Evaluating a toothed work piece for machining based on accumulated pitch

Abstract

A method of evaluating a toothed workpiece for machining according to a predetermined machining process. A workpiece spindle is rotated to bring selected leading and/or trailing tooth flanks each into a predetermined position relative to a probe to generate a signal indicative of the instantaneous rotational position of the spindle and the instantaneous rotational spindle positions corresponding to each generated signal are recorded. Theoretical spindle positions corresponding to each selected tooth flank are provided, and the difference between respective recorded spindle positions and the theoretical spindle positions for each selected tooth flank is calculated to yield a measured error value. The maximum and minimum measured error values for leading tooth flanks and/or trailing tooth flanks are selected and a maximum accumulated pitch variation (P.sub.V) is calculated for the leading tooth flanks and/or trailing tooth flanks. The maximum accumulated pitch variation (P.sub.V) is compared to predetermined pitch variation tolerance limits comprising an abort tolerance (T.sub.A) and a modified process tolerance (T.sub.M) whereby the predetermined machining process is aborted if P.sub.V .gtoreq.T.sub.A, the predetermined machining process is modified if T.sub.M .ltoreq.P.sub.V .ltoreq.T.sub.A, and the predetermined machining process is carried out if P.sub.V <T.sub.M.