The following causes can be considered.
Solutions
Make sure the paper type in the printer settings matches the actual paper type.
List of Paper Type
When printing on plain paper,use a higher quality setting.
Windows
Select High from Quality on the printer driver's Main tab.
Mac OS
Select Fine as Print Quality from the print dialog's Print Settings menu.
Quality:
Select the Maintenance > Print Head Alignment > Horizontal Alignment menu on the control panel to align the print head.