XY Skew Calibration Test Part

Correct your printer's skew in the XY plane using this calibration part. XY skew causes parts printed flat to become stretched on one diagonal. Squares become parallelograms, circles become ellipses, etc.

Align the part with the diagonals of your print bed, then measure the lengths of the legs after printing. You can calculate the correction factor for use with a script such as gskewer using this formula: xytan = 1 - sqrt(4b^2 / (a^2 + b^2) - 1). In this formula, a is the size of the part on the +x/+y to -x/-y diagonal, and b is the size of the part on the +x/-y to -x/+y diagonal.

The nominal size of a and b is 150 mm.

Example

Here are actual measurements from calibrating my own printer. Although I used mm, the formula will work with any units. This was using PLA.

Measured lengths of legs: a = 149.2 mm, b = 150.08 mm

xytan = 1 - sqrt(4 * 150.08 ^ 2 / (149.2 ^ 2 + 150.08 ^ 2) - 1) = -0.00586

After applying the skew correction, the next part came out much closer: a = 149.62 mm, b = 149.60.