The Effect of Electric Spark Cutting Markers on Surface Roughness Using the Full Factorial Response

Electric Discharge Machining (EDM) is a nontraditional manufacturing process that uses electric spark discharges to machine electrically conducting materials. Surface roughness (Ra) is considered one of the most important factors in EDM process. When it increases, it affects negatively the performance of the EDM process and the tolerance of resultant part. The aim of this research is to optimize the surface roughness using different current, pulse on time and pulse off time factors, then compare it with the predicted results using full factorial response. AISI M2 steel is frequently machined using EDM due to its high hardness and therefore it was used as a workpiece using copper as an electrode material. Different experimental parameters, which affect surface roughness, were used in EDM process. The full factorial response, adopting a face-centered central composite design (FCCD), was performed experimental layout design and analysis. The experimental results showed that surface roughness changed significantly under specific settings. Maximum surface roughness (Ra) was (9.01μm) got when current of (42 A), pulse on (200 μs) and pulse off (4 μs) parameters were used, while a minimum surface roughness (Ra) of (2.31 μm) could be got when current of (10 A), pulse on (100 μs) and pulse off (12 μs) parameters were used. The best-predicted value for using full factorial response was 98.25%.