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Moineau stepper extruder

Posted by ttsalo 
Moineau stepper extruder
January 05, 2012 11:05AM
Hello everyone, I'm currently developing a paste extruder based on the Moineau pump principle. In theory that design should work well as an extruder, as it has completely non-pulsating output and can pump pretty much anything. Running it with a stepper motor should allow controlling the extrusion just like in a hot plastic extrusion head.

Here's what I have so far: Exploded view. From the bottom, there is a conical nozzle, then the pump stator body and on the top, the pump inlet body, with NEMA17 mount and an inlet pipe. The stepper motor drives the pump rotor with a spider coupling, modified into a long shaft from this thing.

I have already printed the pictured parts and after I fix the designs of the motor couplings and get them printed, I'll be running some actual tests.

I'm not sure if PLA printed stator and rotor will seal well enough to reliably pump fluids. Commercial designs seem to use a molded elastomeric stator. Does anyone have experience with these things?

Also, what sort of paste would be a good starting point for trying this out? I'm thinking of paste made from water and wheat flour. That at least seems to be easy to clean up and non-toxic.
Re: Moineau stepper extruder
January 06, 2012 06:42AM
I wasn't aware of this principle of a pump, yet. Nice catch.

A slurry from wheat and water might be ok for initial experiments, but for usable parts plaster or silicone is likely better. Wheat shrinks heftily when drying.

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Re: Moineau stepper extruder
January 06, 2012 09:41PM
Here's the complete design: [www.thingiverse.com]

I did a test run (extruding into air) with slightly runny wheat dough: [youtu.be]

Now I'm just missing a printer to put this on... I wonder if printers with moving print surfaces are suitable for this sort of printing or should I try to find a Darwin-style design where the print plate only moves in Z? The Unfold ceramic extrusion project page says that the print plate should not move or it might break the object while printing.

Edited 1 time(s). Last edit at 01/06/2012 09:44PM by ttsalo.
Re: Moineau stepper extruder
March 25, 2012 05:04PM
I did a test with a Makerbot a while ago and the object did not collapse as I feared (maybe the acceleration features smooth out rapid shakes?) But more tests need to be done to be sure over this issue of moving print beds.

Cool design, but you know by now from my comments on Thingiverse winking smiley
Re: Moineau stepper extruder
March 26, 2012 05:33AM
It probably depends on all of the following: the material, the shape of the object and the acceleration...

I broke my plastic printer (well, the extruder) so I haven't been able to test this, but I made a design where the stator is constructed by placing a cylindrical insert into the pump. This piece can then be separately printed from elastic material or formed by casting in place, using a separate, removable plastic piece to form the stator hollow.

For this purpose, I bought a roll of plastic called TPE (thermoplastic elastomer) from Orbi-Tech. It's quite flexible, hardness Shore A 50 if I had to take a guess (it didn't come with proper specs). It should be possible to print the stator piece from that. That, along with sealing the motor shaft, should allow the extruder to seal properly and maybe even pull a partial vacuum.
Re: Moineau stepper extruder
April 08, 2012 11:29AM
Tomi, could you share the design for that, I have the same flexible material here.
Re: Moineau stepper extruder
December 13, 2013 08:03AM
I am modelling the cavity of the stator as a 3d part. Next I will make a silicone model out of it. That will become my rubbery stator. I hope this way I get a good sealing for the rotor, as I have not had much luck with my quite viscous paste till now.
Re: Moineau stepper extruder
December 13, 2013 03:21PM
I like this idea.

You might try Oogoo silicone, it's inexpensive to make.

Can it self prime, and pump from a non pressurized reservoir clay of toothpaste consistency?

Maybe a pot with an auger to push the clay down, and into the pump might be all that is required.
Entrapped air needs to be guarded against, or you will experience gaps in your object.
Re: Moineau stepper extruder
December 13, 2013 04:18PM
Thanks a lot for the Oogoo tip. I'm just reading how to make it here: [www.instructables.com]

I will report back with my results. I really hope it will prime itself.
Re: Moineau stepper extruder
December 15, 2013 03:12PM
I did the test, oogoo silicone worked wonders and the resulting pump can prime itself (I was testing with fabric softener).
Re: Moineau stepper extruder
December 16, 2013 09:03AM
That's really neat!

Please make a video showing how the moineau pump is assembled and the non-pulsating pumping!

If the size of the moineau pump is sufficient, test pumping toothpaste.
Toothpaste would be very close to the consistency required of clay to be useful for 3d printing.

I have a few ceramics project in mind, and this would be a fantastic tool to employ!

Re: Moineau stepper extruder
January 13, 2014 10:00AM
Some more testing was done and videos were attached to the thing [www.thingiverse.com]

Self-priming is quite limited to a few inches of height and only if the stator is lubricated with some liquid before.

But for my project I am now testing an auger valve: [www.thingiverse.com]
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