Manufacturing method of plugged honeycomb structure

A manufacturing method of a plugged honeycomb structure in which a plurality of cells are separated by porous partition walls and formed so as to communicate with two end faces of the honeycomb structure, and plugging portions arranged so as to plug one of two opening ends of each of the cells, the method comprising:

• attaching a transparent sheet to an end face of the honeycomb structure;
• picking up an image of the end face;
• with respect to cells other than cells positioned at an outermost peripheral portion of the honeycomb structure, recognizing positions of the cells other than cells positioned at an outermost peripheral portion of the honeycomb structure on the sheet by subjecting the picked-up image to image processing;
• with respect to cells positioned at the outermost peripheral portion of the honeycomb structure, recognizing positions of the cells positioned at the outermost peripheral portion of the honeycomb structure on the sheet by calculating positions of the cells positioned at the outermost peripheral portion from an average cell pitch calculated from the positions of the cells other than the cells positioned at the outermost peripheral portion of the honeycomb structure recognized by said image processing;
• subjecting the positions of the sheet corresponding to the cells to be plugged to a perforation treatment based on the recognized positions;
• submerging an end portion of the honeycomb structure into a plugging slurry in which a material of the plugging portions is slurried for selected plugging portions;
• and filling end portions of the cells to be plugged with the plugging slurry through holes made by the perforation treatment in the sheet to form the plugging portions.