Superabrasive grinding with variable spark-out and wheel dressing intervals.

摘要

During grinding of successive workparts with a superabrasive wheel in a rough grind stage at a high wheel infeed rate and a finish grind stage at a relatively low infeed rate with spark-out stages after each of the rough and finish grind stages, the duration of the spark-out stage after rough grinding is made dependent on the condition of the grinding wheel and corresponds to the time needed for removing workpart material for the reduction of the grinding wheel motor power from the high rough grind level to the lower finish grind level. The duration of the spark-out stage will therefore be variable from one workpart to the next as the condition of the wheel changes. In addition, the interval of wheel retruing or dressing (i.e. number of workparts ground between wheel retruing) is variable as determined by the condition of the wheel. In particular, when the rough spark-out stage for a workpart is completed in a time shorter than a preselected minimum time indicative of a wheel that is in need of retruing. Typically, the occurrence of a drop in wheel motor power from the rough to the finish level during the preselected time interval is sensed and activates a memory circuit to store the fact that the machine needs to be placed in the wheel truing mode.