CN117444829A - Discharge driving abrasive flow compound grinding method and device based on energy conversion - Google Patents
Discharge driving abrasive flow compound grinding method and device based on energy conversion Download PDFInfo
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- CN117444829A CN117444829A CN202311522184.3A CN202311522184A CN117444829A CN 117444829 A CN117444829 A CN 117444829A CN 202311522184 A CN202311522184 A CN 202311522184A CN 117444829 A CN117444829 A CN 117444829A
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- 238000000227 grinding Methods 0.000 title claims abstract description 155
- 238000000034 method Methods 0.000 title claims abstract description 57
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 31
- 150000001875 compounds Chemical class 0.000 title claims abstract description 10
- 239000012530 fluid Substances 0.000 claims abstract description 32
- 239000002245 particle Substances 0.000 claims description 121
- 239000007788 liquid Substances 0.000 claims description 43
- 239000000463 material Substances 0.000 claims description 20
- 239000002131 composite material Substances 0.000 claims description 19
- 238000007599 discharging Methods 0.000 claims description 16
- 239000007767 bonding agent Substances 0.000 claims description 14
- 229910003460 diamond Inorganic materials 0.000 claims description 12
- 239000010432 diamond Substances 0.000 claims description 12
- 239000007790 solid phase Substances 0.000 claims description 10
- 239000000725 suspension Substances 0.000 claims description 10
- 238000003860 storage Methods 0.000 claims description 9
- 230000008719 thickening Effects 0.000 claims description 9
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 8
- 239000006061 abrasive grain Substances 0.000 claims description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 4
- 229910000420 cerium oxide Inorganic materials 0.000 claims description 4
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims description 4
- 239000004408 titanium dioxide Substances 0.000 claims description 4
- 229910052582 BN Inorganic materials 0.000 claims description 3
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 3
- 239000004020 conductor Substances 0.000 claims description 3
- 239000010954 inorganic particle Substances 0.000 claims description 3
- 229920000620 organic polymer Polymers 0.000 claims description 3
- 229920000642 polymer Polymers 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 230000000694 effects Effects 0.000 description 17
- 238000003754 machining Methods 0.000 description 14
- 238000005498 polishing Methods 0.000 description 8
- 238000010892 electric spark Methods 0.000 description 6
- 238000005520 cutting process Methods 0.000 description 4
- 238000010008 shearing Methods 0.000 description 4
- 230000005684 electric field Effects 0.000 description 3
- 239000012761 high-performance material Substances 0.000 description 3
- 239000003058 plasma substitute Substances 0.000 description 3
- 230000003746 surface roughness Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007385 chemical modification Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005111 flow chemistry technique Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002459 sustained effect Effects 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B31/00—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor
- B24B31/10—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor involving other means for tumbling of work
- B24B31/116—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor involving other means for tumbling of work using plastically deformable grinding compound, moved relatively to the workpiece under the influence of pressure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B1/00—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B31/00—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor
- B24B31/12—Accessories; Protective equipment or safety devices; Installations for exhaustion of dust or for sound absorption specially adapted for machines covered by group B24B31/00
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B57/00—Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents
- B24B57/02—Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents for feeding of fluid, sprayed, pulverised, or liquefied grinding, polishing or lapping agents
Abstract
The invention discloses a discharge driving abrasive flow compound grinding method and a device based on energy conversion, wherein the method comprises the following steps: (1) Adding free abrasive fluid between a micro-grinding tool and a workpiece to completely submerge the micro-grinding tool and the workpiece; (2) Setting a discharge power supply, connecting the positive electrode of the discharge power supply with a workpiece, connecting the negative electrode of the discharge power supply with a micro grinding tool, and setting the voltage, the current limiting value and the frequency parameter of the discharge power supply; (3) Setting a micro grinding tool, enabling the grinding tool to rotate relative to the workpiece, and enabling the micro grinding tool and the workpiece to perform reciprocating relative motion along the direction perpendicular to the thickness direction of the workpiece; (4) And (3) after the micro grinding tool reciprocates once, setting the grinding tool to feed along the thickness direction of the workpiece, and repeating the step (3) for processing until the feeding reaches the set thickness, and stopping the rotation of the grinding tool.
