HP Deskjet 3520 Inkjet Printer - Manual (Page 47)

automatically cleaning print cartridges
If your printed pages are missing lines or dots, or if they contain ink streaks, the
print cartridges may be low on ink or may need to be cleaned.
Click here to check the print cartridge ink levels.
If the print cartridges are not low on ink, follow these steps to clean the print
cartridges automatically:
1. Go to printer maintenance .
2. Click Clean Cartridges .
3. Click Clean , then follow the onscreen instructions.
If your printouts are still missing lines or dots after cleaning, replace the print
cartridges.
Caution! Clean print cartridges only when it is necessary.
Unnecessary cleaning wastes ink and shortens the life of the cartridge.