There is increasing use of computer aided design (CAD) systems for i mechanical design. They make it convenient to present drawings in 3D to the designer, and hence offer a better view of parts mating together at assembly. Parts are drawn in CAD to nominal dimensions and can be checked for interference, using extreme case tolerances.
Not all CAD systems can be used for tolerance analysis; some of the mechanical parts can be created using different CAD system formats, and cannot be mated together as an assembly on master CAD screens without the use of expensive translators. Tolerance analysis involves the understanding of the functionality of the product and knowledge of the processes that are used in making the parts. Even if the CAD system has been used for making the prototypes, and parts were mated successfully at that stage, a separate tolerance analysis study should be done to ensure high quality in production.