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Stovetop recycling of HDPE swarfSunday, May 03. 2009Trackbacks
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sorry, I forgot you can't embed images
This tray I mean. It's a teflon tray if that turns out to be neccesary.
http://lakeland.scene7.com/is/image/Lakeland/12370?$normal$
As I said. It was a worn small frying pan that I didn't need any more.
This is quite interesting!
And this technique might be getting close to getting rid of reprappers' depencence on expensive plastic welding rod.
Imagine that one turns swarf (or pellets) into a disc of plastic 3mm thick. I'm envisioning using a large frying pan, resulting in a disk with appreciable volume of plastic.
One could then imagine a rotary "peeler" to cut the disk into a long spiral piece (~like the groove in an old vinyl record, played with a hot-wire in place of the stylus.) In cross section, this would be square, 3mm-on-a-side.
This spiral could then either be fed directly into a extruder designed to handle a square cross section (I think a pinch roller would do well here.) Or th spiral could be straightened and the cross section re-formed by gentle heating while rolling. -- And thence fed into a conventional reprap extruder.
Hmm, I was just thinking of something a bit simpler.
1: Print out a simple plastic spiral.
2: Hammer a sheet of teflon-covered metal onto the plastic spiral, producing a sort of mold.
3: Heat, sprinkle, just as above.
4: Get a long spiraled plastic rod. It's not quite cylindrical -- it has a cross-section more or less like a letter D, and it's spiraled, but it's probably close enuogh.
Interesting.
Have you tried a standard turbotherm domestic oven. Mine goes up to 220 easily (I used it to heat up brass busshings for pressing into acrylic without splitting) and can be verified using a jam thermometer.
As the heat is all over even, hot air, your plastic shouldn't heat unevenly and bubble like your toaster oven.
You want to melt the top, as you've melted the bottom? I would just flip it like a pancake.
Better still, have you seen those George Foreman grills? The concept is basically a small plug-in electrical appliance, with a teflon-coated heating surface on the bottom and another one that's hinged on top like a clamshell. You put your cheese sandwich, meat, whatever in and you close the lid. It's now being heated on both sides in a teflon-coated moulded shape. The major selling point of the George Foreman grill is that the whole thing's at a slight incline, and the runny cholesterol-filled juices run out of your food so it's not as greasy.
Imagine if the teflon surface wasn't the shape of a sandwich, but rather shaped to be a mould of a spiral. You'd presumably end up with the HDPE melting into the shape of spiral filament. If that doesn't work, I'd try something like a spaghetti maker - add in a heating element and it's basically the same process, yes?
A good idea to have cheap machinable HDPE is to mix HDPE with wax (the one my girlfriend uses to get legs waxed is cheap and can be coloured)
HDPE is found everywhere and it's cheap but I've not found a way to grind HDPE at home efficiently.
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