Semi-ductile cutting regime technology for machining Zerodur glass-ceramic microstructures

Abstract

Zerodur glass-ceramic has potential uses in many fields from aerospace to electro-optical industries due to its extremely low thermal expansion coefficient. However, being extremely hard and brittle makes it difficult to process using traditional machining methods. This paper deals with a novel hybrid technology for machining 3-D microstructures using Zerodur glass-ceramic. Based on a Semi-ductile cutting depth, experiments are conducted using different cutting modes: regular cutting, current-feedback cutting, and a current-feedback control strategy with high-frequency vibration-assistance. High-frequency vibration-assisted cutting creates extremely shallow microcracks on the surface of the glass-ceramic that facilitate the removal of material. It was also found that the designed diamond tool with a −70° rake angle and negative rake angle of abrasive-grains can produce an exceptional negative rake-angle press-cut effect helping to suppress brittle-fracturing from occurring. Experimental results show that the proposed ‘high-frequency vibration-assisted cutting’ mode with a ‘self-controlling cutting force’ can automatically adjust the tool feed-rate on-line, increasing the material removal rate and protecting the glass-ceramic against brittle-fracturing. A 3-D microstructure made of Zerodur glass-ceramic is successfully machined under semi-ductile regime cutting, confirming the feasibility of the proposed technology, and opening-up the potential for micromachining hard-brittle materials such as Zerodur glass-ceramics for commercial applications.