MOPA laser marking machine alumina blackening principle: 

The mechanism of anodized aluminum blackening is to focus a high energy density laser, using special frequency and density and adjustable pulse width to achieve a film thickness of 5 in a very short time. -20um anodized aluminum layer further oxidizes and changes the color of the surface material.

The thickness of the film directly determines the effect and efficiency of blackening. Generally, it is easier to blacken when the film thickness is 10-20um. When the film thickness is less than 8um, the oxide film is too thin and is easy to break, causing white spots to appear. It is necessary to increase the pulse frequency and increase the filling density. In addition, the surface treatment process of anodized aluminum will directly affect the blackening effect. Sandblasting and surface drawing are common processes. The thickness of the sandblasting will have different effects on the marking effect. The finer the sandblasting particles, the better the blackening effect. . It is recommended that the film thickness of anode aluminum is 10-15μm, so that the overall blackness effect will be better.