Wire Guide was created for the delta that I've been building. Having designed printable rails, the rails don't have a continuous hollow for wires, so I'll have to run them along the exterior rails. The guid is designed to clip onto the rail. There are 2 gudie designs, short and regular. The short guide holds wires out about 10mm from the rail, the other 20mm.

These work with metal rails, but if they print too loose, you can always print them 1 to 2 percent smaller or use a t-nut and screw to stop them from sliding down a vertical rail.