3D-printing problem used to create self-folding objects

A flat sheet of plastic (top) becomes a three-dimensional rose when heated

Cheap 3D printers often have a problem called “warping”, in which the objects they print tend to curl as they harden. Now, however, scientists have harnessed the power of deformation to create flat elements that bend in predetermined 3D shapes when heated.

The Fused Deposition Modeling (FDM) 3D printers are the most economical, and they build objects by placing a continuous filament of molten thermoplastic. Unfortunately, as the plastic cools and the residual stress is relieved, it can contract and deform.

Directed by assistant professor Lining Yao, a team from Carnegie Mellon University has developed a technique known as Thermorph, which takes advantage of this phenomenon. It uses a standard FDM printer to create flat sheets, by depositing two types of thermoplastic: one that is prone to deformation, and one that is resistant to deformation.

Depending on the way the user wants the finished folded product to have, the customized software automatically controls the speed at which the plastic prone to deformation is placed on specific areas of the sheet, in addition to controlling the order in which it is placed. deposit the two plastics. different places.

When the resulting flat and rigid sheet is placed in water warm enough to soften it (but not enough to actually melt), it will deform in the areas where the first plastic was deposited more quickly, causing it to permanently crease. those places: the faster it is deposited, the more it will fold. The direction of the fold is determined by the order in which the two plastics were placed.

So what is the point? Well, according to the university, self-folding flat materials are faster and cheaper to produce than solid 3D objects, they are also easier and less expensive to send. And although the objects created so far have been relatively small, the team believes that the technology could be expanded easily, to create flat package products that are “assembled” simply by using a heat gun.

“We believe that the general algorithm and existing material systems should eventually allow us to manufacture large, strong and self-folding objects, such as chairs, ships or even satellites,” says internal researcher Jianzhe Gu.

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