Canon BJC-3000 - Manual (Page 219)

219 Troubleshooting - Printout is Unsatisfactory
Printed surface scratched
Check 1 Are you printing on thick paper?
If you print on thick paper, the print head may scratch the printed surface of
the page.
If you experience difficulty when printing on thick paper, clean the print
head.
Cleaning the Print Head
Check 2 Is the paper thickness lever set correctly?
When you use thick paper such as envelopes, T-shirt transfers and banner
paper for printing, set the paper thickness lever to the Down position.
If the printed surface is scratched or stained on plain paper, it is also helpful
to set the paper thickness lever to the Down position.
Check 3 Are you printing on curled plain paper?
If curled plain paper is loaded with the curl bowing up, the print head may
scratch bottom edge of the paper.
Remove the plain paper, turn it over, and load it in the auto sheet feeder
again.