Whilst this is not strictly AR, it is related as it will give me the ability to build more stuff. It was actually bought for my work requirements but I reckon you guys will still find it interesting.

This is the WorkBee 1000x1000mm cnc machine. I purchased the cnc and various other parts form multiple locations to build the unit that I wanted. This machine comes as a kit which makes it cheaper, but there is some work involved in putting it together. When i say work it was fun work.
I decided to house the cnc on a home made bench sitting on top of two large rolling tool chests. The two chests were bolted together back to back giving me 12 drawers of extra storage and a small section between them to house the computer.
The electronics for the cnc include the Arduino and the cnc sheild, and I also upgraded the steppers to high power steppers which them also required me to use external controllers. I ended up mounting all of the electronics under the spoil-board (the timber top that the machine will cut into if it goes too far through the job) leaving the computer in between the two.
I am using a computer running Ubuntu Desktop 18 for the controller that connects to the arduino via usb. I was originally looking for an ethernet connection so that I could keep the computer further away, but in hind-sight you really need close access to the controls when lining up the workspaces and zeroing out the Z-axis.
Initially, I clamped a biro to the Z-axis and got it to draw some pictures. This allowed me to get familiar with the controls and the workflow. It also allowed me to calibrate the machine ensuring that the end result was the right size.
Once I had the spindle installed and I received a few different routing bits, it was time to actually cut something. So I cut a few test shapes out of 3mm MDF, and all three cuts worked fine. So I then moved on to try making a PCB circuit board. My first attempt failed mainly because the 0.1mm v-bit that i bought from ebay turned out to make a 0.8mm cut (minimum) so whilst it cut the tracks out, it actually cut all of the track out. So I bought two new bits from a more reputable seller locally here in Australia. This one worked out fine.
Feel free to contact me if you want to know more about the cnc. I will probably just post a gallery below of some of the jobs that i have completed on the cnc. (Those that I can anyway – some designs are commercial-in-confidence)