Method of cylindrical and shoulder grinding

Abstract

An improved grinding machine includes a grinding wheel which is moved along a path extending at an acute angle to the axis of rotation of a workpiece. The workpiece is movable along its axis of rotation. During plunge grinding operations, the workpiece can be reciprocated along its axis of rotation. During transverse grinding operations, it is necessary to compensate for the acute angle of the path along which the grinding wheel is moved relative to the axis of rotation of the workpiece. This may be done between traverse grind strokes by initiating movement of the grinding wheel toward the workpiece from a position in which the edge surface of the grinding wheel is offset from the plane of a radially extending shoulder surface. Upon completion of a grinding operation, the wheel is retracted to a clear point. Different clear points are used so that the grinding wheel is retracted to only the extent necessary when finishing portions of a workpiece having different diameters. The position of an edge surface of the grinding wheel along the axis of rotation of the workpiece is indicated by data stored in a Z-axis register. Data corresponding to the distance a face surface on the grinding wheel is spaced from the axis of rotation of the workpiece is stored in an X-axis register. The data stored in both registers is changed when the grinding wheel is moved toward and away from the workpiece along the path which extends at an acute angle to the axis of rotation of the workpiece. However, the data in only the Z-axis register is changed when the workpiece is moved along its axis of rotation relative to the grinding wheel. The data in the Z-axis register is adjusted to compensate for the distance which a reference surface on the workpiece is offset from a zero datum position during an initial workpiece locating operation. To reduce the likelihood of wheel breakage, operation of the grinding machine is automatically interrupted when the current required to drive the grinding wheel exceeds a relatively low predetermined amount during high speed positioning movements of either the grinding wheel or the workpiece. If the current required to drive the grinding wheel exceeds a rated operating load by a predetermined amount during a grinding operation, the grinding operation is also interrupted. Fine and coarse pulse generators are provided in association with drive shafts for moving the grinding wheel and the workpiece. The outputs from the pulse generators are compared and if there is a predetermined difference in the outputs of the fine and coarse pulse generators associated with a particular drive shaft due to a malfunctioning of the grinding machine, operation of the grinding machine is interrupted.