The propagation and accumulation of dimensional shrinkage for ring-to-ring structure in investment casting

Abstract

The deformation of wax pattern and the solidification of the metal have the major influences on the final dimensions of casts in investment casting. However, the two main casting process steps and casting geometry affecting the dimensional shrinkage were not quantitatively studied. In this study, the dimensional shrinkage has been investigated with a ring-to-ring cast. The displacement of wax pattern and its corresponding casting are measured by 3D laser scanner, and the inner cavity dimensions of the ceramic shell are measured by industrial computerized tomography (ICT). The external diameter in outer ring is, on average, contracted with 0.849% in wax pattern and 2.559% for casting. A direct linear relationship of dimensions in outer ring is established between the wax patterns with its castings. The quantitative results show that the shrinkage of unconstrained dimensions is dominantly influenced by metal thermal contraction in casting process. The empirical analysis models developed could be employed and analyzed for the impact of casting geometry and process on dimensional changes in investment casting.