Measurement of wire electrode temperature in WEDM

Abstract

Wire temperature is an important parameter in the wire electro-discharge machining (WEDM) process because overheating of the wire can cause the wire to break. It is difficult, however, to measure the wire temperature directly under the condition that the wire is emerged in water and surrounded by the workpiece. Only mathematical analyses by now have been reported to determine such temperature but limited by the assumption of convective heat transfer coefficient and the percentage of energy distribution. Based on the relationship between the wire temperature and the value of its resistance, this paper proposes a measuring system that has been developed to experimentally track and record the average temperature increment of the wire electrode for the WEDM process. With this system, the average temperature increment of the wire under discharges can be as high as 130°C. The average temperature increment of the wire under normal discharges has also been measured for low discharging energy. A typical application of this system is finally discussed in this paper. By measuring the average temperature increment of the wire electrode heated by Joule heating energy, the convective heat transfer coefficient in WEDM is experimentally determined.