An object-oriented support tool for the design of casting procedures

Abstract

The design of a casting system for a given shape depends to a great deal upon the skill of the engineer, who must make a number of decisions. Of prime importance in the formation of these decisions is the construction of the so-called modulus model of the shape, which gives a crude approximation to the dynamic cooling and freezing order of parts of the shape. Several computer-based modulus models as support tools for the engineer have been attempted, usually based on the superposition of a regular grid of cells on the shape, and iterative calculation of freezing, cell by cell. In this paper, an alternative approach is described which more closely models the engineer's expertise. There are two main elements to the expertise. First, a casting is systematically broken down into elements with known casting properties, and the suitability for casting based on the modulus model is applied to this assembly of elements. Second, is extensive knowledge of past cases (both sound and otherwise) of castings. There are advantages in an approach that models this engineering expertise, and which allows for a higher degree of interaction with, and early feedback to, the engineer. The system is naturally object-oriented, based on traditional classifications of shape elements which have evolved over many years in casting design. This classification also provides natural keys for a case-based reasoning system. Experience with a prototype system is described, and test results for a limited set of cases are discussed.