To prevent fine cracking on the cavity surface of a metallic mold by blowing cooling air on the cavity surface of the metallic mold to lower the temp. to a specified temp. and thereafter, spraying parting agent.
A blowing device 21 is inserted between the metallic molds 12, 13 and a temp. detector 25 is positioned to the starting point of blowing to measure the temp. of the cavity surface 11 of the metallic mold. The blowing quantity of the necessary cooling air is calculated from this temp. and this cooling air and this cooling air is blown onto the cavity surface 11 of the metallic mold from a cooling air blowing nozzle 27. At the time of cooling the cooling surface 11 of the metallic mold to 200-250°C which easily sticks the parting agent, a specified quantity of the parting agent is blown from a liquid agent spraying nozzle 28 to stick the parting agent on the cavity surface 11 of the metallic mold to a desirable thickness. Since the metallic mold temp. is beforehand lowered to a prescribed temp. by the cooling air having small cooling capacity, the temp. history by the parting agent is different to receive and the development of the fine crack on the cavity surface 11 of the metallic mold can be prevented.
YONEYA HIDEO
HIRATA AKIRA