Description
Technical Field
The invention belongs to the technical field of material surface precision machining, and particularly relates to an energy conversion-based discharge driving abrasive flow compound grinding method and device.
Background
The surface microstructure of the high-performance material can enable key parts to obtain better product service performance, and the high-performance material can be widely applied to the fields of aerospace, biomedicine and photoelectric communication, such as semiconductor chips, high-performance cutter microstructures, optical curved surface microstructures, medical micro-channels and the like. This places higher demands on the machining accuracy surface quality and integrity of the machining process, resulting in better operational stability and reliability.
The traditional microstructure machining method is a mode of carrying out precise forming by cutting and removing chips by intermittently contacting fixed abrasive particles with the surface of a workpiece at a high linear speed. Although the microstructure shape machined in this way is very precise, the process cutting heat can cause significant abrasive wear, making the machined surface quality and integrity low, and the micro-grinding tool dressing process very difficult and inefficient.
In order to solve the technological defects generated by the processing of the fixed abrasive particles, energy fields such as laser, electric spark, chemical modification and the like are introduced to carry out auxiliary processing on the microstructure. The high sustained heat of the laser and spark locally heats the work surface, resulting in the creation of heat affected zones and subsurface thermal cracks. Although the chemical mechanical polishing is not damaged, the processing efficiency is too low due to the dispersion of abrasive particles in the liquid, and the polishing cannot be applied to the forming processing of microstructures. At present, how to process the surface microstructure of a high-performance material with high efficiency and high integrity is a bottleneck to be broken through.
In order to solve the problems, the combined machining method of the electric spark and the abrasive flow of the working blade of the air compressor (CN 202111063399.4) aims at the difficult machining problem that the dimensional accuracy of the blade edge of a single working blade of the air compressor in numerical control milling and abrasive belt grinding is difficult to ensure, so that the machining quality of the blade is ensured, the machining efficiency is improved, and the machining cost is reduced. However, the electric spark and abrasive flow processing in the method is only combined processing with sequential process sequences, and the in-situ microstructure forming and polishing cannot be realized. In addition, the inventive method does not allow for high integrity surface finish with low damage and roughness.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides a pulse discharge driving abrasive flow compound micro-grinding method based on discharge energy conversion, which is used for carrying out micro-structure surface processing on a workpiece, wherein free abrasive liquid flows between a bonding agent and the workpiece and serves as a discharge medium in the processing process. The method comprises the steps of removing workpiece materials through high-speed rotation shearing of solidified abrasive particles on the surface of a micro-grinding tool, and simultaneously, driving fluid media with a shearing thickening effect to flow in a blade outlet space of the solidified abrasive particles between a tool bonding agent and the workpiece due to high-speed rotation, so as to generate a pressure field similar to a sine curve and hold free abrasive particles which are randomly distributed. And pulse electric spark discharge is generated between the tool bonding agent and the workpiece at the same time, and when an electric field breaks down a medium, discharge energy is transmitted into free abrasive particles through free abrasive liquid medium, so that the tool bonding agent and the workpiece obtain certain impact removal force in the discharge plasma expansion process, and the pulse discharge energy also has the effect of softening the surface of the workpiece. Under the action of a fluid pressure field and discharge impact force removal, the medium fluid generates a shear thickening effect, free abrasive particles held by solid phase particles flow to the surface of a workpiece along the linear speed direction of the micro-grinding tool, scratch, plow and micro-cut the surface of the workpiece, remove a subsurface damaged layer generated by diamond abrasive particle processing on the surface of the micro-grinding tool, and reduce surface roughness, edge burrs and residual stress.
The invention is realized at least by one of the following technical schemes.
The pulse discharge driving abrasive flow composite micro grinding method based on discharge energy conversion comprises the following steps:
(1) Adding free abrasive fluid between a micro-grinding tool and a workpiece to completely submerge the micro-grinding tool and the workpiece;
(2) Setting a discharge power supply, connecting the positive electrode of the discharge power supply with a workpiece, connecting the negative electrode of the discharge power supply with a micro grinding tool, and setting the voltage, the current limiting value and the frequency parameter of the discharge power supply;
(3) Setting a micro grinding tool, enabling the grinding tool to rotate relative to the workpiece, and enabling the micro grinding tool and the workpiece to perform reciprocating relative motion along the direction perpendicular to the thickness direction of the workpiece;
(4) And (3) after the micro grinding tool reciprocates once, setting the grinding tool to feed along the thickness direction of the workpiece, and repeating the step (3) for processing until the feeding reaches the set thickness, and stopping the rotation of the grinding tool.
