Application of screw theory to constraint analysis of mechanical assemblies joined by features

Screw Theory is used to provide mathematical models of assembly features, allowing the determination of positioning constraints imposed on one part in an assembly by another part based on the geometry of the features that join them. Several feature types have been modeled, and it is easy to model new ones. A user of this theory is able to combine members of this set to join two parts and the determine whether or not the defined features set over-, under-, or fully-constrains the location and orientation of the part. The ability to calculate the state of constraints of parts in an assembly is useful in supporting quantitative design of properly constrained assemblies in CAD systems. Locational over-constraint of parts can lead to assemble ability problems or require deformation of parts in order to complete the assembly.