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How to 3D Print Multimaterial Objects Using a Single-Nozzle 3D Printer

Let’s say you can only afford a single-nozzle FDM 3D printer, but you want to print a multimaterial part. You can stop at each material transition point in the process and swap out the spools, but this pause-and-resume approach comes with challenges; most notably you may need to purge the tip to flush out the first color before adding the second, for instance if the color switch is extreme.

A research collaboration between students from Meiji University, Osaka University and Texas A&M University has come up with a new trick called Programmable Filament. With this method, their software analyzes the design of your part and determines exactly how much filament is required between switches. It then generates a print file where you basically use multiple filaments to print a single new filament.

In other words, you feed a red filament into the printer and it starts printing out what is essentially a new spool. The researcher’s G-code has programmed in pauses signified by beeps; this lets the operator know to purge the tip, switch to the next spool, then hit the resume button. The printer then stitches the transition in–seamlessly, according to the paper–and continues printing the spool, in the shape of a large spiral.

At the end of this process, you’ve got a new custom spool that changes material at various points based on your exact object to be printed. Here’s a demonstration:

You’re probably wondering “Isn’t this just a more time-consuming version of pause-and-resume?” Not if you’ve got a lot of color switches throughout your design. Remember that the new “spool” is actually printed out as a large spiral, so does not need to be produced in a continuous fashion. In other words:

“The boat [above left] is printed using five different materials, requires only four exchanges (equal to the number of materials minus 1); however, if printed using a regular approach by manually exchanging the material every time a layer meets the new color segment, 211 exchanges are required, which is the number of extruder exchanges appear in G-code—not ideal in practice.”

Another question I had was “Is this truly multi-material, or just multi-color of the same material?” The researchers say they’ve combined PLA, ABS, TPU, nylon and PVA and that their joinery method “sufficiently compensates [for the inherent] fragility” of joints between the materials. If you want to read the technical details of how they’ve managed this, you can dive into the full research paper here.

https://www.core77.com/posts/102662/How-to-3D-Print-Multimaterial-Objects-Using-a-Single-Nozzle-3D-Printer