To improve flattening of the two surfaces of a sheet by a method wherein a sheet is held by a holding device having a holding surface approximately in a shape complementary to the first surface of a sheet, a second surface is machined by a surface machining means, and thereafter, the sheet is held by a holding device having a flat holding surface, and surface processing is applied on the first surface.
When surface processing, such as surface grinding and surface polishing, is applied on the two surfaces of a sheet 1 provided on both surfaces with an uneven surface and a warp, a holding device 2 having a holding surface 2a approximately in a shape complementary to that of the first surface 1a of the sheet 1 is first used. In such a state that the first surface 1a is brought into contact with the holding surface 2a, the sheet 1 is held. Surface machining of the second surface 1b of the sheet 1 is effected until the surface processing attains a broken line, and the second surface 1b of the sheet 1 is surface-machined in a flat. The sheet 1 is turned over, and the sheet 1 is held by a holding device 3 in such a state that the second surface 1b is brought into contact with the holding surface 3a. Surface processing of the first surface 1a of the sheet 1 is effected until surface processing attains a broken line, and both the first and second surfaces 1a and 1b are completely flattened.
IWAKATA SEIICHI
SEKIKAWA SHOHEI
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