Cleaning Thermal Print Heads of a POS Thermal Printer

Thermal Print Heads for POS applications are manufactured using Thick Film Technology. A resistive coating is printed onto a ceramic substrate and because of the coatings restive nature heats up when an electrical current is passed through it. Most print heads have a protective coating which in turn covers the think film resistive coating.

As a consequence of how they are made, it si fairly easy to damage a thermal print head, so they should be handled with care. If you are not wearing latex gloves do not touch the ceramic substrate or thermal print head. Doing so will deposit grease and other contaminates on the print head which will reduce the life of the print head.

Be sure to control the ingress of dust into the printer mechanism and onto the print head. Dust on the surface of the print head will cause scratches which will not only shorten the life of the print head, but can permanently damage the print head prematurely.

Some manufacturers recommend cleaning of the print head every three months, some after every roll that is used. Use your discretion, keep the printer clean it minimises wear and prolongs the life of the printer.

Print head surfaces should be cleaned with a cotton swab, or cleaning stick which has a small amount of cleaning fluid applied to it. The cleaning fluid should be free of acids and alkalis or other fluids which might damage the print head. Cleaning solutions recommended by EPSON, CITIZEN and other manufacturers are:

Print Head location

Where do you find the Print head on a POS printer? This depends on the brand. For a number of printers the print head is contained in the main case. Examples of such printers are EPSON, TPG and JAVELIN to mention just a few. CITIZEN put the printhead for some models in the fold down lid. Consult your printer handbook.

It is helpful to know what you are looking for, so you can identify the print head for cleaning.

Below is a picture of the inside of an EPSON TM-T88IV which shows the location of the print head.

EPSON TM-T88III, TM-T88IV print head location

Figure 1 - EPSON TM-T88III, TM-T88IV Print Head Location

A picture of the front of a printhead

 

Contributing Factors to Premature Printhead Failure

Normal abrasive wear of the printheadís protective coating occurs due to friction, regardless of the materials used or the maintenance performed. Once the protective coating is worn away, the printhead elements will be damagedóresulting in printhead failure. For this reason, the printhead can be considered a consumable item and may require periodic replacement over the life of the printer. This abrasion may be more aggressive when the following conditions occur.

Contributing Factor  Recommendation
Use of Direct Thermal Media in Non-Ribbon Applications. If there is a choice of using a ribbon or not using a ribbon choose to use a ribbon in the printer. Direct Thermal media requires the paper surface be in direct contact with the print head elements. This increases friction and can cause a reduction in print head life when compared to a similar application using ribbon. The quality of the media and its compatibility with the thermal printing is important. To minimize abrasion, be sure you are using high-quality Direct Thermal media from a proven supplier. 

If applicable, you may want to consider using a Thermal Transfer media with a ribbon.

Build up of Paper Dust Paper dust can collect on the platen at the outer edges of the media or ribbon, creating a grinding wheel effect. This can abrade the print head glaze, which will result in print head failure. Clean all paper dust build up on the platen and print head. Brush or blow the dust in the media path and clean the platen with a lint-free cloth and isopropyl alcohol around the entire circumference of the platen.
Print head Pressure Excessive pressure increases friction on the print head assembly, resulting in higher abrasion. Print head pressure should be evenly balanced across the media. A balance of darkness and pressure should be used to generate an acceptable image on properly matched materials. Note: This only applies to printers with adjustable pressure settings. Printers with a single moveable head pressure toggle should centre the toggle over the media width.

Printers with dual-pressure toggles adjust both evenly over full-width media or reduced outboard pressure for narrower widths. This allows the pressure to focus over the narrow media more efficiently.