DIE FOR MOLDING RIM

PURPOSE:To reduce the cost of a casting mold and to improve molding accuracy by bonding an inside layer made of a Bi-Sn alloy having the die surface coinciding with a product shape and the thickness equal to the thickness of a product to a high-rigidity back up body by casting. CONSTITUTION:A hollow male board 13 is fashioned in accordance with a prototype 10 and a male mold 15 transferred with the curved face 11 of the prototype 10 is previously formed. Sheet wax 16 is separately stuck to the prototype 10 and a model 18 of the back up body 4 is fashioned by the outside surface 17 of the wax and flask, then the back up body 4 is cast of a cast iron. Runners 21 are bored to the body 4 and said body is mated with the mold 15, by which a casting mold having a cavity 22 is obtd. A Bi-Sn alloy is cast into the cavity 22 to form a die 1. The inside layer 5 made of the Bi-Sn alloy forms the exact die surface and the time required for forming the same is shortened. The need for correcting the casting mold is eliminated and the cost of the casting mold is reduced; in addition, the molding accuracy of the product is improved.