A framework for extendable freeform surface feature modelling

Abstract

The need for more efficient freeform feature modelling cannot be overemphasized. Freeform shapes are applied in many areas, including automotive and aerospace industries. In these applications, precise design functions need to be reflected in the final product. This requires advanced freeform feature models that are extendable and that provide sophisticated, yet user-friendly facilities, such as user-defined freeform features, intuitive parameters and effective constraints to guarantee model consistency. This paper extends, in a new framework, two aspects of freeform surface feature modelling: design of features and design by features. Design of features includes creation of new user-defined freeform surface features and their management. This functionality is supported by the freeform feature library management system, which enables the user to create new feature class definitions. Design by features is supported by a new freeform surface feature model, which extends the usual two-level parametric model structure with a third, intermediate level, called the partially evaluated model. Its capability to explicitly capture feature interactions, and support for intuitive attachment of features and parameters in the model, enables the new feature model to be extendable with, for example, new parameters. Curve parameters enable intuitive shape manipulation according to declared constraints. A running example model is used to demonstrate design of features and design by features, which includes advanced model variation.