Finite Element Analysis of Solidification in Rapid Freeze Prototyping

Rapid freeze prototyping (RFP) can generate three-dimensional ice patterns from computer-aided design (CAD) models by depositing and solidifying water droplets layer by layer. One important issue of the RFP process is how to fabricate the ice pattern to desired accuracy in an acceptable short time. The waiting time between two successive layers is a critical factor. A waiting time that is too short will lead to unacceptable part accuracy, while a waiting time that is too long will lead to an excessive build time. Finite element analysis is employed in this study to predict the solidification time of a newly deposited water layer and to develop a better understanding of heat transfer during the RFP process. ANSYS Parametric Development Language (APDL) is utilized to develop software for the prediction of solidification time. The result is used to investigate the effect of various process parameters on the solidification time of an ice column and a vertical ice wall. These parameters include environment temperature, heat convection coefficient, initial water droplet temperature, layer thickness, and waiting time between two successive layers. Experiments are conducted and the measured results are shown to agree well with simulation results.