Building Block Synthesis of Self-Supported Three-Dimensional Compliant Elements for Metallic Additive Manufacturing

Abstract

Compliant mechanisms gain motion through the elastic deformation of the monolithic flexible elements. The geometric design freedom of metallic additive manufacturing enables the fabrication of complex and three dimensional (3D) compliant elements within mechanisms previously too complicated to produce. However, the design of metallic additive manufactured mechanisms faces various challenges of manufacturing restrictions, such as avoiding critical overhanging geometries and minimizing the amount of support structure, which has been reported in a few cases. This paper presents a synthesis approach for translational compliant elements, involving building blocks based on leaf-type springs and covering building orientations between 0° and 90°. In particular, this range is approached by the synthesis of self-supported 3D building blocks with orientations of 0°, 45°, and 90°. The compliant elements are built based on linear and circular plane curves and compared numerically according to their mechanical performance to create preferable building blocks. The applicability of the presented procedure and the manufacturability of the compliant mechanisms are proven by printing individual 3D building blocks and their serial aggregation with laser based powder bed fusion. Consequently, several prototypes are demonstrated, including a bistable switch mechanism and a large displaceable rotational spring joint. In addition, a small-scale highly maneuverable segment of a surgical instrument with a grasping mechanism at the distal end is proposed.

A Dfam Framework for the Design of Compliant Structures

“…Additive manufacturing (AM) allows CMs to be produced at a microscopic scale, which is impossible for rigid-body mechanisms due to their complexity. This also increases compliant mechanisms' portability over traditional mechanisms due to generally reduced size and lightweighting properties (Danun et al, 2020;Kiener et al, 2021).…”

Laser Forming of Compliant Mechanisms

“…Metal 3D printing is a current method of fabricating metal compliant mechanisms, but the technology can result in component anisotropy, high production costs, and a discontinuous manufacturing process that present challenges in some applications [5]. However, there is some research starting to be done on improving additive manufacturing for metal compliant mechanisms [6]. Outside of additive manufacturing, metal is difficult to machine on the mesoscale, with electrical discharge machining (EDM) being one of the few viable options.…”

Pseudo rigid body model for a nonlinear folding compliant mechanism

“…Cellular structures comprised of CM unit cells have been optimized for a desired compliance with the assumption of a linear displacement profile [22]. There are also FEA models that simulate the nonlinear deflection of compliant beam elements, considering Hookean material behavior [23]. In general, these FEA-based CM design methods consider large deformation behavior through geometric nonlinearity, but are limited to linear material behavior.…”