Integration of advanced stiffness-reduction techniques demonstrated in a 3D-printable joint

This work details the integration of three distinct methods for altering the stiffness of compliant joints: lattice flexures, compound joints, and static balancing. The methodology for applying these strategies is discussed in detail. Lattice flexures are a flexure modification that leads to low motion-direction bending stiffness. Compound joints improve a compliant joint's load-carrying ability and off-axis stiffness. Static balancing in this case is achieved through the addition of an auxiliary energy storage device. To statically balance a compound lattice-flexured cross-axis flexural pivot, the load-dependent stiffness behavior of a cross-axis flexural pivot (CAFP) with two lattice flexure types is determined. A balancer spring design is developed that is fully 3D-printable. The balancer is combined with a compound lattice-flexured CAFP. Physical hardware is 3D printed in titanium and its torque-displacement behavior is measured. The resulting device requires 1% of the actuation energy of a conventional CAFP of the same dimensions and material.