Case studies of troubleshooting in connection with uncontrollable chips

Abstract In this paper two case studies of troubleshooting in connection with tangling chips are presented. The first case deals with machinability of a CrMo structural steel to raise the working ratio of machine tools that consist of a line type production system. The main factors making the machining operations inefficient are tangling chips and inconsistent tool changes. Machining tests under changing material properties and cutting conditions have revealed that the selection of an appropriate tool geometry with a chip former is essential. The change of material properties by heat treatments has little influence on the reduction of the downtime. The operation ratio of the production line has been increased from 78.1 to 85 percent through the reconsideration of tool paths, cutting conditions and tool-change time. In the second case, chip disposability of various types of inserts has been investigated to make progress towards unmanned machining of aluminum heat-rollers, where occasional tangling of chips was a major problem. Turning experiments have revealed that the increase of the depth of cut and the use of an insert with a positive rake angle and a suitable chip former are both recommended for the rough turning of the workpiece.