What to Do When a QR Code Turns Black

The problem of blackening that occurs after the application of a QR code is often caused by the material characteristics or improper process parameters.The company's engineers can analyze the causes of black spots on QR codes, share material pre-treatment methods, and offer tips on adjusting laser marking parameters, all of which help users improve the clarity of their markings.By following these tips, you can easily solve the problem of blackening.

Why does the QR code turn black when it's marked?

Let's first understand the fundamental cause of hair turning gray.In most cases, high temperatures produced by the laser cause oxidation on the surface of metal (especially stainless steel and aluminum alloys), resulting in a darkened layer.If it is made of plastic, it could be due to the carbonization of the material or the leaching of additives.Another common problem is that the parameters are set too high, which "burns" the material.

The key is the preliminary processing.

Surface cleaning of the material.

Don't underestimate this step! After wiping with alcohol, remember to use a lint-free cloth to clean the parts a second time. In particular, be sure to remove the rustproofing oil from the metal parts and the mold-release agent from the plastic parts. These substances will carbonize when heated and cause the blackening.The advice is to use an ultrasonic cleaner, which is two levels higher in terms of cleaning power.

Special materials are pre-oxidized.

Some aluminum alloys can be anodized to prevent the blackening, and also to increase the contrast of the marking.If stainless steel is used, then a passivation treatment can be done beforehand to form a stable oxide film on the surface.But be sure to control how long you process them. Over-processing is as bad as under-processing!

There is a trick to calibrating laser parameters.

Optimal ratio of power to speed.

Remember this saying: "Low power, slow speed; high power, high speed.We started at low power, for example at 10 % power and a speed of 0.8 meters per second, and gradually adjusted it.If you see the edge of the QR code start to become clear, stop immediately, don't be greedy and raise the gain any more.

Frequency and density of packing can be adjusted.

The frequency should be set between 20 and 50 kHz, and the density parameter should not exceed 0.08mm.When actually operating, you can use the "progressive heating" mode, which avoids local overheating.If you see smoke or smell burning, stop immediately and adjust the parameters.

Daily maintenance tips.

The laser lens must be cleaned at least once a week. Dust on the lens can cause the laser beam to focus incorrectly.Different materials should be kept separately. Metal parts should be placed in moisture-proof boxes.Before you start, do a small test run, especially if you have changed materials. Test out the QR code on a small sample.If you have trouble with stubborn blackening, you can try changing the protective gas (for example, using argon instead of air).

These are all techniques we've learned from our own experience, and they may take a little bit of time to get the hang of, but once you've found the right combination of parameters for your own equipment, the quality of your marking will be much more consistent.If you have any questions, please feel free to leave a comment!