Geometrical adaptive control of machining straightness in end milling

Abstract

The geometrical adaptive control is applied to end milling in order to compensate for the straightness error which is caused by the inaccuracy of guideway and tool deflection. The location error, the mean deviation of the tool path from the desired surface, is compensated by shifting the table in the direction perpendicular to the finished surface and the waveness error, the difference between the maximum and the minimum deviations, is corrected by the adjustment of the feedrate using a stepping motor during machining process. The extended Taylor``s equation is adopted as a relationship between the tool deflection and the feedrate based on the basic metal cutting theory. In order to estimate the time varying parameters in the relationship, the exponentially windowed recursive least squares method is performed using post process measurement data obtained through a proximity sensor. Experimental results show that about sixty percent reduction in the waveness error can be achieved within a few steps of parameter adaptation under wide operating ranges even if the parameters do not converge to fixed values.