Effect of Pulse on Time and Pulse off Time on Material Removal Rate and Electrode Wear Ratio of Stainless Steel AISI 316L in EDM

Abstract

The electrical discharge machining (EDM) is one of the non - traditional cutting processes , used in many important applications such as dies and auto industry . This thesis focuses on the study of machining responses such as material removal rate (MRR) and electrode wear ratio (EWR) under the effect of different machining conditions in EDM process . The process parameters are pulse on time (Ton) , pulse off time (Toff) and electrical current (Ip) . The main purpose of this work is to achieve best MRR and least EWR using copper electrode with fixed diameter (10 mm) for the machining of stainless steel AISI 316L with a constant thickness (0 . 8 mm) . Different values for the Ton (25 , 50 and 75) µs , Toff (9 , 18 and 25) µs and Ip (16 , 30 and 50) A were used . The results of experiments showed the main effects of machining conditions on MRR and EWR . Where , the MRR increased with increasing the Ton , MRR decreased with increasing the Toff and MRR increased with increasing Ip . While , the EWR decreased with increasing the Ton , EWR decreased with increasing Toff until access to a specific Toff then EWR increased with longer Toff and EWR increased with increasing Ip . The maximum MRR is (48 . 16 mm 3 / min) at Ton (75 µs) , Toff (9 µs) and Ip (50 A) and minimum EWR is (0 . 179 %) at Ton (75 µs) , Toff (9 µs) and Ip (16 A) . The results showed that the response surface methodology (RSM) that have been performed using Minitab 17 software . It can predict the machining responses with a good accuracy where it gave the coefficient of determination (R - sq) that determines the degree of fit between the experimental and predicted data . Higher value of R - sq shows a better fit . The values of R - sq are (97 . 46 %) for the MRR and (96 . 34 %) for EWR . Also , the SPSS 18 software was used to predict the machining responses with a good accurac INTRODUCTION lectrical discharge machining (EDM) is one of the most commonly used non - conventional machining processes which have been a great help to the manufacturing and processing engineers to produce complex forms on any conducting material or alloy [ 1 ] . It has unique feature that using thermal energy to machine electrically conductive materials [ 2 ] . Also , non - conductive materials can be machined successfully by using EDM technique [ 3 ] . The very hard and brittle materials can be easily machined and also to the required shape [ 4 ] . EDM differs from most traditional machining operations that it does not make physical contact between the tool and workpiece , eliminating mechanical stresses , vibration and chatter problems during machining [ 2 , 5 ] . It is widely used in manufacture of mold and die , auto industry , aeronautics , medical equipment , sports and optical instruments and other applications [ 6 ] . Mohan and Chandan (2008) [ 7 ] studied effect of the different values of Ip , Ton and Toff on the MRR of machining tool steel AISI D2 by using copper electrode in EDM process . Also , RSM was used to develop model for MRR . Harpreet and Amandeep (2012) [ 8 ] studied the effect of Ton and Toff on machining die steel AISI D3 as workpiece using copper and brass electrode in EDM process . Singh Jaspreet et al . (2013) [ 9 ] studied the impact of three values of Ton , Toff and Ip on MRR in EDM for stainless steel AISI 202 . The design of experiments was E