Since 2 1 century, the automobile industry in China has maintained the momentum of sustainable development. Before 1990s, the leading product of domestic automobile industry was truck. After nearly ten years of development, a gratifying pattern with cars as the leading factor has emerged. The strategic shift of automobile industry to focus on developing cars has brought unprecedented development opportunities to the equipment manufacturing industry. Among all walks of life, the automobile industry has the highest correlation with the equipment manufacturing industry. Relevant data show that more than 50% of machine tools and more than 60% of industrial robots in the United States are used in the automobile industry, so the United States has become a big machine tool producer and an automobile kingdom. The development history of automobile industry in developed countries proves this point. The development of automobile industry has promoted the equipment manufacturing industry, especially the machine tool manufacturing industry. The promotion of machine tool manufacturing industry supports and ensures the prosperity of automobile industry from technology and technology. As an important part of machine tool manufacturing, forging machinery is closely related to the development of automobile industry. Taking typical automobile stamping parts and forgings as examples, this paper discusses the application of forging machinery in automobile industry.
Process equipment of typical metal sheet stamping parts
In the whole automobile production, stamping, welding, painting and assembly are collectively referred to as the four major processes of automobile production. According to statistics, among more than 2,000 automobile parts, sheet metal stamping parts account for more than 40% according to the number of pieces, and the status of stamping process equipment in the automobile industry can be seen. Nowadays, automobile production highlights the personalized characteristics of automobile models, which makes the cycle of changing models shorter and shorter. The change of vehicle type is mainly manifested in the change of body shape and structure, which adapts to the ever-changing sheet metal stamping parts. Sheet metal stamping parts can be roughly divided into three categories, namely, body panels, body structural parts and small and medium-sized stamping parts. Body panels and body structures are parts with the function of maintaining the shape of the body, such as doors, roofs, side walls, trunk lids and so on. , and are the main parts of sheet metal stamping parts. Small and medium-sized stamping parts are scattered in automobiles, such as wheels, clutches, automobile air conditioners, micromotors and other parts, and there are a large number of stamping parts. Undoubtedly, when studying the process equipment of typical automobile sheet metal stamping parts, the process equipment of body panels should be treated as a leader.
Technological equipment of metal covering parts
Since the industrial production of body panels, mechanical presses have been the main equipment, and the typical combination is a stamping production line composed of a double-acting mechanical press and multiple single-acting mechanical presses. Although the form of stamping production line has been widely used, its connotation is constantly changing. First of all, with the improvement of single machine automation level, the application of automatic quick adjustment technology and automatic quick die changing technology enhances the flexibility of stamping production line; Secondly, the structure of stamping production line has been continuously improved, from manual loading and unloading assembly line to semi-automatic stamping line and automatic stamping line; Thirdly, the multi-station press enters the stamping production line, and laser processing and stamping processing are integrated to form a generalized stamping automatic line, which is more meaningful for technological progress.
Figure 1 multi-station press
It is obvious to all that the forging machinery industry in China has made great progress in the technology and equipment of body panels. Through the scientific and technological research since the Eighth Five-Year Plan, the independent development ability of forging machinery industry has been obviously improved. On this basis, the relevant enterprises have provided dozens of stamping production lines for China automobile manufacturers by introducing the design and manufacturing technologies of famous companies such as Schuler, Wirseen and Komatsu, or cooperating with foreign manufacturers, and occupied a place in the international market.
At present, the rapid development of stamping technology for automobile body panels is remarkable, which is mainly manifested in the addition of hydraulic press, the use of multi-position press and the maturity of flexible technology.
As mentioned above, mechanical press is the main body of stamping production line, and no other equipment can shake its dominance for a long time. However, with the breakthrough of some key technologies of hydraulic press, the advantages and potential of hydraulic press in stamping have been fully exerted, the productivity has been obviously improved, and the problems of stroke synchronization and interlocking with conveying device have been satisfactorily solved, thus the trend of hydraulic press becoming the main engine of stamping production line has emerged. Of course, this does not mean that the hydraulic press will replace the mechanical press. Although all hydraulic presses can be used in the stamping production line, they can also be mixed with mechanical presses, but the stamping production line composed of mechanical presses is still the mainstream.
The stamping production line widely used in the early days consists of a double-acting mechanical press and several single-acting mechanical presses, with a workpiece turnover device between them. The appearance of multi-station automatic sheet metal press is favored by the automobile industry because of its characteristics of completing multiple processes at one time, compact structure and high production efficiency. As the main machine, the application of multi-station press in stamping production line is much more difficult than that of single machine, and a series of technical problems such as driving system, conveying system and testing system must be solved. In recent years, with the solution of the above technical problems one by one, it is possible for the multi-station press to enter the stamping production line as the main machine.
