If there is one thing I have learned form many years in the recycling industry, it’s that plastics are very fickle. They are picky about moisture, temperature, flexibility, and color. Plastic don’t tend to get along with other plastics. That is, to say, they don’t blend well if they are different or even the same in some cases. They like to be as similar as possible in the most favorable conditions as possible; clean, dry, and uniform.
For those reason, plastics recycling can be a difficult and frustrating industry. Sometimes you find a great source of materials and other times you get someone’s garbage. It takes a lot of time and patience to find good sources of material and even if you do, the materials might not process the way you or your client needs them to process.
So when I set out to start recycling 3D printing filaments, I decided to do some research about the current recycling movement in the 3D printing industry. The one that stood out the most seemed to be home recycling and extruding. The idea that with the right equipment, one could granulate and then extrude your old printing scraps into new filament. To be honest, when I first read about the idea and successful funding campaigns I was very impressed. The idea of handling your own scraps at home was cost effective and efficient.
The idea is great but the execution and practicality of it is, in my opinion, misguided. I have read a number of product description and selling points for a number of machines and for the most part, they equipment does what it is supposed to; melt your plastic scraps into filament. The one selling point on many machines that really stuck in my mind was that one could take their recyclable from home (specifically your old milk jugs), chop them in a blender, then extrude to make your own filament at home. This is a terrible idea.
Now, this is not to say you can’t recycle your old milk jugs into filament, it’s just that you shouldn’t and it won’t work. First, using post-consumer waste for any application where it’s not first properly washed and cleaned is a bad idea. Food contaminants can ruin a machine for a variety of reasons. Second, just because it’s plastic doesn’t mean it’ll work in a 3D printer. One has to take into account, melt temperatures, density, melt flow, and a number of other factors to make a successful product. Most plastics are engineered to be either blow molded, injected, or extruded and thermoformed. Sometimes you can work within the parameters of a plastic to process it in a different way, but most times it just won’t work.
Aside from the engineering challenges listed earlier, the finishing process of filament is also an issue. Diameter tolerance is impossible to monitor at home. RePLAy 3D’s manufacturer uses industrial laser monitors to gauge the diameter of the filament, and that is after a series of calibrated water baths to ensure the plastic cools uniformly throughout the spool. It’s an expensive and complicated set-up that require and trained engineer to build an operate.
While it is a great idea, the execution of the home filament extruder has room for improvement. It has created a false sense of sustainability in the 3D printing industry and not yielded the intended results. RePLAy 3D hopes to give the 3D printing industry a real sustainable solution to scrap plastics and finally present a viable closed-loop product to printers big and small.