1. GK420d Desktop Printer User Guide
  2. Troubleshooting
  3. Print Quality Problems
  • GK420d Desktop Printer User Guide
Print Quality Problems

Print Quality Problems

If print quality problems occur, use these sections to resolve issues.

No print on the label.

The printed image does not look right.

  • The printhead is dirty. Clean the printhead.
  • The printhead is under temperature.
  • Adjust the print darkness and/or print speed.
    • Use the
      ^PR
       (speed) and
      ~SD
       (darkness) commands referenced in the ZPL Programming Guide.
    • Use the
      D
       (darkness/density) and
      S
       (speed) commands in the EPL Programmer’s Guide.
    • Manually adjust print darkness with the six-flash sequence of Feed Button Modes.
    • The Windows printer driver or the application software may change these settings and may require a change to optimize print quality.
  • The media being used is incompatible with the printer. Use the recommended media for your application, and always use Zebra-approved labels and tags.
  • The printhead has worn out. The printhead is a consumable item and will wear out due to friction between the media and the printhead. Using unapproved media may shorten life or damage your printhead. Replace the printhead.
  • The platen may need cleaning or replacement. The platen (driver) roller may be losing traction due to:
    • Foreign objects attached to its surface,
    • The rubbery smooth surface has become polished and slippery, or
    • There is damage to the usually smooth and flat print surface such as from box knife cuts.

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.
  • The printer needs to be calibrated. Refer to the two-flash sequence of Feed Button Modes.
  • 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 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, see Status Light Descriptions.
  • 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 Device.
  • 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 to print this label.

An EPL 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 printer has label dispensing enabled, the printer may be waiting for the label to be removed. The liner/web must be properly threaded through the label dispenser mechanism (peeler) to correctly operate in label dispense mode, refer to Label Dispenser Option.
  • If the status LED is on or flashing, see Status Light Descriptions.
  • Make sure the data cable is correctly installed.
  • A communications problem has occurred. Make sure that the correct communications port (USB) on the computer is selected. See Connecting your Printer to a Device.