When you get a 1kg spool of filament, you get 1000g in a nice, round strand that you can run through your printer. But you also got a spool, which is another 215g of perfectly good plastic, so are you just going to throw that away?
These spools are often made from really good materials like polycarbonate or ABS, and I think it would be a shame to toss them, especially because most of the plastics we chuck into the recycling bin don’t get recycled, they get burned for energy. And what you buy as “bottles made from 100% recycled materials” or “recycled” filament, that’s typically just made from re-melted production scraps that have never left the factory and most likely would have been reused anyway.
The most logical thing for me to do is to try and get the most out of the material that I already have sitting around. While I’m at it, I could also turn the useless 3mm filament that I still have into 1.75mm, mix in some old prints, and finally make use of that bag of ABS pellets that I bought and only ever managed to extrude into a couple meters of filament.
This is going to involve shredding and re-extruding filament, so I got in touch with 3devo from the Netherlands, and they loaned me one of their filament extruders, as well as their flagship plastic shredder and granulator unit. Those are quite the machines, but they are too big and too heavy to use in my studio. They were delivered on a pallet with a semi-truck, and they are sitting in my garage right now, so let’s go check them out.
3devo Plastic Shredder GP20 and Filament Maker ONE Composer
The first thing that came out was the filament extruder – this is the Composer 450, and it’s surprisingly compact. If you look at commercial filament extrusion lines or even the extrusion line that I built a couple of years ago, those are usually at least a couple of meters long, but the 3devo extruder routes the molten plastic and the filament around the corners, so it manages to fit the extrusion screw up top, the cooling, puller and diameter measurement unit into the side, and then around the last corner, you have the entire spool winding setup.
They are also including some PLA to get you started, and a bag of HDPE-based cleaning and purging material, this will come in very useful later.
The Filament Maker ONE
The machine has you doing an onboarding process that teaches you the absolute basics, and you end up with however much of the PLA you want to turn from granulate into filament. And this turned out pretty well! I didn’t clip the start of the filament into the spool well enough, so it slipped on the spool a couple of times, which means the winding isn’t perfect, but the extruder part is ready to use.
The Plastic Shredder
The plastic shredder is a different beast. This one requires some assembly, but I underestimated how massive this was going to be. You can get this with just the shredder, just the granulator, or both assembled into one unit, but having both stages as a single block means there’s no way I could lift this off the palette, even with some help. So I grabbed my engine hoist and lifted it onto its base, everything gets screwed down, and then the feed hopper and output container get attached.
Did you notice the tabs that are sticking out of these parts? Well, those are safety interlock switches. Because the core shredder mechanism in this is naturally pretty dangerous when used wrong, the machine can only run when all the side covers are closed and when the hopper and outfeed container are installed, making it impossible to get your hands or any other body parts into any of the dangerous bits. Each one of these tabs is keyed differently, so you can’t just override these by sticking a screwdriver in. I think that’s a cool detail and it’s refreshing to see things done correctly.
Using the shredder is as straightforward as you might think. You chuck parts into the hopper and there’s a little conveyor belt built into it that will automatically regulate how quickly the material is being fed into the shredder. You can set the RPM and all that, but I just left it on full speed, and that seemed to work fine.
Trying to get spools in here requires some extra prep work, you would need a ginormous shredder to grind them down in one go. What I found works best is scoring the sides and then snapping them off, which gave me 8 separate side bits and a central core to shred down.
But what are we actually shredding here? Filament spools aren’t all made from the same material. The most common one I had was polystyrene. Polycarbonate is also used quite a lot and one of the older spools was polypropylene. But the ones I wanted to start with were the ABS ones. Many of the spools weren’t marked, so to get more ABS, I had to start guessing.
You can get a rough idea of what plastic you are dealing with by scratching and smelling it, which probably is not super healthy, so don’t try this at home. But I found three more spools that could be ABS. I cut all of those up into rough bits and chucked them into the shredder, and let me tell you, watching spools get shredded is enormously satisfying.
