Nov 21, 2018 | By Cameron

Makefast Workshop, the Delaware-based design and fabrication studio that brought us LightNudge, published a tutorial on their hacks page detailing how to 3D print coils/springs in mid air without support material. For all the overhang masters out there, this is a remarkable accomplishment.

3D printing unlocks geometries and shapes not possible with other forms of manufacturing, but each type of 3D printer has its own limitations. With FDM (fused deposition modeling) machines, one of the greatest limitations is overhangs, or any angle greater than 45°. Each part is 3D printed from the bottom up, with successive layers building atop one another. So if a part has steep dips and valleys on its underside, that part would need pillars of support material underneath the overhanging areas to be 3D printed. Support material can be costly and leaves imperfections when removed from parts, so most designers try to avoid overhangs by using angle-reducing chamfers and fillets in models that will be 3D printed on an FDM machine.

The Makefast duo Maura Atwater and Adam Kumpf are problem solvers with degrees from Wellesley College and MIT, respectively, and they tackled the overhang problem like any other: with a little common sense and a lot of trial and error. They realised the fundamental issue with overhangs is the layers. The solution: rather than extrude layers on top of each other, extrude directly onto the extruded stream itself.

Thermoplastics like ABS and PLA used in 3D printing have excellent glass-liquid transition properties, meaning they melt and solidify consistently and predictably when heated and cooled. By extruding the plastic very slowly, the print head is directed to move at the same rate; the fans on the print head cool the extrusion almost as quickly as it comes out, allowing it to solidify in place as a single stream. They wrote a command to generate the custom g-code necessary to instruct a TAZ 6 how to print without layers, “we made a short javascript function that traces out the desired 3D path, setting temperature, feedrate, fan speed, etc. along the way.”

There were some hurdles to overcome, such as moisture pockets in older filament that pop and interrupt the delicate flow rate. A very consistent flow and movement is required, so vibrations could also cause failure. An interesting finding was that extruder pull and push have to be factored in more as the part gets taller, which makes sense considering how cantilevers work. This means that the g-code for a cylindrical spring flares out at the top to compensate for the inward tug of the extruder that becomes more apparent the taller the print goes.

Still, the springs are significantly stronger than other 3D printed springs that would suffer from delamination between layers when stressed. Their source code is freely available as well as the g-code to print several sizes and shapes on a TAZ 6. While it’s a neat thing to see a spring printed as a single stream of plastic, the greater reward will be seeing these control settings implemented into slicing software. If slicing software could include coding to very slowly extrude a looping pattern around the edge of a part where there’s overhang, the use of support materials would be much less necessary and parts would even be stronger. Slicing programs are always improving, so slicing coders, take note of this one.



Posted in 3D Printing Technology



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Danielle wrote at 3/20/2019 12:29:42 AM:

Where can I find your g-code? I am trying to 3D print a PBT and ABS structure on a Stratasys FDM 3D printers; however, I am not sure how to access the javascript code to be able to change the setting temperature, feedback rate, and fan speed. How did you do this? Or did you hardcode this in the printer's slicing software? Thanks

I.Am.Magic wrote at 11/22/2018 11:35:31 AM:

I remember doing this back in 2012

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