Aluminium Casting Alloys - Aleris

The minimum values are also dependent
on the casting alloy and the elongation of
the casting. In pressure die casting, the
minimum wall thickness also depends
on the position of and distance to the
gate system.
Generally speaking, the wall thickness
should be as thin as possible and only
as thick as necessary. With increasing
wall thickness, the specifi c strength of
the cast structure deteriorates.
Determining casting-compliant wall
thicknesses also means, especially with
sand and gravity die casting, that the die
must fi rst of all be fi lled perfectly. During
subsequent solidifi cation, a dense cast
structure can only occur if the shrinkage
is offset by feeding from liquid melt. Here,
a wall thickness extending upwards as a
connection to the riser may be necessary.
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Aluminium Casting Alloys
Another possible way of avoiding material
accumulations is to loosen the nodes.
At points where fi ns cross, a mass accumulation
can be prevented by staggering
the wall layout.
The corners where walls or fi ns meet
should be provided with as large transi-
tions as possible. Where walls of different
thickness meet, the transitions should
be casting-compliant.
Where the casting size and process
permit, bores should be pre-cast. This
improves the cross-section ratio and
structural quality.
Apart from the points referred to above,
a good design also takes account of
practical points and decorative appear-
ance as well as the work procedures
and machining which follow the actual
casting operation.
Fettling the casting, i.e. removing the
riser and feeders, must be carried out as
effi ciently as possible. Grinding should
be avoided where possible. Reworking
and machining should also be easy to
carry out. Machining allowances are to
be kept as small as possible.
Essential inspections or quality tests
should be facilitated by constructive
measures.