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Experience In Laser Marking Process Analysis - What Is The Cause Of Uneven Marking Effect Of Laser Marking Machine?

Sep 16, 2019
1.it may be that the level of the machine is not adjusted, that is, the laser lens or field lens is not parallel to the processing table.
Since the two are not horizontal, the length of the laser beam passing through the field lens and reaching the processed object is inconsistent, that is, the focus position on the material is inconsistent when the laser is marked. Eventually, the energy of the laser falling on the workpiece will have an inconsistent energy density, which will result in unevenness in the material.
2.it may be that the laser marking machine is out of focus
Because each laser-marked field lens has a corresponding depth of focus range, and the use of defocus marking can easily lead to a large range of marking patterns, the edge is at the focal depth limit or beyond the depth of focus, which is easier Causes unevenness in effect. Therefore, the method of defocusing marking must consider laser energy.
3. it may be that the laser output spot is blocked or not round enough

The laser output head, fixed fixture and galvanometer of the laser are not adjusted, which causes some spots to be blocked when the laser passes through the vibrating lens. The spot on the multiplier is non-circular after being focused by the field lens, which may also cause the effect of the laser marking machine is not uniform.
In addition, if the galvanometer deflecting lens is damaged, for example, the film layer is damaged. When the laser beam passes through the damaged area of the lens, it does not reflect well. Therefore, the laser beam is inconsistent with the laser energy in the damaged area of the lens and the non-damaged area of the lens, and the laser energy ultimately acting on the material is also different, so that the effect of laser marking is not uniform.

4. It may also be the cause of the material, such as inconsistent film thickness or physicochemical properties on the surface of the material.
The material is sensitive to laser energy, and usually, under the same material, the laser energy reaches a material damage threshold is certain. When the thickness of the material coating is different, or some other physicochemical treatment processes are not uniform enough, the absorption or reflection of the laser to the material will be different, which will result in uneven effect after laser marking.
5. it may be a thermal lens phenomenon
When the laser passes through the optical lens (refraction, reflection), the laser lens generates heat to produce a slight deformation. This deformation causes the focus of the laser field lens to rise and the focal length to become shorter. If the machine is fixed and the distance is adjusted to the focus after the laser is turned on for a while, the laser energy density acting on the material changes due to the thermal lens phenomenon, resulting in uneven marking effect.
In addition, if the laser-marked field lens is dirty or ccovered withdust, the thermal lens effect will be more noticeable. Or the dust outside the field lens is uneven. Then, when the laser is marked, the thermal lens effect is different in every place of the field lens, and the dust also has a certain occlusion on the laser. That way the effect of laser marking will be uneven.