great thread!
Quick question: does anyone know how to use the lulzbot dimensional accuracy stl file to calibrate their printer? http://download.lulzbot.com/Mini/1.03/novelties/make_test_parts/dimensional_accuracy_test.stl
or the other calibration files on the lulzbot download site?
Like what the dimensions are supposed to be and what margin of error is typical in a calibrated machine? Am i the only one who has tried printing these?
Calibration objects are intended to be used with a good set of digital vernier calipers. Typically they will be a set number of mm thick for measurement, or will make a hole that should be x mm wide, or a geometric shape that should be uniform on all sides. Others show how well you can bridge a gap, or what degree of overhang you are able to print. Typically a calibration object with measurable walls or blocks will be a whole number mm measurement unless it says otherwise. On round holes, you want the correct size, and uniform x and y dimensions. A squished hole is indicative of a loose belt. The name of the game is measure, adjust, reprint, repeat.
And if you are trying to get you size calibration accurate, make sure you have dialed in your extrusion first. If your e-steps are off, your dimensions will be as well. The Mini seems to come with the e-steps set a bit high, resulting in a slight over-extrusion. THis makes your outside dimensions a bit on the large side, and the diameter of holes a bit small.