The Reason For Uneven Laser Engraving Effect
Laser radium engraving technology has gradually entered people’s daily life, such as mobile phone back shell patterns, light switches, plastic buttons in the central control of automobiles, and the fonts (patterns) in them may be realized by laser radium engraving technology. When laser engraving patterns, processors may often encounter such a question: “Why is the effect of laser engraving uneven?”There are several reasons for the uneven effect:
- The level of the machine table is not adjusted properly, that is, the galvanometer lens or field lens lens is not parallel to the processing table;
- Since the two are not level, the distance between the laser beam and the object to be processed will be inconsistent after passing through the field lens. Finally, the energy of the laser falling on the object to be processed will have inconsistent energy density, which will show the effect on the material. uneven.
- The laser output spot is blocked, that is, after the laser beam passes through the galvanometer and the field mirror, the spot is missing and not round enough;
- The laser output head, fixing fixture and galvanometer are not adjusted properly, which causes part of the light spot to be blocked when the laser passes through the galvanometer. evenly.
- There is also a situation that 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 of the laser beam passing through the damaged area of the lens is inconsistent with that of the non-damaged area of the lens, and the final laser energy acting on the material is also different, so that the marking effect is uneven.
- Use off-focus to mark a certain range of content;
- Because each focusing lens (field lens) has a corresponding focal depth range, and the defocusing method will easily lead to a large-scale marking pattern, the edge is at the focal depth critical point or beyond the focal depth range, so it is easier to causing unevenness in the effect. Therefore, the method of off-focus marking must consider the problem of laser energy.
- Thermal lens phenomenon;When the laser passes through the optical lens (refraction, reflection), it will cause the lens to heat up and cause slight deformation. This deformation will raise the focus of the laser and shorten the focal length. If the machine is fixed and the distance is adjusted to the focal point, after the laser is turned on 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. (For the thermal lens phenomenon, please refer to the previous WeChat article).
- Material reasons, such as inconsistent film thickness on the material surface or changes in physical and chemical properties;
- Materials are sensitive to laser energy. Usually under the same material, the laser energy reaches a certain material damage threshold. When the thickness of the material coating is different, or some other physical and chemical treatment processes are not uniform enough, it will also cause unevenness in the effect of laser marking.