In modelling flexure based mechanisms, generally flexures are modelled perfectly aligned and nominal values are assumed for the dimensions. To test the validity of these assumptions for a two Degrees Of Freedom (DOF) large stroke compliant mechanism, eigenfrequency and mode shape measurements are compared to results obtained with a flexible multibody model. The mechanism consists of eleven cross flexures and seven interconnecting bodies. From the measurements 30% lower eigenfrequencies are observed than those obtained with the model. With a simplified model, it is demonstrated that these differences can be attributed to wrongly assumed leaf spring thickness and misalignment of the leaf springs in the cross flexures. These manufacturing tolerances thus significantly affect the behaviour of the two DOF mechanism, even though it was designed using the exact constraint design principle. This design principle avoids overconstraints to limit internal stresses due to manufacturing tolerances, yet this paper shows clearly that manufacturing imperfections can still result in significantly different dynamic behaviour.

The studied collecting electrodes for electrostatic precipitators are cold-rolled formed. Here Sigma 750 open section was manufactured of DC01 steel grade. Length of the electrodes ranged from 8 to 13 meters, all were thin-walled of 1.5 mm. Tolerance of their manufacture is strictly set. A database of material properties, chemical composition, and a set of final tolerance of manufactured profiles has been collected. At first basic statistics for the data has been done. Finally statistical relation between the material composition and profile geometrical tolerance has been studied, next between the material mechanical properties and profile geometrical tolerance has been examined.