I can finally say that this design is perfect for publication. The XHTC is an automatic tool changer based on Renè Jurack's design. To see the procedure for this design I can only recommend the video. There is also a playlist where you can get more information. The design of the STL files is finished, but the whole cabling and control is not yet.

Update 25.8.2019: >After a nice holiday in Russia and Southern France I get back to you!

>So that XHTC is ready for the next winter season (the time where I work most on my projects) I have reworked the entire electronics of the XHypercube and mounted it neatly on an MDF board.

>I also improved the small "XHTC Extruder Head" from my last video and got it running.

>All this I will present in my next video, so watch my channel https://www.youtube.com/user/xpixer , there will be a new video soon :)

Update 2.5.2019: >I have sat down to the improvements of the magnet holder. Many things I didn't like so much and so I went back to Fusion 360 to remove some bugs.

>The first thing with the tool change, I wasted too much free space with the cables and the too long pogopins, so that I could attach only 2 tool holders on a length of 300mm to my Hypercube. Therefore I had to remove all parts that protruded from the back of the magnet holder. So I built a cable channel for the lower magnetic ball and led all signal cables from above to the pogopins via channels.

>The second thing that I never liked is gluing in the magnetic balls. Here I built a kind of press fit, the balls are pressed into the frame and hopefully hold better than with the glue solution.

>Otherwise, I'm already so far with the headers that I can try a multicolor printing. More news will follow.

>Please check the last picture in the gallery.

The design supports compact tool heads, all electrical connections are only made with one tool change. I'll add more stuff to that. I am currently initiating the change with a script stored under "GCODE Scripts / (before, after) Tool change" in Octoprint from version 1.3.8. You can find the templates in the github: https://github.com/xpix/XHTC

It is still a prototype, but if you want to try it, here is all the information you need.

This is a collection of all links relevant to this project.

Fusion360 Design: http://a360.co/2DpOXs6

Video: https://youtu.be/xUQaVA273kA?t=1m42s

Diskussion:
http://forums.reprap.org/read.php?245,789306,802669#msg-802669

PCB for Pogo-Pins: https://aisler.net/p/RTBZFDAH

This is a list of all uses external Parts for XHEAD Project:

Neodym magnet balls 10mm https://www.ebay.de/itm/122187457941 5pcs 5.99 Euro

Neodym magnet quader 5x5mm https://www.ebay.de/itm/251544600651 10pcs 3.99 Euro

Washer DIN 9021 M6 https://www.amazon.de/dp/B06XNNVD4F 10pcs 1.00 (9.37 for 100)

Superglue https://goo.gl/DTFZqt 1pcs 3.99 Euro

Needles from bearing 2.5x10mm https://www.ebay.de/itm/302593794786 2pcs 0.20 Euro (6.99 for 100)

Pogo Pins http://www.ebay.de/itm/272957602294 5pcs 4.43 Euro (8.86 for 10)