It is difficult to decide whether this kind of problem is due to wetting or to dot placement error
(described below). The type of grain could be a clue: in the case of wetting issues, dots tend to
aggregate into bigger dots, with empty spaces in between. A magnifying glass can be useful to examine
the print in more detail.
Here are some tips for solving this problem:
◦
Increase the optimizer level.
◦
Increase the drying power.
◦
Increase the number of passes.
◦
Change from 6 to 4 colors (less ink on the substrate).
●
Substrate advance. Grain in a print can be increased by incorrect substrate advance, due to
mispositioning of the dots.
To check the substrate advance, go to the Internal Print Server and select Printer > Advance
Calibration. See
Substrate-advance test print on page 107.
To correct the substrate advance, see
Substrate-advance compensation on page 106. In most cases,
this will solve the problem. However, you are recommended to run the OMAS Diagnostic Tests from the
Print Care window as soon as the substrate is unloaded, to avoid having the same problem with other
substrates. See
Clean the substrate-advance sensor on page 178.
If the problem persists, try adjusting tension and vacuum settings according to the table below, step by
step (a to c), until you find settings that work.
●
Printhead alignment. This is a clear contributor to grain. If printheads are not correctly aligned, the
misplaced dots could correlate directly to the severity of the graininess.
246 Chapter 10 Troubleshoot print-quality issues ENWW
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