Effects of Machine-Tool-Workpiece Stiffness on the Wear Behaviour of Superhard Cutting Materials

Abstract

The need to justify the high costs of superhard, highly brittle polycrystalline cutting materials through full utilization has led to new aspects regarding effects of vibrations on wear behavior of cutting tools. For example, certain wear appearances, such as cracks, etc., must be avoided in order to make resharpening of the cutting edge possible. The present investigation deals with the problem of how tool wear, cutting forces, and vibrations on tool and workpiece are influenced by changes in the stiffness of the machine tool-workpiece-tool system in turning with cubic boron nitride (CBN) and milling with polycrystalline diamond (PCD). The wear behavior of the CBN cutting edges is similar to tungsten carbide tooling when the system is relatively stiff. If the system does not provide enough stiffness, the wear behavior will be similar to ceramic tools. In the latter case, wear typically occurs in the form of cracks on both the rake face and the flank. However, the required rigidity of the system for the application of CBN cutting edges is not higher than that for using ceramic tools. In the case of low system stiffness in milling with PCD, wear forms such as rounding of the cutting edge appear and develop more quickly. Furthermore, higher damping in the area of the spindle leads to better wear behavior. However further investigation is required to determine how this phenomenon can be used in order to minimize wear of PCD.