Granule Extruder meets local store

A threaded rod, washers and a lot of nuts, also a lot of work, but everything from the local store.The second turn would fit also, but I broke the inner ring while fastening the nuts.



I used M3 threaded rod and nuts, the washers are M5x20.It is planned to fit in a 22mm copper tube with an inner diameter of 20mm. The screw has an outer diameter of 19 to 19.5 mm when the washers are bended.

Why M5 washers and such a lot of M3 nuts?
There are three reasons for the M3 nuts and one of them is related to the M5 washers.
1.
If you fasten a M5 washer carefully between two M3 nuts it is self centering because of the bevel on the outside of the nuts. This also works with some other combinations like M5 nut and M8 washer.
2.
The nuts fill the space between the inner side of the thread and the center of the screw. So there is not so much jb weld needed to fill the gaps.
3.
The nuts are a good base for a unitized pitch system, this is a good help for experimenting and sharing results.
I used 3 nuts for each of the first two turns and 4 nuts for each of the next two turns. The last turn should be about 5 nuts ...

Not a good help for experimenting is washer bending. It is no nice work to bend them and you have to take care to keep the diameter.

There was no test today because of the broken second turn.



My next project will be the time extruder, but I don't know when to start

Edited 3 time(s). Last edit at 08/17/2008 09:53PM by uplift.

I wonder if a bulb auger bit would work. Somerthing like one of these: [www.amazon.com] Might be a bit on the large side.

Why not just use a regular wood auger type drill bit?

Neat concept. I'm afraid your outside diameter won't be constant though, which would mean that you won't be able to get a pipe that fits around it and forms a tight seal.

The challenge was an auger from local store material. I haven't seen any 'ready to buy' version and I also was totally into my washer idea
My reference was the wiki granule extruder. Except for the linked drill bit experiences report I think that the faces of the thread (from outer diameter to outer core) are too small to transport the needed amount of granule or even get the granule in case of a bit <10mm. Also it looks like a drill has to run too fast for such a viscous liquid.
The drawings of professional extruders show that the core diameter is increasing to the end of the auger. This looks to me like a way to increase compression and you could do that on a drill bit too. Another way to do that is to modify the pitch. In case of the washer auger you can combine both ways to get a shorter auger or increase compression with higher efficiency.
I was afraid that there would be no way to build an extruder with the needed efficiency and tolerances at home. The wiki auger has a difference of 0.5mm between the inner diameter of the tube and the outer diameter of the auger and the face of the thread (on one side) seems to be about about 3.5mm.
The washer auger fits with a difference of 0.5mm to 1mm to an standard 22mm copper plumbing pipe. With M5x15 washers it will fit the same way to a standard 18mm copper pipe. The washer thread has a face (also on one side) of about 6mm. I thougt if I can't make it tight the same way, I have to make it bigger. Tolerances are related to the size of the object
My first tries will show if it is tight enough. I decided to wait with testing until I get some PE granule this week, the only granule I could get before the weekend was PVC and I was told to not do this at home.

This is a schematic diagram of some options given by the modulary thread-washer concept.
The counterrotating M5 section is only to show what might be possible, my dad came up with this idea when we were talking about ways to get more compression. I hope there will be enough pressure without that, it also does not make much sense to increase the core diameter before the heater section.
There was no space left to add something like a stern tube, this is to keep the granule in the reservoir away from the hot, turning parts.
edit1:
I know that a M3 threaded rod might be too weak for that, it is just to show the relationship betweeen washer nut combinations.
/edit1



edit2:
Sorry, the M5x25 and M5x30 should be M8. Both, M5 and M8 are available in 25mm and 30mm
/edit2

If the extruder will still get to hot I will use two of them, so they can change running and cooling every two hours.

Edited 2 time(s). Last edit at 08/19/2008 12:03PM by uplift.

... i think when the size of the nozzle-output is much smaller, than the slit(s) between the auger-blades and the enclosing tube, you can't extrude with a constant rate - the 'back-welling' should be bigger than the extruding.

When used a mincer (meat-grinder) i notized a similar behaviour, when the holes were blocked ...

Viktor

I do not know if this will work, haven't tried it yet.
Like mentioned in the posts before I am also afraid that there is too much slack and too less pressure, and kyle too.
It looks like the fluid is very viscous, the wiki extruder uses nearly the same slack but half the blade size. My mom used a mincer for cookies, sometimes she had to press on the input to keep the output. So maybe there is a point where enough granule is pressing on the fluid and the way through the nozzle is easier than against the masses.
The wiki extruder worked, it only got too hot. Before have seen that I thought something like this would never work. (also mentioned before)

Edited 1 time(s). Last edit at 08/19/2008 11:54AM by uplift.

Forrest Higgs Wrote:
-------------------------------------------------------
> Why not just use a regular wood auger type drill
> bit?

My guess is that because they are designed to pull material toward the drive motor they would not work properly in reverse. Perhaps a long auger could be ground down to make a shaft on the other end.

well in theory couldn't you just flip the wood auger drill the other way. Grind off the shank and grind off one or two revolutions frrm the other side so you have some place to attach "stuff".

I just ran the drill bit I was using backwards. Nothing to it.

Just thought of a possible way to minimize the slop around the edges and mitigate my previous concern: use oversized washers, and then lathe the entire assembly down to the correct size once it has been assembled.

Of course, I still haven't heard a compelling advantage that this has over the wood auger idea... that seems much simpler.