The automobile industry currently faces many challenges which
may greatly impact on its foundry operations. One of these
challenges, consumers'' demand for greater fuel efficiency,
can be met by reducing the weight of castings used in automobiles,
and minimizing engineering tolerances. In answer to this particular
demand, engine foundries have begun to either produce cylinder
blocks or other castings with aluminum rather than cast iron.
However, if a reduction in weight (thin wall and near-net shaping)
can be realized with cast iron, there would be numerous merits from
the perspective of cost and compactness and there would be much
more flexibility in automotive parts design.
In view of this, we created a new cast iron foundry production
line which incorporates the following various technologies: 1)
preventing mold deformation by using synthetic ceramic sand having
a low coefficient of thermal expansion, 2) increasing the
dimensional accuracy of molds using an air-flow and squeeze molding
process and a cold box core making process, and 3) establishing
foundry technology such as pouring conditions and a gating system
necessary for thin wall molding. These technologies enabled us to
successfully mass produce a thin wall, lightweight cylinder block
having a wall thickness of 3 mm with a dimensional dispersion of
\mD\mP0.6 mm (ISZ engine, employed in the Toyota''s Vitz
and Yaris).
Making the walls thin has enabled the weight to be reduced by
approximately 5% compared with the past. Furthermore, including the
effect from a near-net shape, a total weight reduction of just
above 10% was able to be realized.