Papers by Author: Muhammad Pervej Jahan

Abstract: Brittle and hard materials are problematic to mechanically micro machine due to damage resulting from material removal by brittle fracture, cutting force-induced tool deflection or breakage and tool wear. As a result, the forces arising from the cutting process are important parameter for material removal. This study was undertaken to investigate the effect of cutting conditions on cutting forces and the machined surface during the glass micro grinding using on-machine fabricated (Poly Crystalline Diamond) PCD tool. Experimental results showed that an increase in depth of cut and feed rate can result in increase of cutting forces and surface roughness as well. Among the forces in 3 axes, force along feed direction is found to be larger, which played a major role in material removal. Finally, it is observed that PCD tool exhibits promising behaviour to machine brittle material like BK-7 glass for producing micro molds and micro fluidic devices, since it has better wear resistance, experiences less cutting forces and generates smooth surfaces with Ra value of as low as 12.79 nm.

Abstract: Present study introduces low-frequency workpiece vibration during micro-EDM drilling of difficult-to-cut tungsten carbide with an objective to overcome the difficulty in flushing of debris and machining instability in deep-hole machining. The effects of vibration frequency, amplitude and electrical parameters on the machining performance, as well as surface quality and accuracy of the micro-holes have been investigated. It is found that the overall machining performance improves significantly with significant reduction of machining time, increase in material removal rate (MRR), and decrease in electrode wear ratio (EWR). The surface quality improves and the overcut and taper angle of the micro-holes reduces after applying the workpiece vibration in micro-EDM. The frequency and amplitude of 750 Hz and 1.5 μm were found to provide optimum performance.

Abstract: Present study aims to investigate the migration of materials onto the surface of workpiece and electrode during fine-finish die-sinking and milling micro-EDM of tungsten carbide using pure tungsten electrode. The effect of materials transfer on the machined surface characteristics is also presented. The machined surfaces have been examined under scanning electron microscope (SEM) and energy dispersive X-ray (EDX) in order to investigate the changes in chemical composition due to the migration of materials. It has been observed that materials from both workpiece and electrode transfer to each other depending on machining conditions and discharge energy. A significant amount of carbon migrates to both electrode and workpiece surface due to the decomposition of dielectric hydrocarbon during breakdown. The migration occurs more frequently at lower gap voltages during finish die-sinking micro-EDM due to low spark gap and stationary tool electrode. Milling micro-EDM suffers from lower amount of carbon migration and fewer surface defects which improve the overall surface finish and reduce surface roughness significantly.