Wire Tension Control of Wire Electrical Discharge Machining Through System Dynamic Analysis

A dynamic modeling technique for the wire transport system of wire electrical discharge machining (wire-EDM) is proposed. Based on the technique, two devices are proposed to control the wire tension. The first device is the active wire feed apparatus, a motor mounted on the wire spool to actively feed the wire. It eliminates the inertial effect of the wire spool on the system, increasing the system fundamental frequency. The second device is a multilayer damped vibration absorber (MDVA). The high-damping MDVA is a flexible device that oscillates as wire tension variation occurs. The perturbation on the wire tension can be attenuated. A physical model of the wire transport system with both mechanisms is constructed, and the effects of both devices on the wire tension are investigated theoretically. Theoretical studies show that the system fundamental frequency can be effectively increased by the active wire feed apparatus, and the MDVA can increase the system damping coefficient. Both devices are mounted on a wire-EDM machine tool to test the wire tension variation. Results show that the wire tension variation can be reduced from 130 gf to 70 gf by mounting the active wire feed apparatus, and the fundamental frequency can be increased from 2.0 Hz to 9.0 Hz. Installing the MDVA on the system slightly reduces variation in the wire tension, but the high frequency perturbation is eliminated to a significant degree. If both devices are installed on the system, the wire tension variation can be further reduced to 43 gf.