Vibration assisted electrochemical micromachining of high aspect ratio micro features

• Micro fabrication of high aspect ratio micro features by EMM on stainless steel.
• Mathematical model of aspect ratio is derived relating EMM parameters.
• 3 MHz pulse frequency was found to be suitable with reduced machining time.
• Coated tool reduced overcut from 95 μm to 24 μm on 900 μm thick work piece.
• Highest aspect ratio of 14.33 achieved during EMM on 900 μm thick work piece.

The most used processes for generation of high aspect ratio microchannels are Nd: YAG laser technology on silica substrate and ultra violate lithography (UV-LIGA) process on metals. There are a few micromachining technologies such as micro mechanical milling, micro electro discharge machining (EDM) and electrochemical micromachining (EMM) for production of high-aspect-ratio micro features on highly stressed and anticorrosive metal like stainless steel. This paper discusses the micro fabrication of high aspect ratio micro features at the intended location on high strength stainless steel sheet of very small thickness to high thickness with highest average aspect ratio 14.33 achieved during microchannel generation by EMM with the help of coated microtool. Mathematical model relating aspect ratio with various parameters and machining conditions is derived to explore the ways to increase the aspect ratio of micro features. Experimental investigations were carried out to know the effect of vibration of microtool, frequency of pulsed voltage, microtool tip shape, thickness of work piece and non-conducting layer coated microtool on high aspect ratio micro features. Vibration of microtool with very small amplitude improved the stability of micromachining due to improved flow of electrolyte.