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Effect of pad and slurry on fixed abrasive polishing of gallium oxide crystal
, Available online  , doi: 10.13394/j.cnki.jgszz.2022-0043
Gallium oxide crystal is the most representative fourth generation semiconductor material with the advantages of high band gap, high voltage resistance and short absorption cutoff edge, and has broad application prospects. Gallium oxide crystal is prone to micro-cracks, scratches and other surface defects in the polishing process, which is difficult to achieve high-quality surface processing and cannot meet the requirements of the corresponding devices. Moreover, the existing polishing process of gallium oxide crystal is complex and inefficient. Fixed abrasive polishing technology has the advantages of controllable abrasive distribution and depth of cut, and high utilization rate of abrasive grain. Fixed abrasive polishing was used, and the effect of pad and slurry on material removal rate and surface quality were explored in fixed abrasive polishing of gallium oxide crystal. The results show that when the hardness of the polishing pad is moderate II, the abrasive concentration is 100%, and the slurry additive is oxalic acid, material removal rate is 68 nm/min, and the surface roughness Sa value is 3.17 nm in fixed abrasive polishing gallium oxide crystal. Fixed abrasive polishing technology can achieve efficient and high-quality polishing of gallium oxide crystal
Development of CAM system for automatic compound dressing of superabrasive grinding wheels
, Available online  , doi: 10.13394/j.cnki.jgszz.2022-0061
In the field of superabrasive wheel dressing, multi-process composite dressing has obvious advantages, but there is no research related to the automation system of grinding wheel composite dressing. In order to make the integration of multiple processes in the composite dressing method more systematic and improve the dressing efficiency of shaped grinding wheels, this paper develops a CAM system by self-developed laser-mechanical composite dressing equipment, which can, according to different grinding wheel section shapes, automatically plan the dressing trajectory under multiple processes and dressing strategies, calculate the dressing toolpath with planar three-axis linkage, automatically generate the machining code, and at the same time design a visualisation interface to simulate the machining process. The results of dressing experiments on 150# diamond bronze bonded grinding wheels show that the system can generate machining programs for laser roughing, semi-finishing and mechanical finishing without collision and overcutting of the machine tool, and significantly improve the programming efficiency of the compound dressing method. And the dressing wheel profile error is within 9.1 µm and circular runout error is 6.1 µm.
Study on the Mechanism and Process Magnetorheological Variable Gap Dynamic Pressure Planarization Finishing
, Available online  , doi: 10.13394/j.cnki.jgszz.2022-0004
In order to improve the polishing efficiency of magnetorheological polishing and realize the high-efficiency, high-quality and ultra smooth planarization of photoelectric wafer, a magnetorheological variable gap dynamic pressure planarization method is proposed. In this paper, the changes of material removal rate and surface roughness of sapphire wafer surface polishing with processing time under different variable gap conditions are studied, and the dynamic pressure flattening mechanism of magnetorheological variable gap is deeply analyzed. The results show that the dynamic change of polishing pressure and the extrusion strengthening effect of MR fluid can be produced by applying axial low-frequency extrusion vibration to MR polishing fluid, and the polishing efficiency and polishing effect can be significantly improved. After 120 min of magnetorheological variable gap dynamic pressure flattening, the surface roughness of sapphire wafer decreased from Ra 7 nm to Ra 0.306 nm, and the material removal rate was 5.519 nm / min. Compared with constant gap magnetorheological polishing, the surface roughness decreased by 49% and the material removal rate increased by 55.1%; By changing the moving speed of variable clearance, the flow field characteristics can be controlled. Choosing the appropriate workpiece pressing speed and workpiece lifting speed is conducive to improve the polishing efficiency and surface quality.
Effect of Fe3O4 Characteristics on Properties of Solid-phase Fenton Reaction Lapping Pellets for Single-Crystal SiC
, Available online  , doi: 10.13394/j.cnki.jgszz.2022-0008
To improve the lapping quality and processing efficiency of single-crystal SiC, solid-state Fenton reaction lapping pellets were prepared. Effects of particle size and concentration of Fe3O4 solid-phase catalyst on the physical properties (hardness, flexural strength, porosity), catalytic performance, and lapping performance of single-crystal SiC were studied. The results showed that with the increase of Fe3O4 particle size, the hardness, flexural strength, porosity, and catalytic performance of the lapping pellets all decreased, the material removal rate (MRR) decreased from 43.12 nm/min to 36.82 nm/min, and the surface roughness (Ra) increased from 1.06 nm to 3.72 nm. As the Fe3O4 concentration increased, the hardness and flexural strength of the lapping pellets decreased, and the porosity and catalytic performance increased. Although the material removal rate decreased, the surface roughness (Ra) decreased firstly and then increased. The MRR decreased from 40.14 nm/min to 33.51 nm/min, the surface roughness (Ra) was 3.25 nm, 1.75 nm and 1.88 nm. In this experiment, when the Fe3O4 particle size and the concentration was 0.5 µm and 29 wt.%, the processing effect was the best, the MRR and the surface roughness (Ra) was 43.13 nm/min and 1.06 nm.