Many expected the use of EDM or electrical discharge machining to dwindle at the turn of the century due to the development of new machining technology. More than a decade has passed since the prediction but EDM remains in use and preferred by many workshops. The reason for this staying power is the lower cost of operation, reliability of EDM machines that allowed them to stay in very good condition, and quality based on the experience of the operator. A newer technology might offer far better potential in terms of quality but until an operator is able to master its operation, that potential will remain as is.
Graphite electrodes have also made EDM machines for applications that are more than just rough cutting. The graphite used for electrodes in sinker EDM have varying grades. The type of grade determines the quality of finish.
Fine grade graphite electrodes are made of particles with sizes between 11 to 20 microns. These electrodes are primarily used for roughing in large cavities in work pieces. The finish is very crude and will require further polishing down the line. Polishing equipment like diamond tools can be used for improving the quality of the work piece right after the EDM process.
The superfine grade graphite electrodes feature particle sizes between 6 to 10 microns. These electrodes are used for creating cavities that larger details. The quality of finish is still very crude will require polishing.
The ultrafine and angstrofine grade graphite electrodes are the ones used for finishing applications. Ultrafine grade features particle sizes of less than 5 microns while angstrofine have submicron particles. These are used for creating intricate details with very high quality finish.
