Evaluation of the lost foam process in terms of casting dimensional accuracy and ecology

The paper discusses some of the major issues that are related with the use of polystyrene foam (of the density above 1,04 /cm3) in the manufacture of investment castings characterised by intricate shapes. Test patterns were made from the high impact polystyrene and from styrene polymers (styrene acrylonitrile SAN). The process of polystyrene patterns removal from ceramic moulds considerably reduces the quality of these moulds in terms of surface microgeometry and dimensional accuracy of castings. The results of the studies can find practical application in the manufacture of near-net-shape castings for industrial applications as well as prototype castings. They may also serve as a tool in evaluation of the rapid prototyping process using polystyrene foam and polymers in the manufacture of investment castings characterised by high dimensional accuracy. The said technology has also been estimated in terms of its impact on the natural environment, taking into consideration the energy consumption during castings manufacture and their later use. It is possible to further improve the casting accuracy, raising it from class CT7 to CT6 according to Polish Standard PN [5].