What is a reasonable level of accuracy, regarding squareness, dimensional tolerances, etc? I am calibrating my printer with with the stock test piece, and after four rounds of calibrating, the XY and YZ axes are square. The XZ axis is still off by about .375mm, which should be fixed in the next test. What is more concerning to me is how the test piece, which should measure exactly 90mm on each edge, only measures 89.2mm along the X and Y axes, and 90.3mm along the Z axis. These linear inaccuracies have been quite consistent on all test pieces, but I don't know how to correct them. Any advice would be appreciated.

What's probably happening is that the X and Z arms cool and shrink when you remove them from the heated bed, but the Z axis cools as you print it so doesn't shrink. You can correct for shrinkage by adjusting the X and Y steps per mm using the M92 command. However, you may find that when you print a larger piece, the XY shrinkage only happens near the bottom of the piece.

Another possibility is that you have backlash in the X and Y axes due to the belts being loose.

Edited 1 time(s). Last edit at 10/09/2014 12:13PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].