Recent innovations in the development of the "Policast" evaporative pattern process

Abstract

The Policast foundry process employs gasifiable expanded polystyrene patterns buried in loose sand and has already been introduced on the industrial scale. Research has therefore been concentrated on those of its features that are still open to further improvement, though satisfactory for the needs of high-volume manufacturing. Its aim is to reduce fabrication costs, improve product quality and make the process as a whole more reliable. Three of the innovations devised and perfected for this purpose are described. The first relates to a new procedure for making the metal tools used to mould the polystyrene foam patterns, based on electroforming, i. e. the electrodeposition of metals on suitably shaped supports that have been rendered conducting. The second innovation relates to a new system for the spheroidization of cast iron. This is carried out in special small ladles located outside the mould. Even so, it is similar in concept, and in terms of quality and yield, to in-mould spheroidization. In addition It is not specific to the Policast process, but can be adapted to any automatic pouring line It is particularly effective in overcoming certain constraints associated with Policast. The third innovation consists of the array of systems used for the instrumental checking of the most critical stage of the Policast process, namely compaction of the sand. These are systems and processes suitable for both on-line checking and experiments in the work-up of new castings.