Prediction of a thermally induced concave ground surface of the workpiece in surface grinding

Grinding is required for high surface quality and precise dimensional and geometrical accuracy. Among the technical problems in grinding, the geometrical inaccuracy of the workpiece due to thermal deformation is of particular concern in precision grinding. Especially, mould steel of low thermal conductivity will deform to become convex during grinding due to the accumulated heat in the workpiece, which induces a concave surface profile of the workpiece after grinding, called over-grinding. This seriously affects the geometrical accuracy and decreases the yield rate. The present study contributes to the calculation of the three-dimensional transient temperature by the finite difference method, and the model construction of the thermal bending moment, stress and deformation of the workpiece using beam theory. The proposed models are discretized by the numerical multi-integral method for solution of the induced deformation of the workpiece. The clamped models predict the concave deformation fairly well. They can be used as the upper and lower bounds of the thermal deformation in surface grinding.