How good is this?

[dean]

Sorta got the xxl up and running. still have to make a threaded wasteboard and wanted to see what the cut accuracy is. I tried out the concentric square and circle idea as mentioned here GRBL $100 & $101 Issue
Only difference is I cut out patterns from 40mm to 190mm in 30mm increments. This first set was with the Grbl settings for x and y at the stock 40 setting.

Thinking I can do better used this data to calculate new values for the Grbl x and y. This is the result:

This seems better in the fact of the squares are more square and circles are less oval. The data is suggesting the bigger the object is then the bigger the deviation from the desired size. Would this suggest I have a setup issue somewhere? Its not by any bad by any means, the fellow who posted his test had more of a consistent deviation from the smallest to largest test cuts.

[MadHatter]

@dean

bigger the object is then the bigger the deviation from the desired size.

If your error scales with the size, then that would indicate the steps/mm value needs to be adjusted.

[Griff (Well crap, my hypometric precursor device is blown…)]

Might want to try this:

Tutorial: Calibrating axis belt stretch on SO3 with a caliper

Seems like a fair number of people have trouble with belt calibration, so here’s another shot at a tutorial using a different method. You need a digital caliper (at least 6"), some clamps, and a block. You don’t need to cut any material like you would with a square-cut type test. Here’s a handy spreadsheet for doing the calculations: GRBL-Calibration.zip (8.2 KB) Getting Set Up: (1) PUT A FRESH BATTERY IN YOUR CALIPER! If you paid less than $100 for your caliper, it almost surely loses c…

I do this monthly, also any time I replace a v-wheel. Sooooo easy once you’ve done it a few times.

[luc.onthego (Luc)]

Thanks for reposting this, I need to do that soon and thank you @mikep for taking the time for posting this in the first place.