Recycling plastics

A relatively frequent topic of discussion has been the use of recycled plastic as feedstock for RepRapping.

While this has obvious desirabilities, it also has real issues, particularly of consistency of product. It is also a topic that inherently benefits from a large scale approach rather than a "man in a shed" approach.

I just noticed an "Innocentre" (whatever that is) "challenge" in this area advertised on Nature's website :

[www.innocentive.com]

This may be of interest to people examining this topic. It's an area with real benefits to be had, but also real, and quite varied, challenges.

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Aidan in Sunny (?) sub-tropical (very) Aiberdeen. Fit like, loon?
What grabs my interest ? Making models of fossils which are preserved as rock that ISN'T THERE.

Most of the recycler designs are for horizontal extruders, like the plastic industry uses. How about a vertical, gravity fed design like for fiber optics?

We can use plastic ooze to our advantage here. PLA oozes even with a tiny orifice, so it should ooze just fine with a larger orifice. Put plastic in a hopper, like a metal funnel with resistors, similar to heated beds. Hang the hopper from a nail in a rafter. Put a water bath below it to solidify the filament, and then some type of motorized reel/spool to wind it all up.

A key problem would be dialing in the right height above the cooling bath in order to get 3/1.75 mm filament. Another would be spooling the filament in such a way so it doesn't disturb the molten filament entering the water.

Edit- here's a video of how fiber optics are drawn: [youtu.be]

Edited 1 time(s). Last edit at 08/24/2011 12:31PM by Buback.

That might work for turning your "cleaned" recyclate into filament.

For the take-off problem, I'd look at using a long thin cooling bath - a length of drain pipe or something similar, plugged at the bottom, then taking the cooled filament out of the bath from the bottom by drawing it up through a thinner piece of rigid(-ish) pipe.

However, the big problem to my mind is preparing the consistent supply of recycled plastic. Unless you have a source of manufactured waste - sprues from an injection moulding facility for example - then you face the problem of sorting plastics into different compositions. Which means identifying them. Which is not easy. Then there are the issues of "filler" added to plastics, which can be many different compositions in many different sizes. Then there are materials dispersed in the polymer, which can affect the physical properties of the plastic (carbon black, or chalk powder, or chopped glass fibre strands). Then the relatively minor issue of pigments in the plastic and dyes on the plastic, both of which can affect the physical properties of the bulk material.
As I thought on reading the cited article, these problems are addressable. But they're not simple problems.

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Aidan in Sunny (?) sub-tropical (very) Aiberdeen. Fit like, loon?
What grabs my interest ? Making models of fossils which are preserved as rock that ISN'T THERE.

Still, some reprap users may want to recycle just their own failed prints (where most of the drawbacksRockDoctor mentions are off the table).

I do like the idea of recycling. Since a while ago I am looking differently to some of the garbage. However, as RockDoctor points out, mixing materiales of unknown sources may not lead to consistent results. I would like to be able to recycle at least my failed prints but as I am still building my reprap now I can wait :-)

Recycling failed prints ... an issue that I had completely not considered.
Most of the "I want to recycle plastic" messages I'd seen had been in the vicinity of "used milk cartons", "old carrier bags" or such like source descriptions.

Excellent point.

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Aidan in Sunny (?) sub-tropical (very) Aiberdeen. Fit like, loon?
What grabs my interest ? Making models of fossils which are preserved as rock that ISN'T THERE.

Quite useful link providing the information about contamination removal from plastics before recycling. We at Replas manufacture plastic recycled products such as plastic profiles, plastic decking, etc so really looking forward for such techniques and ideas!

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