Further, the free abrasive fluid is a suspension formed by dispersing solid-phase particles in a liquid medium and adding free abrasive particles in the liquid medium and fully diffusing the particles; the solid phase particles are organic polymer or inorganic particles; the liquid medium is oil, water or polymer liquid; when the solid phase particles and the liquid medium are in a ratio of 1:1-2:1, the suspension has a shear thickening characteristic.
Further, the free abrasive is made of diamond, alumina, titanium dioxide and cerium oxide particles, and the average diameter of the particles is 0.05-40 mu m; when in use, the free abrasive particles are smaller than the outlet edge height of the fixed abrasive particles on the surface of the micro-grinding tool, so that the free abrasive particles flow in a gap between the bonding agent and the surface of the workpiece; the mass fraction of the free abrasive particles in the suspension is 1-30%.
Further, in the process of rotating the micro-grinding tool, the free abrasive particles in the fluid are subjected to a pressure field determined by the rotating speed of the micro-grinding tool, and the flow force brought by the pressure field is as follows:
wherein F is n For positive pressure experienced by the loose abrasive particles, p n D for maximum fluid pressure of process a Is the diameter of free abrasive particles, gamma is the fluidThe direction of the pressure field.
Further, the parameters of the discharge power supply range from 0 to 40V of open-circuit voltage, 0 to 0.5A of current limiting value, 100 to 5000 mu s of pulse period and 0 to 100% of duty ratio.
Further, in the pulse discharge process, the energy for generating a single pulse discharge is determined by the input setting of a discharge power supply, and the expression is as follows:
wherein E is d For discharging energy in a single pulse, t p U (t) and I (t) are real-time variation values of voltage and current in the pulse discharging process;
the energy converted to free abrasive particles in the liquid is given by the following expression:
E ab ＝K ab E f ＝K ab K f E d (3)
wherein E is ab K for conversion to energy of free abrasive particles ab Energy conversion coefficient K for free abrasive particles f Is the energy conversion coefficient of the free abrasive particle liquid.
Further, the workpiece material is conductive material, and the resistivity is less than 10 -5 Ω·cm。
Further, the free abrasive particles are subjected to the flowing force caused by the pressure field caused by the rotation of the micro grinding tool and the impact force caused by the pulse discharge in the free abrasive fluid, and the volume of the material removal is controlled by adjusting the pressure field and the pulse discharge energy, wherein the material removal depth of the free abrasive particles is obtained by the following expression:
wherein m is a Is the mass of single free abrasive particle, v n Normal velocity of single free abrasive particle, E ab F for conversion to energy of free abrasive particles n Is subjected to free abrasive particlesPositive pressure of (h) a The impact depth of free abrasive particles on a workpiece is shown as sigma, and the plastic flow stress of the workpiece is shown as S a Is the projected area of the free abrasive particles.
Further, the diameter of the micro grinding tool is 0.1-5 mm, abrasive particles on the surface of the tool are diamond and cubic boron nitride particles, the particle mesh number is 70# to 1000#, and the rotating speed of the micro grinding tool is 1000-60000 r/min when the micro grinding tool is used.
The pulse discharge driving abrasive flow compound micro-grinding device for realizing the compound micro-grinding method comprises the following components:
a micro-grinding tool consisting of abrasive particles affixed to a surface;
the pulse discharging device comprises a discharging power supply and connecting wires, and the positive and negative ends of the power supply are respectively connected with the workpiece and the micro grinding tool through the connecting wires and are used for performing pulse discharging in the running process;
the liquid storage device is used for storing free abrasive grain liquid and is provided with a placing space for connecting wires, and the workpiece and the micro grinding tool are immersed in the liquid storage device to realize immersed processing;
a micro grinding tool driving device connected with the grinding tool, wherein the grinding tool can rotate under the driving of the grinding tool driving device;
the workbench device comprises two moving parts, wherein the first moving part is used for enabling the workpiece and the micro grinding tool to move relatively along the thickness direction perpendicular to the workpiece, and the second moving part is used for enabling the workpiece and the grinding tool to move relatively along the thickness direction of the workpiece.
