Quality Assessment through In-process Monitoring of Wire-EDM for Fir Tree Slot Production

Abstract

Against the background of an increased importance of in-process quality measurement – especially for manufacturing of safety critical jet engine componets – this paper deals with the development of a process monitoring tool for process quality assessment and correlating surface integrity evaluation of Wire-EDM for fir tree slot production. For the last trim cut, which is the relevant cut for the final surface integrity, a correlation between process data and surface integrity aspects is set up. The process data are read out from the machine tool's controlling device to obtain a position depending signal of mean gap voltage for the quality assessment. Two demonstration runs showed the work capability of the monitoring tool for cutting the often applied nickel-based turbine alloy Inconel 718. On the one hand a failure free slot machining process and on the other hand a manipulated machining process with enforced short circuits were conducted. For the manipulated process these instabilities were successfully detected. A cross section view analysis of both fir tree slots results in best surface integrity qualities for the first run, which shows the potential to machine fir tree slots by Wire-EDM, and failures in the surface of the manipulated run due to short cuts. These failures were additionally correlated with the position depending signal. With the developed monitoring tool a first approach was designed to build up an in-process and position oriented quality assessment for the production of fir tree slots by Wire-EDM.