Fibers can also be installed in thin 3D printed parts using aligned embroidery. Here an array of thin squares was hinged together with embroidered threads, then 3D printed pyramids were added on top. The resulting part is more flexible than an all 3D printed part would be.
But how can we integrate an embroidered fiber layer into a thicker part? At a height greater than the embroidery machine can accommodate (~5mm)? This tutorial demonstrates how to laser-cut holes in a water soluble stabilizer to allow upper layers of a print to fuse with parts below the fiber layer. In these test structures, a fishing line (4 lb tensile strength) goes around and through holes in printed features. At some locations, the fishing line is deliberately trapped between the print layers, creating an anchor point. These test structures contain the basic ingredients for a robotic structure such as a 3D printed grasshopper leg with tendons and a hinge.
In the above figure: Workflow for inserting a fiber layer in a 3D printed mechanical part. Different fiber paths pass through, around and within 3D printed features. a) The needle locates alignment marks on a laser-cut water soluble sheet, and an aligned embroidery pattern (inset) is generated. b) The pattern is embroidered and c) inserted at a pause point in a 3D print file (inset). d) Before and e) after dissolving the water soluble sheet and freeing the hinged 3D printed features.