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CNC plasma cutting technology application and development in steel production

In modern large-scale steel plant, whether it is heavy steel, light steel structure, or in buildings, equipment, ships, and other different steel industry, cutting material in the production chain are the first channel key manufacturing processes, "cutting and welding" Su Iron and steel tailor said, which mainly refers to the application of the wide range of large thermal cutting. Thermal cutting began in the beginning of the last century, acetylene gas cutting by hand in France, then in the world wide popularity of long-term follow, along with the development of productive forces, thermal cutting by hand ordinary evolutionary development, and developed a number of new gas as well as the use of new cutting principles of the new industrial gas cutting equipment, increasingly high degree of automation, material being processed also expanded from ordinary carbon steel to stainless steel, nonferrous metals and other materials, and even non-metallic materials, cutting precision and efficiency to an unprecedented level . CNC plasma cutting machine is one such advanced technology, the production process needs, we are promoting a new type of automated cutting equipment.


1. The principle of plasma cutting and flame cutting, and the similarities and differences


CNC plasma cutting in the 1950s in the United States successfully developed, is a set of numerical control technology, plasma cutting technology, power technology in one mechatronic devices. Its basic principle of discovery and development, thanks to technological innovation in the United States in World War II aircraft industry, from the flame is still widely used in cutting change from. As the two main ways of cutting it is necessary to heat both the similarities and differences, a comparison of the characteristics, in order to use them for more targeted and easy selection. Therefore, the principle should be clearly understood and differences of plasma cutting and flame cutting. First, a gas flame cutting (currently mostly propane gas high combustion value gas) plus oxygen combustion heating cutting steel processing temperatures thousands of degrees. Plasma cutting and cutting the required heat energy principle is very different, the first look at what is plasma? Now know that there are four states matter, as the temperature increases, in turn presented as solids, liquids and gases tri-state, when the gas when the temperature further increases, the energy between the molecules so that complete separation, in which the atoms collide with each other due to intense electrons freed from such atoms, dissociated into positive ions and electrons (or positively charged nuclei), then enter the substance a new state called the fourth state, called plasma, the plasma is struck between the release of huge amounts of energy to produce and maintain a higher temperature, up to thousands of degrees, which should be "hot plasma "(as distinct from" cold plasma "). This nature for plasma cutting, such as generated by electric currents, coupled with constraints, can produce very high current density plasma arc, according to the working gas used, divided into oxygen, argon plasma arc cutting, etc., according to bound manner, divided into water and then compressed plasma arc cutting, magnetic field constricted plasma arc cutting, etc., and the current development of the plasma system, using only compressed air and electricity. Usually plasma cutting machine by the electronic control systems, mechanical devices and nozzles according to the principles of the different ignition control system is different. Electronic control system to produce high-temperature plasma arc heat, compressed air is compressed by the nozzle, (similar to gas welding), it will be partially melted metal cutting and high-speed air blown to form a thin, narrow cutting seam. From the cutting effect, flame cutting and plasma cutting notch quality vary greatly, plasma incision narrower, better smoothness generally do not need sanding, flame cutting are often required artificial slag milling, but usually only plasma cutting 30mm or less steel (and non-ferrous metal plate), still thicker steel flame cutting, and multilateral straight cutting flame cutting machines in general use.


The effect of differences in flame cutting and plasma cutting is another intuitive that, since the arc with different temperatures, flame cutting of sheet metal plays a melting and blow-off effect, and high-temperature plasma arc, as well as outside in addition to melting oxide evaporation process, often cutting smoke tobacco, and therefore had to use a lower plate sink or other dust measures. However, comprehensive comparison of various aspects of the advantages and disadvantages, plasma cutting because the cutting speed, good quality cut, perforation time is short, do not use electricity only cutting gas so high upfront investment and lower the cost of late, these unique features make it in technology Selection advantage more prominent, and thus more and more market attention. Visible, depending on the purpose and scope of the two kinds of cutting mode or has a clear division of labor oriented.


