Automatic flatness measurement

If the gantry is sagging by 3mm, and I don't see any obvious problems with the methodology, cutting it flat is more like dishing it, which is going to be impossible to clamp to and get solid contact beyond a small fraction of a millimetre,

The only solutions are to rigidify the gantry (hopefully without too much weight) or lighten the carriage/spindle (if it's making a gantry sag by 3mm, the gantry probably doesn't have the capacity to take 1500W of cutting power anyway). This would include the Z axis motor, rails, etc. There may be a happy medium of both.

Of course if you're palletizing arrays and each part is, say, less than 4" square... Would it matter? Maybe not.

 

Thanks for your answers. I did additionnal measurement by adding 1kg weight on the spindle. Result approximately 0.1mm vertical mouvement, in mahority due to x axis stuffbess but we see also other effects (not fully consistent).
So that lead possibly out of the 3.5 mm observed on the measurement to 0.5mm/0.7mm due to lack of stiffness. Surfacing or compensating the base board will help in fact.

 

Very nice. That sounds plausible by my experience with 1500mm C-Beam. Doing this stuff without defined planes can be difficult, probably requires a laser-based solution.

Though a base board that's out by that much sounds... Odd. Is the subframe good?