Thermal dilatation in functional tolerancing

Functional tolerancing is classically based onto dimension chains to respect functional requirements. Tolerance synthesis deals with dimensions optimization in order to maximize tolerances. This method is classically used taking into account only geometrical defaults. Mechanisms concerned with significant variation of temperature in different stages of functioning, require taking into account thermal expansion. This expansion has a direct impact onto clearances and dimensions of the mechanism. The purpose of this paper is to consider thermal expansion of parts integrated within functional tolerancing. In particular, this paper will compare the effects of tolerancing, thermal expansion and uncertainties of temperature in order to know if uncertainties must be included in the tolerance chain or can be neglected as second order. A basic experimental mechanism is used to show this method and the differences between the two approaches.