by emmett, published
A Moineau pump is a type of positive displacement pump with steady flow (no pulsing). This type of pump is common in the food processing industry because it can efficiently pump slurries (like soup) without crushing the contents. This one pumps 32 cc/revolution (neglecting whatever leaks back through the seals) and is capable of pumping water (milk is shown for contrast).
I thought this might be useful as a paste extruder or something of that nature. It's better than a peristaltic pump because no flexible hose is needed (which tend to reduce efficiency and wear out), plus it doesn't pulse.
Print out one of each part except the gap. The gap isn't printable, it's just there to model the shape of the internal cavities between the rotor and stator so you can visualize how each compartment moves upward while staying sealed away from the others at all times. One whole compartment is visible, along with portions of three others.
The rotor slides down into the stator; it's a tight fit, but that helps it seal. Once it's lubricated by whatever you're pumping, it'll go easier. The crank twists onto the rotor; no need for glue. It'll stay tight as long as you're pumping the right way (fluid moving toward the crank), but it'll fall off if you turn it backwards.
No need to prime the pump, just submerge the base in fluid and crank away.
A parametric OpenSCAD file is included so you can change the parameters to suit your needs. It will display the pumping rate based on your choices. You can also change the tolerance, though I found it works fine with zero, just relying on the flexibility of the plastic. I also made the wall thickness exactly two tread-widths wide, so the dimensions would be accurate. You may want to change this for your printer.
UPDATE: Thanks to Proton for making an animated version of the OpenSCAD file. This version is now included, so you can control the animation for yourself.