Yet another calibration print. I designed this specifically to calibrate edge over-extrusion and backlash.

Features:

• X and Y axis labels for easy identification
• 110mm long with right angle for checking skew
• 10mm, 5mm wide boxes and holes
• 10mm, 5mm tall sections
• Backlash indicator
• "Backlash free" over-extrusion indicator
• All exterior corners are rounded off to eliminate corner over-extrusion

See instructions for use.

Tips:
Measure filament diameter and print a 100% infill 20mm calibration cube to calibrate packing density.
Make sure the axes are oriented properly in your slicer.
Print at whatever resolution and infill you most often use.
Let the part cool before you measure it.
Try to avoid measuring the layers on the build plate, because they tend to squish out more.

Recommended procedure for use:

1. Print basic calibration piece at 100% scale:

• Check the vertical face between any box and hole. If the vertical face is not continuous (eg there is a ledge), you have backlash. Small amounts are normal for consumer grade printers. (Makerbot's Replicator 2 and 2x usually have more on Y than X.) If needed, tighten your printer's belts and reprint.

• Measure overall length of X and Y arms. If X and Y differ by more than 0.5mm, consider adjusting printer's steps/mm in software/firmware to compensate.

• Average X and Y lengths.

• Divide 110mm by average length to find thermal shrink scaling factor.

2. Scale up piece by thermal factor and reprint 2 more pieces.

• Confirm X and Y arms are both 110mm +/- 0.5mm or other desired precision. Re-scale and re-print if desired. (It's never going to be perfect.)

• Measure X and Y on all 10mm boxes to get a feel for the repeatability of measurements. (You can calculate the standard deviation if you want.) Do not bother adjusting software settings if your calculated error is less than the normal variation between identical printed sections! Try slowing down your print or reducing slop in your printer hardware instead.

• Measure the 45mm outside and inside edges on both axes. Average the X values and Y values from two or more prints for better accuracy.
  [Edge Over-Extrusion] = [Outside Edge - Inside Edge] / 4

This is the amount that the outer shell extends past the intended edge of the part. A positive number means edge over-extrusion and a negative number means edge under-extrusion. (Printing insets with an overlap will artificially magnify this effect.) If the value is larger than ~0.1mm, consider adjusting your slicer's extrusion width settings. If the X and Y values are very different, your nozzle may be slightly clogged or worn at the tip.