Calculating correction factors for subsequent printing operations by weighting measured alignment differences

An apparatus comprising:

• an input sensor device to detect a position of a first registration mark printed on a substrate during an earlier printing operation;
• a printing device to print a second registration mark on the substrate during a current printing operation at a position on the substrate relative to the first registration mark based on the detected position of the first registration mark and a correction factor;
• an output sensor device to measure an alignment difference between the position of the first registration mark and the position of the second registration mark;
• and
• a controller to calculate a new correction factor for a subsequent printing operation by weighting the measured alignment difference according to a difference between the measured alignment difference and a previous measured alignment difference.

A non-transitory machine readable storage medium encoded with instructions executable by a processor, the machine readable storage medium comprising:

• instructions to detect a position of a first registration mark on a substrate;
• instructions to print a second registration mark on the substrate at a position on the substrate relative to the first registration mark based on the detected position of the first registration mark and a previously calculated correction factor;
• instructions to measure an alignment difference between the position of the first registration mark and the position of the second registration mark;
• and
• instructions to calculate a new correction factor by weighting the measured alignment difference according to a difference between the measured alignment difference and a previous measured alignment difference.