| 摘要 |
PROBLEM TO BE SOLVED: To execute grinding with the optimum uniformity by comprising a speed ratio control means for selectively controlling a speed ratio between a rotating speed of a disc-shaped grinding wheel and an auto-rotation speed of a matter to be grinded corresponding to a size of the matter to be ground. SOLUTION: A matter to be grinded 2 auto-rotates at a rotating speedω1, so that the positions of A point and C point on a circumference of the matter to be ground are alternately changed on a grindstone 1, and the grinding amount of A point and C point are almost equalized to one another. On the other hand, B point of the matter to be ground 2 is on a center of autorotation, so that its grinding amount is determined on the basis of the rotating speedω2 of the grinding wheel 1 and a center distance L regardless of the rotating speed of the matter to be ground 2. A condition to equalize both grinding amounts is represented by an expression: 1/2 [rω1-(L+r)ω2+rω1+(L-r)ω2]=Lω2, andω1:ω2=(r+L):r is the optimum ratio of rotating speeds. Concretely the optimum ratio ofω1:ω2 is properly changed by a control means on the basis of a size (radius) (r) of a wafer under the consideration that a size of the grinding wheel 1 is fixed, and the center distance L is also fixed. |
