Sci­en­tists de­velop 3D print self-fold­ing ma­te­ri­als

Chemical Industry Digest - - Science Pages -

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.

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