I also shredded down the 3mm filament I had, and here, the hardest part was getting the filament down to a size where it was going to fit into the shredder. Cutting a coil like this with a saw is nearly impossible. What I ended up doing was to unspool the entire thing, and then to cut it in half with some sharp tin snips. This was a tangly mess to feed through the shredder, but if you don’t stuff too much material in there at once, the shredder makes surprisingly quick work of it. I shredded down a batch of 3mm Matterhackers and Ultimaker ABS, some DAS Filament PLA, a mixed batch of Polyalchemy PLA, a couple of filament leftovers, and a bunch of printed parts thrown in for good measure.
There is a noticeable difference between the smooth, consistent feel of factory-made granules, so-called “virgin” material, and the less homogeneous mix of coarser particles with a bunch of finer dust that you get from shredding. With all this shredded material ready to go, I wanted to start turning it into filament.
Because I expected the shredded filaments to work pretty well, I wanted to start with the shredded ABS spools. I knew that drying your input material is key to getting good extrusion results, so I grabbed a heated filament dry box and blasted the granulates for a couple of hours on the highest setting, which, for this one, is 70°C. I heated up the extruder to the ABS preset and just had a go.
And here is where I started screwing up. First of all, I still had PLA in the extruder, and I purged that out straight with ABS, at ABS temperatures. Not great!
PLA and ABS don’t mix, they don’t create a copolymer, so it’s messy, and also, you cook the PLA, and the last thing you want to have is hard, charred plastic in the extrusion screw. You are supposed to use an HDPE-based material as an intermediary to purge out the PLA at PLA temperatures, then go up to ABS temperatures, and drive out the HDPE with your actual ABS. The HDPE intermediary works at both temperature ranges and doesn’t degrade in the same way that the PLA sure did when I was cooking it just now.
But once all the PLA was out, I got a nice, consistent extrusion from the shredded ABS spools, so I started feeding it into the spooler, hooked it onto an empty spool, and just let it rip. And the filament I was getting looked really good. The diameter consistency and the surface finish were good, so I just let it extrude and took a break.
When I came back, I had probably around 250g of filament on the spool, but instead of a smooth, round filament, I was getting a surface that was rough and torn up, and the diameter consistency was all over the place.
It was getting late, and I had a call with 3devo the next morning anyway, so I shut off the extruder and I was going to ask them about it then.
One of the things that 3devo specializes in is not just designing and selling these machines, but they also include one-on-one coaching with their materials experts. These machines are intended for material development and prototyping, so every use case will be different and have some unique challenges they will work through with you.
And I have got to give it to them, they were very courteous about it, but they also very clearly let me know that I screwed up here. First of all, extruding a mystery mix of ABS spools is perhaps a bad idea from the start, but also, before I turned off the extruder, I should have purged out all the mystery filament with the HDPE purging material, and if I was unlucky, just leaving the plastic in the hot meltzone of the extruder and shutting it off could have cooked it enough by now to cause some serious issues. That was in the manual, but you know how good I am at reading through those.
So the rest of my day was spent purging out half-burnt ABS, and eventually making my way back to plain PLA and running a verification run with that, which still had some occasional blobs in it from leftover mystery ABS. I felt confident that whatever was still in there should come out once I’d run some higher-temperature material through it. And that’s exactly what I did!
This time, though, I grabbed the Polylac 747S ABS resin that I knew had worked before on my own extruder. The first go I had with it was still a little bubbly, so I threw it back into the dryer for another two hours, and after that, I got a nice spool of super consistent, tight-toleranced ABS, that honestly, except for the spooling, could pass as store-bought filament. The machine and the process work, it’s just that perhaps my shredded ABS spools weren’t the best material to start with.
But I got a tip from the 3devo process engineers: I should try the polystyrene spools instead, since those were, all clearly labeled as Polystyrene, and they all came from the same manufacturer: Häfner. I should have the best chance of getting a usable batch of material with that. I had a standard 1kg spool, a small 250g sample spool, and a larger 2.2kg one, that I had to take to my miter saw to get into smaller chunks, but after that, the shredder just tore it down into granulate with no problem.
After a bit of drying, unlike the ABS spools, the shredded polystyrene started extruding really well. I got a couple of tiny bubbles in there, so I dried the second refill a bit longer. This extruded much better than the ABS spools and is definitely going to be worth printing with.
