Print Misalignment
Overprinting of subsequent colours fails to align precisely at the back end of the sheet as it moves through the press. Tail-end misregister often results from the mechanical deformation of the substrate under pressure. While the front edge remains gripped and stable, the back edge is free to move or stretch.
Mechanical Cause
As the paper travels between the blanket and the impression cylinder, the squeeze can cause the material to fan out or elongate. Tail-end misregister is particularly problematic on lighter weight stocks that lack the stiffness to resist these forces. The physical distance between the cylinders also plays a role in how the paper settles.
Any inconsistency in the paper moisture content will aggravate the problem.
Corrective Measure
Adjusting the packing under the plates allows press operators to change the print length of the later colours. This compensation helps to pull the image back into alignment with the first pass. Tail-end misregister can be minimized by selecting paper with high dimensional stability and controlled fibre orientation.
High precision sensors on modern presses detect the position of register marks and adjust the timing of the cylinders in real time. Final output is sharp from the lead edge to the very back of the sheet.
