When the sheets are delivered to the stacker shift tray, uncurled sheets and sheets with downward curls cause strong friction on the leading edges between sheets. This may result in sheets that have failed to be delivered staying near the paper exit.
If this happens, other sheets may slip under the delivered sheets, so that the delivered sheets may be curled when loaded.
This may occur if:
A4 or larger coated paper weighing up to 135 g/m2 (50 lb. Cover) is used.
<How the problem occurs>
Uncurled paper or downward curled paper is delivered to the stacker tray.
The leading edge of the sheet, while delivered, causes strong paper-to-paper friction against the top sheet of the stack. As there is no air gap between the sheets, and the delivered sheet becomes stuck.
The trailing edge of the sheet, while delivered, is left in the paper exit.
The next sheet to be delivered slips under the sheet still in the paper exit and bends back.