Edge grinding

An edge grinding machine in which a workpiece is rotated relative to a rotating grinding wheel having a groove formed in its surface for grinding the periphery of the workpiece to size and shape, in which a spark erosion electrode is mounted for rotation with the workpiece, and the wheel to be formed and reformed is axially shifted and advanced, so that the region thereof which is to be formed with a groove or containing a groove which is to be re-formed can be engaged by the spark erosion electrode as the latter rotates about the workpiece axis, and forming and re-forming of the groove in the grinding wheel is performed by rotating the grinding wheel at high speed while simultaneously rotating the electrode around the workpiece axis so that spark erosion is performed around the whole of the circumference of the groove.

A method of forming the external peripheral surface of a forming wheel carried by a work spindle, in which the forming wheel is used to form and re-form grooves in grinding wheels for grinding an edge profile and a notch profile in a wafer mounted for rotation about the same axis as the forming wheel, and in which a stationary grooved electrode is mounted to the machine and is adapted to be moved into close proximity to the edge of the forming wheel mounted on the workpiece spindle so that part of the arcuate extent of the said circumference is embraced by a groove within the electrode, and electro-discharge machining is performed as the forming wheel is rotated so as to form the desired profile around the periphery of the forming wheel to enable it to continue to perform its forming and re-forming task.

A machine having fitted thereon an arcuate electrode adapted to be moved towards and away from the circumferential edge of a forming wheel, the forming wheel being mounted on a work spindle to the rear of a workpiece mounting device such as a vacuum chuck, and means for advancing the electrode so that a groove therein embraces the edge of the forming wheel to allow electro-discharge machining to be performed on the circumferential edge of the forming wheel.

A method of positioning a grooved grinding wheel relative to a disc-like circular workpiece for edge grinding the latter using the groove in the wheel to produce two converging frustoconical surfaces around the rim of the workpiece, comprising the steps of mounting the workpiece for rotation about a first axis, mounting the grooved grinding wheel for rotation about a second parallel axis, effecting relative movement between the workpiece and the wheel to engage the rim of the wheel within the groove, performing a preliminary grind, separating the wheel from the workpiece, measuring the peripheral rim of the workpiece to determine the accuracy of its form relative to a template or to stored data relating to the desired form, axially adjusting the position of the wheel and therefore the groove in response to the measurements made in the profile of the rim produced by the preliminary grind, re-grinding the rim with a second preliminary grind with the grinding wheel located at the axially shifted position, measuring the profile of the ground rim of the workpiece as before, adjusting the axial position of the grinding wheel again, re-grinding the ground periphery of the workpiece and repeating the measuring and axial shifting steps until the rim profile possesses the desired accuracy, and utilizing the final position of the grooved grinding wheel for grinding future wafers.