CPT International 01/2019

MOLD AND COREMAKING
Photo: Soplain
Inorganically bound sand cores with different graphite contents, which influences the thermal conductivity of the sand binder mixture and
thus the hardening times.
Development of a new process
for fast electrical hardening of
inorganic sand cores
Inorganics are becoming increasingly important for the production of sand cores. The
development of a new process for the hardening of inorganic sand cores by means of
electricity aims at the faster and more cost-effective production of inorganic sand cores.
Further advantages such as low energy consumption and homogeneous hardening are
promising.
Wolfram Bach, Welsleben, and Eric Riedel, Magdeburg
Introduction
The use of cores is indispensable for the
foundry industry. Complex, internal and
thin-walled geometries as well as indentations
are not possible without lost
cores. Thus, they pave the way for innovative
casting technology solutions in
order to meet the high demands placed
on modern castings today and in the
future. Core production is therefore of
great importance in terms of variety,
complexity and surface quality. Core
shooting in cold box or hot box processes
has been established for many
years. The cold box process, on one
hand, is characterized by the fact that
the sand cores are hardened in nonheated
boxes by a compressed air amine
mist gassing. The required binder for
cold box usually consists of a two-component
system consisting of phenolic
resin and polyisocyanate. The hot box
process, on the other hand, usually uses
moist bound molding materials, which
are completely hardened in the core box
by absorbing the stored heat energy.
Despite the extensive use and high
productivity of core shooting, many
companies are working on further and
new developments in the field of core
production. One of the most important
developments at present is certainly the
additive manufacturing or the colloquial
3-D printing of lost cores. A development,
which is advanced among others
by ExOne, Voxeljet, the BMW AG or
Bosch Rexroth, in order to name only
some companies, and which shows
again that the Additive Manufacturing
procedures are versatile applicable and
are becoming increasingly important.
The motivation behind this develop-
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