Electrical discharge machining of CVDITE CDE and SYNDITE products

This paper by R.H. Olsen, R.C. Dewes and D.K. Aspinwall(1) initially reviews the composition and manufacture of CVD diamond and specifically CVDITE CIDE and makes comparisons with PCD products. The electrical discharge machining of PCD is also briefly reviewed. Experimental work is presented to determine the electrical resistivity of both CVDITE and SYNDITE using a 4-point probing technique. Subsequent machinability tests are reported involving the electrical discharge wire machining and electrical discharge grinding of both materials. Resistivity measurements indicated that the SYNDITE CTB010 was approximately 5 times more electrically conductive than CVDITE CDE. When using operating parameters recommended for PCD (current, voltage, frequency etc.), productivity of the CVDITE CDE was typically similar to50% of that for the SYNDITE PCD products when wire machining and similar to85% when electrical discharge grinding. Measurements of diamond surface roughness after sparking were, however, substantially better for the CVDITE CDE which was as low as similar to0.15 pm R-a. In comparison the diamond layer of the CTB010 (10 mum grain size) measured -0.25 mum R-a, with evidence of subsurface undercutting.