Modification and adaptation of wire lag model based on surface feed for improving accuracy in wire EDM of Ti-6Al-4V alloy

Dimensional accuracy in parts manufactured by wire EDM (WEDM) can be lost due to wire lag (where the wire electrode bends into an arc away from the machining direction). Wire lag effects are at issue when extremely narrow tolerances on curved or sharply angled geometries are desired. The feasibility of a program to modify machining G-code to compensate for wire lag at sharp corners is investigated here. Program development was informed by machining experiments. First, the effect of surface feed rate on profile accuracy was investigated. It was found that feed influences wire lag and profile accuracy. A wire lag model is demonstrated, and methods for developing modifications to incorporate both surface feed and eliminate the need for an ex situ measurement to minimize wire lag are presented. A method for relating pulse duration and voltage to each plasma discharge’s area is demonstrated. Lastly, an outline for a program that compensates for wire lag at threshold angles is shown. It is found that the developed application can predict wire lag or corner error within ±10% of the experimental value. It is also found that profile accuracy can be significantly improved using a cutback method by calculating the amount of wire lag from the modified model and modifying CNC G-codes using the developed application to apply cutbacks at designated corners.