Method for the production of negative form

摘要

Two-part negative moulds for coreless moulding are formed using patterns which (as a consequence of their outer shape) cannot be separated from the mould in a straightforward, simple manner. Parts of the model preventing separation of the mould are removed; these parts are replaced by parts with an identical shape made of a material which during casting of the mould is neither deformed nor separated from the pattern. The material of the replaced pattern parts remains sufficiently soft not to damage the mould in the pattern removal process. As a consequence of the opposite effects of shrinkage of the moulding and expansion of the negative mould, a clearance (of the order of 5% in the case of clay mouldings) is produced which makes mould separation possible. The mould itself is also claimed.