Study on interpolation algorithms of CNC machine tools

The machining accuracy in a CNC machine tool greatly depends on the interpolation algorithm which consists of the interpolator and the acceleration/deceleration algorithm. In the conventional interpolation algorithm, there exists a path error between the desired curve generated by the interpolator and the coordinated one from the accelerated/decelerated traveling distances along the X, Y, and Z axes. This path error representing the machining accuracy is affected by the kind of acceleration/deceleration. The machining accuracy in parabolic acceleration/deceleration is best while that in exponential acceleration/deceleration is worst. To overcome this problem, they propose an interpolation algorithm, which applies acceleration/deceleration to the minute increment component of the parameter of the desired curve. The proposed interpolation algorithm guarantees the better machining accuracy than the conventional one which adopts the parabolic acceleration/deceleration. The experimental results obtained from the actual machining through a milling center are shown to agree well with the analyses.