An Attempt to Measure a Temperature Distribution of Wire on WIRE EDM.

Abstract

A maximum cutting speed of WIRE EDM is restricted by a wire rupture during WIRE EDM. Normally it is said that too high machining speed supplies high temperature on the wire and causes the wire breaking. But it was difficult to measure the wire temperature during EDM because the wire is moving and surrounded by a workpiece material. Only a mathematical analy- sis5) is tried to obtain a temperature distribution assuming a heat transfer coefficient, but not considering a effect of water flow. We already found that a discharge concentration occurs just before the wire breaking1)2). Then the discharge concentration may be the main reason of the wire rupture. In this case a local wire temperature may increases so high but not a averaging wire temperature. But it depends on machines. If an ON/OFF control in power supply was so fine as to avoid the dis- charge concentration, the averaging wire temperature may be already so high, and the preven- tion of discharge concentration may be a fruitless effort for the machining speed. Then it is important to know the real wire temperature to develop the machining speed on WIRE EDM. In this report we describe an attempt to measure the wire temperature distribution from discharging currents and voltages during WIRE EDM. Results show that the averaging wire temperature may be 100C or less