built by hand in home shops all around the world
Sure, but I can't imagine myself taking on a project like this with such a small time budget without CAD tools, spreadsheets, etc. It was really nice to just pop the dimensions into the firmware and have them work.
It is a complicated project. Every location in the working envelope has a different step/mm resolution. It is all simple triangle math, but it is nice be able to play with values and see it graphed in real time on a spreadsheet.
What is controlling this?
It runs standard 3 axis G-Code using modified versions of standard Arduino firmware (Marlin, Repetier). The 3 linear actuators are labeled in firmware as X,Y,Z, but the GCode is translated on the fly into the moves required to get the motion you want. It is sort of like the way an arc move is broken down into line segment moves on some systems.