Regression Equations to Determine the Stages of Electric Current in Electrical Discharge Machining (EDM) According to the Level of Desired Surface Roughness with Shortest Processing Time

¹ Mechanical Engineering Department, Petra Christian University, Jl. Siwalankerto No.121–131, Surabaya, 60236, Indonesia
² Mechanical Engineering Department, Chung Yuan Christian University, Chung Li District,R.O.C., 200 Chung Pei Road, Taoyuan City, 32023, Taiwan

^* Corresponding author: ralimin@petra.ac.id

Abstract

Electrical Discharge Machining (EDM) is one of the most common non-conventional machining processes used in the manufacturing of die and mold. In the process of EDM, practitioners usually face a problem, which is how to shorten process time and determine the point where the current should be changed so that the resulted surface roughness is not too high due to the use of large current at the beginning of the process. The purpose of this study is to determine the point when to change (reduce) the current in order to obtain the desired surface roughness and shortest processing time. From analysis of data, experiment was obtained some regression equations, those are: average surface roughness (R_a = 5424 + 0.698 I) which is used to find the final current to obtain the desired final surface roughness, peaks to valleys average roughness (R_z = 5.73 + 3.418 I) which is used to find the changing point for initial currentand duration of processing time (t =10^{3.164 + 0.4714 I}) which is used to estimate the duration of processing time with the input of initial and final currents.