Basic principles: Work
Program tables (see pages 27 - 29 and sep-
arate slides)
The program table on page 27 contains all
necessary data for automatic casting of a BEGO
alloy. Every alloy is assigned to a separate program
location. These program locations are called up by
the caster.
BEGO alloys are stored at program locations 111 to
197. Program locations 001 to 030 are available for
non-BEGO alloys. These program locations must
be provided with data (see page 26).
Casting and preheating temperatures
The casting temperatures indicated for BEGO alloys
in the program tables apply to the standard wax-ups
described in this operating manual. Because of the
numerous parameters that influence the casting
result, these casting temperatures can only be
regarded as reference values.
It is very important to provide for an adequately
preheated mould which is not placed in the machine
until just before melting in order to minimize cooling.
The preheating temperatures given in the operating
manual should be complied with, even if casting has
been carried out successfully thus far at low mould
preheating temperatures. Due to automatic casting
at an optimal casting temperature, a mould that is
too cool may cause the melt to harden prematurely
whereas this could be compensated for by means of
a higher casting temperature in manual casting.
Crucible inserts
To melt special groups of alloys, it is necessary to
put in a graphite or glassy carbon insert in addition
to the ceramic crucible (see program tables). In
principle, the glassy carbon insert can be used
instead of the graphite insert. It has a significantly
longer service life than the graphite insert. The alloy
is then indirectly heated via the hot graphite insert.
To ensure that all alloy components have reached
the casting temperature, preheating is carried out
up to the liquidus point (the melt becomes liquid).
Furthermore, the casting temperature is maintained
for a certain time during melting before readiness for
casting is indicated.
Alloys with a high palladium content are cast without
a crucible insert as a rule. If alloy laminae line up
during heating and are therefore not heated
adequately (failure to "couple" to the induction field),
an insert can be used:
a graphite insert in the case of palladium content
less than 35%, a glassy carbon insert that reliably
prevents the inclusion of carbon in the case of
palladium content over 35%.
Graphite inserts wear out due tu use and have to
be replaced in time!Worn graphite inserts can be
recognized by their weight (graphite ~ 6 g, glassy
carbon ~ 5 g), but also by the fact that the temper-
ature increase takes place more slowly from
casting to casting during the melting process.
The casting temperature can no longer be
reached with worn graphite inserts!
Graphite inserts are sensitive to impact and must
only be used in flawless condition. Particularly
cracks lead to abortion of the casting process.
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