MOLD FILLING CHARACTERISTICS IN LOST FOAM CASTING PROCESS

A computer aided thermometric technique was used to study the mould fi lling characteristics in the lost foam casting process. The effect of melt temperature on the filling behaviour in plate castings was invest igated. Experiments were conducted at temperatures of 190, 490, 715, a nd 1115 degrees 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 studies. The re sults indicate that the filling behaviour is essentially governed by t he polymer degradation processes occurring at the metal front. The mel t temperature determines the rate of polymer degradation and hence has a substantial effect on fill characteristics. Top, bottom or side gat ing systems can be used to achieve relatively uniform filling of the m ould. The filling rate with polymethylmethacrylate patterns is lower t han with polystyrene patterns. Process parameters associated with the polymer pattern, including density, bead size, and degree of fusion, m ay have an appreciable effect on the filling behaviour.