Fettling noble metal castings, esp. jewellery or dental prostheses - where gypsum cluster moulds are clamped on drum rotated in liq. contg. abrasive, esp. glass beads

摘要

Castings are made as a cluster in a gypsum mould via centrifugal casting; and the mould is clamped to a drum rotating rapidly in a tank contg. a suspension of abrasive mineral particles in a liq., so all the gypsum is removed from the cluster. Pref. tank contains a drum made of a circular row of bars mounted between two discs and rotated, pref. with oscillation. Rubber straps ending in hooks are pref. used to clamp the moulds onto the drum bars; and the liq. in the tank is pref. at pH 8.5, contg. glass beads of size 50-100 mu and 300-400 mu as the abrasive. All the mould residues are removed, leaving clean, bright castings.