I just read your article in RepRap Magazine. Thanks, it was very interesting. I knew nothing about Moineau pumps before. It seems to me that the rotor looks very much like a rope thread, described in ISO 10208, which is used in the Rock Drilling industry. Maybe it would be possible to use something like a part of an Atlas Copco MAI SDA R32L as the rotor. It would have to be cut to a suitable lby hgn98009 - Paste Extrusion Working Group