Making a 3mm scrap/granule feed extruder

I have started to make a 3mm extruder that will directly feed a Rapman 3.1.
This will be a vaccum air removed system (hopefully) that will be fed with raw granules or ground scrap.
i'll provide links to pics and more details as soon as the pic uploads properly.

Awesome - I look forward to your progress! I should be saving my scraps/fails!

With a number of injection moulding companies near me it should keep me supplied in either new granules or scrap plastic for a while

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Andrew

Based in Slough, United Kingdom

Here is a link to the info and a pic so far. LINK scroll down to the pic then read the blurb for it to make more sense.
Sorry if the explaination isn't all that clear. It should make more sense as I post more pics as it comes together.
If you need a better idea of the principle, have a google for clay pugging machines whihc use a vacuum chamber to get air out of the clay while they mix it. Its about the closest thing to what I am trying to do.

Edited 1 time(s). Last edit at 08/14/2011 12:49PM by ablainey.

I have access to 160 injection molding machines - 40 tons to 3500 tons. If you need any information please let me know. Yesterday, I ordered a Huxley for me. I think your work on granule extruder is really important for spreading the Rep Rap exponentially.

I will also start working on a granule extruder, as soon as I get my huxley and understand the basics.

Best of Luck.

Awesome, I can't wait to see pictures

Had a bit of time to do some more and here is some pics.
First pic shows how the new granule extruder will be mounted above the printer. The reason for the height is so the silicone hose can move without causing much stress on the print head.

Second shows a close up of the extruder. This is a 16mm auger bit inside a co2 capsule. with an outer gas tight chamber made from an aerosol can (just bits I had lying about). This extrudes directly into the printers filament feed. There is no heaters or thermistors on the new extruder yet (Im still waiting for parts).

Third pic shows the granule hopper (an old Butane can) and vibration agitator. There will be plywood rings put inside the can to stop it crushing. the top will be sealed and have a vaccum gauge and vaccum line to the pump put through it. Finally there will be a screw top feed port on the side for filling the hopper with granules.
The 22mm T coming out of the bottom of the hopper will have a polycarbonate disk epoxied in to make a viewport so I can see the granules.
The agitator is just a motor with an offset blob of epoxy which will vibrate the silicone vaccum tube. This will help the granules flow down to the extruder. The tube is 16mm OD, 12mm ID. The agitator is jubilee clipped onto a short bit of 22m copper pipe which is held in place by some 'O' rings so there is no squashing of the hose.

Edited 3 time(s). Last edit at 08/24/2011 12:05PM by ablainey.

Would a screw work for pushing the granules down bit like a mince making machine?

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__________________________________________________________________________
Experimenting in 3D in New Zealand

@NelsonRap
Yes thats it. Google Auger drive for more info on this kind of conveyor/pump/drive. Augers are used for lots of things like grain etc. Its really handy that we can use very cheap wood auger bits for auger drives.

Rather than add support to the can/hopper I found an old antisiphon bath trap in the shed, so decided to use it for the hopper as it splits in half. Cut the ends off the can and epoxied the trap in the middle (after sawing a few pipe connectors off it). It makes a really good vacuum chamber due to the tappered shape, thick walls and already had a nice 'O' ring seal at the join. (ive also added a 5mm acrylic disk to the view port)

second picture is the vacuum gauge with the Pump running. It only takes about 2 1/2 seconds to totally evacuate the air from the chamber/hopper and granule feed tube and then it holds at -1bar with the pump off.

The only problem is the vaccum is soo good the feed tube crushes a fair bit and It looks like it will be enough to stop the granules feeding properly so I will have to change it for a thicker hose.

Apart from the hose issue, all I need now is the heating and temp sensing parts. (Cant wait to get it running!!!!)

Edited 1 time(s). Last edit at 08/28/2011 07:57AM by ablainey.

Pic of the view through the viewport of granules going past into the feed tube.

Here is a person extruding plastic with nozzle that is fed from chamber that is driven by wood drill bit

He uses the plastic for bacterial (etc...) growth to his plants...but what if, we did not squish the plastic, but we pushed the plastic through a 3mm nozzle, vertical screw (wood drill bit) and drop the filament that comes from the nozzle straight to a water chamber that would solidify the filament and it could be put on reel...

Phew...long sentence. But anyway, what do u think?


[www.youtube.com]

@Mikko Kosonen
Thats really good. It proves the wood bit idea works, but I shouldn't need as much motor power and gearing as he is extruding at a much faster rate.
thanks for the link!

My other idea was to make a vessel that would hold for example 2.0kg of granules. We would melt the granules in the vessel (180-200 degrees or whatever) and there would be a valve on top, and valve on bottom.

After the bottom valve there would be a 3mm nozzle which would output the product.

To the top valve, one would put a constant, steady, air pressure to drive the filament out to a water chamber where it would be collected again on a reel...

Dunno how good the product would be...I have seen one extruder somewhere and its output was like....dogs s¤#t

Mikko Kosonen Wrote:
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>
> Dunno how good the product would be...I have seen
> one extruder somewhere and its output was
> like....dogs s¤#t


LOL. I can imagine it.
I think the big heated tank idea should work in principle. Downside is the really long heat up time, but if you are using it to make rolls of filament then its not a problem. I am trying to bypass the whole filament idea.
One problem you might get is the need to keep the air pressure constant so the output is at a steady rate. It may be easier just to use a plunger to extrude it if you are melting a fixed amount everytime?

Just surfing through reprap videos on youtube, found this, so it seems somebody actually has a "working" granule feeder. At least one point in video it shows a basic screw feed..

[www.youtube.com]

Thanks for that. Interesting. The extrusion looks quite thick and I wonder how much problem trapped air is?