The Tool Changer: Prior art

The idea of a tool changing 3D printer has been around for a while, but I haven't found many implementations. By far the best well known is E3D's tool changer. E3D is a leading manufacturer of 3D printer parts. Last year, they announced a tool changing 3D printer. They haven't yet released any tools besides 3D printer heads, but they are already selling beta versions. Their design uses a core XY movement configuration, and has the heads hard wired to the electronics. In an interview, they expressed their plans to replace the wires with pogo pins, which detach with the tool. The tools are attached with a kinematic coupling and a spring loaded latch.
On hackaday,io, I found a hobbyist who had made their own tool changing 3D printer. Their design uses the same core XY movement, and hard wired electronics. The tools attach using magnets and pins. This project is interesting because it does not require changing the printer firmware. All of the tool changing is handled through custom GCode. Additionally, a USB microscope is used to compensate for alignment issues.
There is also the Mark2 magnetic tool changer. It also uses magnets, and is meant specifically for the Ultimaker 3D printer. This project is also entirely open source.
In general, my research into previous project show a couple points:

• None of these systems yet have tools other than 3D printer heads.
• All of these systems use core XY or similar movement systems.
• None of these systems disconnect the tool electrically when it is not in use.

I have done some more research and come to some other conclusions. I will post that in another post.