the shop’s initial testing in ceramics machining involved the use of CBN cutters, but with the added element of heat. “When the question of machining ceramics came up, we
began investigating the use of heat to improve the process,” said Jeff Staes, director of technical services at Reliance Tool. “First, we used an acetylene torch to heat the ceramic material prior to machining it, but we needed a lot more heat than the torch could produce and a way to pinpoint ex- actly where the heat would be applied on the material/workpiece. This was where a laser entered the equation.” According to Staes, the positioning of the laser beam in relation to the cutting tool is critical in the process. The laser must be pinpointed in an exact area just ahead of the cutting insert to, in a sense, preheat/soften the material to a plasticized state so it can be easily cut. However, he warned that there is a finite heating level, and precise temperatures must be consistently maintained or the material could be damaged. The process uses a 300-W laser with a built-in sensor that also incorpo- rates a secondary laser to measure part surface temperature. A vacuum system extracts the dust/chips that result from the process and could interfere with the laser’s beam. While CBN tooling worked in the be-
ginning stages of developing the ceramic machining system, Staes said that insert life was quite short, so the shop decided to try polycrystalline diamond (PCD) inserts from Seco. The shop, working closely with Seco, developed special edge parameters for these inserts that boosted cutter life well beyond that of CBN. Seco’s PCD 30M multi-micrograin inserts, which were new at the onset of Reliance’s research, are used for the ceramic machining system. The inserts incorporate two different grain sizes,
as opposed to just one. For the PCD 30M inserts, grain sizes are 30 and 2 μm. In combination, they provide levels of both toughness and wear-resistance unlike any other PCD grade, CBN or carbide insert.