Mould filling characteristics in lost foam casting process

Abstract

A computer aided thermometric technique was used to study the mould filling characteristics in the lost foam casting process. The effect of melt temperature on the filling behaviour in plate castings was investigated. Experiments were conducted at temperatures of 190, 490, 715, and 1115° C. The effects of polymer chemistry and density on the filling behaviour were determined. The influence of gating system and ingate cross-section on the filling patterns was also studied. The results indicate that the filling behaviour is essentially governed by the polymer degradation processes occurring at the metal front. The melt temperature determines the rate of polymer degradation and hence has a substantial effect on fill characteristics. Top, bottom, or side gating systems can be used to achieve relatively uniform filling of the mould. The filling rate with polymethylmethacrylate patterns is lower than with polystyrene patterns. Process parameters associated with the polymer pattern, including density, bead size, and degree of fusion, may have an appreciable effect on the filling behaviour.