Appendix I
ZCast Design Guide - 22
7 Mold Preparation
After the mold is designed and printed in a Z Corporation 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 180°C (350°F) to
230°C (400°F) 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.
Final Depowder – Immediately prior to pouring, gently rub the mold surface to
knock off any loose material and blow dust away with compressed air.
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.
Clamp – Carefully close the mold with the cores in place. Clamp with C – clamps or
similar and orient in the proper direction for pouring. Attach pouring cups and
risers if necessary (use core paste to glue in place).
Pour – The mold is now ready for metal.
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