A matrix approach to the representation of tolerance zones and clearances

This paper presents a matrix approach coupled to the notion of constraints for the representation of tolerance zones within CAD/CAM (computer-aided design and manufacture) systems. The proposed theory, reproduces themeasurable ornon-invariant displacements associated with various types of tolerance zone. This is done using the homogeneous transforms commonly associated with robotic modelling.This matrix representation is completed by a set of inequalities defining the bounds of the tolerance zones. Moreover, the generation of the model and its mathematical definition allows for its use in the representation of clearances and for the computation of tolerance transfer. An example illustrates the application of the model to a simplified gear pump mechanism.