Looks like fun! 
https://www.youtube.com/watch?v=1QHJksTrk8s
<LINK_TEXT text=“https://howtomechatronics.com/projects/ … sed-robot/”>https://howtomechatronics.com/projects/scara-robot-how-to-build-your-own-arduino-based-robot/</LINK_TEXT>
This is not what I want to know for robots like ABB robots. But it is looks good and simple