A New Tool Wear Examination Model by Least Square Method for Shearing Process of Thin Metal Sheet

A new method that accounts for material loss in the normal direction has been developed. Most research applied wear length and wear area to present the status of the tool. Nevertheless, these methods cannot detect the wear in the normal direction of the contact surface between tool and material, and cannot make accurate judgments in precision machining process. In the proposed model, both of the least square lines of the inspected positions and the least square planes of the examined flanks calculating by the wear depth of measuring points are used to infer the relative wear indices, such as flank wear angle, wear depth of punch top face, straightness error, area loss, and volume loss of punch flanks. By using these indices more objective estimations can be acquired than that of wear length and wear area. A series of shearing experiments of thin phosphor bronze sheet are executed to explore the effects of shearing parameters on punch flank wear, and several regressive equations are derived to express the relationships between the wear indices and number of shearing strokes.