Compared with the prior art, the invention has at least the following beneficial effects:
1. because the micro grinding tool and the workpiece have good conductivity, the micro grinding tool and the workpiece can generate a certain impact force on free abrasive particles due to multiple pulse discharge, and the thermochemical modification effect is generated on the surface of the workpiece; the free abrasive particles in the free abrasive fluid can be driven by the high-speed rotation of the micro-grinding tool to micro-cut the workpiece material, so that plastic removal is generated; the free abrasive particles driven by pulse discharge can remove burrs and subsurface remained after the micro-grinding tool is processed, reduce the surface residual stress, achieve the effect of surface polishing, improve the surface quality of the microstructure processing to a certain extent, and achieve the effect of high surface integrity or high material removal rate. In addition, by blending and updating the free abrasive liquid component, the processing efficiency and polishing quality can be controlled.
2. Because the micro grinding tool and the workpiece have good conductivity, in the running process of the device, the micro grinding tool and the workpiece can generate a certain impact force on free abrasive particles through multiple pulse discharge generated by the pulse discharge device, and the thermochemical modification effect is generated on the surface of the workpiece; the free abrasive particles in the free abrasive fluid of the liquid storage device can be used for micro-cutting the workpiece material under the high-speed rotation driving of the micro-grinding tool driving device, so that plastic removal is generated; the free abrasive particles driven by electric discharge can remove burrs and subsurface remained after the grinding and micro-cutting tool is processed, reduce the surface residual stress, achieve the effect of surface polishing, and improve the quality of the processed surface of the microstructure to a certain extent. In addition, by blending and updating the free abrasive liquid component, the processing efficiency and polishing quality can be controlled.
Drawings
FIG. 1 is a schematic diagram of a pulsed discharge-driven abrasive flow composite micro-grinding method based on discharge energy conversion;
FIG. 2 is a schematic diagram of an apparatus according to the present invention in an embodiment;
FIG. 3 is a graph showing the distribution of the fluid pressure field during high speed rotation of a micro-grinding tool;
FIG. 4 is a graph of energy variation of a pulsed discharge between a micro-grinding tool and a workpiece;
FIG. 5 is a scanning electron microscope photograph of a conventional grinding and pulse discharge driven abrasive flow composite micro-grinding process;
FIG. 6 is a laser confocal three-dimensional profile scan photograph of a conventional grinding and pulse discharge driven abrasive flow composite micro-grinding process;
reference numerals:
the grinding tool comprises a workpiece-101, a fixed abrasive particle-102, free abrasive particles-103, solid particles-104, a pulse discharge 105, a discharge expansion wave-106, a free abrasive liquid pressure field-107, a free abrasive particle flow direction-108, a machining burr-109, a subsurface damage layer-110, residual stress-111, a micro grinding tool bonding agent-112, a workpiece-201, a workbench-202, a micro grinding tool-203, a micro grinding tool driving device-204, a free abrasive liquid-205, a liquid storage device-206, a discharge power supply-207, an anode connecting wire-208 and a cathode connecting wire-209.
Detailed Description
The conception and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below to fully understand the objects, features and effects of the present invention. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention.
In the description of the embodiments of the present invention, if an orientation description such as "upper", "lower", "front", "rear", "left", "right", etc. is referred to, it is merely for convenience of description and simplification of the description, and it is not indicated or implied that the apparatus or element referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.
