Five Solutions to the Laser Marking Problem

Highly reflective metals are prone to uneven burning or blurred markings when laser etching.These solutions cover parameter optimization, pre-treatment processes, and equipment upgrades, and are designed to help improve the quality of marking and production efficiency.

Why are highly reflective metals difficult to mark?

We all know that metals like copper and aluminum alloys are highly reflective, and that most of the energy of a laser beam is reflected back.This is like shining a flashlight on the water surface, where the light scatters and cannot be gathered.The result is either that the marks are too faint to see, or that the energy is too high, leaving the surface pitted.

Optimizing parameter combinations.

A golden ratio of power and speed.

Don't just turn up the power and blast away. Try dropping the power to about 70 % of the standard value and halving the marking speed.It's like cooking meat, which needs to be done slowly over a low flame, allowing the metal to absorb the heat without evaporating immediately.

A little trick for adjusting the frequency.

By adjusting the frequency of the pulses from the commonly used 20kHz to over 50kHz, the high frequency and short pulses can effectively break through the "light shield" of the metal surface.This is similar to the principle of using a series of quick punches to hit the same point, and eventually one of them is bound to break through the defenses.

Surface treatment.

The coating is also specially designed.

A laser absorption enhancer is sprayed onto the bottle before laser marking to create a uniform matte coating.I have seen the effects of this trick myself. A certain hardware factory was stamping copper plates, and after spraying the plates with WD-40, the characters changed from a "blurred mess" to "crisp and clean.

The key to oxidizing.

A weak acid solution is used to oxidize the surface to form a dark film.Pay attention to controlling the soaking time. Generally three to five minutes is enough. Soaking too long will corrode the material.After using, thoroughly rinse with clean water.

Special wavelengths make a difference.

Green lasers are especially effective against highly reflective metals, and the 532-nanometer wavelength is absorbed three times more than the traditional 1064-nanometer infrared wavelength.Although the equipment is a bit more expensive, the yield rate is higher, so the overall cost is actually lower.I've seen a company that makes electronic connectors that changed their equipment to use green light sources, and their scrap rate dropped from 15 % to 2 %.

A good match.

Nitrogen or argon gas nozzles are added to the laser head, and the gas pressure is controlled between 0.2-0.5MPa.This trick both blows away the slag and keeps the work area cool.Remember that the purity of the gas must be at least 99.5 %, and don't try to save money on this.

A new approach to mixed media.

First, an electric chemical etching process is used to make a shallow marking, then a laser is employed to do the finishing work.This combination of approaches is especially suited to situations where both depth and accuracy are required.Last year a client making aerospace parts did just that, completing a job that would have required three reworkings in one go.

Don't be in a hurry to try all these methods. It's suggested that you try the two zero-cost methods of adjusting parameters and surface treatment first.In fact, in many cases there's no need to replace equipment at all; just by adjusting the parameters you can solve 80 % of the problems.If that doesn't work, then we'll consider installing the Green Light equipment.