Plastic filament is the basic consumable for any FDM 3d printer. It’s the raw material that your printer will melt and deposit to create your great looking models!
You can make plastic filament from existing scrap plastic of the same type, or from new plastic pellets (or a mixture of the two sources). It requires a machine to melt and extrude the plastic, and another to wind the plastic filament, once extruded, onto a spool for use.
We all wish we could recycle failed prints and even old soda (or pop, water or juice) bottles into useful material for our 3d printers. The short answer is yes, you can create filament from scrap or from plastic pellets. The problem comes with the cost. A new spool of 1kg (2.2lbs) of PLA filament (including the spool that it comes on) will cost in the realm of $20.00US. The machines to melt and recycle the plastic can run from hundreds to thousands of $US, making it a nice to have, and not a financial necessity.
If you run a 3d printer farm, and you’ve got a lot of printers all going at the same time, then you may find that you have enough of a need for a recycling system to make it worth your while. If you are purchasing for a MakerSpace, for example, a system like this might be a really good idea.
Preparing Scrap Plastic For Turning Into Filament
You can purchase brand new PLA or ABS pellets that will work really well in any of the filament makers listed below. The real problem is that the price for a kilogram of PLA pellets is in the realm of $20.00US, just like a spool of already made, brand new PLA filament. So what’s the point? Why am I buying an expensive set of machines, only to get out what I put in, but with a lot of work?
Really, the pellets are there to add to scrap plastic, to give that scrap some virgin plastic to mix in. The mix of scrap and virgin plastic makes far better filament, and that’s why it’s worth having around. So how do I prepare the scrap?
Scrap plastic can come from several sources. Soda, juice and water bottles are likely made from PET plastic. If you’re making PET filament, this is an excellent source of plastic. Plastic bottle caps, however, are made from HDPE plastic. This too can be made into filament and used.
For PLA or ABS filament, however, you’re likely relying on failed 3d prints to recycle into filament to make new prints. You’ll collect any models that you aren’t using, have failed, or have broken. Also, any support material, from supports to rafts, can be recycled from all of your prints. The trick is to keep like plastic scrap with like. Take a garbage bag for PLA plastic and only put PLA in it. Do another bag for ABS, if you use that. You get the idea. Keep it all separated. Plastics have different material properties that you don’t (normally) want to mix.
How To Make Your Scrap Plastic Tiny Enough To Make Filament
There are lots of ways to take bits of plastic, or chunks of plastic, and turn them into shredded, tiny bits, ready to be extruded. The goal is to get bits of plastic no larger than 5mm (or 0.2″) on any dimension. This is the best size to put through the machines to extrude new filament.
One of the easiest is to use a cookie sheet, and put some baking paper on it. Pile on a bunch of plastic scrap, enough that when the mass melts, it will fill the bottom of the cookie sheet to a depth of no more than a quarter of an inch. Place in the oven or on a hot element so that the cookie sheet gets hot enough to melt the plastic. Once you have a gooey mess that looks like a melted, flat sheet, remove the heat and let the plastic and sheet cool.
Once the plastic is cooled, you can take the sheet and break it up into smaller bits. The melting and re-cooling makes the plastic sheet somewhat brittle, so it breaks apart easier. Break up the sheet into smaller bits that will fit into a plastic bag, then take a hammer to the bag and break up the bits even further. Once you’ve got smaller bits (like around an inch or smaller) then it’s on to the blender.
You can either buy a new, cheap blender, or a used blender or use a blender you’ve got that’s collecting dust. Use a blender with a power rating at or higher than 1000 watts, so that the motor doesn’t overheat when you make it chop up plastic bits. Add in your plastic (maybe not all of it at once) and shred it. Take the result and sieve the results using a 5mm sieve. You could 3d print this, of course. Anything that doesn’t go through gets sent for round two, back into the blender.
- Stacking sieve set (including 5mm sieve) that can be modified
- 6mm and 3mm sieve set with funnel. The design can be modified for 5mm.
Don’t blend your plastic too long in any one burst. The motor and the friction will combine to melt the plastic together, if you’re not careful, defeating the purpose. Avoid this by blending in bursts, with some cool-down time if you find it getting hot (or you can smell melted plastic, or worse, electronics!)
You could use an ultrasonic knife to shop up the melted plastic sheet, but this seems like an expensive method to break up scrap plastic. In case you’re into cool gadgets and want one anyways, here’s a link to one:
- Ultrasonic knife on Amazon: https://amzn.to/39Z8Tpf
Here’s a professional grade shredder that you can use in a more industrial setting, but it seems like a large expense for what you’re using it for:
- Professional-grade shredder and granulator. Can handle over 5kg (11lbs) per hour: https://3devo.com/shred-it/
Finally, you can do a lot of work and repurpose a cross-cut paper shredder that can tear apart your scrap plastic, but again, seems like a lot of work for something that can be done a little simpler using the method above:
- Create a shredder from a paper shredder.
Once you’re done shredding and sieving and shredding again, you’ll have a pile of 5mm or smaller bits of plastic, ready for extrusion into filament.
How Do Filament Extruder Machines Work?
Plastic, as either small scrap bits, or as virgin pellets of plastic, enter a hopper. From there, they’re pushed forward via a mechanical auger through a tube, pushing the bits towards a hot extruder tip. This is essentially a similar tip to what’s on your 3d printer. The auger not only meters out a small amount of plastic continuously, it pushes it forward to create pressure.
The plastic is heated beyond it’s melting point and pushed through the extruder. Out comes a thin stream of plastic filament. Perfect! This filament is left to hang for a distance, cooling along the way, and then wound onto a spool for use in your 3d printer. The fancier spool winders will speed up or slow down based on the diameter of the filament, as a method to adjust the diameter.
By the time the plastic gets to the spool, it’s cool enough that it won’t bond to itself, and will wind up, ready for use. Fancy winders will even move the feed back and forth, making for neat filament spools by the time you’re done.
When the last of the plastic is done, or you shut off the extruder, you can snip off the plastic and immediately, that plastic filament is ready for use.
What Filament Extruder Machines Are Available?
The 3devo Filament Maker, listed below, is a one machine setup, that combines the extrusion with the winding. It’s very slick to watch. The other machines are all two piece affairs, one a melter/extruder and the other a winder. In between is an air gap to allow cooling. Some add fans to this stage to get the optimal amount of cooling for the filament before it winds onto the spool.
- 3devo filament maker
$5388.00US (converted from Euros, plus shipping from Europe)
- Filastruder Build Kit
The combination of Filastruder and Filawinder seem to be the most economical, coming in at roughly $500.00US or so. The other machines are fancier, more automatic, but vastly more expensive.
I could see using this combo for a MakerSpace or even as a device that a bunch of friends all pitch in and share. For me, I’ll stick to the $20.00US spools of virgin PLA. If you’ve got one of these filament setups, I’ll try and save my scrap for you!