Papers by Author: Cong Rong Zhu

Abstract: To improve the machining efficiency as well as surface roughness, a series of experiments employed fixed abrasive tools are carried out for stainless steel substrate, and influences of properties of fixed abrasive tool on the lapping process are studied. It is found that the resin is the best bonding material in this study. The surface roughness under different concentration of bonding material is similar, and the material removal rate (MRR) increases as the concentration of bonding material decreases from 50% to 20%. But too little of bonding material results into low bond strength that causing low material removal rate. It is also found that higher shear strength, lower wear rate, and the shear strength of the tool with 35% bonding material is the highest. It is obvious that the surface roughness and material removal rate decline as the grit size decreases. The roughness of surface lapped with resin bonded 4000# SiC abrasive tool comes to 18nm, and the material removal rate is 0.63μm/min.

Abstract: Studies on chemical mechanical polishing (CMP) for silicon nitride (Si3N4) balls with CeO2 abrasive carried to investigate the mechanism of chemo-mechanical action between silicon nitride and CeO2. It is found that CeO2 is more effective to obtain smooth Si3N4 balls than other abrasives, and extremely smooth Si3N4 balls with surface Ra 4nm were obtained after polishing. XRD test is used to detect the reaction resultants on the ball surface, and the results show that SiO2 is the main resultant of the chemical reaction between Si3N4 and CeO2, and the test results confirm the correctness of thermodynamic analysis based on Gibb’s free energy of formation. It is also found that water play as a key factor in CMP.

Abstract: Silicon nitride ceramics materials have excellent properties such as small density, high rigidity, high Young's modulus, high wearability, good thermal stability and chemical stability, which make it become one of the most appropriate materials for rollers of high precision bearing. Chemical Mechanical Polishing (CMP) technology is employed to have an ultra-precision machining process for silicon nitride ceramics materials workpiece and the effects of workpiece surface roughness in different abrasive are discussed in this research. The XRD and SEM technology are used to take phase analysis and surface profile detection for the finishing workpiece polished with CeO2 abrasive. The chemical reaction mechanism and the material remove mechanism of silicon nitride ceramics materials in CMP process with CeO2 abrasive are both analysed and discussed in this paper. The research result shows that an extremely smooth surface of silicon nitride ceramics materials workpiece with roughness 5nm Ra is obtained after CMP process with polyurethane polishing pad and CeO2 abrasive.

Abstract: To obtain the amorphous alloy films with superior properties by method of electrochemical deposition, the accuracy requirement for the copper substrates for Alloy Films is extraordinarily strict. The ultraprecision lapping technology for the copper substrate employing polyurethane polishing pad and flannel pad is studied in this paper, surface roughness, material removal rate and change process of surface construction of copper substrates are discussed. The influences of the different lapping parameters on the surface roughness, material removal rate and the influences of lapping load on copper substrate surface formation in the ultraprecision lapping process of copper substrate are both discussed. Experiment results show that the surface scratch will disappear by employing polyurethane polishing pad and flannel pad, and an extremely smooth surface of copper substrate with roughness 6nm Ra is obtained in the final finishing lapping process.

Abstract: Tungsten carbide which is a hard and brittle material was ground by cast-iron bonded diamond wheel with ELID (Electrolytic In-Process Dressing) technique, for the purpose of getting high efficiency, super-precision machining. Three kinds of cast-iron bonded diamond wheels with different grain size were adopted to get different grinding efficiency and surface quality of workpieces. The grinding properties of cast-iron bonded grinding wheels with different grain size and the ground surface quality of tungsten carbide are discussed in this paper. The experiment results indicate that, under the same feeding amount, the grinding efficiency of the wheel with bigger grain size is higher, and it could make the dimension accuracy of the workpiece controllable, but the wheel with smaller grain size could get better ground surface quality. The two grinding phases are decided by the ratio between the size of abrasive grain and the thickness of the oxide layer on the grinding wheel.

Abstract: This paper focuses on the application of Taguchi method for optimization of SUS440 stainless steel polishing process parameters to obtain the best finish. An optimization experiment for polishing stainless steel with SiO2 was designed by Taguchi method. Surface roughness Ra is considered as criteria for optimization. Influence of parameters involving load, speed, and slurry concentration for a given workmaterial with given abrasive (material and size) are discussed, and the optimum polishing conditions are figured out. Compared with single parameter experimental results, it illustrates that the experiment design based on Taguchi method can successfully applied to determine the optimum processing conditions for SUS440 stainless steel polishing process.