meets the requirements of environmental protection production.

[0017] It can be seen that the ultra-precision grinding method with controllable ductile domain processing scale proposed in the present invention can achieve high-efficiency and low-damage processing of workpieces such as silicon carbide and calcium fluoride, is green and environmentally friendly, and fully meets the requirements of industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Attached Figure 1 It is a schematic diagram of the ultra-precision grinding method with controllable processing scale in the ductile domain.

[0019] Attached Figure 2 It is a schematic diagram of a magnetically controlled homogenization device.

[0020] Attached Figure 3 It is a schematic diagram of multi-edge cutting with porous diamond abrasive.

[0021] Attached Figure 1-3In: 1—frequency controller, 2—RF generator, 3—matching device, 4—oxygen, 5—flow control valve, 6—water vapor, 7—constant temperature box, 8—plasma torch, 9—inner sleeve, 10—outer sleeve, 11—magnetic pole, 12—grinding wheel, 13—control unit, 14—porous diamond abrasive grains, 15—workpiece, 16—workbench, 17—iron core, 18—copper coil, 19—joint, 20—modified layer. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of those skilled in the art, Figure 1-3 The present invention is described in detail.

[0023] The present invention discloses an ultra-precision grinding method with controllable ductile domain processing scale. The controllable ductile domain processing scale is to modify calcium fluoride and silicon carbide workpieces through magnetron plasma to reduce the hard, brittle and difficult-to-process characteristics of the workpiece materials, and the magnetron homogenization device evenly expands the concentrated beam plasma ejected by the plasma torch, thereby reducing the action temperature of the plasma concentrated beam, expanding the modified area, and realizing controllable modification of the workpiece surface modification depth and modified area. The ultra-precision grinding is to form multi-blade micro-cutting under the action of porous abrasive particles. The ductile domain grinding depth of the porous abrasive grinding wheel is the sum of the thickness of the modified layer and the ductile domain removal depth of the material itself, and can also be less than the sum of the thickness of the modified layer and the ductile domain removal depth of the material itself. Compared with the single large cutting edge cutting of traditional abrasive particles, the multi-blade cutting of porous abrasive particles can significantly reduce the processing damage of the material, improve the processing surface quality, and avoid the problem of low processing efficiency caused by frequent dressing of fine-grained grinding wheels to obtain high surface quality. The present invention uses a porous diamond grinding wheel and a magnetron homogenized plasma modification to efficiently coordinate the modification, which can not only achieve low-damage processing of silicon carbide and calcium fluoride workpieces with controllable ductility domain processing scale, but also the modification and grinding can be carried out simultaneously, with high processing efficiency, meeting the requirements of industrial production.

[0024] The invention discloses an ultra-precision grinding method with controllable ductile domain processing scale, comprising a plasma generator, a magnetron homogenizing device, a grinding device and a workpiece (15). The plasma generator comprises a radio frequency generator (2), a matching device (3), oxygen (4), a flow control valve (5), water vapor (6), a constant temperature box (7) and a plasma torch (8). The oxygen (4) and water vapor (6) enter the plasma torch (8) through the flow control valve (5) and discharge through electrodes to generate plasma. The plasma ionization rate is regulated by the radio frequency generator (2) and the matching device (3). The water vapor (6) is placed in the constant temperature box (7) to ensure the supply of water vapor. The plasma contains hydroxyl radicals (OH - ), oxygen ions (O -), etc., which acts on the surface of the calcium fluoride workpiece to chemically react to generate calcium hydroxide and calcium oxide modified layers (20), and acts on the surface of the silicon carbide workpiece to generate silicon oxide modified layers (20). The hardness and brittleness of the modified layer (20) are greatly reduced. The thickness of the modified layer (20) is about 0.1-10 μm, which can be selected according to actual conditions. The magnetron homogenization device is composed of an inner sleeve (9), an outer sleeve (10), a magnetic pole (11), and a frequency conversion controller (1). It is installed at the end of the plasma torch (8) through the inner sleeve (9). The magnetic pole (11) is composed of an iron core (17), a copper coil (18), and a joint. (19), the copper coil (18) is wound on the iron core (17), the iron core (17) is installed on the inner sleeve (9) and the outer sleeve (10), the joint (19) is connected to the frequency conversion controller (1), the frequency conversion controller (1) controls the current to control the magnitude and frequency of the magnetic field, the magnetic field strength of the magnetic pole (11) is regulated by the frequency conversion controller (1), and the magnetron homogenization device evenly expands the concentrated beam plasma ejected from the plasma torch, on the one hand to reduce the concentrated action temperature of the plasma, on the other hand to expand the modified area, so as to achieve controllable modification of the surface modification depth and modification area of ​​the workpiece. The grinding device is composed of a grinding wheel (12) made of porous diamond abrasive grains (14), a control unit (13), and a workbench (16), wherein the porous abrasive grains can be made by a thermochemical etching method or an oxidation-reduction method, the porous abrasive grain diameter and the etching hole diameter need to be determined and selected in combination with the workpiece material and the thickness of the modified layer (20), and the control unit (13) can be configured according to performance requirements to control the grinding wheel processing process parameters.

