Recycler! New Gada Prize team!

Forrest, I was thinking about your research here:
[objects.reprap.org]

I think it would work, with the Rotary Shaper
[objects.reprap.org]
but I haven't tried it yet.

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

I've created this as one example of how people like you, dear reader, might want to start a team and discuss things. I don't think the "core" or old-guard RepRap developers are going to stuff this competition.

For one thing, we're outnumbered. And you're smarter than we are.

For people who are wondering what is going on, [[GadaPrize]] is here:
[objects.reprap.org]

I've been thinking about trying a generic kitchen food processor - the appliance you use to turn 2 kg of carrots into shreds. I'll try it once I have a granule extruder built.

It may help to chill the plastic parts in a freezer first.

(Tacked that up on the wiki as well.)

I tried HDPE in a liquidiser and a mincer, but neither worked. I didn't try freezing though, but I feel you would need a very low temperature to make HDPE brittle, I could be wrong.

Putting it through a paper shredder breaks it into thin strips and repeatedly putting those through gives small chips. Not sure how long the shredder would last with this sort of abuse.

Attacking it with a milling bit gives fine powder of course.

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[www.hydraraptor.blogspot.com]

I tried HDPE in a liquidiser and a mincer, but neither worked. I didn't try freezing though, but I feel you would need a very low temperature to make HDPE brittle, I could be wrong.

Freezing is just an idea to prevent melting and gumming, not to cause embrittlement.

Attacking it with a milling bit gives fine powder of course.

I think the answer involves rotary blades of some kind. Milling bit only works if you can control and move the chunks. All though, if you invert the milling bit or mount it in a wood router, you can make a chute to feed the plastic down to the bit.

I'll try the discs-blades of my cuisinart soon.

What does your liquidiser blade look like?

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Engineers call the process of cutting stuff "chip formation", apropos of nothing.

The problem with cutting HDPE is it is one of those plastics that gets stronger when you stretch it until it is incredibly strong and very very thin. That makes it hard to cut with anything that shears it, like scissors.

The liquidiser was an old Kenwood one with two triangular blades angled upwards. It just stirs the plastic round and does not cut it. Perhaps a very fast one like the "will it blend model" would work.

The mincer just jams solid due to the strength of the plastic. Neither had melting issues.

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[www.hydraraptor.blogspot.com]

I remember working for a time with what used to be ICI's polyester films division.

When they extruded, stretched, processed and finaly slitted polymer chips into plastic film. They were left with residue. Mostly trimmings.

I am not entirely sure how but they chopped/ground this up small enough to be re-mixed with the virgin polymer chips and put through the process all over again. So minimising waste.

This all worked great apart from yellowing. Each time the plastic was heated and extruded again if there was too much of the recycled plastic in the mix it seemed to leave the results with a yellow sort of burnt tinge. Basicaly their process engineers worked out what the maximum re-mix ration was such that the effect was undetectable in the final product.

Chiping waste then would appear to be a doable route (I don't think they froze it) and it needs to be no smaller than the maximum chip size that you can extrude into filament.

I wonder if the same cutting sort of mechanism that tree chippers use would work but on a finer scale....

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Necessity hopefully becomes the absentee parent of successfully invented children.

What about using a meat grinder? Something that worked in progressive stages, so that large objects to be recycled and something like a tree shredder cuts them down to smallish chunks. Then a coarse grinder to get them to the chip stage. A meat grinder to make a coarse powder, and maybe a wheat grinder like pair of counter rotating disks to grind that to a fine powder.

Mike

There is a RepRap oriented group at Delft Technical College in the Netherlands doing some work on this.

[reprapdelft.wordpress.com]

They aparently have a plastics shredder on campus. I'd love to know what the blade setup is...........

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Necessity hopefully becomes the absentee parent of successfully invented children.

... here is a multi-shredder shown 'in detail': Monster-Shredder

Edited 1 time(s). Last edit at 03/06/2010 02:18PM by VDX.

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Wow that is cool

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Necessity hopefully becomes the absentee parent of successfully invented children.

Anybody have a 3D model of that that we can print out?

[www.youtube.com]

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[www.urbansurvivalists.com]

Polymorph. 20 bucks got me a kilo of the stuff. You'd need a funnel with an agitator though, to keep it moving to the melter. It's the same price per lb as the white ABS from makerbot.

>>>What about using a meat grinder? Something that worked in progressive stages, so that large objects to be recycled and something like a tree shredder cuts them down to smallish chunks.<<<<

I was thinking along the same lines as you with the meat grinder along with the reuse of a few other kitchen tools. I put some time into the idea of using a "dumpling pan" and further a "pasta maker". [probersideas.blogspot.com].

