Scientists develop 3D print self-folding materials
Researchers from Carnegie Mellon University have developed 3D print self-folding materials. The technique, known as Thermorph, could be the first step towards products like flat-pack furniture that assumes its final shape with the assistance of a heat gun, or emergency shelters that are shipped flat and fold automatically into shape under the warmth of the sun. Self-folding materials are quicker and cheaper to produce than solid 3D objects. This makes it possible to replace non-critical parts and produce prototypes using structures that approximate the solid objects. This new method uses an FDM printer, the least expensive type of 3D printer.
FDM printers lay down a continuous filament of melted thermoplastic, which contain residual stress. As the materials cool and the stress is relieved, the thermoplastic tends to contract, which can result in warped edges and surfaces, a problem referred to as warpage. The researchers took advantage of this property by varying the speed at which thermoplastic material is deposited and combined warp-prone materials with rubber-like materials that resist contracture. When flat, hard plastic is placed in water that is hot, but not hot enough to melt, it will turn soft and rubbery, triggering the folding process. The researchers replaced the 3D printer’s open source software with their own code, which automatically calculates the print speed and patterns necessary to achieve particular folding angles.
To demonstrate the Thermorph platform, the researchers designed and printed complex self-folding geometries with up to 70 faces, including 15 self-curved geometric primitives and 4 self-curved applications, such as chairs, a bunny and flowers. According to the study, the new method saves between 60 and 87% of the printing time for all of the shapes chosen when compared to standard 3D printing, as published in ACM Digital Library.