Shell moulds mfr. using thin facing sand layer - and backing layer of coarse sand only contg. small amt. of resin

摘要

Process for mfg. shell moulds for foundries are mfd. by applying a mixt. of sand and resin to a hot pattern. Two successive mixts. of sand and resin are used to form the shell, the first mixt. consisting of a fine sand with a high percentage of resin which is applied to the pattern to make a thin shell, after which a second mixt. of coarser sand contg. a smaller amt. of resin is used to obt. the required thickness of the shell mould. The time and temp. are pref. controlled in the first stage so only a thin shell is obtd., and the pref. machine uses two dump-boxes for the two mixes, or a box divided into two compartments. An expensive mixt. of fine sand and a high resin content is only used for a very thin shell so the mfg. costs are reduced.