2.The basic system configuration of CNC plasma equipment

CNC plasma cutting equipment is generally summed up in three parts: Part machine, CNC and software components. The whole machine from the rail, rack, rack and pinion, speed reducer, servo motor, gas systems, cutting nozzle, dust and other cooling system components; Second, computers, power systems, servo motion control system as the core of a full set electrical systems hardware; computer software, compared with the third part, the following proposed classification profile.

2.1 Plasma arc cutting mode and power plasma arc cutting way to have the traditional high frequency high voltage mode and new non-high-frequency manner, many domestic companies are still using high-frequency high-handed way, foreign technology and other representatives of the US Treasure some domestic companies and new technology companies, the use of non-high-frequency arc technology. The type of power is usually enhanced magnetic flux leakage transformer power thyristor rectifier power supplies, power inverters and chopper power four. More generic Treasure MAX200 is a constant, providing continuously adjustable current 40-200A secondary conversion chopper power supply, these brands are currently more professional and sophisticated technology in the production and performance, there are more and more domestic products into the market competition. 3KV high-voltage high-frequency arc required to produce more high-voltage and high-frequency oscillation 150-200KHZ between the workpiece and the electrode, the breakdown of neutral gas medium to form an arc, the circuit is divided into short-circuiting and non-short-circuit type, this arc method It has a high success rate of arc, but electromagnetic interference caused by more serious, can not be used in CNC automatic cutting and electromagnetic interference demanding applications. Non-contact ignition frequency arc also known, requires direct contact with the electrode and nozzle gas pressure against the short circuit and ignite a small arc without high frequency oscillator inside the product, eliminating the high-frequency electromagnetic interference generated by high voltage discharge, reduced the harm to human body. This type of arcing electrode arc highly controlled manner to put forward higher requirements, the general set up a special arc voltage height control system.

2.2 servo control system

CNC cutting machine is a kind of numerical control technology and precision machinery closely integrated mechatronic products, technical performance has been far beyond the contour cutting, semi-automatic car like primary products, adapt cut any complex graphics. According to the size of the processing, mechanical structure may be in the form of gantry, cantilever, desktop portable CNC cutting machine, the choice of plasma or flame cutting head, as well as more specialized NC intersection Cutting, robot cutting machine, laser cutting machines. In medium-sized gantry, cantilever, for example, CNC plasma cutting machine is essentially a proprietary multi-axis cutting CNC servo system, computer control center, in the direction of two-axis cutting head above graphical motion control, in order to achieve cutting processing purposes.

2.3 arc voltage height control

Mentioned above, CNC plasma cutting of arc, arc voltage control demanding manufacturers use more specialized arc voltage height control to achieve this requirement. Plasma arc voltage height control principle is to use the basic plasma power constant current characteristic, plasma arc cutting by detecting the change in voltage to measure plasma cutting torch height change process to achieve a high degree of control over the cutting torch. Usually has several basic functions, the initial automatic positioning, power boost function perforated and broken arc torch collision, given the actual arc voltage display monitor, manual and automatic operation. Treasure products are high-performance self-supporting height control, should be mentioned, many of the domestic use of the product, performance has fully meet the engineering requirements, import substitution is very common use.

2.4 industrial computer programming and automatic nesting software

CNC plasma cutting system control center, is a set of industrial computer as the core, monitor, keyboard, integrated visual programming graphics cutting controller. In addition to the system it is usually equipped with Windows operating systems, CNC control system, but also need to install special automatic nesting software programming. A good horse with a good saddle, with corresponding with CAD / CAM programming software features drawing, editing and importing cutting pattern to be able to easily implement the entire system will be cut even more powerful, convenient, smart and reliably perform complex processing functions. Development Site software company authorized FastCAM automatic nesting software programming, the industry is currently very popular for a two-dimensional drawing cutting CNC programming software system, compared with the general traditional CAD software, not only can the usual CAD FastCAM graphing software to facilitate entry machine, cutting into the software, can also be used to clear the compression fitting and other optimization methods, to complete the cleaning DXT / DWG file extra points overlapping body compression curve fitting small entities, automatic recognition transition circle automatic common edge, by the side of the bridge, and so some of the details connected smart features that make it a higher intelligence and interactivity, and improve cutting quality assurance, which is one of the software's core technologies, especially FastCAM nesting optimization techniques, can effectively improve the utilization rate of steel nesting effectively save steel, improve processing efficiency.


