Plastic recycler

Hi All,

I've been thinking about a machine to recycle old/bad prints and maybe other plastics that you find around the rubbish bin.

Basically something along the lines of a small meat grinder with a heated nozzle.

For simplicity I was thinking of using a large drill bit in an accurate (reamed) tube being rotated backwards (used as an archimedes screw to push the contents toward the tip rather than the normal rotation that pulls stuff away from the tip).
Then cut a small access port to the bit towards the end of the threaded section.
When you're spinning the drill, anything poked into the port will be mashed by the drill bit and then pushed to the other end of the tube.

So now, just screw on a heated nozzle and you can extrude your own filament.

Has anyone tried anything like this or can spot any potential flaws before I start?

Max

There have been a few attempts to build a non-filament extruder, but no breakthrough success so far. Most try to not extrude to filament, but directly in a print extruder on the Mendel, of course.

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The biggest trouble that people have had with the "do it yourself" filament extruders is keeping the filament diameter consistent. As filament is drawn from the extruder, it will be stretched in varying amounts according to the pressure inside the extruder, the extruder's temperature, and how much tension there is on the uptake. Professional extruders deal with this by drawing the filament through a water bath to cool it, by using a roller system to regulate the filament speed, and by tightly regulating the pressure and temperature inside the extruder.

If one cannot keep the plastic diameter consistent... I know there are ways to mesure the amount of flow of a liquid. Not a cheap let alone easy solution.... The only thing that comes to mind is molds, but I bet air bubbles would hender that idea..

if we had a good way to measure the diameter of the outgoing filament, i bet having movable rollers would not be too hard.

Maybe a laser pointer going through a glass rod with a webcam looking at the resulting gap in the laser line (sort of like a 3d scanner). Or just have the webcam look directly at the extruding filament (but that might be much noisier). Then, just adjust the position of the roller (I'm thinking something like a stepper motor attached to a threaded rod drive; doesn't need to be too fancy but fine adjustment might be required).

That design might even be mostly printable, and we could be able to get away with air cooling if we don't need to extrude very quickly.

Once I get my 3d printer fully operational I will def try to prototype this.

Had a few minutes, threw this together pretty quickly, it's by no means accurate, but it generally proves my idea. The green is basically a hopper. Could have grinders in it for reclaiming already printed models etc, but it's primarily for granules/shredded plastic. Anyway, all the bits go into the melting area (red square) where they're liquefied and pushed into the nozzle (red cylinder). To prevent over expansion, it goes through a cooling nozzle/chamber (blue cylinder) which cools the liquid plastic to solid (black part) before it leaves the assembly and is coiled for use later.

Basically, the plastic is melted and pushed through a heated nozzle that's the desired thickness, it's then rapidly cooled to a solid form and pushed out of the assembly. Since it's melted in a vat and injected in liquid form, it should be relatively air free, and with enough material loaded, it should be able to be reasonably pressurized to prevent under thickness. And since it's cooled while it's still enclosed, it shouldn't expand.

I've actually got a bunch of better ideas for v2. So I'll probably learn to use blender so I can better explain it.

Extra-Titanian Wrote:
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> Basically, the plastic is melted and pushed
> through a heated nozzle that's the desired
> thickness...

What's pushing the plastic?

Gravity

Maybe the volume (weight) in the hopper would help, but this is ABS/PLA so I do not expect much there.

What if the PLA was heated to a liquid and then pushed out the nozzle like a syringe? The heated area would have to be larger to accomidate the syringe but I think you could get uniform pressure. I was thinking also that there might need to be a water bath at the bottom so that he heated PLA doesnt bend or stretch.

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