In the contemporary automotive stamping production, various new types of stamping equipment, advanced mechanized systems, new processes, stamping, and intelligent control technologies have been adopted gradually, which has greatly improved the stamping production efficiency and finished product quality, and reduced the cost of mass production.
The modern automobile industry has the characteristics of large-scale production, small vehicle models, rapid variety change, and multi-model co-production. As a result, the car body covers also become large-scale and integrated. These trends require that stamping technology and equipment continue to be flexible. With the development of automation, high-flexibility and high-efficiency automated press equipment is gradually replacing the traditional rigid production line and has become the mainstream of stamping production in the world.
The following author will introduce the technical progress and application of stamping equipment, mechanization system, stamping technology and die, intelligent control and other aspects.
Stamping equipment
For a long time, traditional stamping equipment has ensured the quality of stamping parts due to its stable production conditions, and the use of molds has been relatively long-lasting. However, lack of flexibility is a significant defect of this production method. The application of integrated control technology and servo drive technology on the press brings more flexibility to stamping production. Large multi-station presses, flexible stamping automatic lines and other equipment are rewriting the history of stamping production.
1. Integrated control
In order to adapt to the flexible production requirements, all the control functions of the press should be integrated so as to realize the menu management of the entire set of molds, including slider stroke adjustment, balancer air pressure adjustment, air cushion stroke adjustment and automatic control system, etc. The parameters of each link. Field bus technology with field communication network, field device interconnection, interactive operation, decentralized function modules, and open functions is the development direction of press control technology, which has a significant role in promoting automation.
The integration of the press control system can realize all control functions of all presses and molds through a single operation interface, including fault diagnosis, mold menu configuration, programmable limit switches, mold monitoring and adjustment, and maintenance of the equipment. It is more convenient, and it significantly increases the effective working time of the press.
At present, the large-scale stamping lines used for the manufacture of large-sized car covers have reached the international advanced level (see Figure 1). The multi-link accuracy optimization compensation technology, the networked automatic mold rapid replacement technology, and the vector exchange frequency modulation have been adopted. Speed ​​main drive technology and multi-point hydraulic overload protection unloading control technology, Ethernet network technology can be used to network with production, real-time monitoring of equipment status, remote communication and remote fault diagnosis, the entire line supports fast feeding system, can be produced per minute 10 to 14 large-size car covers.
Figure 1 3 200t large press line produced by Jinan No.2 Machine Tool Group
2. Servo drive
The new servo press adopts a highly adaptable servo drive technology, which combines the flexibility of the hydraulic press with the high efficiency advantages of the mechanical press. Companies can provide their users with various types of stampings in large and small quantities. The production capacity has increased dramatically. Komatsu Japan and Schuler of Germany have developed and produced such servo presses (see Figure 2). At present, FAW Toyota Motor Co. and Guangzhou Toyota Motor Co. have adopted such equipment.
Figure 2 New servo press developed by Schuler GmbH in Germany in 2007
The most prominent feature of the servo drive system is that the motor is directly connected to the eccentric crank gear, and the speed of the motor can be arbitrarily adjusted, so that the movement speed of the crank mechanism can be arbitrarily adjusted, and the press speed can be arbitrarily increased or decreased.
Another major feature of servo presses is the high degree of matching. Because the motor speed of the servo press can be adjusted steplessly, it is possible to achieve stepless adjustment of the punching and punching forces in the stamping process, so that the working curve of the press is matched with various application requirements. In order to ensure the precise movement of the crank, the user can achieve or maintain a constant punching speed by decelerating and drawing. This can not only improve the quality of the plate processing, but also extend the life of the mold.
The speed change and control of the servo press have been rationally optimized, and an integrated module has been adopted. It is manufactured according to a modular structure. If it does not need to use its servo function, the machine can work like a conventional press and keep it. Constant power and travel.
