To build a pellet/scrap plastic to filament machine.
June 15, 2012 08:46PM
I posted this earlier the mechanism to make pellets to filaments, or scrap to filament would be creating a hopper cooking cone and an exit point for filament. I have not prototyped it, but it should work for under a few hundred dollars.

That filament would be cooled after being forced out of final 3mm or 1.75mm tube by applying pressure to the hopper that would push on the molten fluid product in the cooking cone. Making sure the cooking area is vacuum sealed that would lower air bubbles being pushed into filament creating gaps. Various ideas for making the system very cheaply have been posted on some other threads.

Pot, big washer in middle of pot, weight or hand/motor driven press or large weight for gravity pressure, copper cooking cone with fins in middle to transfer heat, stirring rod suspended into liquid fluid through pressure washer. Then coper tubes that can maintain molten temperature till reaching 3mm or 1.75valve would be attached to funnel, and a cooling tube would be attached to end of the extruder device of that product.

At the point where the filament leaves the cooling tube a device like the filament feed device would be used to limit the speed of product leaving the tube. That would create back pressure to ensure the product is solid without gaps and of a consistent diameter. On the valve there would be a second exit point where any pressure above that needed to push product out at a set speed would vent molten product to be recooked and be reused in another batch.

The extra pressure release valve allows for the speed of output to always be at whatever pressure is required to reach the set speed, any pressure above that would be forced out the venting tube. the size of that valve or path that valve leads to, a length of bended copper, could be used to control the extra pressure that would be needed to keep the forces pushing on both sides of the molten plastic as it cools to filament form.

So bottom pressure would be added friction of having to go through a mechanism that maintains speed by turning like the filament feeder. Top pressure would be the press pushing on hopper washer. And to moderate that pressure to some value to not be more then needed a relief valve would wind through a cooper tube, adding some frictional pressure of the turning of the product. A pressure valve could be used also, but cheaper to just wind a tube.

The system would have a consistent pressure pushing out filament,
and a pressure pushing up by slowing speed of filament leaving,
and extra pressure above some set need of two pressures pushing on cooling filament both from below by speed moderation of exit filament, and above by press down on hopper pressure would be vented.

Make the pot a cylinder with rings around the tube of sheet metal to get constant surface of the cylinder and able to handle any pressure or vacuum, use a bicycle tube to gasket the inner washer in hopper to the inner surface of the sheet metal pot, and a reverse bicycle pump to create vacuum pressure before cooking. Use weight or motor driven press to create pressure for output. Could have temperature and pressure sensors to govern the movement of press, or just do it by hand and let the valve absorb any over pressure.

Robert Eastwood
Re: To build a pellet/scrap plastic to filament machine.
June 15, 2012 09:05PM
To make a valve that has 1.7mm exit, and for tubes for heating and cooling copper tubes that have a 1.75mm inner diameter copper tubes can be found at these locations

Copper tubes to make an extruder length to be cooled or to make the nozzle or valve probably could be found at one of these sites

Or for a MacGyver approach.
Put a 1.75mm filament through the middle of a few of them to increase the length of a tube, add some product that can glue them together like JB Weld, assuming it handles heat at melting temperature used for input pellets. Although some other material would have to be used for a thermal insulator, any pieced of high temp material with a hole drilled through it would work.
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