Large economical CNC cutting machine design
Design of large-scale economical CNC cutting machine Guo Yongping, Dong Qinghua, Jiang De (Chengde Petroleum College, Chengde 067000, Hebei). The design purpose is simple machine operation, low price, high reliability and convenient maintenance. The design of the child is a numerical control system, using the industrial computer as the control platform, in the design, production overcomes many problems such as electromagnetic compatibility, system reliability, high production cost, has achieved the design purpose, and passed the new product identification.
At present, stearyl cutting is commonly used in steel cutting in China's machinery processing industry, while most of the foreign companies' cutting process uses numerically controlled oxyacetylene or numerically controlled plasma arc cutting, which not only improves material utilization, but also improves product quality. Optimized the working environment and improved work efficiency. The reason why CNC cutting can not be popularized in China is mainly because of: funding problems, equipment failure maintenance problems, and operation problems. The control system of the domestic CNC cutting machine is produced from abroad, and its operation is more complicated, requiring operators to have higher quality and special training. The survey found that for users, the product update is not frequent, the shape and size of the parts to be unloaded are relatively limited, and the operation of the machine is simple and reliable. Therefore, the existing CNC cutting machine does not satisfy the user. To this end, it was decided to design a large-scale economical CNC cutting machine that is suitable for most users and suitable for national conditions.
1 design requirements include: mechanical parts, CNC parts, cutting devices and other parts.
Applicable direction: It can be applied to a wide range of applications. It can be used for large-scale parts cutting in large enterprises, and can be used in small machinery factories for small-scale production of small parts.
Technical level: Its comprehensive technical level requires more than domestic products of this kind, close to the world advanced level.
Production cost: The comprehensive cost is lower than the existing similar cutting machines in China.
Machining accuracy: Processing accuracy exceeds current national standards.
Applicable materials: carbon steel, stainless steel, non-ferrous metals.
Failure rate: The average obstacle-free time is greater than 3000h. The workpiece size: greater than 50mx30b, the maximum arc difference compensation radius is greater than the programming mode: graphic automatic programming f manual ISO code editing.
Cutting speed range: The overall design is to achieve the above design goals, and the design optimization is emphasized, the system is modularized, and the processing is simplified. To this end, multiple sets of design were carried out in the design of each part of the cutting machine, and the processing comparison and preliminary tests were carried out, and finally the optimal design was selected. The CNC cutting machine is mainly composed of the following parts: the main part of the mechanical part is to support 1=6 to cut the torch!
- Planar linkage, and each torch can move independently in the direction to adjust the distance between the cutting tip and the steel plate. At the same time, it also supports the installation and necessary movement of the numerical control device and the gas distribution pipeline.
In order to achieve the above functions, and at the same time facilitate processing, control and installation and commissioning, it is decided to adopt a gantry structure as a whole, that is, one of the left and right longitudinal rails is supported by a traveling vehicle, and 1=6 laterally movable cutters are mounted on the beam. The torch trolley moves the beam in the longitudinal direction by two walking vehicles on the longitudinal rail. At the same time, the torch on the beam drives the torch to move laterally along the beam. Thus, for the torch, its motion is a composite motion of the longitudinal and lateral directions, so it can be swayed into any plane curve motion in the horizontal plane, see. In order to transform into a torch, it is necessary to change the rotary motion of the servo motor into a linear motion of the torch on the traveling vehicle and the beam. The optional solution is a screw-mesh movement pair, a toothed belt, and a gear-tooth movement. Vice, roller, linear motor, etc. Finally, after balancing the comprehensive performance and test, the driving method of the gear-spindle motion pair was selected. The ball bearing was used in the combination between the traveling vehicle and the track, and finally two longitudinal traveling vehicles and several lateral traveling vehicles were formed.
The numerical control part of the numerical control part is used for the automatic ignition of the cutting machine, the automatic drilling, the differential compensation operation of the torch movement, the ignition and extinction of the plasma arc, the echo of the working state, and the man-machine dialogue. This part is the core of the entire cutting machine, and its performance has a decisive influence on the success or failure of the final design. Therefore, it has been repeatedly demonstrated and tested and improved, and finally reached the design requirements. The first is display and control. In order to achieve the usage habits of most domestic users, the operation is simpler and more intuitive. It is decided to adopt the Chinese menu plus 1: Guo Yongping 964, a male I welding equipment and materials Lin Shuhong machine tool numerical control technology and its application. Beijing: Mechanical Industry Press, graphic display, in order to speed up development, improve system reliability, reduce production costs, the human-computer interaction part is a common industrial computer. Its advantages are reliable operation, strong anti-interference ability, good software versatility and low price. After the industrial computer is used, the human-computer interaction software can be conveniently developed on the high-level language platform, which makes the control and display interface simple and convenient, and at the same time greatly speeds up the development of the system. For the underlying control hardware, in order to increase the characteristics of the developed system and improve the flexibility of control, it was decided to develop the controller by itself. The microprocessors that can be used by the controller include single-chip microcomputer, DSP, MPU, etc., taking into account performance and development costs, and finally choose INTEL's 8XC196KC series of single-chip microcomputers.