In the description of the embodiments of the present invention, if a feature is referred to as being "disposed", "fixed", "connected" or "mounted" on another feature, it can be directly disposed, fixed or connected to the other feature or be indirectly disposed, fixed or connected or mounted on the other feature. In the description of the embodiments of the present invention, if "several" is referred to, it means more than one, if "multiple" is referred to, it is understood that the number is not included if "greater than", "less than", "exceeding", and it is understood that the number is included if "above", "below", "within" is referred to. If reference is made to "first", "second" it is to be understood as being used for distinguishing technical features and not as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the pulse discharge driving abrasive flow composite micro-grinding method based on discharge energy conversion of the embodiment, free abrasive liquid flows between a bonding agent and a workpiece and serves as a discharge medium in the machining process. The method comprises the steps of removing workpiece materials through high-speed rotation shearing of solidified abrasive particles on the surface of a micro-grinding tool, and simultaneously, driving fluid media with a shearing thickening effect to flow in a blade outlet space of the solidified abrasive particles between a tool bonding agent and the workpiece due to high-speed rotation, so as to generate a pressure field similar to a sine curve and hold free abrasive particles which are randomly distributed. And pulse electric spark discharge is generated between the tool bonding agent and the workpiece at the same time, and when an electric field breaks down a medium, discharge energy is transmitted into free abrasive particles through free abrasive liquid medium, so that the tool bonding agent and the workpiece obtain certain impact removal force in the discharge plasma expansion process, and the pulse discharge energy also has the effect of softening the surface of the workpiece. Under the action of a fluid pressure field and discharge impact force removal, the medium fluid generates a shear thickening effect, free abrasive particles held by solid phase particles flow to the surface of a workpiece along the linear speed direction of the micro-grinding tool, scratch, plow and micro-cut the surface of the workpiece, remove a subsurface damaged layer generated by diamond abrasive particle processing on the surface of the micro-grinding tool, and reduce surface roughness, edge burrs and residual stress. The method specifically comprises the following steps:
(1) Adding free abrasive fluid between a micro-grinding tool and a workpiece to completely submerge the micro-grinding tool and the workpiece; the free abrasive fluid is a suspension formed by dispersing solid-phase particles 104 in a liquid medium and adding free abrasive particles 103 in the liquid medium and fully dispersing; the solid phase particles 104 are organic polymers or inorganic particles; the liquid medium is oil, water or polymer liquid; the suspension has shear thickening properties at a ratio of 1:1 to 2:1 of solid particles 104 to liquid medium.
The free abrasive 103 is made of diamond, alumina, titanium dioxide and cerium oxide particles, and the average diameter of the particles is 0.05-40 mu m; the free abrasive particles 103 are smaller than the height of the bonded abrasive particles 102 protruding from the micro-tool bond 112 at the surface of the micro-tool in use, such that the free abrasive particles 103 flow in the gap between the micro-tool bond 112 and the surface of the workpiece; the mass fraction of the free abrasive particles in the suspension is 1-30%.
The free abrasive is made of diamond, alumina, titanium dioxide and cerium oxide particles, and the average diameter of the particles is 0.05-40 mu m; the free abrasive particles 103 are smaller than the outlet edge height of the fixed abrasive particles 102 on the surface of the micro grinding tool in use, so that the free abrasive particles 103 flow in a gap between the bonding agent and the surface of the workpiece; the free abrasive particles 103 account for 1-30% of the mass fraction of the suspension.
The workpiece material is conductive material, and the resistivity is less than 10 -5 Omega-cm, such as metal materials, can also be used for surface processing of semiconductor materials (resistivity between 1mΩ -cm and 1gΩ -cm), such as monocrystalline silicon, monocrystalline silicon carbide, etc.
As a preferred embodiment, the diameter of the micro-grinding tool is 0.1-5 mm, abrasive particles on the surface of the tool are diamond and cubic boron nitride particles, the mesh number of the particles is 70# to 1000#, and the rotating speed of the micro-grinding tool is 1000-60000 r/min when the micro-grinding tool is used.
(2) Setting a discharge power supply, connecting the positive electrode of the discharge power supply with a workpiece, connecting the negative electrode of the discharge power supply with a micro grinding tool, and setting the voltage, the current limiting value and the frequency parameter of the discharge power supply;
(3) Setting a micro grinding tool, enabling the grinding tool to rotate relative to the workpiece, and enabling the micro grinding tool and the workpiece to perform reciprocating relative motion along the direction perpendicular to the thickness direction of the workpiece;
(4) And (3) after the micro grinding tool reciprocates once, setting the grinding tool to feed along the thickness direction of the workpiece, and repeating the step (3) for processing until the feeding reaches the set thickness, and stopping the rotation of the grinding tool.
