The assembly model is created graphically by adding symbols at selected locations on an existing CAD model of the assembly. The first task is to define a local coordinate system for each part. Diagram showing the location of the part DRFs. DRFs are the local coordinate systems in each part. Datum selection determines which dimensions contribute to assembly variation.
Datums also influence how parts are fixtured for production and inspection.
The DRFs for the hub and the ring are located at the same coordinates. The modeler will place the DRF labels on top of each other. This makes it necessary to use the zoom function to ensure the correct DRF is selected for each joint. 2.5 Kinematic Joints Kinematic joints describe the degrees of freedom within the assembly, i.e. the small adjustments that occur between mating parts to accommodate manufacturing variations. The kinematic variations CATS solves for are these degrees of freedom that exist in the different joint types.