Geometric and static conditions of assembly

A table with three uneven legs standing on an uneven floor is a good example of static determination. We can determine the reactions of the legs for arbitrary loading for the table by using the laws of statics. The assembly of that statically determinate table/floor couple is without problems. The table with four legs is at once overdeterminated. Overdetermination is, for example, the four‐throw crankshaft lying not on two, but on four bearings. The correct assembly of such a crankshaft needs very high precision in manufacturing and supplementary assembly. This article deals with the influence of static overdetermination on the requirements of the precision of parts and on the supplementary fitting work of assembly. The article is linked to the author’s former article “Knowing your orientation” (Assembly Automation, Vol. 16 No. 2, 1996). The aim of both articles is to build up a theoretical base of DFA science.