Metal Marking: Controlling Depth

This course covers practical techniques for controlling the depth of laser marking on metal, including laser parameter adjustment, methods for measuring layer depth, and solutions to common problems.This practical guide helps operators control the depth of the marking more precisely, thereby increasing processing quality and efficiency. It is suitable for reference by technical personnel in the metal processing industry.

Why is layer control so important?

The depth of the mark affects the product's appearance, wear-resistance, and functionality.Too deep a color will fade easily, but too deep and the structure of the material may be damaged.Eighty percent of the problems we encounter with blurry labels or oxidized colors are related to the depth of the engraving.

Practical techniques for adjusting parameters.

Don't adjust the laser power.

Power is the "master switch" that controls the depth of penetration, but don't go to the maximum right away.The power should be set at 70 % of the recommended level for the material being used, for example 15-20 watts for stainless steel.If you notice that the ink is turning yellow (an indication of oxidation), reduce the power appropriately. Don't reduce it by more than 3 watts at one time.

Speed and frequency must match.

When the speed is fast, the depth is shallow, but the efficiency is high. When the speed is slow, it is easy to burn through.From personal experience, I would suggest using a medium speed (600mm / s) and a frequency of 20kHz.When encountering a complex pattern, the speed is reduced to 400 mm / s, and the frequency is increased to 30 kHz. In this way, both clarity and heat buildup can be controlled.

A primitive way to measure depth.

Nail scratch test.

Temporary judgment: Don't blindly trust instruments! If you use your fingernail to lightly scrape the surface of the marking at a 45 ° angle, you should be able to feel a depth of about 0.02 millimeters. If you cannot feel a clear difference, then the depth is less than 0.01 millimeters.The method may be crude, but it's very practical in the workshop.

Key points for using the microscope.

When using the 200x microscope, remember to clean the sample surface first.The trick is to apply nail polish to the side of the sample before cutting it, which creates a clear color boundary in the cross-section that makes it easier to measure. This reduces the margin of error by over 30 %.

When faced with a problem, first examine these three points.

Some are deep, some shallow.

In 90 % of the cases, the problem is a dirty lens or a loose laser head.Every month, the lenses must be wiped with alcohol, and when tightening screws, a torque wrench must be used. Many old-timers tighten screws with their hands, but the difference between 0.3 and 0.5 Newton-meters of torque directly results in a 0.005-mm deviation in depth.

The edges are blurred.

First check the compressed air! If the water content of the compressed air goes beyond the standard, then the edges of the marking will look like a Chinese ink painting.The problem was solved by adding three levels of air filters to the pneumatic system, which lowered the humidity to below 15 %.

The surface of the material changes color.

In particular, if you are having problems with black marks on aluminum, try narrowing the pulse width.The last time we were laser marking car parts, we switched from 10 ns to 7 ns. The blackened layer was obviously thinner, and the depth was stable around 0.015 mm.