User manual

Appendix I
ZCast Design Guide - 20
6.4 Stiffening Ribs
Increase the strength of your mold with the addition of stiffening ribs. You can use the Make
Fixture
2
functionality in the ZPrint software, or you can create a rib lattice in your CAD system of
choice. In either case, rib thickness should be roughly one half inch (0.5 in or 13 mm) in
thickness. Rib spacing is subjective. However, as a guideline, distances greater than four (4)
inches (102 mm) should not be spanned without placing a rib in between walls or adjacent ribs.
NOTICE
Spacing ribs more than four inches is not recommended because of
possible part deformation during the molten metal process.
6.5 Venting
Perhaps the most important
concept in ZCast mold design is
venting. The mold must be
properly vented to avoid entrapping
gases in the cast part, and more
importantly, to avoid violent release
of gases through the molten metal.
For those familiar with traditional
sand casting, it will be observed
that a ZCast mold (even when
properly vented) may smoke more
than conventional foundry sands.
Vents can be small holes (usually
at high points in the casting)
extending through the cope to the
atmosphere. These are often small enough (0.125 in or 3 mm is recommended) to freeze off
before the metal reaches the exterior of the mold.
Vents also must be used in cores (Figure 9). When molten metal comes in contact with ZCast
compounds, out-gassing occurs. If the cores are solid, the gas would have nowhere to go but
2
For more detail, attend online ZCast Design Guide seminar or refer to the ZPrint software help section
Figure 7: Addition of
stiffening ribs printed in the
shelled mold