There’s new software that can help sort 3D print scraps for recycling into properly coloured filament.
There’s much discussion about recycling thermoplastic scraps generated by 3D printing. Failed prints, removed support structures, brims, old model versions, and leftover filament normally end up in the landfill. That’s because none of that carries the required recycling marks that would be recognized at local recycling depots.
Because of this, some have developed systems for recycling these scraps into usable 3D printer filament. Scraps are first shredded into small, uniformly sized bits, and then heated in an extruder. After extrusion, the filament is carefully cooled to maintain dimensions and spooled up for use.
That all sounds great, but there are two problems.
The first is that the commercial equipment required to perform the shredding and extrusion tends to be quite pricey. It’s possible to purchase hundreds, maybe a thousand spools of filament, for the cost of the equipment. This is why recycling isn’t widely done.
However, some operations have rigged up open-source designs to perform some of this work at lower costs. It is becoming more common to see this setup in some larger makerspaces, for example.
The second problem is colour. Typically, when scraps are made from material with many different colors. When they are ground up and mixed together, the resulting filament colour is unpredictable.
Well, that’s not quite true. The recycled filament colours tend to be bland: greys, browns, and similar. That’s what you get when you mix random colours.
But now there’s a way to do this in a more predictable manner. Researchers have developed an open-source tool called “SpecOptiBlend” to help manage the production of colour filaments from recycled sources.
Here’s how it works:
- Sort waste PLA scraps by major colour (e.g. red, green, blue, black, etc.)
- Shred and compress each colour separately into uniform bricks
- Measure reflectance spectrum of each brick using a standard light source and spectrometer
- Use SpecOptiBlend to compute the blend ratios to match a desired target colour.
- Collect correct weights of those coloured bricks and regrind into pellets.
- Extrude pellets into filament of the target colour.
The system works because it involves the use of well-understood spectral reflectance theory. It is apparently possible to produce highly desirable colours predictably using this approach.
However, the available colour palette is dependent on the number of input colour scraps. With a more varied range of input colours, SpecOptiBlend is able to produce formulas for a wider range of output filament colours.
This could be of considerable interest to any operation producing filament from recycled sources, and might generate more sales due to a better selection of colours that aren’t grey.
Combined with open source filament recycling systems, this could enable makerspaces to more effectively produce usable 3D printer filament from scraps.
Via ELSP
