Canon BJC 3000 Reference Manual page 207

Check 3
Is Print Quality set to Fast in the printer driver?
Changing Print Quality to Fine in the printer driver may improve the quality
of printed straight lines. Follow the procedure below.
Windows
1
Open the Printer Properties dialogue box.
2
Click the Advanced button in the Main tab.
3
In the Quality tab, drag the slide bar to right to select Fine.
Macintosh
1
When using Manual for printing, click the Details button in the Printer
Properties dialogue box.
2
In the Quality panel, drag the slide bar to right to select Fine.
Check 4
Is the paper thickness lever set correctly?
If straight lines are printed uneven or broken after changing the setting of
the paper thickness lever on the front of the printer, re-align the print head.
Aligning the Print Head
Troubleshooting - Printout is Unsatisfactory
Straight lines are broken
207