CENTERING MOLDING ASSEMBLIES
E. I. Suzdal’tsev,
D. V. Kharitonov,
and A. N. Khramov
Translated from Novye Ogneupory, No. 12, pp. 13 – 18, December, 2008.
Original article submitted October 22, 2008.
Methods are surveyed for centering molding assemblies as used to mold large ceramic blanks from aqueous
slip. Existing and promising future methods of centering are examined, with emphasis on their advantages and
shortcomings. The analysis shows that video centering is the most promising method.
The molding assembly (Fig. 1) is a basic component in
producing ceramic blanks by slip casting in porous molds,
which consists of two basic parts: the core 1 and the porous
mold 2, which provide respectively the internal and exterior
profiles of the shaped blank 3. When this assembly is
brought together, the main problem is good centering of the
core relative to the outer mold, since its accuracy largely
governs the quality of the blanks, and also affects the toler-
ance allowed for mechanical working and consequently the
consumption of material.
This is particularly important for making large ceramic
blanks (height up to 1500 mm and diameter at the base up to
450 mm) such as nose cones for flying vehicles, where the
thickness differences in the nose part sometimes attain two or
As regards improved core centering, there are many de
vices and methods designed to do this in making large ce
ramic components from aqueous slip. In a patent , a de
vice is proposed (Fig. 2) that employs self-orientation of the
core. That effect in the opinion of the authors of the patent
 is attained because the core 1 joined to the supporting
flange 3 by a spherical hinge 5 and elastic insert 4 takes a
strictly vertical position under gravity. However, although
that idea is original, it is difficult to apply under actual indus
trial conditions for the following reasons. Firstly, in self-ori
entation (under gravity) of the hinged core, one needs very
accurate adjustment of it on the coordinate axes of the basic
surfaces relative to the central axis of the inner surface of the
porous mold. Secondly, with such an assembly, the porous
mold must be set strictly vertically to eliminate any deviation
between the axes of the core and the inner side of the mold.
Failure to meet these conditions may lead to the axes of the
core and the inner face of the porous mold not coinciding,
which produces thickness variation in the formed blank.
One can avoid lack of coincidence between those axes in
the opinion of the authors of a patent  by using the device
shown in Fig. 3. When the core 1 has been set up in the cav-
ity of the porous mold 2, a centering device 4 is placed in the
slip pouring unit 3, in which the centering rod 5 is placed co-
axially with a central hole, with scope for axial displacement.
The centering rod is introduced into the hole at the nose of
Refractories and Industrial Ceramics Vol. 49, No. 6, 2008
1083-4877/08/4906-0441 © 2008 Springer Science+Business Media, Inc.
ONPP Technology Group, Obninsk, Kaluga Region, Russia.
Fig. 1. Molding assembly for making
ceramic blanks by slip casting: 1 ) core;
2 ) porous mold; 3 ) blank.
Fig. 2. Molding assembly for producing
ceramic blanks from aqueous slip :
1 ) core; 2 ) porous mold; 3 ) supporting
flange for core; 4 ) elastic insert; 5) sphe