>>Attacking it with a milling bit gives fine powder of course.<<<

I ruled this out a long time ago. KISS, this is the key IMHO >>>>The problem with cutting HDPE is it is one of those plastics that gets stronger when you stretch it until it is incredibly strong and very very thin. <<<

Use as a starting point various temps, within progressive stages to reshape and reuse the plastics for infill.

The device would operate kinda like how they crush cars down to a chunk. For our purposes, the plunger will push the plastic into an extruder to “reform” the plastic into tootsie roll size, or the preferred filament size rewound into a spindle.

If I had the time I would build it

I added a comment to pump based extruders like that. If you have a piston (better be steel in this case for the forces exerted) that has a port on the top side that opens when the piston is fully drawn back. Then it is easy to let pellets, granules, or chunks fall by gravity feed into the piston. Then as you force the piston forward it seals the port and starts compressing the plastic. If the other end is heated and has 3 mm orifice, it should produce filament in pulses. I seem to remember that ABS degrades a bit with each heating, so the heater should be kept lower than extruder temperatures and higher pressure in the piston used instead to meld all the particles together. A cam shaft or other set of variable linkages should be used to move the piston fast when it is withdrawing, pause for a moment to fill at the end of the back stroke, fast to begin compressing, then go to greatly slowed down with more pressure as it nears full compression. The whole cycle probably needs to go slowly so the plastic has more time to 'ooze' into filament form.

Mike

Edited 1 time(s). Last edit at 03/24/2010 05:13PM by rocket_scientist.

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Team Open Air
Blog Team Open Air
rocket scientists think LIGHTYEARS outside the box!

I am really interested in getting involved with this. Once I have something valuable to contribute I will post it up.

Would a scaled up nutmeg grinder work? A rotating perforated barral with the plastic pressed up against the edge so that the plastic is gouged rather than shreded.

yellowfrog Wrote:
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> Would a scaled up nutmeg grinder work? A rotating
> perforated barral with the plastic pressed up
> against the edge so that the plastic is gouged
> rather than shreded.


I don´t think shredding is the problem.
Extruding filament from powder without trapped air,
with consistent diameter and shape and
without the feeding-mechanism clogging up
due to molten plastic is.

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Is this thing supposed to be self replicating, easily sourced, or completely open to vitamins? Real machines use a worm gear style auger. I see no reason why this isn't achievable.

[www.harborfreight.com]

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.

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

I've been doing a lot of plastic machining lately. I've noticed that I'm producing an enormous amount of fine grit ABS powder by buzzing a 1/2" four flute end mill @ ~4000rpm, and using a feedrate of around 3inches a minute.

I'm not sure if this is economical unless used as a recycling process.

JohnnyCooper Wrote:
-------------------------------------------------------
> Real machines use a worm gear style auger. I see
> no reason why this isn't achievable.

With just a worm-gear feeding into a hot-end
it was already established in practical tests
that the worm-gear heats up too much, thus
melting the powder and clogging up the thing.

So using metal for a single worm-gear was found
to fail. Who is actually up for designing something
that may perform better instead of listening just
commenting?
Better yet, who here actually started working on something?

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* Blog
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I've been doing a lot of plastic machining lately. I've noticed that I'm producing an enormous amount of fine grit ABS powder by buzzing a 1/2" four flute end mill @ ~4000rpm, and using a feedrate of around 3inches a minute.

Ah, but you've got a well-defined block of plastic clutched in a vise. Now imagine feeding irregularly shaped pieces of plastic into it via a chute, or inverting it as if it was a garbage disposal.

Which might work.

So using metal for a single worm-gear was found
to fail. Who is actually up for designing something
that may perform better instead of listening just
commenting?
Better yet, who here actually started working on something?

Please don't pick fights with people, Marcus.

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

SebastienBailard Wrote:

> Please don't pick fights with people, Marcus.

Well, I just haven´t seen any designs and
would like to build, evaluate and improve one.
The´s a growing bag of plastic. Sorted by material and color
and it´s waiting to be recycled one day.

After I found starch-based bioplastics inadequate
(extreme shrinking, days of drying time) I have nothing
to concentrate on next.

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Quote

So using metal for a single worm-gear was found to fail.

Two examples of (obviously) working worm extruders made in metal:

[dki-online.de]
[www.maschinenbau-heilsbronn.de]

(Found in the German RUG)

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Here's an extruder nozzle for this design:
[www.3dcontentcentral.com]

And as an stl.

Obviously: nichrome wire is wrapped around the spooled area.