How Do Thermal Transfer Printers Work?

Barcodes, Clothing Labels, and Ribbon Printing

Thermal transfer printers are printers which work by melting a coating of ribbon, sometimes called a 'foil', so that it stays glued to the material. Thermal transfer printers are primarily used to print barcode labels, but are also used to print plastic labels for chemical containers, and sometimes to print clothing labels. They compare to direct thermal printers, which have no ribbon.

Setup

Thermal transfer printers use a fixed-width thermal print head, which is pressed onto a paper or plastic label. The paper or plastic is fed into the machine with driver rubber rollers, called platens. Operators insert the thermal transfer ribbon (foil) between the paper and the print head. The ribbon is made of a polyester film that has been coated on one side with wax, wax-resin, or pure resin ink. The ribbon is spooled onto reels, sometimes close to 2000 feet in total length. These reels feed into the machine, driving through the printing machine in sync with the paper/plastic medium. Speeds of up to 12 inches of label per second may be reached.

Melting and Computation

On the print head, which stretches the length of the print head (4, 6, or 8 inches, typically), tiny pixels are heated and cooled to melt the ribbon's ink off the polyester film and onto the paper/plastic. The ink dries instantly, enabling very quick printing. Label printers have evolved to make full use of this quick printing, by using large processors and data storage capabilities to be able to produce label images at the same speed as the printing of the label images. For example, the controlling computer requests a series of barcodes from the printer, complete with specific instructions concerning barcode type, size and location along the label, and data to be included. The printer then will use complex algorithms to construct the barcode, according to strict rules for accurate printing, to ensure compatibility to a wide range of barcode readers.

References

• RFIDRadio.com: What are Direct Thermal and Thermal Transfer RFID Printers?
• Zebra.com: Direct Thermal and Thermal Transfer Printing