I made two spools, this lavender one is the mixed shredded PLA filaments and printed parts, and I was really surprised by how well the different colors ended up mixing together, making this really beautiful chalky color. The other one is the ABS spools, but instead of taking just the recycled material, I used a special recipe of two cups ground spools, and two cups Polylac ABS, baked at 70°C for two hours, and out came a perfectly fine spool of not-quite-black ABS, and it had none of the surface tearing issues that I got with only extruding the shredded spools.
So how do these print? I printed little low-profile clamps designed by TaylorsMake on the Prusa XL because it has jam detection and five toolheads – if I clog one because my filament had some junk in it, I can leave it, worry about it later and move on to the next one.
Pure ABS and Polystyrene Spool Filament
Let’s start with what didn’t work – and that’s both the pure ABS and Polystyrene spool filament. One thing that I realized after the fact with all of the materials is that I should have dried them more. So, occasionally, I got little steam pockets in the final filament that would be too big to fit through the extruder, and the XL would send me a notification and be like “A little help here please!”. On top of that, I didn’t clean off the labels well enough in the polystyrene spool material, and that ended up creating an unmeltable residue that clogged the nozzle.
More aggressive solvents that would clean off the labels are hard to use with styrene material because they also start dissolving the spool itself. But even for the bit that did print, the material looks brittle and “dry” for lack of a better word. It might just be that these spools were already made of recycled, low-grade material because it doesn’t matter that much for a spool.
On the other hand, the filament made from the ABS spools did look a bit better. I used the start of the filament that still extruded smooth, and that managed to print this much until the filament got snagged. Not the best result, but the material itself seems a lot more promising, and with a little more drying, it could totally be usable.
50% Fresh ABS / 50% ABS Spools
But The 50/50 mix of the same base material and some fresh ABS is where things started coming together. This material was much more consistent to extrude and printed really well. I think adding this much fresh material is a pretty good sweet spot to still make use of a considerable amount of old plastic, but then push the material properties toward an area where you know it’s going to be a usable material, too.
100 % virgin ABS and PLA
And what should be no surprise at this point is that the filaments made from 100% virgin ABS and PLA granulate are also printed perfectly – these are every bit as good as store-bought material. The mixed PLA batch also worked. I got one tip from 3devo: If you are starting from different kinds of input materials like, in this case, shredding both old filament and 3D prints, it’s a good idea to run the shredded material through the shredder again to get more consistent particle size, and as a result, a more uniform extrusion.
Now if you’re wondering about whatever happened to the blue Ultimaker and Matterhackers PLA filament that I shredded – I think I managed to contaminate it with just the tiniest amount of particles from the shredded ABS spools, and that messed up the extrusion consistency. Any amount of ABS contamination just came out as a solid chunk, and I should have cleaned out the shredder more thoroughly when I was done with the ABS spools.
I think that experience does a great job explaining why you so rarely see commercial recycling happening of 3D printed parts – if you collect PLA from a bunch of different people, and there is just a single ABS part mixed in, congratulations, you have just ruined an entire batch of shredded material. The recycling companies that do exist get around this by a) mostly relying on perfectly clean industrial waste, like sprues from injection molding parts, and b) by grinding down anything that’s being sent in into a really fine powder, so that if there is any kind of contamination in there, it’s just going to be a speck of dust and pass right through your printer’s nozzle. But grinding it down so much also degrades the polymer itself, so that’s not great either.
I feel like I have got a decent grasp of using these machines now. The question is, what do you want to see me use them for? Let me know in the video’s comments, and if we get a crazy enough suggestion in there, I might be able to keep the 3devo machines for a little bit longer before I have to send them back.
We can do compound plastics, additives, fibers, glitter, you name it. Anything that fits through a 3D printer nozzle is fair game.
And if you’re working on a project that involves recycling plastics for 3D printing, or even creating a brand-new material that you can’t just buy as filament off the shelf, get in touch with 3devo and talk to one of their materials experts at the link in the description about how you can put these machines to use in a free two-month trial!
Thanks for watching, keep on making, and I’ll see you in the next one.
The printed clamps are the ”CNC low profile clamps” by TaylorsMake
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