Local temperature response to pulsed discharges in electronic discharge machining (EDM) environment

We report on local temperature measurements performed during single discharges in electronic discharge machining (EDM) environment. Measurements have been performed with two different setups. One being a thermal device consisting of 14 thin film Au-Pd thermocouples. This device with 4-μm² large junctions was patterned using standard photolithography. The distance between the junctions (i.e., the local resolution of the device) is 20 μm, whereas the sensitivity is 10 μV/K at 150°C. The other setup being a fast infrared charge-coupled device (CCD) camera with home made control electronics. An acquisition rate of 80 000 pictures/s with a 10-μm local resolution was obtained. Using standard electron discharge machining (EDM) equipment, the temperature response due to a single discharge was measured with both the equipment, which show excellent agreement. The maximum temperature measured on the backside of a 20-μm-thick foil is 590°C. Analysis of the thermovoltage noise pattern allowed precise determination of the beginning and duration of the discharge. The numerical simulation of the process is presented and discussed.