How Laser Power Affects the Depth of Color on Metals

The power of the laser is a key factor in the coloring process.This article examines the relationship between the thickness of the metal oxide layer and the laser's power, and analyzes how the laser's power can be used to precisely control the depth of color of the metal and its color stability, offering practical suggestions for industrial design and processing.

Why can laser power change the color of metals?

You may have seen laser-etched color designs on metal, but have you ever thought about the principle behind it? When a laser hits metal, the heat causes a very thin oxide coating to form on the surface.The thickness of the membrane differs, and this causes the wavelength of the reflected light to vary. The color seen by the human eye naturally differs as well.The power of the laser determines the speed and thickness of the oxide layer, which is the "switch" for changing the color.

Actual color effects for different power levels.

We carried out a comparison experiment using 304 stainless steel.

Low power (20-40 watts).

The lower the power, the weaker the laser energy, and the slower the oxidation.It is suitable for fine, gradual effects, such as the halo around the logo, but its color stability is not so good, and it requires repeated testing.

Medium power (50-80 watts).

This is the most commonly used range, with a balanced oxidation speed and thickness.The saturated colors such as dark blue and purple are mostly printed at this setting, and the success rate for the coloration of the raised lettering on mobile phone cases and the patterns on tableware can be 90 % or higher.

High power (90W +).

If the voltage is too high, the oxide layer will be burned through, and the color will turn gray or black.However, if you want an industrial look, such as a gunmetal gray texture, you can raise the power and speed up the scan, but you must be careful not to let the exposure time exceed 0.5 seconds.

How do you adjust the power most easily in practice?

Don't rush to switch on the machine. First, remember three points of caution.

First look at the material and then decide on the parameters.

The power required for stainless steel and titanium is very different.For example, if you want a purple color, you might need 65 watts of laser power for stainless steel, but only 45 watts for titanium.

The more times they are scanned, the more stable they become.

It's better to use a medium power and sweep twice than to use a high power and sweep once.This is especially important when coloring a large area, because the color can be applied evenly and it is less likely to scorch.

* Have sample test cards ready.

The scraps of paper from the cutting process are then used to make color blocks in increments of 10 W.I put them up on the wall next to my workbench as a reference, and they are much more intuitive than the parameter tables.When encountering a new batch of materials, he can first adjust the machine using the test cards, saving at least half an hour in the process.

And a little trick for those who know: When it's hot in the workshop, remember to lower the power by 3-5 watts.Metals are affected by heat in the environment, and the rate of oxidation is faster than normal. This slight adjustment can reduce the color variation in the finished product.