3 large multi-station press
The large multi-station presses for flexible stamping production represent the highest level of today's international stamping technology, and are the development direction of the stamping forming production equipment for auto body panels. The large multi-station press integrates machinery, electronics, control and inspection technology, which can realize automatic, intelligent, safe operation, high productivity, high quality parts, low overall cost, and meet the needs of mass production in the automotive industry. . Of course, the press's own technology and performance have also been continuously improved and developed in the practice of more than a decade, such as: the shift station uses a variable-speed multi-linkage mechanism, a numerically-controlled hydraulic stretch pad instead of a double-action press, and a field bus Application of control technology.
At present, famous automakers in Europe and the United States use large-scale multi-station presses and cross-bar type automatic presses to mass produce body panels (see Figure 3) to meet the highest standards of precision and surface quality for contemporary automotive stampings. In China, there are currently no large-scale multi-station presses used by automobile manufacturers. The main reasons are: First, the one-time investment of equipment is relatively large; Second, domestic automakers start late, and the company's existing press equipment is still in service. This also restricts the improvement of automobile stamping technology in China to some extent.
Figure 3 Multi-station press used by a foreign automaker
4. Flexible stamping automatic line
Most of the flexible press automatic lines consist of a double-action stretch press or a multi-link single-action stretch press and 4 to 5 single-action presses to produce large-scale body panels with high safety and good stamping quality. The automatic loading and unloading system is arranged on the production line. It is composed of a destacker, a cleaning oiler, a centering feeder, a loading and unloading robot (robot), and a shuttle (turning) conveying automatic conveyor. The material is fed from the blank to the stamping. All lines are automatically completed. The maximum production beat is 6-9 times/min. The entire press line is about 60 to 80 meters long, and about 6 to 7 operators are required.
Some companies use the international advanced high-speed compact press lines, which can quickly increase the production efficiency of presses. Sheet alignment uses today's advanced optical camera system for positioning. Tensile presses use numerically controlled hydraulic stretch pads. Each advanced automated unit is equipped with a robot. This eliminates the need for shuttle conveyors, shortens the conveyor distance, and reduces the distance between presses. The production cycle can be up to 10 pcs/min.
With the ever-increasing competition in China's auto market, the appearance quality and intrinsic quality of automobiles have become an indispensable fact for auto manufacturers to compete in the market. Therefore, the use of mechanized and automated production methods for stamping production is to improve the appearance of automobiles. The most effective way to quality.
5. Commissioning press
Mass-produced automotive stamping enterprises shall deploy debugging presses for each large press automatic line in order to shorten the trial time of metal forming dies and increase the operating rate of large press lines.
The commissioning press mainly selects the hydraulic high-speed test press and the tensile mechanical press, especially the mold test time on the production-type mechanical press can be reduced by 80%, which has great application value. The development trend of trial-type mechanical presses is the use of multi-link stretch presses equipped with numerically-controlled hydraulic stretch pads, with parameter settings and state memory functions.
Mechanized system
The rapid development of the automobile industry has been promoted by the development of automatic stamping production lines, the mechanized transformation of stamping production lines, and the manufacture of large-sized vacuum-fed stamping machine tools for the production of automotive side panels.
For domestic auto stamping parts manufacturers, the most valuable technology enhancements are concentrated in the automatic transportation of stamping parts, automatic transfer devices, and the automation of stamping equipment and product-oriented stamping production.
Because the limit of the hydraulic technology is not easy to break during the deformation process, it can only benefit from the automation of the machine, and it can not only benefit from the automation of the machine in the stamping process, but also should benefit to the new areas outside the stamping process technology. The transfer of stamping parts and the benefit of stamping parts off the assembly line will be profitable in all areas where economic benefits can be obtained.
The new integrated rapid transfer system (see Figure 4) can directly transfer between the press and the press, producing a cycle time of 12 to 15 times/min. The end of the robot arm can be programmed automatically for angle adjustment to fit the die slot position. In the production process of large and extra large stampings, the firm and powerful stampings conveying mechanism can be widely used not only in the stamping of large workpieces and the production of two-piece stamping (two finished products in one stamping), but also in automobiles. Parts are widely used in the production process. The swing arm type stamping part transfer system will give the stamping equipment great support and help in rapid mold change. It realizes the simultaneous output of the stamping mold and the workpiece, thus laying the foundation for realizing the multifunctional stamping production line.
