DEVELOPMENT OF A METHOD FOR MONITORING
THE COMPLETION OF ASSEMBLY OF CERAMIC BILLETS
DURING MOLDING FROM AQUEOUS SLIPS IN GYPSUM MOLDS
E. I. Suzdal’tsev,
D. V. Kharitonov,
and A. V. Dmitriev
Translated from Novye Ogneupory, No. 6, pp. 46 – 50, June 2008.
Original article submitted August 14, 2007.
A method and a device are proposed providing continuous monitoring for assembly of ceramic billets.
The suggested system makes it possible to monitor objectively fulfilment of the requirements of a production
process that ultimately reduces scrap in preparing ceramic billets from aqueous slips.
In the production process for manufacturing large
complex shaped ceramic objects a most critical production
operation is molding ceramic billets by slip casting. During
slip casting there is pouring of aqueous slip into the cavity of
a porous mold made of hygroscopic material (gypsum) and
retention within it for a certain period of time. Formation of a
billet is accomplished due to capillary suction forces of the
mold material that gives rise of movement of liquid phase
towards the mold wall; here together with the liquid over the
direction towards the mold wall there is also movement of
slip solid particles. The liquid accumulates in pores of the
mold, and solid particles settle and are packed at the walls
gradually forming an enlarging layer.
One of the main problems in molding ceramic objects
from aqueous slips is correct determination of the instant of
completion of the assembly, since errors often lead to billet
scrap. The main form of scrap is related to incomplete
assembly of billets due to early breakdown of the mold which
in turn leads to an insufficient allowance for subsequent
operations (machining), and holding an entirely assembled
billet in the mold which often leads to billet shrinkage on the
rigid core, and as a rule to breakage.
In spite of the fact that slip casting for large ceramic
billets has been used extensively since the 1960 – 1970s, up
to now in order to solve this problem nothing better has been
proposed than poking the assembled billet though the
feeding unit with a metal rod. As the practice of use of a
metal rod has shown, it not only does not provide sufficient
precision for determining the end of billet assembly, but it
has one marked disadvantage, i.e. in case of incomplete billet
assembly loading with a metal rod causes structuring of the
suspension in the mold cavity forming a different density
through the material thickness, development of microcracks,
other billet defects (Fig. 1), and scrap in the stages of molding,
heat treatment and even machining. Therefore development
of an efficient monitoring system for assembly of ceramic
billets during slip casting from aqueous slips is an important
In molding a large number of different large complexly
shaped ceramic billets from slips of different chemical
composition it was noted that the amount of diminution in
slip in the pourer for each specific article is almost un
changed. This is due to the fact that a reduction in slip
volume in the mold cavity during billet molding only
depends on slip parameters and the specific volume of slip
required for filling the casting mold, which for each specific
object is a constant value. Thus, knowing the amount of slip
Refractories and Industrial Ceramics Vol. 49, No. 4, 2008
1083-4877/08/4904-0286 © 2008 Springer Science+Business Media, Inc.
FGUP ONPP Tekhnologiya, Russia.
Fig. 1. Defects caused by poking a billet with a metal rod through