INCREASE IN THE SERVICE LIFE OF FORMING SURFACES
OF MOLDING UNITS. PART 2. STUDY OF THE EFFECT
OF OPERATING PROPERTIES OF MOLDING UNITS
ON THEIR OPERATING LIFE
E. I. Suzdal’tsev,
D. V. Kharitonov,
and A. A. Anashkina
Translated from Novye Ogneupory, No. 3, pp. 35 – 38, March 2010.
Original article submitted October 27, 2009.
The effect is considered of such operating properties as the design of a molding unit and the method of drying
gypsum molds, on the life of the forming surface of molding units. Avoidance of the disadvantages revealed
combined with results obtained in part 1
of this work make it possible to increase the service life of molds by
more than a factor of three
Keywords: gypsum, porous mold, molding unit, mold drying.
Apart from starting raw material quality, the operating
characteristics of molding units affect the service life of gyp-
sum molds, and this is confirmed by analyzing the operation
of a mold manufactured from high quality German gypsum.
Studies have shown that in spite of the best quality gypsum
the service life of a mold increased in all by 50% (from 12 to
The main criterion by which the degree of inadequacy is
assessed is presence of cracks within its working surface
(Fig. 1). As a result of work carried out, two main operating
factors were established with a capacity to lead to the occur
rence of this class of defects: mold design and its drying re
EFFECT OF MOLD DESIGN
In order to prepare large complexly shaped preforms by
slip casting molds are used whose general form is presented
in Fig. 2. The mold consists of the following main parts: a
perforated metal frame 1, within which there is a gypsum
casting 2, copying the outer profile of a preform; an upper
support flange 3 and a lower flange 4.
By analyzing the nature of crack distribution (see Fig. 1)
it is possible to note that almost all of them start from the
boundary of the gypsum with the metal support flange and
then propagate through the mold surface. The main reason
for this crack propagation in our opinion is the groove in the
lower part of the support flange (see Fig. 2, position 5 ) made
by the intention of designers to function as a key for securing
gypsum. The situation is aggravated by the fact that tradi
tionally the forming surface of a gypsum mold is prepared as
Refractories and Industrial Ceramics Vol. 51, No. 2, 2010
1083-4877/10/5102-0095 © 2010 Springer Science+Business Media, Inc.
FGUP ONPP Tekhnologiya, Obninsk, Kaluga Region, Russia.
E. I. Sudal’tsev, D. V. Kharitonov, and A. A. Anashkina, “In
crease in the service life of forming surfaces of molding units.
Part 1. Study of the improvement of molding unit forming surface
material quality,” Novye Ogneupory, No. 2, 30 – 38 (2010).
Fig. 1. Example of crack propagation in the working surface of a