Oki LD670 User Manual page 218

Note : The roll paper must have no deformities. Using roll paper such as that
shown in the figure below may cause a paper jam, uneven printing, or other
printing problem.
Note : If the loaded roll paper is loose (slack) as shown below, take up the slack
before printing on the paper. Printing on roll paper that is loose may cause
a paper jam, uneven printing, or other printing problem, which will prevent
the printer from detecting paper near end conditions.
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