Abstract: A required inventory calculating system includes a first section for calculating product importance level coefficients, a second section for calculating procurement risk level coefficients, a third section for calculating general coefficients by multiplying the product importance level coefficients by the procurement risk level coefficients, a fourth section for calculating required inventory periods respectively with respect to raw materials or partly finished products by multiplying the general coefficients by a predetermined longest inventory period, and, if the required inventory periods are shorter than a predetermined shortest inventory period, setting the required inventory periods as the shortest inventory period, and a fifth section for calculating required inventories respectively for the raw materials or the partly finished products by multiplying required quantities of the raw materials or the partly finished products required to supply the products to customers or wholesalers in a predetermined p

Abstract: A dressing ring includes a ring-shaped dressing member for dressing a processing stone. Preferably, the dressing member has an opening in which a workpiece is arranged when the workpiece is ground. Also preferably, the dressing ring further includes a ring-shaped support plate having an upper surface on which the dressing member is fixed. In addition, a grinding method of the workpiece includes the steps of holding the ring-shaped dressing member on a holding surface of a chuck table, holding the workpiece in the opening of the dressing member such that a back surface of the workpiece is located higher than the upper surface of the dressing member, grinding the workpiece by grinding stones of a grinding wheel, and dressing the grinding stones with the dressing member on the holding surface.