How to get the best print quality from your thermal label printer.
Firstly we need to think about how thermal printing works, their are two types of thermal printing direct thermal and thermal transfer. The best way to think about direct thermal is that the ink is in the label when heat and pressure are applied to the surface of the label it creates an image. Thermal transfer uses label and ribbon, the ink from the ribbon is transferred to the label when heat and pressure is applied creating an image.
Explained below are the primary factors that will help you achieve the best print quality for your thermal printing application.
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The quality and type of labels/ribbon has an effect on the print quality.
More important in thermal transfer applications, if your ribbon and labels don’t match then you won’t get a good quality transfer. There are lots of different types of labels/ribbons for different applications, a general rule is wax ribbons goes best for uncoated paper, wax resin ribbons for coated paper, resin ribbons for synthetic materials.
This rule doesn’t always apply when picking labels and ribbons it’s important to consider what properties you want the labels to have e.g. chemical resistance/smudge resistance. Testing is a must, try different types of sample ribbons to find your perfect match.
Direct thermal labels can be uncoated or top coated, uncoated labels have a rougher surface and lower resistance to heat, light and smudging. A top coated version adds an extra layer of protection and smooths out the bumps in the label surface creating a more consistent print with extra protection from heat, light and smudging. -
The amount of heat applied has a significant effect on the print quality, if the temperature is too low it will cause poor transfer in the case of thermal transfer or faded print in direct thermal. When the temperature is too high you will either get a bleeding effect so text, barcodes and images will appear blurry in the worst cases the ribbon will snap or the labels will stick to the ribbon.
Setting the head temperature too high also causes unnecessary wear on the printhead, the elements will fail quicker than if set correctly leading to more frequent printhead replacements.
Typically direct thermal labels require a temperature setting in the middle of the road to achieve a solid print quality, e.g. 10-20 darkness on a Zebra printer. Thermal transfer differs with the media combination typically lower-medium heat for wax ribbons, medium-high heat for was/resin ribbons and high heat for resin ribbons.
You should always try and get away with the lowest heat setting possible that gives you a good consistent print.
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The next factor is printhead pressure, now a lot of desktop/mobile class of thermal printers don’t have a pressure adjustment as it is pre-set so you don’t have to worry about it for example if you have a TSC Auto ID DA220 label printer or a Zebra GK420d.
However if you have an industrial class label printer such as the TSC Auto ID T8000 or Zebra ZT411, there are pressure adjustments that can be performed to change how much pressure is applied to the printhead.
Just like the temperature setting you want to use as little printhead pressure as possible while maintaining good print quality. It’s important to balance the temperature and pressure together to achieve good print quality while avoiding wear on the printhead. Typically increased pressure causes more wear on the printhead than increasing the temperature slightly, that’s why it’s a bit of a balancing act.
You can get faded print across the whole label if the pressure is too low or excessive wear, labels jamming if the pressure is too high. Some label printers have multiple pressure adjustments so faded print on one side can be caused by uneven printhead pressure settings, it’s important these are configured correctly based on your label width if you’re unsure about how to set it up consult the user manual of your label printer. -
Print speed is the last major factor that has an impact on your print quality. Using higher print speeds with standard temperature settings can produce faded print. This is because the printhead element has less time over the same position on the label so less heat is applied.
Generally 4 or 6 Inches per second is the sweet spot for getting good quality and speed. If your application requires a higher print speed such as 8 or 10ips you will need to increase the printhead temperature to get good print quality. I would advise only doing this if absolutely necessary as again higher temperature and print speed will increase the wear on your printhead.It’s also possible to have too slow print speed, for example running at 2 inches per second without reducing the temperature can cause some ribbons to snap or bleeding on direct thermal labels. To prevent this happening to you, you can either increase the print speed or reduce the printhead temperature.
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Importance of preventative maintenance
When a thermal printhead/platen roller gets clogged with labels, dirt or dust from the environment it can cause a host of print quality issues. Such as fading or inconsistent print in specific places as well as no transfer at all; To mitigate these factors you should regularly clean the printhead, platen roller and paper path it is recommended to perform this after each roll change in direct thermal or after each ribbon change in thermal transfer. While this may seem excessive or impractical for some businesses it should be performed as regularly as possible, this build up is the most common cause of printhead element failure.
Consult your user manual for how and what you should use to clean your thermal label printer.
Conclusion
A mixture of good quality compatible media, optimised printhead temperature, pressure and print speed are required to achieve the best print quality while mitigating wear on your thermal printer.