The Good, the Badge and the Ugly

The thermal card/badge printer is a critical operational piece of technology used in any access control system. Ironically, while being one of the most expensive components of a system, it is often the least understood by the end user and/or the security dealer that sold the system.

Knowing some of the deep, dark secrets of how the thermal printing process works — along with being able to better maintain and service a valuable printer — will go a long way to having a happier badging system customer.

Maintaining Print Head Is a Priority
The most expensive and critical part of a thermal card printer is the thermal print head (TPH). There are plenty of ways to keep the TPH alive and healthy. The TPH is a precision-engineered array of almost microscopic heater elements which, when pulsed with the correct amount of voltage, will provide a precise level of heat. These dots of heat are then transferred to a resin- or wax-based colored ribbon/film, which is then melted onto a card’s surface (direct to card) or onto a clear film that is then laminated to an ID card.

As we go through this article, I will emphasize the heat-transfer process of the TPH. As we all learned way back in Science 101, there are heat conductors and heat insulators. This is why we would use a hot pad to protect our hand when picking up a hot pan. One of the biggest culprits in the thermal printing process is dirt from media (cards) or environment and residue build-up from cheap and nonmanufacturer-specified printer transfer ribbons. This dirt acts as a dangerous heat insulator.

It must also be understood that the ribbon acts as a kind of heat sink for the TPH. If the expected amount of heat cannot be easily transferred to the ribbon, it will build up on the TPH. This heat build-up due to dirt will, in turn, cause premature failure of the heater elements in the TPH. The visible results are a missing pixel or white line on the printout. At that point, the damage is done and the customer is most likely facing a voided warranty and expensive replacement of the TPH.

I have also seen a very vicious cycle develop. This dirt build-up on the TPH will reduce the critical transfer of heat from the TPH to the ribbon. Since the colored media is not heating up as it should, the printed cards look lighter than expected. The customer looks to see how they can correct this and makes an adjustment that increases the voltage to the TPH elements.

Since we are dealing with a dirty TPH, the only thing this will do is make the TPH hotter and cause faster decay of the TPH heater elements — more dirt build-up, more heat, etc. This can cause a TPH to last only months, instead of a year or more. It can be a very expensive lesson for the customer and a very embarrassing moment for the dealer. Let’s look at ways we can avoid this from happening in the first place.

Tips for Safeguarding Print Heads Hopefully, you can now understand that the TPH must be regularly and properly cleaned in order to maintain the operational life the manufacturer intended for it. Actually, most manufacturers are very conservative in their TPH warranties and a proper printer maintenance program can often exceed the warranty time period, making for an even happier customer.

All that being said, the end user should be made aware upfront that even with proper use and maintenance, the TPH is made of precision heating elements that will wear out and need replacement at some point in the future.

With most printers, and their associated TPHs, manufacturers will recommend the TPH be cleaned after each new printing ribbon is installed. The common practice for end users is to use a manufacturer-specified cleaner card, which is typically saturated with an alcohol cleaning solution. Do not reuse the cards. Technicians can clean the TPH by hand only with 99-percent pure isopropyl alcohol. Other cleaning solutions can damage the TPH and void a warranty. Manufacturers also recommend using fiber-free, foam-type cleaning swabs, eliminating small fiber residue left in the TPH printing area.

Any time a technician works inside a printer and, in particular, around the TPH, they should be wearing a grounded wrist strap to guard against any stray static electricity being discharged into the printer. The very tiny TPH heater elements are particularly susceptible to static discharge.

Additionally, the colored ribbons during printing operations can be the cause of static build-up as they run across a TPH if the operating environment is dry. I have seen this happen in the dry winter months up north. Make sure the manufacturer’s specified operating environment, both temperature and humidity, is properly maintained.

How to Avoid Warranty Woes
Be warned that manufacturers carefully review under a microscope a TPH that comes back for warranty replacement. A microscopic view of heads damaged by ESD (electrostatic discharge) look like they have been hit by a bolt of lightning, in which case a warranty request would usually be declined. A large number of TPH warranty replacement requests are also declined due to being dirty and poorly maintained.

Training is very important for both the service technician and the end user. Since many people today use inkjet printers, they are not familiar with how thermal-transfer printing works. Having properly trained technicians along with regular maintenance programs can be a very profitable program for security dealers.

Dealers should strongly encourage printer maintenance contracts. At the bare minimum, end users as well as service technicians should read written material like this article. I encourage manufacturers as well to write separate white papers for end users explaining the importance of proper printer and TPH cleaning and maintenance.

Make sure that colored ribbons are not loaded backwards. Ribbons have two distinct sides; the shiny surface is to run across the TPH and transfer heat, while the other resin-/wax-coated side faces the card. In most cases, the ribbon rolls are keyed so that they can only be put on one way. If they are not keyed and are put in backwards, you will immediately start coating your TPH rather than the card — spelling almost certain sudden death for the TPH.

Speaking of adjustments, I must re-emphasize that the thermal printing process is a fine balance of printing with the correct heat, media (cards, ribbons), speed and pressure. The pressure on the ribbons from the TPH must be even across the card. From time to time, factory-set pressure screws and other adjustments may need tweaking depending on the thickness and type of card stock being printed.

Also learning to slightly adjust the speed of the printing can help with different card and ribbon material. Learning to become sensitive to these printing adjustments will result in the high-quality images your manufacturer intended.


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