In the process of rotating the micro-grinding tool, the free abrasive particles in the fluid are subjected to a pressure field determined by the rotating speed of the micro-grinding tool, and the flow force brought by the free abrasive particles is as follows:
wherein F is n For positive pressure experienced by the loose abrasive particles, p n D for maximum fluid pressure of process a The free abrasive particle diameter, gamma is the direction of action of the fluid pressure field.
As a preferred embodiment, the parameters of the discharge power supply range from 0 to 40V of open-circuit voltage, 0 to 0.5A of current limit value, 100 to 5000 mu s of pulse period and 0 to 100% of duty ratio, and are selected according to the material removal amount and the surface polishing quality.
During the pulse discharge, the energy of the single pulse discharge 105 is determined by the discharge power input setting, and the expression is:
wherein E is d For discharging energy in a single pulse, t p U (t) and I (t) are real-time variation values of voltage and current in the pulse discharging process;
the energy converted to free abrasive particles in the liquid is given by the following expression:
E ab ＝K ab E f ＝K ab K f E d (3)
wherein E is ab K for conversion to energy of free abrasive particles ab Energy conversion coefficient K for free abrasive particles f Is the energy conversion coefficient of the free abrasive particle liquid.
The free abrasive particles are subjected to the flowing force caused by the pressure field caused by the rotation of the micro grinding tool, such as the flowing direction 108 of the free abrasive particles and the impact force caused by the pulse discharge in the free abrasive fluid in fig. 1, and the volume amount of the removed material is controlled by adjusting the pressure field 107 of the free abrasive liquid and the pulse discharge energy, so that the effect of high surface integrity or high material removal rate is achieved in the plastic domain processing or brittle domain processing range, wherein the material removal depth of the free abrasive particles is obtained by the following expression:
wherein m is a Is the mass of single free abrasive particle, v n Normal velocity of single free abrasive particle, E ab F for conversion to energy of free abrasive particles n Is positive pressure exerted by free abrasive particles, h a The impact depth of free abrasive particles on a workpiece is shown as sigma, and the plastic flow stress of the workpiece is shown as S a Is the projected area of the free abrasive particles.
The pulse discharge driving abrasive flow compound micro-grinding device for realizing the compound micro-grinding method comprises the following components:
a micro-grinding tool consisting of abrasive particles affixed to a surface;
the pulse discharging device comprises a discharging power supply and connecting wires, and the positive and negative ends of the power supply are respectively connected with the workpiece and the micro grinding tool through the connecting wires and are used for performing pulse discharging in the running process;
the liquid storage device is used for storing free abrasive grain liquid and is provided with a placing space for connecting wires, and the workpiece and the micro grinding tool are immersed in the liquid storage device to realize immersed processing;
the micro grinding tool driving device comprises a high-speed main shaft and a motor connected with the high-speed main shaft, the micro grinding tool is fixed on the high-speed main shaft through a chuck, the high-speed main shaft drives the micro grinding tool to rotate, the grinding tool driving device is connected with the grinding tool, and the grinding tool can rotate under the driving of the grinding tool driving device;
the workbench device comprises a first moving part and a second moving part, wherein the two moving parts are machine tool guide rails, the workpiece and the micro grinding tool are fixed on the machine tool guide rails through clamps, the guide rails are driven by a motor to drive the workpiece and the micro grinding tool to move, the first moving part is used for enabling the workpiece and the micro grinding tool to move relatively along the thickness direction perpendicular to the workpiece, and the second moving part is used for enabling the workpiece and the grinding tool to move relatively along the thickness direction of the workpiece.
