Working towards the minimum surface damages and failure analysis of Joule heat effects in manufacturing diamond cutting tools

This study explores the fracture morphology for the minimum damages on the machined surface when wire electrical discharge machining (WEDM) polycrystalline diamond (PCD) cutting tool inserts. Usually, material removals from PCD blanks involve electro-thermal energies which produce mechanical forces and thermal effects; their interactions via parametric control then result in unexpected surface damages such as chipping-off, cracks, delamination, grain dislodgement, craters and graphitisation. As a result, the produced PCD inserts' tool life is shortened. In this work, to minimise the surface damages with the least compromise on the productivity, the underlying mechanisms of material removal and the corresponding surface roughness were revisited, from the modified Joule heat models to the validation experiments. The root causes of the surface damages on the PCD inserts in association with the discharging energy were geometrically defined and analytically postulated; whilst the corrective actions were implemented via experiments with statistical examinations. The results suggested that the controlled discharge energy could effectively increase the material removal rate, while also reducing the minimum surface damages on the coupled crater area, crack areas and chipping-off volume. In the proposed prevention plans, some predictable results in groups involving multiple criteria optimisations were confirmed, with a good balance between the least surface damages and the material removal by practical production runs. The effects and causes of control pa-rameters on the surface damages are presented in statistical plots and micrographs with quan-titatively and qualitatively analysis. The underlying mechanisms are resolved and discussed in detail.