PURPOSE: To enable pull-out of the whole core from a cast product by enabling the shrinkage of a core resin part at the time of becoming the soft condition to easily shrinkage-deform the whole core.
CONSTITUTION: Molten metal is poured into a cavity between a metallic mold and the core, and solidified to cast the cast product. An undercut or the cavity part in the cast product is formed with the core 1. This core 1 is constituted with the thermoplastic resin and formed with the core resin part 3 constituting the part at least contacting with the molten metal in this core, and the shrinkable structure formed in the core resin part 3 so as to be possible to shrink the core resin part 3 when the temp. of the core resin part 3 raises and becomes the soft condition. The shrinkable structure 4 is constituted with a hollow part or gas hole parts 4A formed in the core resin part. At the time of pulling out the core 1 from the product, the core is pulled out while applying the fine vibration and twist force, etc. By this method, the pull-out force can be transmitted in the soft condition and the whole core can be pulled out.
OKADA MASAMICHI
OKADA YUJI
SHIRAKAWA HIROICHI
SEKI AKIRA
YASUKAWA MASAO
OZAKI MASAYASU
TAMURA SHIGEKI
OTA ATSUSHI