Figure 2 Series Press Production Line
Flexible technology tends to be mature, which is the most important technological progress in the production of body panels. First of all, the numerical control of the equipment that constitutes the stamping production line lays the foundation for the automation of the stamping production line. The improvement of flexible transmission technology, off-board simulation technology and off-line programming technology, especially the practical application of mold system including automatic mold library, automatic mold identification and extraction, automatic adjustment of mold working parameters and other functions, indicates that the flexible technology of body panels has matured, making it possible to produce large-scale panels in a personalized, ordered and just-in-time manner.
The appearance of flexible stamping automatic line indicates that the development of flexible technology is gradually complete. The basic structure of the flexible stamping automatic line is still a double-acting press and several single-acting presses arranged in series. There is a stack unloading device in front of the double-acting press, which consists of a loading car, a hydraulic jack, a magnetic delaminator, a vacuum material suction elevator, a double-material detector, a magnetic roller table, a double-material ejector, a cleaning and oiling device and a feeding device. A feeding device is arranged between the double-acting press and the single-acting press, including a feeder, a turnover device, a conveying device and a feeder; The feeding and discharging device between single-acting presses consists of a feeder, a conveying device and a feeder; After the last single-action press is the palletizing device, which consists of a feeder, a conveyor and a palletizing car. In addition, automatic quick die changing system, automatic quick adjustment system, fault detection system and waste removal and transportation system are all essential. Due to the full application of robot technology, microelectronics technology and hydraulic technology, not only the automation of stamping process is realized, but also the flexibility of production organization is brought.
The automatic stamping production line of large multi-station press represents an advanced combination mode, which should be paid special attention to. The continuous improvement of large-scale multi-position press and the demand of large-scale automobile panel production have promoted the development of automatic stamping production line of large-scale multi-position press. The original combination consists of a double-acting stretching press and a single-acting large multi-station press, and a set of turnover device and synchronization device are equipped between them, which improves the production rhythm and reduces the floor space to a certain extent. The configuration of the second generation production line is greatly simplified. A multi-station press with double-acting stretching stations is provided with a stacking unloading device and a stacking device in front of and behind it, thus forming an automatic stamping production line. Most multi-position presses have four columns and three sliders. The first station below the first slider is a double-acting stretching station, and the rest stations are single-acting stamping stations. Because the stretching station adopts the way of reverse stretching, it avoids the turnover of the workpiece, so there is no need for a turnover device, which further improves the productivity and reduces the occupied area. The appearance of CNC hydraulic air cushion large multi-position press abandons the traditional concept of double-action drawing process and truly combines drawing with other stamping processes. The hardware of automatic stamping production line is still the main machine equipped with unloading device and stacking device. The main machine is a multi-station press with numerical control hydraulic air cushion, and the numerical control hydraulic air cushion is its technical core. Numerical control hydraulic air cushion can adjust the blank holder force of deep drawing by four-angle control, so as to realize single-action deep drawing. Replacing the traditional single-acting press with numerical control hydraulic air cushion not only simplifies the structure of the press and cancels the turnover device, but also realizes the optimal control of blank holder force, improves the quality of deep-drawn parts and reduces the rejection rate of parts.
The demand for equipment in China's automobile industry has been diversified for a long time, so the production technology of large panels is also varied. With the development of technology, many enterprises have or will transform the manual loading and unloading assembly line into semi-automatic stamping line and automatic stamping line, but few enterprises adopt flexible stamping automatic line. Due to the high cost and technical problems, it will take some time for the automatic stamping production line of large multi-station press to be popularized and used in China. At present, China's forging machinery industry can not only independently provide traditional stamping production lines, semi-automatic stamping lines and automatic stamping lines, but also provide flexible stamping automatic lines and automatic stamping lines for large multi-station presses.
Process equipment for forming wheels with steel plates
Automobile wheels are mainly divided into combined wheels and integral wheels in structure, and there are steel plate molded wheels and aluminum alloy wheels in material. At present, the wheel formed by composite steel plate occupies a very important position, and the situation that the whole aluminum alloy wheel dominates the world will not appear in the short term. The wheel formed by composite steel plate is mainly composed of rim and spoke, and the production technology of rim and spoke has always been concerned. At present, there are two methods to produce steel rings, one is rolling production, the other is spinning production; There are two main methods to produce spokes, namely, stamping forming process and spinning forming process.
