MODELS SHOULD BE DESIGNED FOR CASTING IN PLACE. Model makers must make allowances for shrinkage factors in rubber molds and waxes. The settings should have pre-knotched prongs and /or channel seats to allow the stones to be snapped into place and hold them securely. Using existing models for gemstone in place casting often results in loose fitting gemstones and fill problems due to inadequate sprues.
LARGER SPRUES ARE NEEDED for casting gemstones in place. The gemstones will chill molten metal during the cast and a well thought out sprue system is necessary to avoid shrinkage in stone set areas. Often a multiple sprue system will be needed to properly feed molten metal to the casting. A 10, 2 & 6 O’clock sprue system may be needed on certain designs to provide adequate fill of the casting.