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.

Surface Topography of Inconel 718 Alloy in Finishing WEDM

“…In finishing, on the other hand, it depends on the intensity of the discharge current peak, the feed rate and, to a lesser extent, dielectric flow rate into the working gap. Klocke et al [18] investigated the use of Topas plus X (TPX) and AGN3C -(AG) coated electrodes in comparison to a standard brass electrode. The authors found that the use of coated electrodes increases the surface roughness Ra in relation to the surface machined with a brass electrode.…”

Physicomechanical Nature of Acoustic Emission Preceding Wire Breakage during Wire Electrical Discharge Machining (WEDM) of Advanced Cutting Tool Materials

“…However, the location of areas with the highest electrical field strength is also affected by contamination of the dielectric fluid in the IEG by electroconductive particles, which are produced during the EDM process [25][26][27][28]. The distribution of dispersed contaminants over the IEG volume is random and depends on a number of factors including the IEG dimensions [23,29,30], the applied voltage [30,31], the pulse frequency and duty cycle of the discharges [30][31][32][33][34], the workpiece and tool materials [33], the speed, at which the dielectric fluid (typically mineral oil) is pumped [30,35], the thickness of the workpiece being processed and the size of particles being removed from the IEG [35,36]. To ensure the stability of the ED process, it is necessary to maintain the removal of contaminants from the dielectric fluid at a rate that is no less than that at which the new electroerosion products contaminating the IEG are produced [35].…”

Unexpected Event Prediction in Wire Electrical Discharge Machining Using Deep Learning Techniques

“…This technology allows for the processing of difficult-to-cut, extremely hard materials with very tight tolerances and with impressive surface finish [ 2 , 3 ]. Nonetheless, trial and error approaches are still required for process optimization due to the above-mentioned limited accuracy of theoretical models [ 4 ]. In this context, artificial intelligence (AI) and more specifically, deep learning (DL) techniques appear to be an interesting approach, provided that massive amounts of data can be collected from the process.…”