PURPOSE: To make a core metal for high molecule entrusion molding into light weight without lowering its strength thereof by providing a lot of slits and grooves in the width direction of a strip-like metal plate in parallel at a constant interval in the longitudinal direction.
CONSTITUTION: A large number of slits 2 and slots 3 in the width direction are provided in the longitudinal direction of a strip-like metal plate 1 parallelly and equidistantly by slit processing and specific rolling. Then, the metal plate 1 is subjected to rolling processing, and elongated in the longitudinal direction thereby to fabricate a core mold. The order of the process for forming slits 2 and the process for forming the slots 3 may be reversed. The length of the metal plated at the time it is rolled and elongated is assumed to be l2 and the length thereof at the time the slits are cut to be l0. The elongation ratio l2/l0 is 150W170%, and it increases by 20W40% as compared with that of conventional method. However, the thickness of the plate does not substantially vary, but the strength is not substantially lowered.
HARADA FUMIO
TSUJIGUCHI SHIYOUICHI
