Precision Grinding of Hard and Brittle Materials

Two novel techniques were used to study the formation of ductile mode streaks during diamond grinding (primary process) of germanium, silicon, and glass that aid the secondary process of polishing. In the first technique asph~ric surfaces were generated on Ge and Si at conventional speeds (5000 rpm). In the second technique high speed grinding (100,000 rpm) of plano surfaces on glass and Si surfaces was carried out Form accuracy, surface finish and ductile mode grinding streaks are discussed in this paper. It was found that resinoid diamond wheels gave more ductile streaks than metal-bonded wheels but better form accuracy was obtained with the latter. Transparent ground surfaces were obtained more easily with Pyrex rather than with BK 7 glass, thus necessitating very little time for polishing. Ductile streaks appeared in abundance on germanium rather than silicon. Both the novel grinding techniques were used on CNC machining centres

Temperature Distribution in Copper Electrode during Electrical Discharge Machining Process

This paper reports on a new method used to estimate the spark radius in the gap during electrical discharge machining (EDM). This method combines the heat flux and energy equations of the copper electrode. The energy partition between workpiece and electrode (tool) due to EDM process was estimated using the ratio of thermal conductivity of the workpiece to that of the electrode. Using the energy partition between the electrode and the workpiece, temperature distribution in the electrode was established and Gaussian heat distribution was used to analyze the energy released from a single spark. The energy released due to a single spark was used to calculate the fraction of energy received by the electrode based on its thermal conductivity. The 3-D temperature distribution in the electrode was carried out using ANSYS version 11.0 and the estimated temperature of the electrode from a single spark was validated by thermal diffusivity of the electrode material. The difference of 6% was recorded between the simulated and calculated temperatures of the copper electrode. Based on the achieved percentage error, the simulated temperature on the copper electrode can be accepted as EDM process