Analysis of the reasons for "non-uniform laser engraving effect"
Laser engraving technology slowly enters people's daily life, such as mobile phone back shell pattern, light switch, car control plastic button, the font (pattern) may be realized by laser engraving technology. In laser engraving patterns, processors often encounter such a problem: "Why is the effect of laser engraving uneven?"
There are several possible reasons for the uneven effect:
The level of the machine is not adjusted, that is, the vibration lens or the field lens is not parallel to the processing table;
Because 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.
The laser output spot is blocked, that is, the laser beam is lacking after the galvanometer and the field lens, and is not round enough;
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.
Use a bias to mark a certain range of content;
Because each focusing mirror (field mirror) has a corresponding depth of focus range, and using the off-focus method can easily lead to a large range of marking patterns, the edge is at the focal depth threshold or beyond the depth of focus, which is easier Causes unevenness in effect. Therefore, the method of defocusing marking must consider the problem of laser energy.
Thermal lens phenomenon;
When the laser passes through the optical lens (refracting, reflecting), it causes the lens to heat up to produce a subtle 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.
Material reasons, such as inconsistent film thickness or physicochemical 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 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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