1. use a bias to mark a certain range of content
Because each focusing mirror has a corresponding depth of focus range, and the method of deviating from the focus will easily lead to a large range of marking patterns, the edge is at the critical depth of the focal depth or beyond the depth of focus, which is more likely to cause effects. Uniformity. Therefore, the method of defocusing marking must consider the problem of laser energy.
2.the laser output spot is blocked, that is, the laser beam passes through the galvanometer and the field lens, and the spot is lacking.
The laser output head, fixed fixture, and galvanometer 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 result in no effect. Evenly.
There is also a case where the galvanometer deflecting lens is damaged and cannot be reflected well when the laser beam passes through the damaged area of the lens. 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, thereby making the marking effect uneven.
3. the thermal lens phenomenon
When the laser passes through the optical lens (refraction, reflection), it will cause the lens to generate heat and produce a slight deformation. This deformation causes the laser focus 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.
4. 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 workpiece is inconsistent. The energy of the laser falling on the workpiece will have an inconsistent energy density, and the effect will be exhibited on the material. Not uniform.
5. Reasons for materials, such as inconsistent film thickness or physical and chemical properties on the surface of the material
Materials are sensitive to laser energy reactions. Generally, 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, it will also cause uneven effect after laser marking.