Mask Mode laser marking system
Mask mode laser marking is also called projection marking. The mask mode laser marking system is composed of a laser, a mask plate and an imaging lens. Its working principle is that the laser beam expanded by the telescope is evenly projected on the pre-made mask plate, and the light is transmitted from the carved part. The pattern on the mask is imaged onto the workpiece (focal plane) through the lens. Usually each pulse can form a mark. The surface of the material irradiated by the laser is quickly heated to vaporize or produce a chemical reaction, and the color change occurs to form a clearly distinguishable mark. Mask mode marking generally uses CO2 laser and YAG laser. The main advantage of mask mode marking is that a laser pulse can produce a complete mark including several symbols at a time, so the marking speed is fast. For high-volume products, you can mark directly on the production line. The disadvantages are poor marking flexibility and low energy utilization.
Array Laser Marking System
Array laser marking system uses several small lasers to emit pulses at the same time. After passing through the mirror and focusing lens, several laser pulses are ablated (melted) on the surface of the marked material to form small pits of uniform size and depth. Each character, The pattern is composed of these small round black pits, generally 5 points in horizontal strokes and 7 points in vertical strokes, thus forming a 5×7 array. Array marking generally uses low-power RF excited CO2 lasers, and its marking speed can be up to 6000 characters/s, which makes it an ideal choice for high-speed online marking. Its disadvantage is that it can only mark dot characters and can only reach 5×7.
Scanning Laser Marking System
The scanning laser marking system is composed of three parts: computer, laser and XY scanning mechanism. Its working principle is to input the information to be marked into the computer. The computer controls the laser and XY scanning mechanism according to the pre-designed program to make the special optical system transform The high-energy laser spot scans and moves on the processed surface to form a mark.
Usually X-Y scanning mechanism has two structural forms: one is mechanical scanning type, the other is galvanometer scanning type.
1. Mechanical Scanning.
The mechanical scanning marking system does not use the changing angle of the mirror to move the light beam, but uses a mechanical method to translate the XY coordinates of the mirror to change the position of the laser beam to the workpiece. The XY of this marking system The scanning mechanism is usually modified with a plotter. Its working process: the laser beam passes through the mirror and the turning light path, and then strikes the workpiece to be processed through the action of the light pen (focusing lens). The pen arm of the plotter can only carry the mirror and move back and forth along the X axis direction; the light pen and its upper mirror (the two are fixed together) can only move along the Y axis direction. Under the control of the computer (generally output control signals through the parallel port), the movement of the light pen in the Y direction and the movement of the pen arm in the X direction can make the output laser reach any point in the plane, thus marking any graphics and text .
2. Galvanometer Scanning Type.
The galvanometer scanning marking system is mainly composed of laser, XY deflection mirror, focusing lens, computer and so on. Its working principle is that the laser beam is incident on two mirrors (galvanometer), and the reflection angle of the mirror is controlled by a computer. The two mirrors can be scanned along the X and Y axes respectively, so as to achieve the deflection of the laser beam, so that The laser focusing point of a certain power density moves on the marking material according to the required requirements, thereby leaving a permanent mark on the surface of the material. The focused spot can be round or rectangular.
In the galvanometer laser marking system, vector graphics and text can be used. This method adopts the graphics processing method of graphics software in the computer. It has the characteristics of high drawing efficiency, good graphics accuracy, and no distortion. It has greatly improved The quality and speed of laser mark. At the same time, the galvanometer marking can also use the dot matrix marking method. This method is very suitable for online marking. Depending on the production line at different speeds, one scanning galvanometer or two scanning galvanometers can be used. Compared with the array type marking, it can mark more dot matrix information, which has a greater advantage for marking Chinese characters.
The galvanometer scanning laser marking system generally uses a continuous optical pump with an Nd: YAG laser with a working wavelength of 1.06 μm. The output power is 10 to 120 W. The laser output can be continuous or Q-switched. The developed RF excited CO2 laser is also used in galvanometer scanning laser marker.
Galvanometer scanning type marking can be used for vector marking and dot matrix marking because of its wide application range, the marking range is adjustable, and it has fast response speed and high marking speed (a few hundred characters can be marked per second) The advantages of high marking quality, good optical path sealing performance, and strong adaptability to the environment have become mainstream products, and are considered to represent the future development direction of laser markers and have broad application prospects.
The lasers used for marking mainly include Nd: YAG laser and CO2 laser. The laser generated by the Nd: YAG laser can be well absorbed by metals and most plastics, and its short wavelength (1.06μm) and small focused spot make it the most suitable for high-definition marking on metals and other materials. The laser wavelength produced by the CO2 laser is 10.6 μm. Wood products, glass, polymers and most transparent materials have a good absorption effect, so it is particularly suitable for marking on non-metallic surfaces.
The disadvantage of Nd: YAG laser and CO2 laser is that the thermal damage and thermal diffusion of the material are serious, and the hot edge effect often makes the mark blurred. In contrast, when marking with ultraviolet light generated by an excimer laser, the material is not heated, only the surface of the material is evaporated, a photochemical effect is produced on the surface tissue, and a mark is left on the surface of the material. Therefore, when marking with an excimer laser, the edge of the mark is very clear. Due to the large absorption of ultraviolet light by the material, the effect of the laser on the material only occurs at the outermost layer of the material, and there is almost no burning damage to the material, so the excimer laser is more suitable for the marking of the material.