A novel methodology for spark gap monitoring in Micro-EDM using optical fiber Bragg grating

摘要： Micro-Electric Discharge Machining (Micro-EDM) are the most considerable micro-manufacturing process used to engineer miniaturized features on any high temperature resistive hard material. The machining parameters in Micro-EDM are very stochastic in nature. The spark gap measure acts as a vital parameter that correlates with other process parameters for enhancement of Material Removal Rate (MRR) in Micro-EDM. Real-time actual measurement of spark gap between the electrodes is highly challenging and is limited due to the small gap measure. The present work is on development of a novel sensing technique for spark gap measurement, based on a Fiber Bragg Grating (FBG) sensor. The sensing system is developed on a cantilever structure bonded with the FBG sensor, for determining accurate spark gap measure with displacement measurement of the tool electrode. The deflection on the cantilever during spark gap generation is translated into strain variations monitored by the FBG bonded over it. Experimental trials are conducted on Micro-EDM set-up with the cantilever beam based displacement sensing with a sensitivity of 10 μm/pm. Real-time spark gap data obtained by FBG are in the range of 1.1-18.6 μm and are validated against a precision measuring instrument. This sensing technology employed for Micro-EDM spark gap measurement establishes a novel technique in micromachining field and formulates a smart system.