Recycler! New Gada Prize team!

$30 dollar meat grinder waiting for a spool extruder nozzle plate to be measured->designed->turned on lathe.

[www.amazon.com]

Edited 1 time(s). Last edit at 06/21/2010 07:11AM by JohnnyCooper.

re: pump/plunger extruder (Prober, rocket_scientist)

You might want to take a look at the design of a agricultural hay baler - specifically, the "small square baler".

It uses an auger, a fork, and a plunger. There are other parts to a baler - such as the pickup, needles, and knotter, but they wouldn't be useful in this application.

The auger collects material (plastic bits, in our case) for the fork to grab. The fork is attached to a special linkage which causes it to move in an oval. It is also timed to the plunger so they won't collide. While the plunger is retracted, the fork drags material into the compression chamber. It then lifts and extends to grab more material as the plunger starts to advance.

When the plunger advances, a knife blade on the fill side of the plunger cuts off anything sticking out of the compression chamber. The walls of the chamber have catches which spring out a little to grab the material, so that there is room for more material.

I didn't find any really good videos, but this one should help a little.
[www.youtube.com]
The plunger is moving towards and away from the camera. You can't see the face of the plunger, but you can see the back of it and it's crank.

Mark

[hackaday.com]

Victoria University students beat me to getting an auger working.

Brilliant design! The wood drill bit was a great choice. Would a waterbath help stabalize the filament diameter?

Is anyone else having trouble visualizing why an auger would drive material forward at any real pressure? Shouldn't the plastic granules just tumble to the front of the screw and then spin clogging the flutes?

In any case: Next step is to convert scrap parts in to granules. Garbage Disposal?

Johnny: As has Capo. [capolight.wordpress.com]

He's got a way to go, sure, but then so does VU. He's also posting quite a lot of good material on his blog about all sorts of stuff related to recycling (including polymer degradation and how it affects recycling).

Great to see progress on this front. I'm currently working on making ABS granules/chips/powder for my Injection molding machine so I'll try and see if I can come up with a good way to grind up plastic of odd shapes and sizes. It may be best to just melt it in a skillet and cast it in to rods to be cut up. If plastic degrades with multiple thermal cycles, perhaps the slurry can be fed directly to the auger recycler in liquid state?

SebastienBailard Wrote:
-------------------------------------------------------
> Is this thing supposed to be self replicating,
> easily sourced, or completely open to vitamins?
> The recycling part of the toolchain? Anything
> goes.
>
> Tim from Michigan-RUG mentions that some buddies
> have achieved good results powdering plastic
> chunks using a rock tumbler.

Seen this? Might we be able to melt plastic, and have the option of making either gasoline or more plastic from it?

It seems this method doesn't require pelletizing before recycling. Also, by re-forming the plastic from the recycled materia people would have the option of creating it in whatever shape they prefer. Like spools of 'spensive plastic the RepRap currently uses.

Edited 1 time(s). Last edit at 10/14/2010 11:28PM by Satori.

I came across a paper today that might be of interest - "Recycling of RP Models by Solution – Casting Technique":
[utwired.engr.utexas.edu]

---

[haveblue.org]

Can't you just melt the plastic into shape through a metal funnel, glue gun filament tube and a press to keep it moving through?

JohnnyCooper Wrote:
> Is anyone else having trouble visualizing why an
> auger would drive material forward at any real
> pressure? Shouldn't the plastic granules just
> tumble to the front of the screw and then spin
> clogging the flutes?

The forward pressure actually comes from friction against the outer tube. Ideally, the plastic will have zero friction with the screw threads, and lots with the inner face of the outside tube. Imagine plastic sticking to the inner surface of the tube, as the screw rotates -- the screw threads will encounter it and force it forward. This is one reason why a tight clearance mate between the screw and the tube is important.

Alternatively, imagine plastic just going around and around as the screw turns, without moving forward (this happen in the reverse case - lots of friction with the screw, none with the surrounding tube, like if you used a PTFE sleeve or something). Imagine that we then crank up the friction on the surrounding tube. The molten plastic travelling around in a circle will shear against the tube, making it want to rotate more slowly than the screw. This will cause it to encounter the screw threads and get pushed forward.

It does take some thinking about, because it's not a simple idea. =)