I thought I would briefly cover how I am making the 3D printed parts for this project.

I'm using OpenSCAD (http://www.openscad.org/) to design the parts. This allows me basically design by programming (going with what I know here). To give you an example, this is a very simple OpenSCAD program to create a 5mm cube with a 2mm diameter hole through it:

$fn = 100;
difference() {
	translate([-2.5, -2.5, 0])
		cube([5, 5, 5]);
	cylinder(r = 1, h = 5);
}

Which produces this:

Once I have a model to print, I export it from OpenSCAD as a .stl file and load it into Cura (https://ultimaker.com/en/products/cura-software) for slicing. I used to use Slic3r (http://slic3r.org/) but I find I get slightly better results with Cura. This gives me a .gcode file that I can transfer to the printer by SD card.

The printer itself is a BQ Hephestos (https://www.bq.com/en/hephestos-prusa), Prusa i3 variant that I've modified to replace the Z axis threaded rods with lead screws.

I will be making the OpenSCAD files available for download under some sort of free licence when I've finished the project.