User manual

Appendix I
ZCast Design Guide - 31
7 Mold Preparation
After the mold is designed and printed in a Z Corp. 3D Printer, there are only a few necessary
steps before you are ready to pour metal:
Mold Wash – Mold wash is used in traditional sand casting to improve the surface
finish of the castings. It is typically a suspension of silica or other refractory materials,
which can be sprayed, brushed or used as a dip to coat the surface of the mold and
cores. It can improve the surface finish of a part to between 60 and 120 RMS. It should
be used with caution. The surface can be built up too much causing unevenness and
flaking. Follow the mold wash manufacturer’s instructions regarding the drying
requirements for such products.
Bake – MOLDS MUST BE BAKED PRIOR TO POURING. A ZCast mold in its
untreated (raw) state contains about 10% moisture per unit weight. Casting molten metal
against untreated material releases large amounts of steam and smoke. To use the
ZCast mold properly, it MUST
be baked in an oven from 350°F (180°C) to 400°F
(230
°C) for between 4 and 8 hours (depending on volume), until it is “bone” dry, and
preferably medium-brown in color on all cavity surfaces that contact molten metal.
THERE WILL BE SMOKE GENERATED WHEN BAKING ZCAST MOLDS;
THEREFORE, THE OVEN MUST BE PROPERLY VENTED.
CAUTION
Bake ZCast molds until all moisture is removed before metal
casting. Residual moisture in the mold can cause the mold
to unexpectedly fail, releasing entrapped gases and molten
metal and causing serious personal injury.
CAUTION
Do not bake ZCast molds in unvented ovens. Irritating and
toxic fumes are formed at elevated temperatures during
oven baking. Ovens must be vented to the outside. Refer to
the ZCast 501 powder MSDS for more information on the
irritating and toxic fumes.
Final Depowder – Immediately prior to pouring, gently rub the mold surface to
knock off any loose material and blow dust away with compressed air.
CAUTION
Depowdering with compressed air will generate airborne
particles. Only trained or supervised individuals should
depowder a mold. Use hood ventilation and safety goggles
or faceshield to protect the eyes and face. Refer to the
ZCast 501 powder MSDS for more information.
Seal – Run a bead of core paste around the parting surfaces to prevent metal from
leaking out of the mold during pouring. Use caution not to block vents.
CAUTION
Do not cast metal parts in molds with multiple sections
without core paste or adhesive. Molten metal may leak from
the mold seams and cause personal injury. Avoid blocking
vents with paste or adhesive.