Appendix I
ZCast Design Guide - 27
11.1.8 Ingates
The metal enters the mold cavity
through the ingates. Ingates typically
feed thicker sections of the casting,
which subsequently, feed thinner
sections. Thick sections, where the
metal will be slowest to cool, should be
allowed to feed thin sections that cool
more quickly and may freeze off before
the entire casting is filled. Sometimes it
is difficult to design a mold this way,
and for this reason (among others)
risers are sometimes placed between
the runner and the ingate.
11.1.9 Risers
A riser helps to feed the casting before
the whole thing solidifies, but it also
helps to minimize the shrinkage in the
casting by serving as a reservoir of
molten metal which can continue to
feed the casting as it begins to shrink.
The riser is typically cylindrical and
MUST stand as tall as the pouring cup.
Failure to do so will result in a
significant loss of material as the level
in the pouring cup reaches equilibrium
with the level at the risers.
Aluminum alloys require extensive use
of risers. Often more than one half of
the casting mass is in the risers!
For more on risering design see:
Basic principles of Gating and
Risering: AFS Cast Metals Institute
Principles of Mutual Casting: Heine & Rosenthal
Castings: John Campbell
ASM Mutuals Handbook, Volume 13
Runners
Ingates
Dirt traps
Casting
Figure 20: Runners lead out from the well. Ingates connect
the runners to the casting. Runners dead end at dirt traps.
Risers
Vents
Figure 21: Risers are often placed at the ingates, but
could be put anywhere. Vents are shown coming off
the high points. Their diameters are small, so they
will likely freeze off before they reach the upper
surface of the cope.
