Inspired by Madox's Mini Centrifugal Pump, I created this one from the ground up using OpenSCAD (and my Geany text editor configuration). The big change is the introduction of water cooling. Without it, the motor gets fairly warm at higher flows. A small portion of the output is routed into the motor cavity and drains out the back via the printed hoses. The motor is sealed on both ends with some Oogoo orings to keep the water out of the motor internals. Healthy application of ABS glue ensures everything is sealed It uses a 7mm motor from a Syma S107 toy helicopter and is powered by a 3.7V lipo battery. I have driven it with PWM and have got excellent variable flow. It could definitely use some optimization but I am pleased with the first cut. Here is a video: http://youtu.be/BDCUHT5uvGk It is designed to be printed with 0 infill aside from top and bottom infill (set to 3 and 3). Note that extrusion width is one of the parameters in the .scad. Set this to your value to ensure proper sizing. Mine is 0.4mm. I used 0.15mm layers. Slic3r did a couple of odd things with the print, including not infilling the second layer of the Motor Cap, which made the top (3rd) layer very sparse. I will have to look into that more.