Grinding polycrystalline diamond using a diamond grinding wheel

Application of ultrahard cutting tool materials is continuously expanding. One example of an ultrahard cutting tool material is polycrystalline diamond (PCD), which is widely used in tool making and machining. However, because of the high wear resistance of PCD it is characterised by low grindability and machinability. So, any mechanism used to machine PCD has to meet specific requirements. Grinding with a diamond grinding wheel is one of the economic ways to machine PCD compacts. This thesis considers the grinding of polycrystalline diamond using a conventional grinding machine and makes machining parameter recommendations to support the optimisation of PCD grinding. The PCD grinding forces are mathematically analysed. These grinding forces are measured using a force sensor installed on a conventional grinding machine. The forces produced during grinding are investigated as a function of in-feed, contact zone, material removal rate (MRR) and oscillation rate. Wheel conditioning, another major aspect of PCD grinding, is studied and optimised in order to reduce the grinding forces, increase the cutting efficiency and achieve maximum removal rates and minimum wear ratios. Grinding wheel wear is investigated as a recognized problem in PCD grinding. A series of experiments are conducted in which the material removal rate, the rate of wheel wear and the grinding forces are measured. The effects of in-feed, sharpening process and work piece hardness on the wheel wear are studied. The edge quality of the PCD compacts is investigated as an important issue in tool making. Factors affecting PCD grinding quality include the in-feed, material removal rate, the condition of the diamond grinding wheel and the rigidity of the grinding machine. These are all studied to find their effect on edge quality. The work presented in this thesis also shows that the capability of a conventional grinding machine designed for non-PCD is sufficient to grind PCD with acceptable quality.