The typical configuration of the automatic production line for producing automobile rims by rolling method can be divided into three parts according to the technological nature: the first part includes an automatic uncoiling unit and a flat shearing unit, which make steel coils into fixed-length plates for processing rims; The second part includes a rounding unit, a welding and seam cleaning unit, a chamfering and flaring unit, which is used to roll the metal plate in the previous process into an annular blank required by the rim; The third part includes a roll forming unit (usually composed of three roll forming machines) and a finishing and expanding unit, which rolls the annular blank into a formed rim. The advantage of rolling technology is high productivity. The productivity of this automatic production line abroad is generally 800- 1200 pieces/hour.
The advantage of spinning technology in producing automobile rims is that by effectively controlling the plastic flow of metal, rims with variable cross-section and equal strength can be processed and the quality of rims can be improved. However, the spinning process has the disadvantage of low productivity. The productivity of typical foreign production lines is usually 200-250 pieces/hour, which is not suitable for enterprises that produce rims in large quantities. The usual practice is to make use of the flexibility of spinning process to develop new products and produce in small batches in turn. Spinning technology The configuration of the automatic production line for automobile rims, the first and second parts are similar to the rolling technology, and the third part is the spinning forming machine instead of the rolling forming machine.
The process of producing spokes by stamping is relatively simple. In the early days, several single-station presses were used to form spokes in turn, and later, multi-station presses were used to complete them continuously on one equipment. The thick-walled spokes formed by stamping can not meet the needs of high-speed driving of automobiles, and the material utilization rate and wheel life are low. Spinning process can obtain variable thick-walled spokes with equal strength, which not only improves the material utilization rate and wheel life, but also increases the safety and reliability of automobile driving at high speed. The typical processes of spinning production line include blanking, strong spinning, trimming and punching. The main machine of spinning production line is CNC spinning forming machine. The first roller pre-rotates the blank to complete the distribution of cloth, and the second roller rotates the wall thickness to a predetermined value.
The production technology and equipment of automobile wheels in China are relatively backward, and the rolling technology and spinning technology have great development space. From the development trend of foreign countries, although the spinning process has the shortcomings of low production efficiency, its advantages such as high machining accuracy, producing variable cross-section equal strength rims and spokes, high stiffness and small rebound can not be ignored, and it is especially suitable for new product development and small and medium-sized batch production. With the continuous improvement of the productivity of spinning process and the improvement of control technology, people may re-examine the evaluation of spinning forming process today when the vehicle replacement cycle is getting shorter and shorter.
Process equipment of typical forgings
Automobile industry is the most important user of forging production enterprises, because about 60% of forgings are used in automobile industry. Compared with the mechanical industry, the automobile industry pays more attention to the precision of forgings, the fine structure of forgings, the molding of hollow parts and the maximum weight reduction. Because of its high strength and reliability, forgings have always been used as blanks of important automobile parts. Typical forgings include crankshaft and connecting rod of engine, gear and shaft parts of gearbox, wheel carrier, pull rod and steering knuckle parts in control system, etc. The forging of typical automobile forgings can be divided into general die forging and special die forging. Ordinary die forging is carried out on the forging hammer and hot die forging press with small flash and no flash, while special die forging adopts cross wedge rolling process, rotary forging process and radial forging process.
Engine connecting rod forging process equipment
There are two main forging processes for automobile engine connecting rods, one is the hot die forging press production line, and the other is the electro-hydraulic die forging hammer production line. The former is suitable for mass production, while the latter is suitable for small and medium-sized batch and multi-variety production methods. The production line of hot die forging press is basically composed of bar stock warehouse, bar automatic arrangement and feeding device, induction heating furnace, discharging device, bar shearing mechanism and hot die forging press. The production line of hot die forging press adopts the forging process of one die and two pieces, the productivity can be as high as 800- 1200 pieces/hour, and the material utilization rate can reach over 95%. Although the hot die forging press production line has economic and technical advantages, it is restricted by many factors, such as large investment, high degree of specialization, high mold manufacturing and maintenance costs, and the operating rate needs to reach more than 70%, which makes many manufacturers daunting. The electro-hydraulic die forging hammer production line produces automobile engine connecting rod forgings, and adopts the forging process of one die and one piece, and the bar is cut into blanks and then heated for forging. The basic components of the electro-hydraulic die forging hammer production line include bar shearing machine, induction heating furnace, feeding device, cross wedge rolling mill or roll forging machine, electro-hydraulic die forging hammer, trimming corrector and so on. With the development of control technology, the electro-hydraulic die hammer can control and adjust the technological parameters such as impact energy, impact times and impact interval time, so as to meet the energy requirements of forging with the best impact force, which can not only improve the quality of forgings, but also prolong the service life of dies. Although the productivity of electro-hydraulic die forging hammer production line is usually only about half that of hot die forging press production line, its investment is only one third of the latter, and the production organization is very flexible, so it is favored by small and medium-sized batch manufacturers.
