Recycled fodder for the 3D printer

You may remember Joshua Pearce of Michigan Technological University from a story I wrote five months ago. He’s the scientist who is encouraging everyone to make their own lab equipment using 3D printers. He and his colleagues, Christian Baechler and Matthew DeVuono of Queen's University, Ontario, have now done themselves one better. They’ve found a way to make plastic filament (the ‘ink’ with which the printers make things) out of discarded milk jugs.

If you have your own 3D printer, you know that you can make an endless supply of cool and useful items. However, like Pearce, you will undoubtedly have realized that the limiting step is keeping your printer supplied with plastic filament. Thanks to the researchers proof of concept designs, which they are providing for free, you too can make your own filament.

The researchers chose discarded items made of high-density polyethylene (HDPE), not because it makes the best filament (it doesn’t), but because such items are prevalent in household waste. A variety of plastic items including bottles made for milk, detergent and shampoo are made of HDPE. These plastic items are washed, stripped of labels, cut into pieces and fed through an office shredder. The shreds are melted and then passed through a homemade extruder to make the filament, which was successfully used in 3D printers.

The process does take some time. To make about 18 meters of filament (about enough for five coffee mugs), you’d need to process 100 grams of plastic. Just extruding that amount of melted plastic took over three hours, and that was after washing and shredding it. Needless to say, some work needs to be done to make the system more practical. Also, there were some consistency issues in the diameter of the resulting filament that need to be addressed. Plus, there's the fact that HDPE isn't usually used in 3D printing. The inks of choice are PLA (Polylactic Acid) and ABS (Acrylonitrile Butadiene Styrene).

But make no mistake, Pearce and his colleagues foresee widespread usage of this new technology. For one thing, the process is far cheaper. You could recycle your own HDPE trash into 3D printer filament for about a dollar a kilogram. Compare that to the current price of commercially available filament of around $40/kg. From start to finish, the recycling process also uses about half the energy that goes into making virgin filament. And of course, these numbers will get much better as the process goes large-scale and becomes automated. Finally, we’d be doing something useful with all that HDPE trash. Saving energy and money and shrinking our landfills: a win for everyone.

By the way, Pearce isn’t the only one with this idea. The makers of Filabot have a shredder/extruder ready for purchase if you’re so inclined.

Baechler, C., Matthew DeVuono, & Joshua M. Pearce (2013). Distributed recycling of waste polymer into RepRap feedstock Rapid Prototyping Journal, 19 (2), 118-125 DOI: 10.1108/13552541311302978.