Wire rupture prevention using on-line pulse localisation in WEDM

Abstract

This paper describes a control system developed to reduce the risk of wire rupture due to the thermal load on the wire. The control is based on a thermal model performing an on-line calculation of the temperature distribution over the wire. The thermal model takes into account the heat input due to the discharges and the evacuation of heat by conduction through the wire and convection to the dielectric. The location of each discharge is determined based on a differential current and/or differential voltage measurement between the upper and lower wire contact. The developed control strategy provides a temporary reduction of the pulse energy, when the calculated maximum temperature over the wire exceeds a critical value. The control enables to eliminate 90 % of the wire ruptures.