Small cast iron parts for automobiles are usually produced in the casting line with the “green sand molding process” using large amounts of sand and requiring considerable space and huge capital investment. Productivity is high when a certain amount of production is secured. However, in order to cope with large fluctuations in orders expected in the future, a cell production process that is compact, flexible, and has lower risks are required. Although “mold castings” that do not use sand are suitable for this process, cast iron parts are accompanied by three problems, namely mold life, chilling of casting, and releasability of the mold and castings. The “shell back metal process (SBM process)” is a suitable method for overcoming these problems. However, in the normal SBM process, since the shell layer and metal mold are thick, costs of supplies and productivity during the cell production process are challenges faced. If the thickness of shell layer and metal mold can be reduced to 1/2 or less by “thin SBM process”, these problems as well as mold casting problems can be overcome. To verify this new process, we conducted casting experiments on a differential case with a shell layer thickness of 2mm and metal mold thickness of 4mm. Productivity and effects on molds and castings were investigated. The following results were confirmed. Chilling did not occur in castings with thickness of 5mm even without preheating of the metal mold. In addition, the mold and castings were easy to release. Rise in metal mold temperature was found to affect metal mold life and cycle time. However, temperature increase can be reduced by increasing the cooling effects at the back of the metal mold. This does not affect chilling of castings. For repeated casting, the cycle time of this process was found to be shorter than the normal SBM process.
