Brother MFC-9450CDN User Manual page 128

Examples of poor print
quality
Curled or wave
118
Recommendation
Make sure that you choose the correct media type in the printer driver
or in the machine's Paper Type menu setting. (See Acceptable paper
and other media on page 9 and Basic tab in the Software User's
Guide on the CD-ROM.)
Check the paper type and quality. High temperatures and high
humidity will cause paper to curl.
If you do not use the machine often, the paper may have been in the
paper tray too long. Turn over the stack of paper in the paper tray.
Also, fan the paper stack and then rotate the paper 180° in the paper
tray.
Follow these steps:
a
Open the back cover.
b
Push the grey lever to the right as shown below.
c
Close the back cover and re-send the print job.
Note
When you have finished printing, open the back cover and reset the
lever back to the original position.