Influence of temperature conditions on the shrinkage of wax patterns for investment casting

Abstract

The study of free linear shrinkage of unfilled (PS50-50, MBC 3-T, Romocast 105, Romocast 152) and filled (Romocast 252, Romocast 325) model compositions for investment casting depending on the ambient temperature was carried out. It has been shown that unfilled model compositions have the greatest free linear shrinkage, and filled ones have the smallest. Moreover, the processes associated with free linear shrinkage proceeded in the samples for a long time (up to 24 h). This is probably caused by the duration of the polymerization processes and the low thermal conductivity of the model compositions. A change in the ambient temperature in the range from –5 to +35 °C has a significant effect on the linear dimensions of the samples from the studied model compositions. The length of samples from unfilled model compositions varies from +0.3 to –0.4%, and from filled ones from +0.2 to –0.15%. When samples from unfilled compositions cooled to –5 °C and subsequently heated to +20 °C, their initial length decreases on average by 0.2 mm, and at heating to +35 °C and subsequent cooling to +20 °C, it increases on average by 0.2–0.3 mm. At similar changes in ambient temperature, the dimensional change of samples from filled model compositions is not more than 0.1 mm.