The principle and application of dot matrix online laser coding technology

The dot-matrix online laser coding technology can realize high-speed and high-precision online coding, which represents the latest development direction of the current online coding technology, and can provide enterprises with efficient and feasible product coding solutions.

First, the introduction of dot matrix online laser coding technology

Dot matrix online laser coding technology uses a galvanometer scanning strategy. As shown in Fig. 1, the coding system controls the scanning path of the laser by the angular deflection of the X and Y galvanometers.

Figure 1 galvanometer scanning strategy

Dot matrix online laser coding technology uses dot matrix characters for online coding. A dot matrix character consists of a series of dots. Figure 2 shows the case of the 5 x 7 dot matrix characters "N" and "C". When the galvanometer is scanned to the red position, the laser exits and the object is laser marked on a point. When the galvanometer is scanned to the white position, the laser is closed and the object is not marked.

Figure 2 laser marking of dot matrix characters

When the coded product moves on the production line, its relative galvanometer scan has a reverse direction velocity error V (as shown in Figure 3). This speed error V is equal to the speed of the production line. Dot matrix online laser coding technology obtains this speed error by monitoring the speed of the production line online, and can generate a compensation signal based on this speed error to drive the galvanometer to offset this error.

Second, the advantages of dot matrix online laser coding technology

Dot matrix online laser coding technology has many excellent features:

(1) Dot matrix online laser coding technology adopts galvanometer scanning strategy. During the scanning motion, the galvanometer is almost immune to external resistance, and has the characteristics of fast speed, stable and reliable motion process and accurate positioning.

(2) Dot matrix online laser coding technology Compared with traditional inkjet coding technology, it does not require ink and other consumables, and is easy to maintain, cost-effective, and environmentally friendly.

(3) Dot matrix online laser coding technology utilizes a high-energy-density laser beam to act on a target to cause physical or chemical changes to the target surface, thereby obtaining high-quality, permanent marks.

(4) Dot matrix online laser coding technology can be easily combined with digital control technology to develop a variety of products.

The above advantages make the dot matrix online laser coding technology have broad application prospects. Currently, in foreign countries, this technology has been successfully applied in actual production. Some companies have developed more mature products.

Figure 3 product produces a reverse speed error when moving on the production line.

Third, the progress of dot matrix online laser coding technology in South China University of Technology

(1) DSP online laser coding control system

Since 2007, South China University of Technology has started research on dot-matrix online laser coding technology. At present, it has successfully developed the DSP online laser coding control system. As shown in FIG. 4, the system consists of a main control unit and a remote operation unit.

Figure 4 Structure of DSP online laser coding control system

Figure 5: The hardware structure of the main control unit of the DSP online laser coding control system

The main control unit can control the light output of the laser and the angular deflection of the galvanometer, and can collect the speed of the production line in real time to generate a speed error compensation signal. Its hardware structure is shown in Figure 5.

The remote operating unit is responsible for the human-computer interaction between the system and the operator. Through the remote operating unit, the operator can perform operations such as programming custom codes, controlling the operation and stopping of the system. After the remote operation unit accepts the relevant operations of the operator, it forwards it to the main control unit for execution. Its hardware structure is shown in Figure 6.

Fig. 6 Remote operation unit hardware structure of DSP online laser coding control system Features of the control system include:

(1) The main control unit adopts the DSP control mode, which has fast calculation speed, high precision and low power consumption.

(2) The remote control unit adopts the embedded solution, which has the advantages of small size, high reliability and low cost compared with the traditional PC.

(3) The open control structure has good flexibility and can be easily applied to a variety of lasers to form different types of coding systems.

(II) Application examples of DSP online laser coding control system

The DSP online laser coding control system of South China University of Technology is becoming more and more mature. By the end of 2009, it has successfully applied it to Nd:YAG laser in cooperation with Dongguan Chuangpu Optoelectronic Technology Co., Ltd., and developed the Nd:YAG online laser coding machine. . At present, South China University of Technology is using the DSP online laser coding control system to conduct research on CO2 laser coding machine, and has successfully developed a prototype.

Figure 7Nd: YAG online laser code printer

1Nd:YAG online laser coding machine

Nd:YAG coders can produce characters, graphics, 1D, 2D barcodes and continuously variable serial number marks on various metal materials and some non-metallic materials; they can be flight coded after being equipped with the production line. Applications include electronics, hardware tools, bathroom equipment, equipment signs, plastics and other industries.

Figure 7 is an external view of the Nd:YAG online laser coding machine developed by South China University of Technology and Dongguan Chuangpu Optoelectronic Technology Co., Ltd.

2CO2 online laser coding machine

CO2 laser coders can produce characters, graphics, barcodes and serial number changes on various non-metallic materials. With the production line, you can fly and code, and the production line speed is more than 60 m/min. Applications include leather, cosmetics, alcohol, tobacco, pharmaceuticals, beverages, and the IT industry.

Figure 8 shows the prototype of the prototype of the South China University of Technology, which is 850mm long (vibrating lens), 200mm wide and 150mm high. It can be easily installed on the lifting platform. The oscillating lens can be rotated 360 in the axial direction of the coder. Ability to code in different directions.

The prototype can be combined with a variety of codes such as serial number, custom production date, custom effective date, and custom string. Figure 9 is a package of medicines coded with the coder, and Figure 10 is a package of beverages coded with the coder. The prototype also features a red light preview.

Figure 10 coding on the beverage package

Fourth, the conclusion

Dot matrix online laser coding technology meets the needs of online fast coding of products, and is a promising online coding technology. At present, the technology has made considerable progress abroad, and it is still in its infancy in China. Believing that the market needs for rapid coding of products, dot matrix online laser coding technology will gradually replace traditional technology into the mainstream.