Analysis of micro-rods machined using reverse micro-EDM

In today's world, microstructures have a wide range of applications in the field of biomedical devices, aerospace engineering, MEMS device elements, etc. In the recent years, reverse micro-electro-discharge machining (R-mu EDM) has evolved from mu EDM that has become one of the promising technologies to fabricate precise components and microstructures of various shapes with high aspect ratio. In this work, micro-tools (rods) of average size (diameter) 182 mu m have been machined using copper sheet from bulk tungsten rod of 800 mu m diameter by R-mu EDM process. Moreover, Taguchi's L16 orthogonal array has also been applied for designing the experiments. Feed rate, capacitance and voltage are considered as the parameters of the process. The response parameters such as machining time, erosion rate and dimensional variation have been analyzed in detail for different combinations of the process parameters. It is a well-known fact that the tool wear is the main culprit and responsible for the error in the micro-rods. Dimensional error has been quantified over the entire length of the micro-rods through the measurement process, and the minimum standard deviation is found to be 1.13 mu m at a feed rate of 5 mu m/s, capacitance of 1000pF and voltage of 120V. Further, machining data have been collected in real time and the behavior of machining time with work feed has been studied. In addition to it, a simple analytical model has been developed for calculating the erosion rate and it is seen that voltage produces more effect on erosion rate and machining time than the other parameters. Additionally, using the feed rate, capacitance and voltage at which minimum deviation took place, an array of 4x4, i.e., 16 micro-rods with 58 mu m diameter and 830 mu m length, has been fabricated on the bulk tungsten rod of 800 mu m diameter.