You got exactly to the point of what is important in an assembly base for the Onefinity. Besides the rectangularity between the axes, the planeness of the assembly surface is crucial for the Onefinity CNC producing accurate results. This was last discussed here, but the QCW frames had not yet been delivered. (cyberreefguru had a prototype). I’m still waiting for it.
Mathematically, three points in space are always in one plane (a table with three feet can not wobble). So in order to make sure our Onefinity CNC is not twisted, we need to check whether the fourth foot is in the same plane as the three others.
There are at least three methods to check this that I know, but since I’m still waiting for the QCW Frame (and also I unfortunately have not enought time and room to do these things at the moment), I planned to check this in the future and to report it here then (under a topic like “How do I make sure my QCW Frame or Table Top is not twisted?” or similar).
One of the question I asked myself at that time was:
Still I have no answer since I’m still waiting for the QCW Frame.