Research On Characteristics And Machining Performance Of Semi-Fixed Abrasive Plate

To attain machining advanced ceramic with the performance of high efficiency, high precision and low surface damage, a semi-fixed abrasive machining technique is proposed. This technique could avoid the surface defects that were caused by large abrasive grains, so the higher efficiency of precision or ultra-precision machining was to be attainned. For characteristics and machining performance of semi-fixed abrasive plate (SFAP), this paper relates to the following studies:Manufacturing process of SFAP was discussed; on this principle, one kind of resin named SSB is adopted as the bonding agent of SFAP. The evaluation characteristic parameters of SFAP include hardness, shear strength, elastic modulus and microstructure. All of these characteristic parameters were tesed. Comparing to 50 wt% and 80 wt% of abrasive concentration of SFAP, 65 wt% of abrasive concentration of SFAP had higher hardness, shear strength and elastic modulus. Under the same 65 wt% of abrasive concentration, smaller abrasives of SFAP had lower hardness, shear strength and elastic modulus. Through experiments of machining silicon wafer, SFAP of ’trap’ charactersitc, which could avoid larger abrasive grains doing harm to the surface of workpiece, was verificated..With the help of scanning electron microscopy (SEM), comparing to micro surface topography of silicon that were machined by free abrasive machining method, fixed abrasive machining method and semi-fixed abrasive machining method, surface topography of silicon machined by SFAP had characteristics of material removal of the two-body abrasion mainly and the three-body abrasion partly.Combining Preston’s equation with the finite element method, the machining mode of SFAP was set up with considing contact pressure between workpiece and SFAP. Silicon wafer as workpiece and accuracy of surface shape as evaluation index, simulation analysis and experiments show that higher hardness and elastic modulus was better to attain machining efficiency; higher relative velocity was also better to attain machining efficiency; higher load could not increase machining efficiency.The hardness of SFAP was lower than that of common grinding wheel, it caused that surface precision of SFAP was easily turning bad and it impacted on machining uniformity. In order to ensure machining uniformity of SFAP, a detailed analysis of the abrasive track on workpiece surface and the relative velocity between workpiece and SFAP, the uniformity of the workpiece machined was to be discussed. Results showed the ratio of workpiece velocity and SFAP velocity was mainly factor to influence on machining uniformity. It could attain better machining uniformity under the same workpiece velocity and SFAP velocity in certain eccentric mode. It could attain better machining uniformity under the higher difference between workpiece velocity and SFAP velocity in uncertain eccentric. Flatness, surface roughness, material removal rate of workpiece and surface status of SFAP were compared after machining experiments. From experiment results, uncertain eccentric mode coud attain better flatness of workpiece and surface status of SFAP; certain eccentric mode could attain better surface roughness and material removal rate of workpiece. It could conclude that machining uniformity in uncertain eccentric mode is superior to certain eccentric mode.With experiments of machining silicon wafer and silicon nitride, it showed that failure of machining performance was related to workpiece material and SFAP in wet status or dry status. When hardness of workpiece material lower than hardness of abrasive, mostly blockage and little releasing abrasive on surface of SFAP was failure of machining performance in dry status of SFAP; mostly releasing abrasive and little blockage on surface of SFAP was failure of machining performance in wet status of SFAP. When hardness of workpiece higher than hardness of abrasive, only little releasing abrasive in surface of SFAP, SFAP had very low machining efficiency. Under same abrasive concentration and experiment conditions, smaller abrasive of SFAP with higher abrasion and lower machining efficiency; Under the same abrasive size, 65 wt% of abrasive concentration had lower abrasion and higher machining effieciency. SFAP in wet status and fluid flow had great influence on SFAP abrasion and machining efficiency.In this dissertation, manufacturing processing and characteristics of SFAP was studied; silicon wafer as workpiece, material removal mode of SFAP was mostly two-body removal mode and little three-body removal mode; higher hardness, elastic modulud, relative velocity could achieve high machining efficiency of SFAP; workpiece in uncertain eccentric mode was benefit to keep machining uniformity of SFAP; SFAP in wet status and fluid flow had great influence on SFAP abrasion and machining efficiency. These were benefits to design, manufacture and application of SFAP.