Edinburgh Napier University

  This research envisages an automated system to inform engineers when opportunities occur to use existing features or configurations during the development of new products. Such a system could be termed a `predictive CAD system' because it would be able to suggest feature choices that follow patterns established in existing products. The predictive CAD literature largely focuses on predicting components for assemblies using 3D solid models. In contrast,
this research work focuses on feature-based predictive CAD system using B-rep models. This paper investigates the performance of predictive models that could enable the creation of such an intelligent CAD system by assessing three different methods to support inference: sequential, machine learning or probabilistic methods using N-Grams, Neural Networks (NN) and Bayesian Networks (BN) as representative of these methods.
After defining the functional properties that characterise a predictive design system a generic development methodology is presented. The methodology is used to carry out a systematic assessment of the relative performance of three methods each used to predict the diameter value of the next hole and boss feature type being added during the design of a hydraulic valve body.
Evaluating predictive performance; providing five recommendations (k=5) for hole or boss features as a new design was developed, recall@k increased from around 30% to 50% and precision@ k from around 50% to 70% as one to three features were added. The results indicate that the Bayesian and Neural Network models perform better than those using N-Grams. The practical impact of this contribution is assessed using a prototype (implemented as an extension to a commercial CAD system) by engineers whose comments defined an agenda for ongoing research in this area.