"Speed-Modulated Ironing" Delivers Programmable Textures, Colors, and More to Your 3D Prints

Researchers from the Delft University of Technology and the Massachusetts Institute of Technology (MIT) have come up with a new approach to extruded 3D printing that, they say, can deliver uniquely customized objects with less waste: speed-modulated ironing.

"Today, we have desktop printers that use a smart combination of a few inks to generate a range of shades and textures," explains Mustafa Doğa Doğan, co-author of a paper detailing the team's work. "We want to be able to do the same thing with a 3D printer — use a limited set of materials to create a much more diverse set of characteristics for 3D-printed objects."

In traditional fused filament fabrication (FFF) or fused deposition modeling (FDM) 3D printing, an extruder pushes molten material through a single nozzle as it moves around the print surface. This produces a 3D object, but always in the color and texture of whatever material was being fed through the extruder — and while temperature-sensitive materials can shift on-demand, cooling and heating the nozzle to change the appearance during a print dramatically increases how long an already lengthy process takes to complete.

The team's solution: a second nozzle, not connected to an extruder but still capable of heating. This follows the first nozzle around the material and brushes up against the top layer, applying variable amounts of heat by modulating its speed — effectively "ironing" the material and triggering temperature-based changes on-demand. "As we modulate the speed," co-author Marwa AlAlawi explains, "that allows the printed layer we are ironing to reach different temperatures. It is similar to what happens if you move your finger over a flame. If you move it quickly, you might not be burned, but if you drag it across the flame slowly, your finger will reach a higher temperature."

By choosing materials that react to different temperatures, the team was able to create objects which can be tweaked during the printing process — using the second nozzle to alter the color, shade, or even texture of the print. Test objects included water bottles with a programmable translucency, a bike handle with variable roughness, and a cube that reproduces black-and-white photographs of famous scientists and inventors on its faces. All proved able to produce better detail than traditional multi-material 3D printing, while printing in far less time and with less energy used.

The team's work is to be presented at the 37th Annual ACM Symposium on User Interface Software and Technology (UIST '24) later this month; a preprint is available as a PDF download from co-author Zjenja Doubrovski under open-access terms.