A Novel Methodology for Spark Gap Monitoring in Micro-EDM Using Optical Fiber Bragg Grating

Micro-electric discharge machining (micro-EDM) is the most considerable micro-manufacturing process used to engineer miniaturized features on any high temperature resistive hard material. The machining parameters of 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 the material removal rate (MRR) in micro-EDM. The real-time actual measurement of the spark gap between the electrodes is highly challenging and is limited due to the small gap measure. This article is about the 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 performing accurate spark gap measurements with the displacement measurement of the tool electrode. The deflection on the cantilever during spark gap generation is translated into strain variations, as monitored by the FBG bonded over it. Experimental trials are conducted on the micro-EDM setup 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 the micro-machining field and formulates a smart system.