Squareness of a machine is very easy to measure. (Basically, all you need is accurate paper with squares and a web cam.) Certainly, measuring it is much easier than getting the machine really square. For example, my machine at the moment is 0.1445% square. In other words, for every 100mm of Y movement the gantry moves 0.1445mm in X.
How about being able to tell the TinyG that?
There would be a setting for squareness, default 0. I would set it to 0.001445. TinyG would then use that, and magically, the gantry movements (and the coordinates displayed) become accurate in real world.
JuKu
Just curious;
1. What type of machine do you have (screw, belt, etc)
2. If you make your "squareness" measurement 10 times, what sort of variation do you get.
The underlying question is one of machine induced variation.
There are those that doubt that a ShapeOko, for example, is reproducibly accurate to .15%.
I have not really collected any data on the subject.
It is a pick and place machine, so thete are no loads to talk about, and that ia likely a big factor. The work area is 370 x 580 mm, and movements are reproducible to 0.1-0.15mm. GT2 belt driven, software slack compensated. So, when I move 500mm, there is 0.65-0.8mm sideways movement. I can measure better than 0.1mm, but I don't know how much better.
I'll see if I can implement this on my system driver level. Even if I might be able to do this, this might be useful in general.