Ordered diamond micro-arrays for ultra-precision grinding—An evaluation in Ti–6Al–4V

Abstract

The surface topography of a conventional diamond grinding wheel can be characterised as having a perplexity of abrasive particles with random crystallographic orientations resulting in different heights of protrusion from the bond and inherent varying inter-particle spacing. The number and effectiveness of the abrasive particles during grinding depends on factors such as the abrasive concentration, the crystallographic shape and the extent of particle protrusion from the wheel’s surface. The consequence of this random layout inhibits the optimal performance of individual abrasives in the process of material removal, and where particles are clustered, chip flow is negatively affected. This paper reports on the evaluation of purpose designed precision diamond micro-arrays for the grinding a case-study material, Ti–6Al–4V and compares their performance against conventional diamond electroplated micro-cutting elements of D91 and D46 abrasive size in an imitated grinding setup. The precision diamond micro-arrays, produced from thick film CVD diamond utilising energy beam ablation offer an optimised layout of abrasive elements, each having a cutting width of 100 μm of identical crystallographic orientation, protrusion height and regular spacing to provide chip flow paths. In addition, the primary/secondary rake angles γ=−32°/+1° and clearance angle α=4.5° of each abrasive cutting element have been controlled in order to provide an enhanced cutting action. The precise layout of the abrasive cutting elements of the micro-arrays produced superior chip flow compared with the diamond electroplated grinding elements; this has been proven by in-depth scanning electron microscopy of the clogged workpiece material on the studied abrasive elements. The results show a 3.5 times improvement to surface finish and a 21.5 times improvement to flatness of the Ti–6Al–4V workpieces when ground with the proposed innovative diamond micro-arrays.