[0025] The working principle of the present invention is briefly described as follows: plasma is formed by oxygen (4) and water vapor (6) flowing into a plasma torch (8) through a flow control valve (5), and then plasma flow is generated through electrode discharge, and then the plasma flow beam is expanded and homogenized through the magnetic field generated by a magnetron homogenization device, thereby generating a modified layer (20) on the surface of the workpiece; then, a porous diamond grinding wheel is used to grind the modified workpiece surface, and the grinding depth is the sum of the thickness of the modified layer (20) and the removal depth of the ductile domain of the material itself, and the modified layer (20) is removed, thereby achieving the high-efficiency and low-damage processing requirements of the workpiece.

Claims

1. An ultra-precision grinding method with controllable processing scale in ductile domain, characterized in that The ductile domain machining scale controllable grinding method involves a plasma generator, a magnetron homogenizing device, a grinding device and a workpiece (15), wherein the plasma generator is composed of a radio frequency generator (2), a matcher (3), oxygen (4), a flow control valve (5), water vapor (6), a constant temperature box (7) and a plasma torch (8), wherein the oxygen (4) is connected to the plasma torch (8) via the flow control valve (5) and the water vapor (6) is connected to the constant temperature box (7) to ensure the supply of the water vapor (6), and the magnetron homogenizing device is composed of a frequency conversion controller (1), a magnetic pole (11), an outer sleeve (10) and an inner sleeve (9), wherein the inner sleeve (9) is installed in the inner sleeve (9) At the end of the plasma torch (8), the magnetic pole (11) is composed of an iron core (17), a copper coil (18), and a joint (19), wherein the copper coil (18) is wound around the iron core (17), and the iron core (17) is mounted on an inner sleeve (9) and an outer sleeve (10), and the joint (19) is connected to a frequency conversion controller (1), and the frequency conversion controller (1) controls the current to adjust and control the magnitude and frequency of the magnetic field. The grinding device is composed of a grinding wheel (12) made of porous abrasive particles (14), a control unit (13), and a workbench (16), wherein the control unit (13) can be configured according to performance requirements to control the grinding wheel processing process parameters. The grinding method with controllable ductile domain processing scale is as follows: 1) The plasma generated by the plasma generator contains hydroxyl radicals (OH - ), oxygen ions (O - ), can react with the material on the surface of the workpiece (15) at a relatively low temperature to generate a modified layer (20), thereby reducing the hard, brittle and difficult-to-process characteristics of the workpiece (15), and the magnetron homogenization device evenly expands the concentrated beam plasma ejected by the plasma torch (8), on the one hand to reduce the concentrated action temperature of the plasma, and on the other hand to expand the modified area, thereby firstly achieving controllable modification of the depth and modified area of ​​the surface modified layer (20) of the workpiece (15); 2) using a grinding wheel (12) prepared with porous abrasive grains (14) to grind the surface of a workpiece (15), wherein the grinding depth is no greater than the sum of the thickness of the modified layer (20) and the plastic removal thickness of the workpiece (15), that is, ensuring that ultra-precision grinding is performed within the ductile region of the workpiece (15); 3) Plasma modification and ultra-precision grinding are carried out simultaneously, that is, the two work together effectively to achieve high-efficiency and low-damage grinding of the workpiece.

2. The method for ultra-precision grinding with controllable ductile domain processing scale according to claim 1, characterized in that The magnetic poles (11) in the magnetically controlled homogenizing device surround the inner sleeve (9), that is, 3 to 10 magnetic poles are evenly distributed in the circumferential direction, and the intensity of the generated magnetic field is controlled by a frequency conversion controller (1).

3. The method for ultra-precision grinding with controllable ductile domain processing scale according to claim 1, characterized in that If the workpiece (15) is calcium fluoride, a calcium hydroxide or calcium oxide modified layer (20) will be generated on the surface of the workpiece. If it is silicon carbide, a silicon dioxide modified layer (20) will be generated on the surface of the workpiece (15). The thickness of the modified layer (20) is 0.1-10 microns.

4. The method for ultra-precision grinding with controllable ductile domain processing scale according to claim 1, characterized in that The porous abrasive grains (14) are porous diamond abrasive grains produced by a thermochemical etching method or an oxidation-reduction method. The diameter of the porous abrasive grains (14) and the diameter of the etching holes need to be determined and selected in combination with the material of the workpiece (15) and the thickness of the modified layer (20).

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