A digraphic approach for dimensional chain identification in design and manufacturing

In order to determine working dimensions and tolerances of a process plan, a tolerance chart is often employed. Dimensional chain identification is a necessary step in the tolerance charting procedures. This paper presents a digraphic representation for the tolerance chart. Two directed trees are generated from working dimensions, blueprint dimensions and stock removals of the tolerance chart. These trees are then used to identify dimensional chains in order to find the relationships among the design and manufacturing dimensions. Furthermore, the concept of a reverse dimensional chain is introduced. The reverse dimensional chains can also be identified from the directed trees. The relationship between the forward and reverse dimensional chains is also discussed. Finally, the applications of dimensional chains to the determination of the working dimensions and tolerances are briefly described.