MATHEMATICAL MODEL DETERMINATION FOR SURFACE ROUGHNESS DURING CNC END MILLING OPERATION ON 42CRMO4 HARDENED STEEL

The most important measures of surface quality during the machining process is the average surface roughness (Ra), and it is mostly caused by many machining parameters, such as true rake angle and side cutting edge angle, cutting speed, feed rate, depth of cut, nose radius, machining time, material hardness, cutting fluid etc. This paper presents a study of development the surface roughness mathematical model during the end milling operation on hardened 42CrMo4 steel from 35 HRC to 55 HRC. The objective of this research is to analyze the effect of machining parameters on the surface roughness quality in CNC end milling. The milling parameters evaluated are spindle speed, feed rate, and depth of cut and workpiece material hardness. The experiment has been designed and carried out on the basis of a three level factorial design. The analysis of the results indicates that the optimal cutting parameters combination for good surface finish is high cutting speed and high depth of cut, as well as low feed rate and low material hardness.