Laser marking technology is one of the biggest application fields of laser processing. Laser marking is a kind of marking method which uses high energy density laser to irradiate the part, vaporize the surface material or change the color, so as to leave a permanent mark.Laser markingcan print all kinds of characters, symbols and patterns, and the size of characters can be from millimeter to micrometer, which is of special significance for the anti-counterfeiting of products.
The "cutting tool" used in laser processing is the focused light point, without additional equipment and materials, as long as the laser can work normally, it can be processed continuously for a long time. The laser processing speed is fast and the cost is low. Laser processing is controlled by computer automatically, and no human intervention is needed in production.
Fiber pulse laser is a kind of laser produced by using glass fiber doped with rare earth elements (such as ytterbium) as the gain medium, which has very rich luminous energy levels. The wavelength of pulse fiber laser is 1064nm (the same as YAG, but the working substance of YAG is neodymium) (the typical wavelength of QCW and continuous fiber laser is 1060-1080nm, although QCW is also a pulse laser, its pulse It is a kind of near infrared laser. It can be used to label metallic and non-metallic materials because of their high absorption.
UV laser is a kind of short wavelength laser. Generally, it uses frequency doubling technology to convert the infrared light (1064nm) emitted by solid-state laser into 355nm (frequency tripling) and 266nm (frequency quadrupling) ultraviolet light. Its photon energy is very large. It can match with some chemical bond (ion bond, covalent bond, metal bond) energy levels of all substances in nature. It can directly break the chemical bond and cause photochemical reaction of materials. There is no obvious thermal effect (some energy levels of atomic nucleus and inner layer electron can absorb ultraviolet photons, and then transmit the energy through lattice vibration to produce thermal effect , but not obvious), which belongs to "cold working". Because there is no obvious thermal effect, UV laser can not be used for welding, generally used for marking and precision cutting.
CO2 is a commonly used gas laser, which has rich luminous energy levels. The typical laser wavelength is 9.3, 10.6um. It is a far-infrared laser with continuous output power up to tens of thousands of watts. Generally, the low-power CO2 laser is used to complete the marking of polymer and other non-metallic materials. Generally, CO2 laser is rarely used to mark metals, because the absorption rate of metals is very low (high-power CO2 can be used to cut and weld metals, which has been gradually replaced by fiber laser due to absorption rate, electro-optic conversion rate, optical path and maintenance and other factors).
The CO2 marking process is realized by using the thermal effect of laser on materials, or by heating and vaporizing the surface materials to expose the materials with deep different colors, or by heating the micro physical changes on the surface of materials with light energy, so that its reflective performance changes significantly, or by some chemical reactions when heating with light energy, to show the required graphics and characters , QR code and other information.