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Status and development of NC plasma cutting technology

in industrial production, metal thermal cutting generally includes gas cutting, plasma cutting, laser cutting, etc. Compared with gas cutting, plasma cutting makes the structure more concise, bright, cutting range wider and efficiency higher. Fine plasma cutting technology has been close to the quality of laser cutting in terms of material cutting surface quality, but the cost is far lower than laser cutting. Therefore, plasma cutting has developed rapidly since it was successfully developed in the United States in the mid-1950s. With the rapid development of computer and digital control technology, CNC cutting is also booming and improving machining accuracy. It shows great advantages in saving materials and improving labor productivity. This promotes the development of plasma cutting technology from manual or semi-automatic to numerical control, and has become one of the main directions of the development of numerical control cutting technology. Numerical control plasma cutting technology is a high-tech integrating numerical control technology, plasma cutting technology and inverter power technology. Its development is based on the common progress of computer control, plasma arc characteristics research, power electronics and other disciplines. CNC cutting technology in China started in the 1980s, while CNC plasma cutting technology started later. However, in recent years, some domestic universities, scientific research institutions and manufacturers have studied the NC plasma cutting technology, and gradually developed and produced various specifications of NC plasma cutting equipment, narrowing the gap with foreign advanced technology

1. Current situation of CNC plasma cutting in China

flame cutting and plasma cutting are the most widely used in plate cutting in Chinese factories. The equipment used includes manual cutting, copying machine cutting, semi-automatic cutting machine cutting and CNC cutting machine cutting. Compared with other cutting methods, manual cutting is random, flexible and convenient, and does not need special cutting equipment. However, the disadvantages of manual cutting and blanking are also obvious, such as poor cutting quality, large size error, large material waste, large workload of subsequent processing procedures, and poor labor conditions. Cutting with the profiling machine can greatly improve the quality of the cutting workpiece, but it must be processed in advance to match the profiling of the workpiece, which is not suitable for single piece, small batch and large workpiece cutting. Although the semi-automatic cutting machine reduces the labor intensity of workers, its function is simple, and it is only suitable for cutting of one shape. Compared with NC cutting, the above three cutting methods are still widely used in small and medium-sized enterprises in China, even in some large enterprises, due to the low efficiency and simple operation of packaging and sorting in plastic recycling due to the improvement of equipment cost and new luminous materials

with the vigorous development of domestic economic situation and "With the acceleration of the trend of replacing casting with welding, the advantages of NC cutting are gradually recognized by people. NC cutting not only greatly improves the utilization rate of plates and product quality, but also improves the working environment of workers and further improves labor efficiency. At present, the NC cutting machines used in China's metal processing industry are mainly flame and ordinary plasma cutting machines, but pure flame cutting can no longer meet the needs of modern production At present, most of the CNC cutting machines in the market demand are CNC plasma cutting machines, which can meet the cutting needs of metal plates with different materials and thicknesses and the processing of metal parts. Therefore, the demand will be larger and larger, but the gap with foreign countries is still extremely obvious, which is mainly reflected in: 90% of the metal processing industry in developed countries is CNC cutting machines, and only 10% is manual cutting; In China, the cutting of CNC cutting machine only accounts for 10% of the total cutting, and the cutting of CNC plasma cutting accounts for a smaller proportion. The reason is that higher equipment cost, complexity, maintenance and operation restrict the further popularization of NC cutting in our country. Therefore, domestic CNC cutting machine manufacturers have introduced foreign control system technology, which has been applied to the cutting field after secondary development, and designed a CNC cutting machine suitable for China's national conditions. The special CNC cutting equipment developed and produced by some manufacturers has reached or exceeded the similar foreign products in technology

the annual market demand of CNC cutting machines in China is about 400~500, and the products are mainly CNC plasma cutting machines. In contrast, thousands of profiling cutting machines are sold every year, and tens of thousands of semi-automatic cutting machines are sold every year. It can be seen that the development potential of China's CNC cutting market, especially CNC plasma cutting market, is huge

1.1 introduction to plasma cutting types

a. ordinary plasma arc cutting. According to the main working gases used, it is mainly divided into argon plasma arc cutting and oxygen plasma arc cutting. Oxygen plasma arc cutting and air plasma arc cutting. The cutting current is generally below 100 a, and the cutting thickness is less than 30 mm

b. re constrain plasma arc cutting. According to the re constraint mode of plasma arc, it is mainly divided into water recompression plasma arc cutting, magnetic field re constraint plasma arc cutting, etc. As the plasma arc is compressed again, its current density and cutting arc energy are further concentrated, which improves the cutting speed and processing quality

c. fine plasma arc cutting. The current density of plasma arc is very high, which is usually several times that of ordinary plasma arc. Due to the introduction of technologies such as rotating magnetic field, the stability of its arc is also improved, so its cutting accuracy is quite high. The surface quality of fine plasma cutting abroad has reached the lower limit of laser cutting, and its cost is only one third of that of laser cutting

