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M556: Axis skew compensation
- Snnn Height of the measured distances
- Xnnn Deviation in X direction
- Ynnn Deviation in Y direction
- Znnn Deviation in Z direction
- Pnnn Apply XY compensation to Y axis instead of X (defaults to 0, requires RRF 3.2-b4 or newer)
- M556 S100 X0.7 Y-0.2 Z0.6
This tells software the tangents of the angles between the axes of the machine obtained by printing then measuring a test part. The S parameter (100 here) is the length of a triangle along each axis in mm. The X, Y and Z figures are the number of millimeters of the short side of the triangle that represents how out of true a pair of axes is. The X figure is the error between X and Y, the Y figure is the error between Y and Z, and the Z figure is the error between X and Z. Positive values indicate that the angle between the axis pair is obtuse, negative acute.
Printable parts for calibrating the deviation from orthogonality can be found at https://github.com/reprappro/RepRapFirmw.... For a fuller explanation of the measuring process, see the RepRap Ltd documentation.