I am trying to come up with a good pattern for calibration the auto squaring. I will eventually turn this into a page for everyone to follow…I hope. We have arrived at a whole new realm of measurements, and know that 0.1mm is fricken tiny.
Just to keep us all on the same page,https://en.wikipedia.org/wiki/Accuracy_and_precision. Accuracy I will try to use the terms in the wiki context, Accuracy (how faithful to dimensions), Precision (repeatability), Trueness (a combination of the two), and referencing the picture above, X=left to right.
The first problem…the pen mount. The pen mount has a really good amount of spring to it so the people with really uneven surfaces can use it without tearing there paper. It is not accurate enough in the Y direction, to fix that I would have to make a more stiff version. The Pen I am using has the least amount of slop in any pen I have ever seen. Needlepoint and clicked into place it seats itself in the “collet” very well.
Second, measuring two lines on a piece of paper is extremely difficult with any precision.
I can say the machine has stupid good precision. Using as light of pressure possible to avoid divots in the 65lb Cardstock, a 0.3mm ball point pen I can run repeat jobs after moving the gantry and auto squaring so good I can not tell they have been re run. Precision=dead nuts in my book.
Accuracy with the pen mount running repeated tests for me along the x axis has been -0.05mm to -0.1mm over 150mm , and -0.2 to -0.4 over 150mm Y.
So if any of you want to run some tests I would love to see what you get.
The one good thing that has come out of this so far is that, we have a way to tension the belts. Start stupid loose, draw a square and measure it, tighten each belt one click at a time. Stop when the number stops changing for that axis’ corresponding line. It does not have to be very tight to get great results. I kept going tighter and saw no improvements, I also couldn’t mess up the calibration so it seems there is a huge window of just right in terms of tension.