Reasons for uneven marking effect of fiber laser marking machine

1. Use off-focus to mark a certain range of content

Because each focusing mirror has a corresponding range of focal depth. During a large range of marking patterns, deviating from the focus will easily lead to below effect. The edge is at the critical point of focal depth or beyond the range of focal depth. So it is easy to cause uneven effect.  Therefore, the off-focus marking method must consider the problem of laser energy.

2. The laser output spot of marking machine is blocked

When the laser beam passes through the galvanometer and field lens, the spot is missing and not round enough.

The laser output head, the fixing fixture and the vibrator are not adjusted properly. Which leads to the blocking of some light spots when the laser passes through the vibrator lens. And the light spots presented on the frequency doubling plate after focusing by the field mirror are non-circular. So it may also lead to uneven effect.

There is another case: the damaged dipole deflector lens. The laser beam is not reflected well as it passes through the damaged area of the lens.  Therefore, the laser energy of the laser beam passing through the lens damaged area is not consistent with that of the lens undamaged area, and the laser energy acting on the material is also different, thus making the marking effect uneven.

3. Thermal lens phenomenon of marking machine

When a laser passes through an optical lens (refracts, reflects), it heats up the lens and causes a slight deformation.  This deformation causes the laser to focus higher and shorter.  If fix the machine and adjust the distance to the focal point, the energy density of the laser acting on the material will change due to the thermal lens phenomenon after a period of time, resulting in uneven marking effect.

4. The machine level is not adjusted properly

The laser vibrator lens or field lens lens is not parallel to the processing table surface.
Since the two are not level, the distance between the laser beam and the processed object after passing through the field lens will be inconsistent. Eventually, the energy of the laser beam falling on the processed object will have an inconsistent energy density, which will show the uneven effect on the material.

5. The reasons for the material

Such as inconsistent film thickness on the surface of the material or changes in physical and chemical properties.
The material is sensitive to laser energy. Generally, it is certain that the laser energy reaches the destruction threshold of the material under the same material. When the thickness of the material coating is not uniform, or some other physical and chemical treatment processes are not uniform, the effect after laser marking will also be uneven.

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