Figure 4 transmission system
Stamping process and mould
In the era of the ever-changing automotive products in the world, the characteristics of mold diversification and short die replacement cycles have become particularly prominent. At the same time, new requirements have been put forward for stamping process technologies, bringing about changes in the production technology of automotive stamping parts.
1. Number of stamping steps
Automotive stampings have good craftsmanship and economy, and the important signs to measure their level are the number of stamping parts, the number and size of the parts of the body assembly, and the structure of the stamped parts. Reducing the number of processes in the stamping process means reducing the number of stamping parts, saving the number of tooling, simplifying the conveying process for the stamping process, and reducing the area of ​​the operator and equipment. This is an excellent measure for saving investment and energy consumption, so stamping manufacturers can The number of stamping process design is an important way to reduce the cost of car manufacturing, and even he does not hesitate to improve the product design to meet the requirements of the manufacturing process. At the same time, reasonable total body components, such as the whole body left and right side panels and roof, are used as large as possible. The cover plate can not only make the car more beautiful and practical, reduce air resistance, but also reduce the number of stamping parts and solder joints, and can effectively reduce the cost.
In the development of the stamping process of the workpiece, the dispersion and concentration of the processing steps is a more complicated issue. It depends on the batch, structure, shape, quality requirements, process characteristics, etc. of the workpiece. For automotive stampings, which are usually mass-produced, they should try to adopt a process-intensive approach and use composite or progressive die for stamping. This will not only increase productivity, but also ensure safe production. Practical experience shows that for compound molds, the number of processes concentrated on one mold should not be too large, generally 2 to 3 processes, and up to 4; for progressive molds, the number of concentrated processes can be more because of the mold structure. The layout of the scope of freedom is greater.
2. Multiple stamping die process
With the promotion of the overall body side stamping technology for mid-to-high-class cars and the increase of press tables, the stamping process has also developed rapidly. Stamping parts such as doors and fenders have evolved from one-piece parts in the past to double-slot production. The production efficiency has doubled, and the latest development has resulted in the production of four-slot slot stampings for the inner and outer panels of the door, and the production efficiency has doubled.
When the output is relatively large, the use of multiple pieces of simultaneous stamping can reduce the cost of molds, materials, and processing. As for the forming process, it is also conducive to the uniform stress and strain symmetry of the material. It also improves production efficiency and reduces energy consumption. Consumption.
The latest development trend of two-piece production is the simultaneous production of inner and outer plates. The advantages are: the quantity of production matches, but also the welding line can be pressed at the same time, and the logistics is smooth and convenient.
3. Progressive die
Progressive combination die has been widely used in the automotive industry in developed countries. Its advantages are high productivity, low die cost, and no need for sheet cutting. The progressive die can save 30% of the cost compared to the stepped die used on multi-station presses, but its application is limited by the depth of stretching, the surface hardening of the strip edge material for guiding and transport, and is mainly used for the stretching depth. Lighter, simple parts.
Intelligent Control Technology
In recent years, the intelligent control technology for stamping production has developed rapidly. Based on the integration of materials and processes, it implements on-line control or intelligent control (also called “adaptive controlâ€) of the stamping process based on existing materials and process databases. First, an on-line inspection system for materials or process parameters is established. When the material properties or process parameters change or fluctuate, the instantaneous values ​​of the relevant parameters are determined on-line by an automatic detection system (sensors and signal conversion systems), and are simulated and analyzed by computer. Optimization software (eg, artificial neural network methods, expert systems) determine the optimal combination of process parameters after the parameters are changed. After the automatic control system adjusts the process parameters, adaptive control of the stamping process can be achieved. The gradual accumulation of new production data can further become the basis for process optimization in the subsequent processing.
Conclusion
The stamping technology and equipment with greater flexibility or flexibility will adapt to the development trend of small-volume, multi-variety, mixed-flow production models, market diversification, and individualized demand, and strengthen the company's ability to quickly respond to market changes.
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