Adjustable Axis Alignment Tool
youmagine
Based on this thing:38300 on Thingiverse and the wooden one that Ultimaker now includes with new kits, each notch moves the pulley forward by 60 degrees. To test how square your axes are, print a single one of these objects, click it in place, and slide it back and forth with two hands. If your 6mm axis doesn't move, you're good to go! Alternatively, print two for calibrating or adjusting purposes. Print at 100% fill, but make sure your slicer can handle thin walls. After printing, use a 6mm drill bit to clean out the respective holes, and then switch to an 8mm drill bit. For more detailed instructions on aligning your axes, check out this link from Ultimaker: wiki.ultimaker.com/Calibrate
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