Abstract: A tool is brought into contact with a radially outer part of an inner wall surface of a scrollwall along an X-axis at a position displaced from the center of a basic circle of an involute curve by a radius of the basic circle along a Y-axis. Thereafter, the tool and the scrollwall are relatively moved along the X- and Y-axes while rotating the scrollwall about the center of the basic circle and keeping a normal direction of the wall surface at a contact point with the tool parallel with the X-axis, so that the tool is brought into contact with the wall surface from the same wall surface. In this way, the inner wall surface the wall surface at the center and the outer wall surface can be continuously processed in the same direction. The processing can be easily corrected based on a processing error resulting from the deviation of the positional relationship from a predetermined one, with the result that the processing accuracy can be maintained at a satisfactory level.

Abstract: A tool is brought into contact with a radially outer part of an inner wall surface of a scrollwall along an X-axis at a position displaced from the center of a basic circle of an involute curve by a radius of the basic circle along a Y-axis. Thereafter, the tool and the scrollwall are relatively moved along the X- and Y-axes while rotating the scrollwall about the center of the basic circle and keeping a normal direction of the wall surface at a contact point with the tool parallel with the X-axis, so that the tool is brought into contact with the wall surface from the same wall surface. In this way, the inner wall surface, the wall surface at the center and the outer wall surface can be continuously processed in the same direction. The processing can be easily corrected based on a processing error resulting from the deviation of the positional relationship from a predetermined one, with the result that the processing accuracy can be maintained at a satisfactory level.