Development of a Folding Tool for Miuri-Structures

Abstract

Folding is the process of forming cellular structures out of a flat raw material. This technology makes it possible to create folded structures with high depths and multiple bending axes. Folding is part of technical origami and therefore is defined by: 1. its geometry, which is defined through folding and requires a folding algorithm, 2. the initial material, which has a negligible thickness, 3. the fact that there is no global strain or general plastic deformation in the workpiece. Current research work focuses on applying this technique to metallic materials with non-negligible thicknesses. Such structures can be used for optical appealing cladding, heat exchangers or core materials of numerous sandwich panel designs. In previous projects with very thin raw materials, it was shown that it is necessary to pre-crease the bending axes on the flat raw material to achieve a defined folding shape. The folding was usually achieved manually. For sheet metal, embossing of grooves in particular appears as a promising approach for pre-creasing. General challenges for folding of sheet metals are the forming of radii and hardening effects on the bending axes as well as appropriate tool concepts for the process. This paper deals with the development of a forming tool to form a complex Miuri-structure made of sheet metal having a thickness of 0.5 mm or more. In a first step a tool is designed and manufactured that is able to fold a simple zigzag structure with one single bending-line orientation. The folding with this tool is investigated experimentally and based on the observations the zigzag tool concept is enhanced to a structure with a tree bending-line orientated Miuri-structure. This paper shows that a complex bending of sheet metals with non-negligible thicknesses is possible if a proper tooling design is taken into account.