Not sure whether there's been any progress on this topic at all but i'll throw my hat in the ring. My old man just retired as head engineer from a plastic recycling company. They didnt have any injection moulding equipment but dealt more so with small and large extruders. There's a bit of science involved when mixing formulas so the extrusion consistency is good etc; if you have any queries i may be able to assist to some degree. I couldnt get my hands on the patent extrusion mix though. It contained mixtures of ABS (styrene), HD (plastic milk bottles), sawdust and maybe one other mystery ingredient. This formula was used in the production of park benches, bollards, 2x8 planks, garden stakes amongst other things. surprisingly... They never touched PET bottles! too hard to process!
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- Posted by Chris b 1 year ago. There are 14 posts. The latest reply is from Chris b.
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progress is interesting, PET from i've been told is hard to process because almost all bottle have 4 different types of plastic on them, the bottle the cap the gasket inside the cap and the label,
separating this stuff by the tonne is done these days in china (we export almost all out recyclable bottles) they shred the whole lot then via vibrating tables and floating separators it can be separated out into the 4 plastics,
after that I'm told the residue can be washed off the PET from the glue they use to stick the label on with a mix of hot water and laundry powder some places use a solvent bath
as for progress , time as usual is a little short, however I'm up to the point where I'm looking at the options as far as shredding the plastic goes, the best option so far is some HSS milling cutters from a horizontal milling machine ,against pet they should last forever and with two opposing interlocking shafts of these they should be able to handle some pretty decent volumes of plastic
with the extruder i've got an auger now and i've drilled out a block of aluminium to make the feeder i've tested it out with some polycapricone granules and they feed through very well
i've got a few things to sort out with the cnc mill and i should be able to have some of the big pieces for the shredder done within two or three weeks, finances depending,I'd love to get if possible some photos of some of those extruders and how they are set-up you'd be surprised how much by way of design ideas you can get from a simple photo
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Sounds like you have been doing some homework, good stuff
I was unclear on why the pet was never used but that makes sense, if theres too much manual cleaning/processing before it can even be shredded, well... thats capitalism for you. Send it to China for the commy peons to sort out. Its a shame because its quite a resilient product!
Now i would love to get you some photos but i'm damn certain that if i were to stroll in there with a camera, i would have a lawsuit slapped on me in a heartbeat. what I probably can do at some stage this week, is sit down with my old man and get some sketches of the extruders and diagramatical info regarding feed, augering, temperatures, moulds or what not. If you want any mechanical specifics, it'll be going from memory so it'll be close but allow some tolerances.
hit me up on mdtcompserv@yahoo.com.au -
with the pet bottles, what most of them do in china is shred everything the bottle label cap the works, then when it's all flakes separate it out, with a vibrating table,
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