Microdrilling of Biocompatible Materials

Abstract

This research studies microdrilling of biocompatible materials including commercially pure titanium, 316L stainless steel, polyether ether ketone (PEEK) and aluminum 6061-T6. A microdrilling technique that uses progressive pecking and micromist coolant is developed that allows drilling of 127 micrometers diameter microholes with an aspect ratio of 10:1. The drilling parameters, dominant wear pattern, hole positioning accuracy and effect of AlTiN tool coating are experimentally determined. The experimental data trend agrees with classical Taylor's machining equation. Despite of fragile and long microdrills, the progressive pecking cycle and micromist allowed deep hole drilling on all the tested materials. Drill wear is more pronounced at outer cutting edge due to higher cutting speeds. However, when drilling 316L stainless steel attrition wear at chisel edge is dominant. Hole quality degradation due to formation of built up edge at the drill tip is observed. Coated drill improves tool life by 122% and enhances hole quality when drilling 316L stainless steel. The hole positioning accuracy is improved by 115% and total hole diameter variation decreased from 0.11% to 0.003% per mm of drilling distance.