23 Cutting device This part is used to realize the cutting of the final plate, which will determine the key indicators such as the type, thickness and processing quality of the cutting machine. There are many cutting methods that can be cut into and can meet the design requirements, including: oxyacetylene flame, high current plasma arc, oxypropane flame, high power laser, ultrasonic beam, high pressure water, etc. Taking into account factors such as equipment investment and equipment operating costs and the company's production habits, it is decided to use oxyacetylene flame as the cutting method for medium-thick carbon steel sheets, and use high-current plasma arc as the cutting method for non-ferrous metals and thin carbon steel sheets. The high-current plasma arc cutting machine selects an inverter-type air plasma arc cutting machine with small interference, light weight and small volume on the numerical control system, which not only reduces the cost but also facilitates flexible installation. The oxyacetylene flame cutting system mainly consists of a large machine cutting torch, a gas separation and a gas transmission, a flow regulation, a gas path control, and an automatic ignition. ! Design Difficulties and Solutions Large CNC cutting machine is a complex system that integrates computer technology, precision machinery manufacturing, motor dragging, digital control, thermal processing and many other disciplines, so design, production, commissioning, installation, maintenance, etc. All the links will encounter difficulties. After many efforts, they have overcome all difficulties and made the prototype meet the design requirements. The following is a summary of the difficulties and solutions encountered during design.
Operation speed and machining precision In the control of the cutting machine, the real-time performance and high complexity are the differential compensation control of the torch movement, and the difference compensation is divided into arc difference compensation and straight line difference compensation, wherein the calculation of the arc difference compensation is more complicated. high. In the 80C196KC, the arc difference complement operation of double word precision requires about 280 state cycles per step, and in the case of a 16 MHz crystal oscillator, about 35, that is, about 28,000 difference compensation operations per second can be performed. What affects both the operation and the accuracy is the pulse equivalent of the torch motion, that is, the movement distance of the torch for each difference of the CPU. According to the design, the highest simulation speed should be 100mm/s, and the minimum pulse equivalent can be reached: 100/28000>0.00357<<.> Pulse equivalent and workpiece size data often have large radius when cutting. Dimensional arcs, such as crane beams, trailer main beams, bridges, etc. This design requires a maximum arc radius of 1000m. When the pulse equivalent is 000625mm, the maximum word length is 29bit, and the actual bit is 4 bit. Therefore, the operation of the 80C196KC is double-word operator. program.
The complexity of the workpiece and the storage space of the controller are limited by the independent controller. In terms of the 80C196KC, the program space and data space separation method of the Harvard structure are adopted, and the data space is further expanded by the spare pins. Under, the more realistic data space can be 64KB. Set the arc and line in the workpiece to occupy 50H, plus the line type and check word, a line needs 10 bit, and the segment arc needs 18 bit, the average is 14biE. Thus, the maximum number of lines that can be stored in a 64KB data space is: 64x1024/14>4681 segments. According to statistics, the average number of parts in the steel sheet blanking is about 1030. According to the 30-segment calculation, the controller can arrange about 100 pieces of workpieces in one process, which meets most processing requirements.
Anti-interference of CNC system The cutting machine is mainly used in the factory's riveting workshop. Most of these workshops are equipped with large-scale machining equipment and electric welding machines, which can generate strong electromagnetic radiation from the spectrum. At the same time, the cutting machine itself also has a plurality of system components, which can also generate strong interference, especially easy to interfere with the normal operation of the numerical control system, causing the system to crash, malfunction, etc., so the anti-interference ability of the numerical control system has very important significance. The main measures taken during the design are: electromagnetic shielding, that is, the numerical control system is installed in a housing with strong shielding function; the power supply is cleaned, and a lot of interference is from the power line into the machine, so there are multiple stages at the lead-in end of the power supply. Filter to eliminate power supply noise; electromagnetic isolation, photoelectric isolation measures at all input and output terminals of the controller, completely isolate the electromagnetic connection between the CNC system and other parts, greatly improve the anti-interference ability; both the computer and the controller It is a digital processing device that has a certain degree of electromagnetic radiation during operation. If the controller is made into a card-type structure and inserted into the bus plug of the computer according to the traditional method, it is difficult to ensure electromagnetic compatibility, so a computer is used in this design. Separation from the controller, using external communication with isolation measures to further improve reliability.
Oxyacetylene flame cutting The reliability of automatic perforation When cutting a workpiece, each cutting of a closed contour, the cutting machine needs to be perforated for the next contour cutting. In the case of thicker plates, there will be more metal splash when perforating, which will affect the service life of the cutting nozzle and reduce the cutting quality. In severe cases, the cutting nozzle will be blocked and cause tempering. Therefore, certain measures must be taken to prevent metal splashing during automatic perforation. There are two main measures: one is to reduce the cutting oxygen pressure during perforation. There are two ways to cut oxygen in the gas supply circuit. The pressure is low for one hole and the other is for high pressure. It is used for normal cutting. Another measure is to increase the height of the torch when punching, so that the height between the cutting nozzle and the steel plate is greater than the normal height when punching, so that the splash is not easy to damage or block the cutting nozzle. When perforating, the controller first switches the cutting oxygen pressure to a lower perforating pressure, and simultaneously drives the torch lifting motor to rotate in the direction in which the torch is raised, and opens the cutting oxygen to start the automatic perforating process. After a certain period of time, the steel plate is hit. When worn, the cutting oxygen is switched to normal pressure, while the lift motor lowers the torch to normal height and begins part cutting. Practice has proved that through the above measures, the reliability of punching is significantly improved, which greatly extends the service life of the cutting nozzle.
4 Conclusion According to the design requirements, different measures were taken for different requirements. Finally, in the actual product inspection, the design requirements were met, and the design was successful. Now the equipment has been put into actual production and sold more than one. In actual use, it saves a lot of manpower and material resources for the enterprise and achieves good results. At the same time, the production cost is obviously lower than that of similar products, which is very suitable for China's national conditions and has certain competitive advantages.
(Finish)
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