Experimental Verification On Criterion Of Material Removal Modes In Micro Ultrasonic Machining

Recently, Micro-electromechanical Systems (MEMS) are widely applied in aerospace, computer, and biomedical science industries. Various micro machining technologies have been and are being developed to meet these requirements. Unlike other micro machining technology, micro-USM has its own specialty. It is a non-thermal, non-chemical and non-electrical process and it can generate micro features with high aspect ratio in brittle and hard material including silicon, glass and ceramics.Similar to any other machining methods, surface integrity is one of the most important factors in evaluating machining performance of micro-USM. It is found that the integrity of machined surface is highly related to material removal modes. Therefore, it is necessary to quantitatively investigate the criterion for brittle-ductile transition based on process parameters.In the previous study, the criterion of material removal mode has been proposed. However, the criterion was concluded from the analysis of limited amount of experimental results. In addition, the machining conditions were also very limited. This paper is to verify the validity of the criterion through extensive experiments under various machining conditions.In this study, a NC system is programmed for the self-developed micro USM equipment. It has functions of preparing micro tools on-line, micro ultrasonic machining, tool wear detection and data saving.To obtain accurate data, the cutting force variation is required to be as small as possible in verification experiments. The force control method is studied. Experiments are conducted to compare the control performances of the traditional control system and PID control system. The results show that the PID control system has a better performance than that of the traditional control system. The amplitude of cutting force variation was shorten up to24%.Using new MUSM cutting force control system, extensive experiments under various machining conditions were designed and carried out in this paper. Results of75out of86samples indicate the validity of the criterion. The coincidence rate is87%. Since the criterion has been verified in this paper, this conclusion can be used to improve the surface quality in micro-USM.