What are thermal printers?
It might be tempting to use a desk-top ink-jet or laser printer to produce labels when you first start to need them, but they are not always the best for printing barcode labels.
Thermal printers are still digital, but they are industrial machines, with fewer moving parts than other types of printer, and are highly reliable. Rather than using toner or wet ink to create the printed image, thermal printers use hundreds of tiny individual heating elements to either activate thermocromic/thermal material (direct thermal) or to transfer pigment from a ribbon (thermal transfer).
The size of the print elements can vary and are typically referred to as the DPI (Dots Per Inch). A higher dpi will enable you to print finer lines, increasing the range of barcodes that you are able to create and also improve print quality of text and images.
Barcode size
If not all, the majority of thermal printers are supplied with a software package. This will comprise the drivers you will need to connect the printer to a PC and will also have a label design element. This will enable you to create labels of any size and populate them with images text and barcodes.
Barcodes created and printed using this software can be extremely accurate, especially if the bars are printed in picket fence format. The software matches the width of the bars to a complete number of printhead elements or dots – you cannot print a bar that is, say, three and a half printhead elements wide. The higher the printhead resolution, the DPI, or dots per millimetre in metric , the greater the choice of possible barcode sizes. Barcode sizes can be defined by the width of the narrowest bar (the x-dimension) or by magnification for some symbols, such as EAN-13s. So you cannot accurately print barcodes of any size, but here is a link to the sizes that you will be able to create and where in the retail supply chain these would be accepted.
Printing directly from the supplied software package or one created specifically for thermal printers will give the best possible print quality.
Pitfalls
Once the printer has been installed it should be possible to print to this just like any other printer, using Word, InDesign, Adobe Acrobat, etc… and the results can be disastrous.
As outlined above, all thermal printers are restricted by the dot size – It is impossible to print half a dot. A barcode imported into a design package may not match the DPI of the printer. When this happens, the printer will either round up or down the width of the bars to the closest available size. The barcode will retain the same overall size, it will however, most probably fail to reach the print quality standard required.
Even if the bar width did match the DPI, each bar would need to be aligned exactly with the dots. Highly unlikely. It may be possible to improve the quality of the barcode by moving it fractionally to the left or right, but realistically, this is all but impossible and the problem of the dot size would remain.
Other print quality considerations
We’ve established that starting with the best possible barcode image is vital, but this will not guarantee scannable barcodes. There are additional steps that can be taken to help maintain print quality including.
Matching thermal ribbon to substrate. Thermal ribbons come in a wide range of grades. The type of ribbon required will depend on the make of printer and also what label material is being used – synthetic materials and paper will need different types of ribbon.
Orientation. Barcodes will print better if they are printed in picket fence rather than ladder format.
Creased ribbon. It is vital that the media is loaded in the printer correctly and that the ribbon is only marginally wider than the label and the backing material. The printhead must to be correctly aligned with the print roller. Failure to do this can mean that diagonal white lines may appear across the barcode. Print that is close to the edge of a label can also cause the ribbon to crease.
Printer settings & upkeep. The temperature/density and speed of the printer must be set correctly and be suitable for the material and design of the label. Dirty or damaged printhead and/or rollers will also reduce the print quality. It essential that the manufacturers guidelines are followed and regular cleaning and preventative maintenance is carried out.
Quality control. Last but not least is quality control including the use of a barcode verifier which should be carried out throughout the print run.
Axicon Labels supply a range of thermal printers and consumables. Our parent company Axicon Auto ID is recognised across the globe for its expertise in barcode verification. For further information on any aspect of barcode quality, please do not hesitate to contact us.