There are several possibilities, but the most likely causes are:

1. Incorrect darkness setting for the installed media
2. Print speed too fast for the installed media
3. Dirty printhead or drive roller
4. Old, dirty, or pitted print media
5. Unsuited media for the application and/or printer
6. Defective printhead
7. Pitted or damaged drive roller

Aside from the possibility of a damaged drive roller or printhead, the printer itself is seldom at fault when print quality is poor. Clean the printhead and drive roller according to the instructions in your printer's User's Guide first, then if the problem persists try fresh media. If that doesn't help, try different print darkness settings and/or reduce the print speed if possible. These measures should improve the print quality.

Increasing print darkness does not always improve print quality. Poor print quality often has nothing to do with print darkness. If the printhead is dirty or the media defective, no amount of printer adjustment will improve the situation.

Also, increasing the print darkness setting does not always increase the actual print darkness. Thermal transfer printers can be set too hot, in which case the ribbon coating does not stick well to the media. There is an optimum darkness value for every printer and print media combination, and much deviation from the optimum setting will result in some degradation in print quality.

Cognitive printers are factory set for the best performance using typical print media. you should not need to adjust darkness very often when using our printers.

Labels that look good may actually be too dark. Excessive print darkness can cause bars to widen, causing unreliable scanning. You may want to try a lower darkness setting if your labels have good contrast but do not scan well. And of course, always make sure you are following the rules of your chosen bar code symbology.

The bars in picket fence codes (codes that have bars perpendicular to the printhead) tend to bleed together less, thus will print and scan more reliably. But you can print reliable ladder codes, if your printer is correctly set up and you are using good print media. If you are having trouble printing ladder codes, try the following:

1. Print your labels at the slowest speed that is available and acceptable for the job requirements.
2. Experiment with print darkness to find the best possible speed/darkness combination for your print media.
3. Use high quality media. If using thermal transfer printing, try rub-resistant ribbon.
4. Print bar codes as large as possible. Larger bar codes scan more reliably.