Real-Time Wire EDM Tool Simulation Enabled by Discharge Location Tracker

Abstract

In Wire Electrical Discharge Machining (WEDM), one of the most limiting factors for productivity, especially during rough cutting, is the wire breakage. Root causes of wire breakage are widely investigated in the literature and three main causes have been identified: mechanical rupture, excessive thermal load on wire and discharges concentration. Since the wire breakage is essentially the limiting factor for WEDM performance, the capability to safely approach the wire electrode exploitation limits is crucial for high performance and high efficiency WEDM. This paper describes a real-time, in-process, Finite Elements Model (FEM) simulation of the tool electrode in WEDM. Using the Discharge Location Tracker (DLT), position and energy of each discharge is known; allowing real-time realistic simulation of the wire electrode thermo-mechanical status. Based on the single discharges crater volume and on the wire unwinding speed, the wire electrode wear is simulated and its radius as a function of the vertical coordinate r(z) is calculated. Then, the thermal equilibrium of the wire is computed using a FEM algorithm, taking in consideration the real-time wear and transport of the wire for Joule dissipation, thermal convection and thermal diffusion. Moreover, the wire heating is also calculated in real-time based on the single discharge position and energy. The numerical model, coupled with the DLT sensor, allows real-time monitoring of the wire electrode thermo-mechanical state during machining.