Prediction equations for cutting forces while oblique machining EN-8 steels employing 'response surface methodology'

Abstract

Investigations have confirmed the existence of a linear relationship between the resultant of the two power components of cutting force and each of the three variables of (1) Depth of cut (2) Feed-rate and (3) Cutting speed in the double logarithmic scale during oblique machining of a plain carbon steel on a centre lathe. A linear multiple regression model was therefore postulated between these three variables and the cutting force response, in their logarithmic transformed state, for prediction purposes of the latter. An experimental design involving two replicates of fifteen ‘different' cutting conditions and nine 'repeats' was employed to formulate a first order three-variable prediction equation using the technique of "Response Surface Methodology". (1) This was then extended to include the quadratic effects of the three variables and also their first order interactions. The three variable first order equation was chosen for prediction purposes on statistical significance basis. A control test series of 30 cuts was then carried out to check the adequacy of predicted forces. The largest variation was only 7%.Some results on the pattern of variation of forces with tool wear and that of surface texture with tool wear were also presented.