Method for producing plugged honeycomb structure

A method for producing a plugged honeycomb structure including a honeycomb structure in which a porous partition wall defines and forms a plurality of cells communicating between two end faces of the honeycomb structure, and plugging portions which are arranged to plug one of two open ends of each of the plurality of cells, the plurality of cells being constituted of outermost circumferential cells positioned in an outermost circumferential portion of the honeycomb structure, and usual cells other than the outermost circumferential cells, the method comprising:

• attaching a transparent sheet to an end face of the honeycomb structure;
• imaging the end face;
• performing image processing of an image obtained by imaging the end face to recognize positions of the usual cells;
• performing perforation processing, on the basis of the recognition of the positions of the usual cells, at the positions on the sheet which correspond to the usual cells to be plugged;
• recognizing, as positions of the outermost circumferential cells, positions each of which is calculated from an average cell pitch of the usual cells whose positions are recognized by the image processing, each of the positions calculated from the average cell pitch being present on an inner side from a circumference of the end face of the honeycomb structure;
• disposing, on the basis of the recognition of the positions of the outermost circumferential cells, virtual perforation regions at positions on the sheet which correspond to the outermost circumferential cells to be plugged, each of the virtual perforation regions being divided into a plurality of squares;
• performing perforation processing of perforating at least one of the plurality of squares in each of the virtual perforation regions, the perforation processing including individually setting positions and a number of squares to be perforated in each of the virtual perforation regions in accordance with each of the positions of the outermost circumferential cells to be plugged to which each of the virtual perforation regions corresponds;
• immersing an end portion of the honeycomb structure into a plugging slurry in which a material of the plugging portions is slurried, after the perforation processing at the positions corresponding to the usual cells and in each of the virtual perforation regions;
• and
• forming the plugging portions by charging end portions of the plurality of cells to be plugged with the plugging slurry through holes formed in the sheet by the perforation processing at the positions corresponding to the usual cells and in each of the virtual perforation regions.