Design of an origami-inspired leaf flexure as an alternative to classical 2D flexures

Abstract

Compliant mechanisms are often used in precision mechanism design as a suspension for translational stages. Their light weight makes them efficient and they do not suffer from friction or backlash. They transmit and transform a finite motion along their degrees of freedom via elastic deformation and provide high stiffness along their degrees of constraint.
However, when they deflect the load bearing capacity in the degrees of constraint reduces considerably due to the risk of buckling induced by off-axis loading. Flexures are made thicker to prevail this phenomenon, but this also results in an increased actuation stiffness and ultimately a reduction in efficiency in their degrees of freedom. In this paper, a new concept is presented based on origami folding principles that exhibits a smaller decrease in support stiffness when it is deflected out of plane. On a conventional leaf flexure, a crease pattern is drawn based on compliant origami-inspired degree-4 joints. To make the origami-inspired leaf flexure out of metal lamina emergent mechanisms (LEM) are used for the crease lines. The prototype is analysed using a FE model which is validated by an experiment. Subsequently, a sensitivity analysis is performed on four characteristic design parameters. The results show that this new origami-inspired leaf flexure with $L = 65mm, w = 40 mm$ and $t = 0.30mm$ made of AISI 1.4301 stainless steel maintains 80.2 $\%$ of its initial support stiffness for a deflection of $y = 3mm$ compared to 36.9 $\%$ for a conventional leaf flexure with the same outside dimensions. However, the absolute support stiffness at $y = 3 mm$ of this new flexure was only 5 $\%$ of the leaf flexure for the same displacement. In conclusion, the decrease in support stiffness was reduced considerably, albeit at the expense of the actual magnitude of the support stiffness. For future studies more research is required on crease line design to improve the absolute values of the support stiffness.