Lattice flexures: Geometries for stiffness reduction of blade flexures

Abstract

Reducing the motion-direction stiffness of compliant mechanisms reduces their actuation effort and simplifies associated static balancing mechanisms. This work introduces a flexure type called lattice flexures and evaluates some of their fundamental properties. Lattice flexures have a reduced bending stiffness when compared to traditional rectangular-section blade flexures of similar size. The motion-direction bending stiffness of two lattice flexure types, called X-type and V-type, are analytically derived, corroborated with finite element analysis, and validated with measurements of physical prototypes. The lattice flexure has the potential to reduce the bending stiffness of some compliant mechanisms by 60–80%, as demonstrated in devices manufactured using 3D printing technologies. It is shown that some lattice flexures exhibit a torsional/bending stiffness ratio as much as 1.7 times higher than an equal aspect-ratio blade flexure, and a transverse bending/motion-direction bending stiffness ratio up to 6.5 times higher than an equal aspect-ratio blade flexure.