Characterization of Thin Flexure Hinges for Precision Applications Based on First Eigenfrequency

Flexure hinges with small cross-section heights are state of the art in numerous precision engineering applications due to their capability for smooth and repeatable motion. However, the high sensitivity to manufacturing influences represents a challenge. We propose a characterization method for flexure hinges based on the measurement of the free oscillation, to enable the consideration of manufacturing influences in the early stages of the design process. Three semi-circular flexure hinges with different cross-section heights and highly accurate geometry were investigated experimentally to compare them with three theoretical modeling approaches. The results for the three flexure hinge specimens showed small deviations to the predicted values from the models which is in agreement with the results of dimensional measurements. With each modeling approach, a deviation of the minimal notch height from the nominal value can be calculated. This value, in turn, can be used as manufacturing allowance for subsequent manufacturing of compliant mechanisms using the same manufacturing method. An exemplary compliant parallel-crank mechanism proves the applicability of the concept to compliant mechanisms with multiple flexure hinges.