Being the constituent for inorganic powder injection molding and the constituent for inorganic powder injection molding

摘要

PROBLEM TO BE SOLVED: To prevent cracks from developing irrespective of the shape of a molded body obtained through an injection molding by a method wherein the mold shrinkage factor and the flexural modulus of the molded body are specifically set.;SOLUTION: In case of the injection molding of a molded body, the shape of which has a large undercut, for example, at the cooling and solidification of the injection- molded body in a mold, the core part of the mold for forming an undercut portion hinders the molded body in its shrinkage. In order to prevent the above-mentioned hindrance from causing cracks, the mold shrinkage factor of a molded body is set to be below 0.5%. On the other hand, when the mold shrinkage factor becomes smaller, the adhesion between the molded body and the cavity of the mold becomes higher, cracks tend to develop in the specified portion of the molded body due to a tensile stress caused at a mold opening. In order to avoid the above-mentioned development or cracks, a flexibility is given to the molded body. For that, an inorganic powder injection molding composition, the body molded out of which the flexural modulus in a three-point bending test of below 790 kgf/m2. can be employed for preventing the cracks from developing.;COPYRIGHT: (C)2000,JPO