Development of Centreless Electric Discharge Grinding Machining Process and Optimization of Process Parameters

Abstract

Aims & Objective: Producing thin walled rotationally symmetrical parts of difficult-to-machine materials by electrical discharge machining is an evolving field of research. Poor heat transmissivity, high hot strength and in-process deflection of thin walled Inconel 600 parts puts great challenge for its processing by conventional machining methods. Methods: In this study a novel hybrid process called centreless electric discharge grinding(CEDG) is employed for machining of Inconel 600 tubes using rotating disc wheel electrode to improve process parameters. This paper details about the experimental findings of the influence of four process parameters viz. pulse on time, peak current, gap voltage, and duty cycle on the responses viz. average material removal rate (MRR) and average surface roughness(Ra). Response surface method’s (RSM) central composite design was implemented to determine the effects of parameters on responses. Analysis of variance (ANOVA) techniques were employed to establish the adequacy of the mathematical models and to analyse the significance of regression coefficients. RSM’s desirability approach was used to solve the multi-response optimization. Results: It was clearly noticed that the peak current and gap voltage were the most influential parameters to affect the MRR and surface roughness. Maximum average MRR of 473 mg per min. was achieved at pulse on time 60µs, peak current 25 amps, gap voltage 40 V, at duty cycle of 8 while minimum average surface roughness of 8.4 µm Ra was obtained at pulse on time 40µs, peak current 15 amps, gap voltage 40 V, and duty cycle 6. Conclusion: Confirmation run was conducted by adjusting the variables at optimal level within the selected range. It was concluded that optimum level of variables can be determined for optimized responses prior to conduct of experiment.