This paper on "Solidification Modelling to Optimise Castings Before Rapid Prototyping" was presented at the NAFEMS World Congress on Effective Engineering Analysis - 25-28 April 1999, Newport, Rhode Island, USA.

Summary

Over the past 15 years or so, the use of computers in foundry industries has steadily increased to speed practical applications and reduce time to market. We will present the experience of Institute Superior Tecnico of Lisbon in the application of finite difference method (FDM) to predict casting defects and to optimise casting geometry, riser size and/or placement, or process parameters, before applying rapid prototyping technology to manufacture conceptual design parts.
The paper will start by presenting new computational methods and technologies that are currently being integrated in Portuguese metal casting industry, mainly to reduce lead-time. Following are presented the FDM techniques to model and simulate casting solidification process for predicting the casting defects. The functions for analysis by simulation, as the critical fraction solid (CFS), the Niyama criterion that is the traditional thermal criterion for shrinkage prediction, and the material density function (MDF), are discussed in detail. The integration of FDM analyses to optimise cast parts prior to prototype or tool manufacturing stage in regard to conceptual design projects will be evaluated. The correlation between practical industrial application and the analysis methods will be presented, and the relative merits of testing and analysis reviewed.
The paper will conclude with recommendations for the appropriate use of computer analysis linked with rapid prototyping technology within the product design optimisation process, illustrating the success of the approach by using the FDM as an industrial case study.