In the principle of the pulse discharge driving abrasive flow composite micro-grinding method based on discharge energy conversion in fig. 1, as shown in fig. 2, before composite machining is performed on a workpiece 201, the workpiece 201 to be machined is first fixed on a workbench device 202, a micro-grinding tool 203 is fixed in a micro-grinding tool driving device 204, and the micro-grinding tool is inclined at a certain angle through a regulator of the driving device 204. The configured free abrasive fluid 205 is added to the liquid storage device 206, immersing the workpiece 201 and the micro-grinding tool 203 therein. The positive and negative ends of the pulse discharge power supply 207 are connected to the workpiece 201 and the micro grinding tool 203 via connection wires 208 and 209, respectively. After the device is installed, setting the voltage, the current limiting value, the pulse period and the duty ratio parameters of the discharge power supply, and outputting. And after the micro grinding tool reciprocates once, the grinding tool is arranged to feed along the thickness direction of the workpiece, and then reciprocates and moves relatively until the feeding reaches the set thickness, and the rotation of the grinding tool is stopped.
In the machining process, the diamond abrasive particles on the micro-grinding surface remove the surface through high-speed rotation, and meanwhile, in the diamond bulge space between the tool bonding agent and the workpiece, a fluid medium with a shear thickening effect is driven to flow due to the high-speed rotation, so that a pressure field similar to a sine curve is generated, as shown in fig. 3.
The tool bonding agent and the workpiece generate pulse electric spark discharge at the same time, when the electric field breaks down the medium, the discharge energy is transmitted into the free abrasive particles through the free abrasive liquid medium, as shown in fig. 4, so that the tool bonding agent and the workpiece obtain a certain impact removal force in the discharge plasma expansion (discharge expansion wave 106) process, and the pulse discharge energy also has the effect of softening the surface of the workpiece.
Under the action of the fluid pressure field and the discharging impact force, the medium fluid generates a shear thickening effect, the held free abrasive particles flow to the surface of the workpiece along the linear speed direction of the micro-grinding tool, the surface of the workpiece is scratched, ploughed and micro-cut, the subsurface damage layer 110 generated by diamond abrasive particle machining on the surface of the micro-grinding tool is removed, and the surface roughness, edge burrs 109 and residual stress 111 are reduced, as shown in fig. 1.
The type, diameter size and mass fraction of the free abrasive fluid medium are determined according to the material quality and surface quality requirements of the workpiece. After the material and surface quality criteria are determined, the rotational speed of the micro grinding tool is determined, and a specific set of experimental data in this example is given below:
table 1 example conditions for pulse discharge driven abrasive flow composite micro-grinding method
Fig. 5a and b are surface scanning electron micrographs of the conventional grinding and the composite micro grinding according to the present invention, respectively, and it can be seen that the present method improves the surface quality.
Referring to fig. 6, which is a sectional profile view of a microstructure after the conventional grinding and the composite micro-grinding according to the method of the present invention, it can be seen that the method improves the processing efficiency of the micro-structure grinding.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention. Furthermore, embodiments of the invention and features of the embodiments may be combined with each other without conflict.
Claims (10)
1. The discharge driving abrasive flow compound grinding method based on energy conversion is characterized by comprising the following steps of: the method comprises the following steps:
(1) Adding free abrasive fluid between a micro-grinding tool and a workpiece to completely submerge the micro-grinding tool and the workpiece;
(2) Setting a discharge power supply, connecting the positive electrode of the discharge power supply with a workpiece, connecting the negative electrode of the discharge power supply with a micro grinding tool, and setting the voltage, the current limiting value and the frequency parameter of the discharge power supply;
(3) Setting a micro grinding tool, enabling the grinding tool to rotate relative to the workpiece, and enabling the micro grinding tool and the workpiece to perform reciprocating relative motion along the direction perpendicular to the thickness direction of the workpiece;
(4) And (3) after the micro grinding tool reciprocates once, setting the grinding tool to feed along the thickness direction of the workpiece, and repeating the step (3) for processing until the feeding reaches the set thickness, and stopping the rotation of the grinding tool.
2. The energy conversion-based discharge-driven abrasive flow composite grinding method according to claim 1, wherein the free abrasive fluid is a suspension formed by dispersing solid-phase particles in a liquid medium and adding free abrasive particles in the liquid medium, and sufficiently dispersing; the solid phase particles are organic polymer or inorganic particles; the liquid medium is oil, water or polymer liquid; when the solid phase particles and the liquid medium are in a ratio of 1:1-2:1, the suspension has a shear thickening characteristic.
