Constraints Automatic Relaxation to Design Products with Fully Free Form Features

Abstract

Feature-based approaches have become popular for the design of products and more widely for the complete product lifecycle management. The geometric model being often used as an intermediate object shared between the different actors of the design process, it is crucial to concentrate on the definition of very powerful tools enabling fast and intuitive definitions/modifications of the product geometry. In this field, we have already proposed the so-called Fully Free Form Deformation Features. They correspond to parts of a free form surface obtained by deformation according to specific constraints and deformation behaviours. Two main control parameters are used: the constraint lines that define both the main directions and the extent of the shape, and the surface behaviours between these lines. Unfortunately, undesirable surface undulations may appear at the end of the constraint lines. This is due to the uncertainty the designer has when defining the blending areas between the different constraint lines. To provide a user-friendly tool, which does not force the user to be very precise, the possibility to relax automatically the end points of the constraint lines is offered. This algorithm is based on an a priori quality criterion which limits the number of inflexion points of auxiliary curves that mimic the shape of the future deformed surface. Once the curvature criterion is satisfied on the curves, the surface deformation process can start while considering the restricted area of the constraint lines.