First, the use of defocusing to mark a certain range of content because each focusing mirror has a corresponding depth of focus range, and the use of off-focus method will easily lead to a large range of marking patterns, the edge is at the depth of focus Point or beyond the depth of focus range, it is easier to cause unevenness of the effect.
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 is lacking after passing through the galvanometer and the field lens, and the laser output head, the fixed fixture and the galvanometer are not well adjusted, and the laser is vibrated. When the lens is partially blocked, the spot on the multiplier is non-circular after being focused by the field lens, which may cause unevenness.
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. Thermal Lens Phenomenon When the laser light passes through the optical lens (refraction, reflection), the lens generates heat to cause 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 the field lens is not parallel to the processing table. Since the two are not horizontal, the laser beam passes through the field lens and reaches the distance of the workpiece. Inconsistent lengths and lengths, the energy of the laser falling on the workpiece will have an inconsistent energy density, and the effect will be uneven on the material. 5. Reasons for materials, such as inconsistent film thickness on the surface of the material or changes in physicochemical properties. The material is 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 not uniform, or some other physicochemical treatment process is not uniform enough, it will also cause unevenness of the effect after laser marking.
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