3. The energy conversion-based discharge-driven abrasive flow composite grinding method according to claim 2, wherein the free abrasive is made of diamond, alumina, titanium dioxide and cerium oxide particles, and the average diameter of the particles is 0.05-40 μm; when in use, the free abrasive particles are smaller than the outlet edge height of the fixed abrasive particles on the surface of the micro-grinding tool, so that the free abrasive particles flow in a gap between the bonding agent and the surface of the workpiece; the mass fraction of the free abrasive particles in the suspension is 1-30%.
4. The energy conversion-based discharge-driven abrasive flow composite grinding method according to claim 1, wherein the free abrasive particles in the fluid are subjected to a pressure field determined by the rotation speed of the micro-grinding tool during the rotation of the micro-grinding tool, and the flow force is:
wherein F is n For positive pressure experienced by the loose abrasive particles, p n D for maximum fluid pressure of process a The free abrasive particle diameter, gamma is the direction of action of the fluid pressure field.
5. The energy conversion-based discharge-driven abrasive flow composite grinding method according to claim 1, wherein the parameters of the discharge power supply range from 0 to 40V of open-circuit voltage, from 0 to 0.5A of current limiting value, from 100 to 5000 mu s of pulse period and from 0 to 100% of duty ratio.
6. The energy conversion-based discharge-driven abrasive stream composite grinding method according to claim 1, wherein the energy for generating a single pulse discharge during the pulse discharge is determined by a discharge power input setting, and the expression is:
wherein E is d For discharging energy in a single pulse, t p U (t) and I (t) are real-time variation values of voltage and current in the pulse discharging process;
the energy converted to free abrasive particles in the liquid is given by the following expression:
E ab ＝K ab E f ＝K ab K f E d (3)
wherein E is ab K for conversion to energy of free abrasive particles ab Energy conversion coefficient K for free abrasive particles f Is the energy conversion coefficient of the free abrasive particle liquid.
7. The energy conversion-based discharge-driven abrasive flow composite grinding method as claimed in claim 1, wherein the workpiece material is a conductive material with a resistivity of less than 10 -5 Ω·cm。
8. The energy conversion-based discharge-driven abrasive flow composite grinding method according to claim 1, wherein the free abrasive grains are subjected to a flow force caused by a pressure field caused by rotation of a micro grinding tool and an impact force caused by pulse discharge in the free abrasive fluid, and the volume amount of material removal is controlled by adjusting the pressure field and the pulse discharge energy, wherein the material removal depth of the free abrasive grains is obtained by the following expression:
wherein m is a Is the mass of single free abrasive particle, v n Normal velocity of single free abrasive particle, E ab F for conversion to energy of free abrasive particles n Is positive pressure exerted by free abrasive particles, h a The impact depth of free abrasive particles on a workpiece is shown as sigma, and the plastic flow stress of the workpiece is shown as S a Is the projected area of the free abrasive particles.
9. The discharge-driven abrasive flow composite grinding method based on energy conversion according to claim 1, wherein the diameter of the micro grinding tool is 0.1-5 mm, abrasive particles on the surface of the tool are diamond and cubic boron nitride particles, the particle mesh number is 70# to 1000#, and the rotating speed of the micro grinding tool is 1000-60000 r/min in use.
10. An apparatus for implementing an energy conversion based discharge driven abrasive flow composite grinding method of claim 1, comprising:
a micro-grinding tool consisting of abrasive particles affixed to a surface;
the pulse discharging device comprises a discharging power supply and connecting wires, and the positive and negative ends of the power supply are respectively connected with the workpiece and the micro grinding tool through the connecting wires and are used for performing pulse discharging in the running process;
the liquid storage device is used for storing free abrasive grain liquid and is provided with a placing space for connecting wires, and the workpiece and the micro grinding tool are immersed in the liquid storage device to realize immersed processing;
a micro grinding tool driving device connected with the grinding tool, wherein the grinding tool can rotate under the driving of the grinding tool driving device;
the workbench device comprises two moving parts, wherein the first moving part is used for enabling the workpiece and the micro grinding tool to move relatively along the thickness direction perpendicular to the workpiece, and the second moving part is used for enabling the workpiece and the grinding tool to move relatively along the thickness direction of the workpiece.
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