Cementitious board and prouss and die for its manufacturing

摘要

A die assembly (10) for providing a gypsum ceiling tile having improved acoustic absorption properties comprises a punch plate (16) having punches (12) which form perforations through a plasterboard tile and indentors (14) which form indentations in the tile. The punches and indentors are arranged in elongate strips to produce fissure-like perforations and indentations. A stripper plate (24) having apertures (28, 28') corresponding to the punches and indentors and a die plate (26) having apertures (30) corresponding to the punches sandwich the tile, and the punch plate is applied to the tile. The application embraces the tile, the die assembly and a method of making the tiles.