A self-regulating feed-rate machine tool for quartz glass micromachining

This paper presents a novel approach to the micromachining of quartz glass using a self-regulating feed-rate grinding-milling technique. To overcome the difficulties in machining hard-brittle materials, a tabletop linear 3-axis CNC machine tool providing grinding-milling at depths of several nanometers is first constructed. A feedback control loop (FCL) design which corrects in real time the feed-rate of the tool is proposed. Load-cells are devised on 3 axes to sense grinding-milling force and provide real-time feed-rate feedback control for protecting the quartz glass against brittle fracturing. Experimental results demonstrated that the self-regulating feed-rate approach creates a proper feedback control over the grinding-milling force; quartz glass is machined layer-by-layer, which realizes a quasi-ductile regime material removal. A twin-slot microstructure with 3 mm in length and a miniature 3-step-shaped pyramid of Ra0.139 μm surface roughness are accomplished. Experimental confirmation of the proposed approach is presented. Satisfactory cutting of two elaborate miniature microstructures reveal that the developed self-regulating feed-rate machine tool is effective, and should be very useful in the manufacture of intricate micro-parts.