Key Engineering Materials Vols. 589-590

Abstract: In this study, two different arrangement lapping disks fixed with brazed diamond pellets were used to lap silicon wafer and alumina ceramic. The effects of the surface morphology, roughness, and removal rate of workpiece caused by lapping pressure, lapping time, workpiece velocity, and disc arrangement were operated with serials experiments. The results of the researches provided guidance for fixed abrasive lapping of hard and brittle materials with the brazed micro powder diamond disk.

Abstract: In this paper, diamond abrasive SG films were prepared by means of sol-gel technology for polishing single-crystal SiC wafers. The effects of machining parameters on processing quality including pressure, rotating speed and polishing time were investigated, respectively. The results indicated that the surface roughness decreased with increasing polishing time. While for pressure and rotating speed, there were inflections existing. Polishing SiC wafer under optimized machining parameters, an ultra smooth surface with the roughness of 3.7 nm could be achieved using 40 μm diamond grits.

Abstract: On the foundation of researching adhesion mechanism of superalloy honing stone, theoretical analysis and mathematical modeling of parameters were made that affecting the wear particle adhesion rate of superalloy honing stone, then inspect and verify the relation between the adhesion rate and processing parameters through the experiment. Draw the conclusion that when the honing pressure increases or the speed of work piece decreases, the adhesion rate α_a will increase.

Abstract: Grinding Mechanism is very complex and difficult, and it can be simplified to a single abrasive grain grinding research. With the analysis of process and result of single abrasive grain grinding from experiment, the purpose can be achieved of understanding the complexity of the grinding mechanism. According to the characteristics of grinding process, the current domestic and international research status of single abrasive grain grinding experiments is introduced. The different experimental methods used by scholars are analyzed in detail, as well as grinding characteristics of single abrasive grain and chip formation mechanism of different characteristics materials. Finally, the current research difficulties of theory and experiment research are analyzed for the single abrasive grain grinding, and the further research direction is made.

Abstract: The path distribution can directly affect the machined workpiece surface quality in lapping and polishing, such as planeness, roughness, etc. In present paper, the influence of rotate speed ratio (RSR) and abrasive position on path distribution was analyzed with a single fixed abrasive. The results show that the RSR and abrasive position has heavy influence on the path distribution. The path distribution with decimal RSR is more intensive and complicate than that with integer RSR, especially complex decimal RSR, and it can be also affected by the abrasive radial and circumferential position, but the shape of path is not changed with different abrasive circumferential position which only affects the initial phase angle of path.

Abstract: In diamond cutting of optical glasses, the magnitude of critical depth of cut for brittle-ductile transition is an important factor affecting the machinability of the work material in terms of production rate and surface quality. In this work, scratching tests with increasing depths of cut were conducted on glass BK7 to evaluate the influence of the cutting fluid properties on the critical depth of cut. Boric acid solutions of different concentrations were selected as cutting fluids in the tests. The resulting scratches were examined utilizing a white light interferometer and the values of the critical depth of cut were determined based on the observations of the micro-morphology of the scratch surfaces produced. Experimental results indicated that compared with the process without cutting fluid action, the critical depth of cut in diamond cutting of glass BK7 can be increased by using boric acid solution as the cutting fluid.

Abstract: The rolling element is the most important component of rolling bearings. Its geometric accuracy and consistency affect greatly the performance and working life of bearings. In this paper, a standard Taguchi L9(34) orthogonal array(oa) is designed to analyse how abrasive size, rotating speed of plates, deflection angle of carrier holes and other factors impacting on precision of cylindrical roller process and achieved the optimized parameters combination by adopting evaluation of Signal-to-Noise ratio and ANOVA analysis(analysis of variance). Under the optimized lapping condition, the roundness,pand s can reach , and respectively.

Abstract: An ultra-precision lapping machine is developed, with precision turning technology to condition lapping plate in situ, pressurizating by cylinder pressure, and cooling frictional heat with inner cooling system, the lapping machine is used for ultra-precision lapping of brittle materials. The design concept and the structure of the key components of the utra-precision sngle-plane lpping mchine are discussed. After precision turning, the flatness of lapping plate is down to 0.002 mm/400 mm, and experimental results show that the flatness of circular grating glass has been greatly improved after ultra-precison lapping.

Abstract: In order to resolve the difficulty in polishing work of complex shape, a new magnetorheological finishing (MRF) technology with a small permanent magnet ball-end tool is developed. Rotary symmetrical magnetic field generated by the small permanent ball-end tool, stiffen a magnetic fluid which is delivered by a slender needle tubing, in contact with a workpiece. The permanent magnet tool is hold by a slender cylindrical shank, so it won’t interfere with workpiece when polishing deep concave cavity. A prototype apparatus is established to study the processing characteristics of this polishing method. MRF spots are taken on stationary workpiece to study the influence of several processing parameters on the material removal function, such as, spindle speed, included angle and minimum gap between polishing tool and finishing-surface. A 3×3mm square on a fused quartz (FS) is polished and the surface roughness decrease from 81nm Ra to 1.5nm Ra after polishing for 100min.

Abstract: Micro Electrical discharge machining (Micro-EDM) is a non-traditional concept of machining. It is very suitable for machining micro parts of Micro-electromechanical Systems (MEMS). However, the application of micro-EDM is restricted for its own shortcomings such as poor material removal rate and high electrode wear ratio etc. In order to overcome this shortcoming, a new piezoelectric self-adaptive micro-EDM (PSMEDM) is developed based on inverse piezoelectric effect of piezoelectric ceramics and its working mechanism and characteristics have been analyzed in this paper. This machining method can realize the self-tuning regulation of discharge gap depending on the discharging conditions, facilitate removing the debris in the machining gap, reduce the occurrence of arcing and shorting and can realize the self-elimination of short circuits, thus the machining efficiency can be improved drastically. The tool electrode wear ratio (EWR) in machining is studied in this paper. Many experiments have been done and the effects of parameters on electrode wear ratio have been analyzed. Experimental results indicate that: 1) The EWR will rise with the increase of open-circuit voltage and main capacitance in circuit because the increase of open-circuit voltage and capacitance result in increase of single discharge energy. 2) The effect of resistance R1 on EWR is light. With the increase of resistance R1, the EWR will decrease slightly. 3) With the increase of resistance R2, the EWR will decrease firstly and then becomes to increase.