Knowing how card printers work is key to meeting your expectations by understanding the process’ limitations and real life operation.
Summary: A card printer uses heat and pressure to digitally print an image into the card surface via a colour ink coated ribbon.
This is how card printers work.
Apart from the obvious difference of printing onto plastic instead of paper, the way a card printer works is different from your conventional desktop printer in that it uses a technology called Dye Sublimation to stain a card.
This is basically a process whereby heat sensitive ink, coated to a ribbon is heated by a print head. The ink turns to a gas and under pressure this gas permeates a plastic card surface layer, in effect staining it the colour of the ink. Using different heat settings the amount of gas that stains the card is varied and this causes shades of that colour to be printed.
Using additional primary colours in an additive process creates a vast range of colour that can yield excellent results in most cases.
The printers also use a technique called thermal printing which melts and fuses the ink on a ribbon to the card surface by heat. This is often used in the black or “k” panel of the ribbon. Also this is the method for printing spot colour ribbons such as metallic gold and silver ribbons. In this process there are no shades of the printed artwork and is mostly used for text and graphics printing.
To seal the gas and thermal printed image to the card a card printer will usually print a clear protective varnish over the card called the overlay or “o” panel. Without this panel the sublimated ink in the card surface would simply sublimate out of the card and essentially fade or vanish entirely.
It is important to understand that card printers print to the surface of a card. The cleanliness and quality of the used plastic card is essential to receiving a quality print.
With direct to card printing it is also important to understand that while most manufacturers claim that their printers can print “edge to edge” the reality is that you should keep a white or unprinted border around the edge of the card. This ensures less rejects and prevents the ribbon from cutting due to the “scissor action” between the card printer head and the card edge when a heated head passes over the sharp edge of the card. While it sometimes works, I have found that it just causes long term problems. Pre-print the cards if you must have true edge to edge or use a re-transfer or indirect to card printer for “over the edge” printing.