The technical development trend of automobile engine connecting rod forging is to improve the mechanization and automation level of forging production line and adopt new forging technology. Obviously, improving the mechanization and automation level of forging production line is the knowledge of people in the industry. It is a common practice in developed countries to adopt mechanized loading and unloading device, mechanized conveying device, manipulator and automatic control technology to transform the assembly line, reduce manual operation links and realize automatic or semi-automatic production. There are two attempts at new forging technology. One is powder forging technology, that is, the blank sintered by metal powder is heated and die forged. The second is high-speed forging forming on a multi-station automatic hot upsetting machine. The former has the advantages of small weight deviation of forgings and can produce forgings with complex shapes, and is especially suitable for advanced engines with high dynamic balance requirements, and is adopted by many manufacturers. The latter is difficult to be accepted by manufacturers because of the high economic batch threshold and expensive equipment.
Forging process equipment for disc gear blank
Disc gear blank is a typical representative of automobile disc forgings. Because of its large quantity, it requires high machining accuracy, high efficiency and low cost. In the early production process, forging hammer, mechanical press, screw press or hot die forging press were used as the main machine, and the bar was cut into blanks and then heated, which was completed in several processes. Low production efficiency, low forging precision, large machining allowance and low material utilization rate. Since the concept of billet refinement appeared, the automatic production line of high-speed hot upsetting machine has become the most ideal choice for producing disc gear billets. The typical configuration of the automatic production line of high-speed hot upsetting machine is material rack, automatic feeding device, induction heating furnace, roller feeding mechanism and multi-station high-speed hot upsetting machine. After the heated bar enters the high-speed hot heading machine, all processes such as blank cutting, shaping, pre-forging, final forging and punching are completed in turn, and the transfer of forgings between stations is automatically completed by the manipulator. The automatic production line of high-speed hot upsetting machine can realize real billet refinement, and the size and shape of forgings are close to the parts to be processed, which improves the material utilization rate and saves the processing time. Forgings have more ideal metallographic structure and mechanical properties, and the productivity is several times or even ten times that of ordinary forging methods, and its comprehensive economic benefits are very remarkable.
Gear shaft forging process equipment
Automobile gear shaft is an important part of gearbox and a typical automobile shaft, which has the characteristics of slender and multi-steps. The traditional process of producing shaft parts is die forging on die forging hammer or hot die forging press, but the forgings produced by this process have low precision, low material utilization rate and large machining allowance. The emergence of cross wedge rolling technology has effectively solved this problem. Cross wedge rolling technology is a new technology with high efficiency, energy saving and material saving. The heated bar enters the cross wedge rolling mill, and the cross wedge rolling die continuously extrudes and distributes metal in a working cycle, forming stepped shaft forgings that meet the requirements of shape and size, and hollow shaft forgings can be produced with pipe as blank. Because the cross wedge rolling process is suitable for processing symmetrical parts, a pair of parts are often arranged symmetrically to design dies, which is beneficial to both manufacturability and productivity. The characteristics of cross wedge rolling process are that one or a pair of parts can be obtained at a time, and the production efficiency is high; Continuous deformation of metal, small deformation force and long die life; Forgings have high dimensional accuracy, small machining allowance and high material utilization rate. The automatic production line of cross wedge rolling is relatively simple, and usually consists of automatic feeding device, induction heating furnace and cross wedge rolling mill. The cross wedge mill has a two-roll flat structure. The flat cross wedge rolling mill is driven by machinery or hydraulic pressure, and two flat templates do linear reciprocating motion to friction roll blanks. The mold of two-high cross wedge rolling mill is a pair of rollers, and the blank is formed in the rotating rollers. The former has simple structure, convenient adjustment, low die cost and high forging precision; Disadvantages are limited travel, small deformation, free travel and low production efficiency; The latter has the advantages of compact structure, continuous production and high production efficiency, but the disadvantages are difficult die manufacturing and low forging accuracy.
Looking at the application of forging machinery in China automobile industry, the level of stamping technology and equipment is higher than that of forging, which is manifested in the advanced technology and equipment, the degree of automation and flexibility of production line, the level of intensive production and many other aspects. Although the domestic forging machinery industry can provide almost all stamping and forging equipment for the automobile industry, it goes without saying that the level and strength of China forging machinery industry is not strong in the international market. The position of forging machinery industry in automobile industry depends not only on the technological progress and structural adjustment of forging machinery industry, but also on the development strategy and market prospect of automobile industry.