3. CNC plasma (flame) cutting in steel production application           

The traditional hand-cut by hand with only the operator hand-eye movement route and speed, precision and productivity is difficult to guarantee the car later appeared cutting, profile cutting in a straight line or curve processing certain complex, relative increase quality and efficiency, but for flexibility and fast processing, single and special batch processing has been limited, and the generation and application of CNC cutting technology, thermal cutting process really make a qualitative leap of changes have taken place. Take the current production status of the steel industry point of view, we can learn CNC thermal cutting has become an important means of processing, equipment investment, and possession of more and more. In some coastal cities, industrial parks, for example, a large steel plant, due to the large-scale H steel processing steel products, with a large number of CNC flame cutting and automatic welding equipment; a shipyard steel vessel due to the requirements of special processing, using eight more than one large CNC plasma cutting machine; I once H-beam steel production plants mainly in the near future to establish long-term strategic partnership with a modern shipyard, the first wife NC automatic, semi-automatic straight cutting machine on the basis of new on two sets of 6M Haibao CNC plasma cutting machine, is now stepping up to thousands of tons of various thicknesses and shapes of the hull base segmented structure plate nesting, CNC plasma cutting equipment show a strong professional processing capacity will produce good economic returns.


4. programming and application examples           

CNC cutting machine in the application process should first be programmed to work, since Fastcam nesting software applications to simplify programming. During the operation requires the use of AutoCAD or other drawing software, save as DXF format. Then open Fastcam nesting software, input data to determine the sheet size, and then feed the next DXF format file into Fastcam nesting software, cutting the prompts to determine the number, according to the specifications sheet, the best save material the principle of the arrangement of the parts adjust and choose the right entry point of the part of the technical requirements. Then output, Fastcam system will automatically generate a program file, this file can be used as CNC cutting machine identification procedures, CNC cutting machine cutting head motion along the trajectory drawn parts. Examples of a cut: the lower shaft bearing member material

After this part two semicircular cut mouth cutting machining needs, we can see that the surface roughness of the cut surface is relatively higher, and a thickness of 60 mill. Such as manually cutting arc is difficult to guarantee a smooth transition and verticality. And because the bulk is not too large, not suitable for profile cutting, CNC flame use to solve the above problem points. Example Two: marine outfitting member

This means if the traditional cutting method is not only difficult to guarantee quality, and efficiency is very low, if the quality and efficiency of CNC cutting equipment and using a plasma head, fast and convenient, cutting can be guaranteed. 5 Conclusion In recent years, with the development of CNC cutting and plasma arc technology, greatly facilitate and meet the construction machinery manufacturing cutting process of technological improvements in the steel production industry, too, its technical development and comprehensive benefits make show good growth momentum of development. The plasma arc cutting machine cutting torch is moving closer slotted precision laser precision fine direction; cutting power to the small power inverters direction, in order to improve power efficiency and arc shrinkage; power cut power to the brake pipe direction development and use of certain compensatory measures to improve efficiency, the emergence of high-power water jet plasma power, development of new technologies will further increase the cutting speed, improve cut quality. For now, only foreign manufacturers, domestic industry, the company has also been aimed at the trends and opportunities to catch up, increasing the intensity of research and development and technology promotion, it can be expected, especially in CNC cutting plasma cutting technology will accelerate the pace of increase , it has a broad space for development.