Detection of Tool Wear Using Characteristic Values of Dynamic Cutting Process (1st Report, Study of Characteristic Values to Detect Flank Wear)

摘要

The purpose of this study is to propose new characteristic values of dynamic cutting process to detect tool flank wear during steady cutting in turning. The characteristic values of dynamic cutting process are evaluated by in-process measurement of dynamic cutting force and vibration of a workpiece. In proposed approach, the standard deviation of dynamic cutting force normalized by the standard deviation of undeformed chip thickness and the cross--correlation coefficient between dynamic cutting force and undeformed chip thickness are investigated as characteristic values of dynamic cutting process to detect flank wear. Furthermore, relation between dynamic cutting force and workpiece vibration in thrust force direction is also investigated by the same way as the relation between dynamic cutting force and undeformed chip thickness. Experiments were carried out on a lathe in orthogonal cutting with a cutting-off tool and a disk workpiece made by a brass plate. As a result of the experiments and considerations, the following characteristic values linearly change with increase of flank wear due to nonlinearlity of dynamic cutting process caused by flank wear. (i) The standard deviation of dynamic thrust force normalized by the standard deviation of undeformed chip thickness increases. (ii) The cross-correlation coefficient between dynamic thrust force and undeformed chip thickness decreases. (iii) The standard deviation of dynamic thrust force normalized by the standard deviation of workpiece vibration in thrust force direction increases.