Wireless Sensing of Discharge Characteristics for Quality Control in Batch Mode Micro-electro-discharge Machining

Wireless signals are inherently generated during the spark discharges of micro-electro-discharge machining (μEDM). This work harnesses signals between 300-750 MHz for the monitoring of batch mode machining quality. In particular, the wireless spectra are used to sense incipient, debris-dominated machining that can be destructive to both the tool and the workpiece. Planar stainless steel (316L) is machined 50 μm deep in a high-density stent pattern with 30 μm features and tool fill factors ranging from 8.4% to 32.9%. In debris-dominated conditions, the 580-750 MHz frequency band shows an increased average strength over an average reference band of 410-480 MHz. The temporal evolution of the spectra permits the discharges to be monitored in a manner that is less affected by circuit parasitics than alternative electrical methods. It is amenable to real-time monitoring of large-scale production.