CPT International 02/2015

Figure 1: Process of inorganic core production: mixing of sand, binder and additives – shooting of the molding material
into the core box – hardening of the core by the heated tool and heated air – removal of the core
Inorganic core making is now found in
many foundries in Germany, particularly
for the production of castings in
the automotive sector. Industrial-scale
inorganic core making is still a challenge,
particularly with respect to integrated
process chains, robotic and
tray handling, and under extreme climatic
conditions.
Exploiting the knowledge and experience
gained from over ten years of serial
production of intake manifolds and
cylinder heads with inorganic cores a
fully linked inorganic core shooting
unit was put into operation at Volkswagen
foundry in Hanover in 2012.
Inorganic core shooting process
including core hardening
The process of inorganic core production
consists of four steps. It begins
with the mixing of weighed quantities
of silica sand, additives and binders
for the molding material. In a second
step, the molding material is
transported to the core shooter and
shot into the core box. In a third step,
Figure 2: Binder bridges in the core (scanning electron microscope photo)
the core is hardened by means of the
heated core tool and heated purging
or gassing air. Finally, the core box
is opened, the finished core is ejected
and ready for further processing
(Figure 1).
A purely inorganic molding material
system consists of silica sand (SiO 2
),
binder (a modified silicate solution)
and additives (synthetic and natural
minerals). The hardening process is a
condensation process, creating a sol-
Casting Plant & Technology 2/2015 25