Summary

This is a cycloidal pump https://en.wikipedia.org/wiki/Cycloid not much unlike gerotor https://en.wikipedia.org/wiki/Gerotor.

Parts should fit smoothly, otherwise get your sandpaper out of the drawer.

Use 16 pcs M3x15 machine bolts for assembly, pref. stainless.
As axel, I've glued a hexbitholder to the inner rotor. Press fit might do it though.

Print Settings

Rafts:

No

                                            <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting resolution"><strong>Resolution: </strong>                     <div><p>0,1 or 0,2 mm</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>20%</p></div></p>                                                        <br>                        <p class="detail-setting notes"><strong>Notes: </strong>                    </p><div><p>Print with accurate setting e.g. "Engineering". Avoid oblong parts by making sure your printer is accurate in the XY-directions.<br>Use 3 walls/perimeters</p></div>

Post-Printing

Might require some scraping or sanding to reach smooth operation. If you feel it snag when turning, it's properly a z-seam that needs to be removed.

For super smooth operation, pump some toothpaste-water slurry in a small suitable container.

Cycloidal pump