No matter what marking technology you use or what material you’re engraving, high-quality marks are key to improving traceability, minimizing counterfeiting, complying with industry regulations, and enhancing quality.
One Ask an Engineer question we often get is “How do I ensure high-quality marks?” To get consistently clear and readable marks, first of all, it’s important to make preventative maintenance programs part of your continuous improvement efforts to avoid costly waste and downtime in the future. But, if you’re noticing blurry, indecipherable or otherwise subpar marks, there are a few ways to troubleshoot:
Measure focal distance
If you’re seeing mark degradation, one of the first things you want to check is your focal distance. Focal distance is the measurement from the object you’re marking, or your marking plane, directly to the laser lens. If the offset between these points is the wrong distance, it can mean the difference between a sharp mark and a blurry mark.
Precision is key. There are several options when it comes to measuring this distance. One common tool is a focal stick. You can also use a laser displacement sensor or a laser pointer to automate this measurement. The bottom line: measure twice, mark once.
(Watch: How to Identify Focal Distance)
This is an obvious yet overlooked issue affecting mark quality. Anyone wearing glasses out there knows that if you can’t see properly, try cleaning your lenses. The same rules apply to your laser marking machinery. Any type of residue buildup, such as oil or dust, in addition to scratches or cracks can disrupt the laser beam path and degrade your marks.
(Watch: Proper Care for Your Laser Lens)
To clean lenses, we recommend using acetone or a low-water-content solution of isopropyl alcohol, 98% alcohol content or higher. To clean lenses, wear protective gloves and apply the solution to a cotton ball or microfiber cloth. Make sure the lens is free of any rough pieces of grit to avoid scratching the lens surface.
Avoid lens issues altogether by developing a regular preventative maintenance schedule to maintain your lenses. Depending on your environment, this schedule could range anywhere from weekly to yearly. Taking the time to ensure your lenses are debris- and scratch-free will give you better marks in the long run.
Lasers displace material as they mark a surface, which creates debris and fumes. Materials with a lower burn point such as plastic can generate a great deal of exhaust. If not properly directed, the plume created by the exhaust can travel back into the laser beam path, which can degrade the laser power, causing blurred marks.
Avoid exhaust-induced laser degradation by making sure you’re extracting the plume in the right direction and with the proper flow. The fume exhaust tubing should be close to the marking plane and drawing exhaust away and out of the laser beam path. Think of exhaust in the laser’s path like headlights on a foggy morning. For clearer, more precise marks, give your laser clearer visibility by properly extracting fumes.