1.2 plasma cutting power supply

the cutting machine power supply with high leakage reactance transformer and secondary side rectification, which was originally widely used in China, has been gradually replaced by the inverter plasma cutting power supply. Its principle is shown in Figure 1. Domestic plasma power supply is mostly used for manual cutting and equipped on trolley cutting machine. In recent years, due to the improvement of performance, it is also gradually equipped for CNC cutting machine, but it still needs to be further improved

1.3 current situation and development of numerical control technology

the rapid development of computer technology has promoted the upgrading of numerical control technology, which has increasingly improved the high-precision, high-speed and efficient functions of numerical control plasma cutting. Numerical control system manufacturers in Europe, the United States and Japan, which represent the world's advanced level, use the rich software and hardware resources of industrial computers to develop a new generation of numerical control system with an open architecture, that is, the development of numerical control system can be oriented to end users on a unified operating platform, and form serialization by changing, adding or tailoring structural objects (numerical control functions), It can easily integrate the special applications and technical know-how of users into the control system, and quickly realize the development of different varieties and grades of products

the open architecture enables the CNC system to have better versatility, flexibility, adaptability and expansibility, and to develop in the direction of intelligence and networking

at present, there are two basic structures of open system:

a.cnc+ industrial computer motherboard. An industrial control board is inserted into the traditional CNC machine. The industrial control board is mainly used for real-time control, and the CNC is mainly used for real-time control based on coordinate axis movement

b. industrial computer + motion control board. The motion control board is inserted into the standard slot of the industrial computer for real-time control, while the industrial computer is mainly used for non real-time control

the CNC system of CNC plasma cutting machine produced in China is mostly independently developed on the basis of introducing foreign CNC technology, and gradually formed a CNC system that is more suitable for domestic users. Generally speaking, the CNC system has the basic functions of similar foreign systems, but compared with foreign advanced CNC systems, there is still a big gap in error recording, networking production, full-automatic production and so on

1.4 anti interference measures of NC plasma cutting system

the cutting power supply has strong electromagnetic interference, which requires that the computer control system must have high anti-interference ability, which can not only resist the high-frequency interference of plasma arc striking, but also resist the interference of ion arc such as high current during operation, but also resist other interference sources at the work site. Through anti-interference design, the reliability of CNC plasma cutting system is improved, and its failure rate is also reduced

2. CNC at home and abroad. 2. Electronic universal series: current situation and development trend of ion cutting of conventional electronic universal material testing machine.

foreign manufacturers of CNC cutting machines are mainly concentrated in Germany, the United States and Japan. In terms of mechanical structure, its development has experienced three stages: cross type (light), door type (small) and gantry type (large), with a wide variety of corresponding models. The manufacturers that can represent the highest level of CNC plasma cutting technology are mainly concentrated in Germany. For example, the cutting accuracy of the fine plasma cutting machine of ESAB company in Germany has reached the lower limit of laser cutting. At present, foreign manufacturers have installed a special cutting manipulator on the gantry cutting machine and developed a gantry special cutting tool with a five axis control system. The system can cut various tracks in space and use special tracking probes, Control the cutting track during the cutting process. In contrast, although cross type, door type and gantry type are produced in China, the breadth is not enough. The product model of the manufacturer is relatively single, and there is no gantry type special profile cutting machine product

in recent years, due to the higher and higher requirements for cutting quality and labor environment, foreign advanced plasma cutting technologies such as large-scale underwater plasma cutting method and fine plasma cutting method have developed rapidly, and the market demand of their corresponding products in China has also increased year by year. In China's plasma cutting equipment production industry, due to the lack of a mechanism for the conversion of plasma cutting theoretical research and production practice, new technologies are not widely used, and the development speed of new products is not fast, which restricts the further development and application of plasma cutting technology

it can be predicted that the time division market demand for the unloading of impact testing machines of CNC cutting machines in China will still be dominated by CNC plasma cutting machines. At the same time, the market demand for large-scale underwater plasma cutting, fine plasma cutting and other advanced cutting equipment widely used abroad is increasing year by year in China

from the development trend of NC plasma cutting industry abroad, intelligent precision cutting will become the future development direction of the cutting industry

3. Conclusion

China's steel output has already reached 100 million tons. Coupled with the vigorous development of manufacturing industry, it will promote the benign development of domestic CNC plasma cutting technology. Generally speaking, the basic functions of CNC plasma cutting in China have reached the level of similar foreign products, but there is still a long way to go to fully reach or exceed the foreign level. Domestic enterprises and scientific research institutions should strengthen scientific research, pay attention to horizontal cooperation between enterprises, form complementary advantages, and strive to further improve in the following aspects:

a. the relevant transformation between plasma theoretical research and production should be strengthened

b. the stability of plasma power supply should be further improved

c. actively develop CNC plasma cutting equipment that is suitable for China's national conditions and is economical and reliable

d. friendly man-machine interface, suitable for cutting and blanking workers

e. network interconnection function. (end)

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