I. Marking a certain range of content with off-focus
Because each focusing lens has a corresponding range of focal depth, and the use of off-focus methods can easily lead to a large range of marking patterns, the edge is at the critical depth of focal depth or beyond the focal depth range, so it is relatively easy to cause effects. Uniformity. Therefore, the method of defocus marking must consider the problem of laser energy.
Second, the laser output light spot is blocked, that is, the laser beam passes through the galvanometer and field lens, the light spot is lacking, and is not round enough
The laser output head, fixed fixture, and galvanometer are not adjusted properly, which causes part of the light spot to be blocked when the laser passes through the lens. The light spot on the frequency multiplier after focusing by the field lens is non-circular. Even.
There is also a case where the galvanometer deflection lens is damaged, and when the laser beam passes through the damaged area of the lens, it cannot be reflected well. Therefore, the laser energy passing through the damaged area of the lens is inconsistent with the laser energy of the non-damaged area of the lens, and the final laser energy acting on the material is also different, thereby making the marking effect uneven.
Third, the thermal lens phenomenon
When the laser light passes through the optical lens (refraction, reflection), it will cause the lens to generate slight deformation. This deformation will increase the laser focusing focus and shorten the focal length. If the machine is fixed, when the distance is adjusted to the focal point, after turning on the laser for a period of time, the laser energy density acting on the material will change due to the thermal lens phenomenon, resulting in uneven marking effect.
Fourth, the machine level is not adjusted properly, that is, the laser lens or field lens is not parallel to the processing table
Because the two are not horizontal, the distance between the laser beam and the processed object after passing through the field lens will be inconsistent. Finally, the energy of the laser falling on the processed object will have an inconsistent energy density. At this time, the effect will be shown on the material Uneven.
V. Material reasons, such as inconsistent film thickness on the surface of the material or changes in physical and chemical properties
The material is more sensitive to laser energy response. Usually under the same material, it is certain that the laser energy reaches the material destruction threshold. When the thickness of the material coating is different, or some other physical and chemical treatment processes are not uniform, the effect of laser marking will also be uneven.