System
description
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2019-10-16
4
–32
Incomplete castings
Figure 29: incomplete castings
Cause
Remedy
Metal or flask too cold.
Please increase casting temperature. If the metal or
mould is too cold, the metal will freeze before complete-
ly filling the mould.
Improperly sprue.
The sprue system should be designed to allow the met-
al to enter easily and without restriction.
Incomplete burn out.
Increase the burn out time at 730 ºC. If the flask is not
properly burnt out it will be impermeable and not allow
gases to escape when the metal enters the mould.
Shrinkage porosity
Figure 30: shrinkage porosity
Cause
Remedy
Incorrect sprue.
Sprues should be attached to the heaviest piece of
the casting. There should be sufficient sprues to en-
sure the casting is adequately fed.
Flask temperature too low
and sprue is incorrect.
The flask temperature should be just hot enough to
achieve complete fill, according to the mass of the
casting material.
