EXPERIMENTAL INVESTIGATION OF VARIOUS PROCESS PARAMETERS WHILE MACHINING GLASS THROUGH MICRO-USM

Abstract

With the emergence of MEMS (micro electro mechanical systems), various micromachining processes have been developed to enhance the use of newer and harder work materials. Production of parts in micro scale, especially with brittle materials, is challenging. A careful selection of the processes for a given_ problem is, therefore, essential to achieve the desired level of precision and quality. When products are miniaturized, it is desired that the dimensional errors are also reduced. Therefore, high precision of micro-machining equipment is required though it is often impossible to reduce the dimensional error in proportion to the size of product. Owing to the excellent optical and mechanical properties, materials such as glass, Zerodur, fused quartz, and silicon are widely used in industry. These materials are hard and brittle. As a result, they are extremely difficult to machine, especially when there is micro-structures fabrication involved. Grinding, lapping and polishing are normally used to deal with bigger sized work-pieces. Laser ablation, micro-EDM (electro-discharge machining) can only effectively produce micro-structures on polymers and electrically conductive materials respectively. The FIB (focused ion-beam) process, on the other hand, is expensive and more suited for research and development. Ultrasonic micromachining has been gaining popularity as a new alternative in fabrication of such parts. Micro ultrasonic machining (MUSM) is considered to be a promising alternative for efficiently and accurately fabricating microstructures on brittle materials_ Being a non-thermal, non-chemical and non-electrical machining process, it has the advantages of no heat affected zone. This work aimed at investigating the surface integrity of the MUSMed glass material and subsequently improves it by modifying the Micro USM process. The research of this thesis contributes to, the establishment of a fundamental knowledge base for Micro USM through experimental and analytical investigations aimed at an understanding of the mechanism of material removal, the effect of machining parameters on the productivity and surface of machined feature. The experimental data presented in this thesis also contributes to build a data base for material removal rates, tool wear rates, and surface quality. It was observed that certain parameters like power rating, slurry concentration, abrasive and static load has a significant effect on material removal rate (MRR) and tool wear rate (TWR). Glass exhibits fair machinability while machined with Micro USM. There is no evidence of any surface damage in form of micro cracking or heat affected zone.