Theoretical study on the effect of form error of grinding wheel surfaces under free form grinding

Free forms can be efficiently generated through the three-dimensional motion of a grinding wheel with round-off. In this method, however, form error of the grinding wheel directly affects machining accuracy. The effects of form deviation of the wheel surface on form error of the generated shape ER have been investigated through computer simulation. The wheel surface is assumed to have waviness with amplitude a and a wave length lambda. It is found that the duplication ratio ER/2a is a function of lambda(2)/(a(.)Rg) and R-g/R-w, where R-g and R-w are the curvature radii of the grinding wheel and the workpiece surface, respectively. The longer lambda is, or the smaller a is, the larger the duplication ratio becomes. When lambda and a are constant, the grinding wheel with large curvature radius is suitable for precision machining of convex surfaces. Form deviation of the wheel surface must be smaller than the objective machining accuracy when it is within a sub-micrometer.