MANUFACTURE OF SHADOW MASK FOR COLOR CATHODE-RAY TUBE

PURPOSE:To prevent the deformation of a shadow mask body due to the press formation thereof via the use of a simple method, even when the radius of curvature of the principal plane of the body becomes large, by providing the second curvature for making a correction for the side deformation of the body. CONSTITUTION:A punch 30 (upper die) and a knockout 31 (lower die) combined therewith are provided, together with a blank holder 32 to surround the punch 30 and a die 33 to surround the knockout 31. The molding plane of the inner punch 30a of the punch 30 has a molding plane 45 with curvature (second curvature) for correcting the side deformation of the mask body of a shadow mask, in addition to a molding plane 44 with the same curvature (first curvature) as the curvature of the principal plane of the mask body expressed by a single function. As a result, the occurrence of side deformation can be restrained, and a shadow mask having the required curvature can be easily manufactured.