  Variational design is a well-recognized CAD technique due to the increased
design efficiency. It often presents as a parametric family of CAD models.
Although effective, this way of working cannot handle design requirements that
go beyond parametric changes. Such design requirements are not uncommon today
due to the increasing popularity of product customization. In particular, there
is often a need for designing a new model out of an existing structural family
of models, which share a structural pattern but have individually varied detail
features. To facilitate such design requirements, a new method is presented in
this paper. The idea is to express the underlying structural pattern in terms
of a submodel composed of the maximum common design features of the family, and
then to build a single master model by attaching to the submodel all detail
design features in the family. This master model is a representative model for
the family and contains all the features. By removing unwanted detail features
and adding new features, the master model can be easily adapted into a new
design, while keeping aligned with the family, structurally. Effectiveness of
this method has been validated by a series of case studies and comparisons of
increasing complexity.
