Troubleshooting
Print Quality Problems
50
P1031442-001 ZP 450 User Guide 12/8/2010
There are long tracks of missing print (blank vertical lines) on 
several labels.
• The printhead is dirty.  Clean the printhead.
• The printhead elements are damaged. 
The printing does not start at the top of the label or misprinting of 
one to three labels.
• The media may not be threaded correctly. Follow the instructions for Loading Roll Media 
on page 9 in the Getting Started section.
• The printer needs to be calibrated.  Refer to the two-flash sequence of Feed Button Modes 
on page 56 in this section.
• ZPL Label Formats - The correct media sensor may not be activated. Manual calibration 
selects the media sensing method for the labels being used (refer to the 
^MN command in 
the ZPL Programming Guide).
• ZPL Label Formats - Verify that the Label Top (
^LT) command is correctly set for your 
application (consult the ZPL Programming Guide).
• EPL Label Formats - The correct media sensor may not be activated for label dispensing, 
blackline or notch sensing, or for Gap/Web sensing.  Manual calibration selects the media 
sensing method for the labels being used (refer to the 
O and Q commands in the EPL 
Programmer’s Guide).
• EPL Label Formats - Verify that the Set Label Length (Q) command is correctly set for 
your application (consult the EPL Programmer’s Guide).
A ZPL label format was sent to, but not recognized by, the printer.
• Is the printer in pause mode? If so, press the Feed button.
• If the status LED is on or flashing, refer to What the Status Light is Telling You on page 46.
• Make sure the data cable is correctly installed.
• A communications problem has occurred. First, make sure that the correct 
communications port on the computer is selected. Refer to Connecting your Printer to a 
Computer on page 17 in the Getting Started section.
• Verify the correct Format and Control Prefix on the printer match what you are using in 
your ZPL programmed label format. The default Format (COMMAND CHAR) is Caret 
(^) character and the Control (CONTROL CHAR) is a Tilde (~) character. Verify the 
characters with the Configuration Status label printout. Refer to the one-flash sequence of 
Feed Button Modes on page 56 to print this label.