Solving the Problem of Black Marks on Metal

The blackening problem is often caused by improper energy parameters leading to oxidation or carbonization.The book explains how to adjust laser energy, frequency, and speed, and teaches you how to optimize equipment parameters to solve problems such as blackening and blurring, and to improve marking results and the appearance of products.

Why do metal engravings turn black?

Many of you who use laser marking machines may have encountered this problem: You choose the right material, but the pattern that comes out is black and blurry, as if it has been burned.Actually, most of the time this is related to the parameters of the equipment not being adjusted properly.Metal surfaces can easily oxidize or carbonize at high temperatures. If the energy is too high, the speed too slow, or the frequency inappropriate, local temperatures can get out of control, causing the mark to turn black.

Three steps to energy adjustment.

First, give all the equipment a thorough check-up.

Don't be in a hurry to adjust the parameters! First check to see if the laser lens is dirty or worn, or if the optical path is aligned correctly.Once, a customer came in, and after adjusting the parameters for half a day with no effect, it was finally discovered that the focusing lens had become dirty with oil.It's like putting on a pair of fogged-up glasses--no matter how you adjust the settings, you're still not going to see clearly.

Energy and speed need to be coordinated.

Remember this golden rule: "If there is a lot of energy, speed up; if it's slow, lower the energy.For example, when marking stainless steel, we recommend using 60 % laser power at 800mm / s.If the lines become gray, then the speed is reduced to 600 mm / s; if they turn black and smoke, then the energy is cut to below 50 %.After a few tries, you'll get the hang of it.

Don't just leave the frequency as window dressing.

Many people ignore the frequency parameter, but it actually controls the laser pulse spacing.When thinning metal, a high frequency of 20-50 kHz can be used to reduce heat buildup. When processing thick sheets, a low frequency of 5-15 kHz is used, allowing each pulse sufficient time to dissipate heat.It's like cooking, where you have to decide whether to stir-fry over high heat or slow-cook over low heat, depending on the thickness of the ingredients.

Some maintenance tips.

After you have finished, remember to wipe off the surface with an alcohol swab.The equipment must be cleaned thoroughly once a week, especially the focusing mirror and scanning mirror.If possible, calibrate the parameters under different temperature and humidity conditions--in summer, with higher humidity, the energy may have to be reduced by about 5 %.

You have to be careful not to step into these holes.

Don't believe the "one size fits all" parameter tables. The differences between the various brands are much greater than you might imagine.I saw someone last time who had adjusted the parameters according to what was on the Internet, and ended up punching a hole in the aluminum plate.It is also suggested that you not try to get everything just right the first time. Fine tuning is a delicate process, and it is suggested that you do not change any parameter by more than 5 % at a time.When he's not sure, he'll try out the technique on a scrap of fabric a dozen times.