User manual

Appendix I
ZCast Design Guide - 21
into the metal. When gas passes through the metal as it cools, it can be trapped, forming pockets
called porosity. To avoid this, the cores can be hollowed with the hollow sections vented through
the core print to the outside of the mold. It is important to keep the venting path away from the
metal path.
WARNING
Inadequate venting in the mold or core can lead to the
unexpected release of entrapped gases and molten metal
causing personal injury during metal casting. Venting paths
in the mold must be arranged and directed away from the
metal path to avoid entrapment of gases.
WARNING
Do not handle molten metal without adequate local exhaust
ventilation. Hot gases emitted by during the casting process
can burn skin and are irritating and toxic. Refer to the ZCast
501 powder MSDS for more information.
6.5.1 Venting Cores
Follow these guidelines to obtain best results when designing vents for your cores:
• The cores should be shelled in by
approximately 0.25 in (6.35 mm)
wall thickness where possible.
• Any single wall of the core should
be no thicker than 0.5 in (13 mm),
or thinner than 0.14 in (3.5 mm).
Very slender cores with thinner
walls are possible over short
lengths, distortion will limit how
long they can be.
• The core vents should continue
through the mold walls and out to
the atmosphere. This should typically be done
through the core print, as far away from the
parting lines as possible (to limit the possibility of metal leakage).
• Depowdering heavily contoured core vents can be a challenge if 0.12 in (3 mm) diameter
vents curve into a tight radius.
CAUTION
Vents not located in the core, vents too close to parting
lines, or vents that break through to the casting surface may
leak molten metal and cause personal injury. Locate vents
in the core, away from the casting surface, and as far as
possible from parting lines.
Figure 9: Venting the core