CLS621 Print Issues

CLS621 Print Issues

This knowledge base article shows you common CLS621 Print Issues when making number plates using our reflective, with simple and easy fixes. The exaggerated images below are meant to represent print problems clearly to help illustrate each issue. And are only really relevant to printing number plates.

Remember most issues are usually caused by not following our recommended conditions for the printer and media. And we suggest you clean the print head regularly, if changing the ribbon or before a production run.


CLS621 Print Issues underburn

Faded areas caused by underburn

Underburn occurs when number plate prints have faded leading edges. This problem may be seen more obviously towards the end of your media components.

  • Cause: Insufficient heat from the thermal head. Workshop temperature is below recommended levels.
  • Resolution: Increase heat settings until the issue is cleared or re-locate the production area to a warmer place.


CLS621 Overburn

Too much heat causes smudged areas

Overburn is when a number plate print has faded, smudged trailing edges and crescent shaped nicks or cuts. Printed areas can also appear slightly smudged or blurred.

  • Cause: Excessive heat in the thermal print head when printing. Temperature above recommended levels or insufficient cooling.
  • Resolution: Reduce the heat settings or clean print head to solve. Re-locate production to a cooler place or provide better ventilation.


CLS621 Spotted

Dirt & dust cause spots

Spotted number plate prints occur because of dusty or damp components, which cause speckles or dots. Remember, one or two spots are normal with thermal printing.

  • Cause: Contamination of plate media, usually from dust or condensation.
  • Resolution: Ensure media and production area is dry, clean and dust free. Keep media in their packets and dry-wipe them before use.


CLS621 Banding

A line or band across a print

Banding or horizontal lines on your prints is usually caused by dirt, grease or excess ink on the print-head.

  • Cause: Dirty, dusty or greasy media components. Print head being contaminated with dirt or ink.
  • Resolution: Clean print head and test print until the issue clears. Always check your components and work environment is clean, double check your printer settings.

Angled Lines

CLS621 Angled Lines

Creased ribbons & tight guides can cause lines

Angled lines on a print occur when the ribbon is creased or wrinkled. This usually occurs when you have just replaced it or the printer has been moved. Another reason for lines is an overly tight media guide on your printer causing components to bend & flex while being fed through.

  • Cause: Creased, loose or wrinkled ribbon. Loose ribbon or winding core on print unit.
  • Resolution: Remove wrinkles from the ribbon using the blue knobs of the holders. Check the ribbon alignment, ensure the adjusters are in the correct positions.
  • Cause: An overly tight media guide can cause your reflective to bend up during operation.
  • Resolution: Move the media guide so it is 1-2mm wider than your plate components.

Misaligned Prints

CLS621 Misaligned Prints

Check your media guides are set correctly

Number plates with a misaligned print occurs when the print unit or media is incorrectly setup. So check you’re loading your components correctly and review the printers setup.

  • Cause: The media guides are incorrectly positioned. Wrong ribbon tension and media adjustment settings.
  • Resolution: Check the sliding guides under the print-unit are correct and media is feeding through. The ribbon needs to be wrinkle free and setup right.

Need Help?

This is a quick article on CLS621 Print Issues, refer to your user guide for more details. Or for further assistance, contact our tech support & customer service team for help. For Ribbons, Cleaning Pens and Alcohol Swabs, try our online NP-Shop – trade account required.

Note: Whilst more robust than laser machines, thermal printers still require a clean and dry operating location.