Heres the potential gears that might drive the extruder. they Currently have a 1:9 Ratio and having two sets combined with this motor from jaycar would be almost perfect RPM of around 100 and should provide enough toque.
The Mixer worked pretty well with HPDE and PET when it was run for about 30 minutes but its really not feasibleA kitchen wizz would probably work better because it would cut rather than munch, but they are expensive for what we might get/use out of it. looked in second hand stores and trademe Heres a quick model of the kind of chopper that would work best for all type of materials and states. Also would look cool when you put a makerbot model into it and chop it. Its Based off the chopper Jono posted awhile back. Depending how finely it chops it may need a second stage to chop it finer. But just speculation at the moment We can possibly make a larger extruder to fit larger pieces in using a 10-15mm screw, but the amount of material that it would push through may be unfeasible, but something to fall back on It has 50 pieces which are 3mm thick. There is a plasma cutter in the workshop that would easily cut them out. Using a mdf template cut on the laser cutter and allowing for the cutting tolerances it would be pretty easy to make. and since its kinda dangerous hand operated would be better. Or it may be a good opportunity to talk to industry and see it we can get someone to supply and or cut the material for us. Have also looked into meat grinders but the way the material is cuts/grinds may be ineffective for our needs and has same issues as we do with extruder. Total dimentions above is W 70 x L 80 x H80 but thats very Flexible
Jason has been trying to extrude some plastic through the screw extruder and see if it has any issues.
In manufacture they use a screw with a variable thread and spacing to increase pressure, move material in different states and maintain temperature within the chamber. So far the best suited is a 8mm wood orger for drilling holes - run in reverse.If this does not work a 10-15mm Coach Screw may be a good replacement. We have underestimated the amount of pressure that can be required within the chamber to extrude the plastic, in a few different machines they use COOLING only because the large pressure causes over heating of the plastic within. If it requires heating it is usually done at the chamber close to the die and uses the radiating heat along the chamber to melt the plastic at a slower rate making it mix better. As the plastic moves along the chamber it will absorb heat from the outside and help to stop overheating towards the hopper. Hopefully, at the moment the steel chamber will give us enough control over the temperature along it.
On the extrusion side with our current screw configuration, some upgrades might be *A heat separation section between the start and end of the die to help cool and keep the plastic in the die shape (high temp plastic, brass,copper which is 5 times less thermally conductive as steel or ceramic - i haven’t check its thermal capacity yet) *A vent to reduce air within the melt section(a vertical metal tube with a plate at the top that has tiny holes or a porous material) *A screen inside part way down the melt section to help clean the Plastic as it moves along the chamber (Metal Plate with holes in it)This also helps with re-aligning the chemical bonds within the plastic and a possible avenue to make re-melting easier within the makerbot and the recyclebot process *Change of material for the Chamber to better control temperatures. *Screw Replacement. And further down the track and easy way to assemble/clean/clear material and replace parts within the extrusion chamber and screw assembly.
Jason has been looking at the variable temperature melting points and it has something to do with re-melt and amount of moisture within the plastic during flake to melt stage.
If the plastic is not kept below a certain Moisture content the water has a chemical reaction within the plastic and causes it to break down back into its primary elements causing a higher temperature to re-melt again. "Ideally the reground pet should be dried to below 0.025% moisture content before extrusion" Seems there are generally two methods. Drying the pre-grind and then flakes, or a Vacuum in the melt and flak chamber(Seems a little intense). hopefully we can get the extrusion and heating a little tuned and see if we really need to go down the “drying” track before investigating further. To make our job easier we really need to keep as much moister away from pre-melted and melting pet as possible.
Hey, Sorry i had to leave today. Jeon bin has been researching with extruding a few different types of plastics and heaps of colours for the maker bot up at kelburn . He said he had some PET extruded and it could be a good insight into the process and see whats really required for us. I’m not sure what was talked about but i will just put my two cents in. For initial trials any PET will work - and then extruded, but re-use of the PET from bottles could be more challenging. They need to cleaned, washed and de-labeled and possibly flaked. It could be a good idea if people bring down a couple of bottles for tue’s and see if we can start the re-use process soon. I assume different colors wont mix in recycling clear might be easier for a start. A quick experiment could be to use the press in the workshop and see if we can extrude some plastic through a pipe and a die, Pet melting point is around 250 ish and shouldn’t be hard to do. An iron might just have enough heat for we need but it could be easier to have indirect heat such as a microwave oven or ..an oven so we can heat the die, hopper…ect all at once and cool individually as needed either outside or inside the “heater”
recycle bot is underway, we have research groups : Plastics research group: Avivid , Jonono, Yauu( melting point, how to crush it, cooling times, blend? sticky? And what you think you should do)
Heating Research group: Louie, D.Cmassive, Mack-attack hot crap.( Irons, teflon coating, Cooling how to? talk to Jen about Recycling research and how they doit. ) Precedent recearch group? : P-diggle, Lukass, BennieResearch how plastic is actually extruded, the ins and outs and how we can apply to our project. recycling research: Jen(you know what to do)
Put all that you find online and bring on tuesday!!!