I n the highly competitive auto ndustry, increasingly it is design that differentiates a vehicle from its rivals and manufacturers are under continual pressure to accelerate design development. Design is inherently an iterative process. As a vehicle design matures; increasing levels of feasibility are introduced and the ' master model' shifts from physical clay to virtual CAD with frequent refinement of the vehicle form. So what can be done to accelerate the design process? Feature- Based modelling For years, Mechanical Design has used parametric software that stores commands ( such as Extrudes and Blends) as features in the Part History. This allows users to quickly generate and modify data via rules or parameters. Until now, it has been widely perceived this approach is not practical for the creation of freeform organic shapes found in automotive-surface design. Historically vehicle surface data has been designed on specialist stand- alone software with changes to the vehicle form resulting ON the surface By Simon Alford, Siemens PLM Software How feature- based modelling can speed automotive design
in lengthy CAD re- work. Deleting and recreating data was often the only feasible route forward. NX Industrial Design software leverages parametric features for freeform designs. Users enter parameters to control values, assign associative constraints and choose when to store features to control model complexity. The result is modifications are propagated throughout the entire Part file. The benefits Given the same reference data, Class- A designers typically produce different results. But because Class- A surfacing is procedural each designer will have repeatedly used lengthy sequences of common commands. By storing these commands as features in the Part file History, the user can ' roll- back' in time to change a feature and the model will subsequently update. Editing the Part History and re- using data effectively eliminates the delete/ re- create cycle that significantly erodes design cycle times. Furthermore, recognizing Class- A surfacing is procedural NX combines lengthy manual construction procedures into single features ( such as styled blends, sweeps and corners) to provide embedded design " sculpting" directly inside of features. Features can also provide alternative themes for a model - a common requirement of Design for all industries. Traditionally, designers modify a copy of the part. However in NX, features can simply be added to the part and grouped together preserving the underlying geometry. In design reviews, these feature ' groups' can be toggled ON / OFF to illustrate alternative design solutions. Features also assist in recognizing the ' cause and effect' of change to a model e. g. surface boundary changes during initial creation and the refinement of surface highlights near completion.