| 摘要 |
PURPOSE:To reduce a fraction defective, by a method wherein until a gap between two platens is decreased to an average machining margin, a surface pressure based on the effective number of workpieces is exerted so that a polishing rate is kept at a value within a given range, and after the gap is reduced to the average machining margin, a surface pressure based on the given number of workpieces is exerted. CONSTITUTION:A control device 20 determines the average machining margin and unevenness of a workpiece 7 based on input data, e.g. machining specification of the workpiece 7, the thickness of the workpiece 7, the number of the workpieces, and gradually determines a polishing rate from a detecting signal, e.g. the number of revolutions, a lowering amount, gap. During the initial stage of polishing where unevenness of the workpiece 7 is high, a machining work is effected at a low surface pressure based on the effective number of workpieces by adding a polishing state, and since a excessive surface pressure is prevented from being exerted on the workpiece 7, the occurrence of damage of the workpiece 7 is decreased. Since, after a low gap at which unevenness of the workpiece 7 is low is reduced to a value equal to an average machining margin, a polishing work is effected at a high surface pressure, a machining speed is improved. |
