1. Concept and advantages of stamping
1.1 concept of stamping
Stamping is a pressure processing method that uses the die installed on the stamping equipment (mainly Press) to exert pressure on the material to produce separation or plastic deformation, so as to obtain the required parts (commonly known as stamping or stamping parts). Stamping is usually cold deformation processing of materials at room temperature, and mainly uses sheet metal to process the required parts, so it is also called cold stamping or sheet metal stamping. Stamping is one of the main methods of material pressure processing or plastic processing, which belongs to material forming engineering. The die used for stamping is called stamping die, which is called stamping die for short. Stamping die is a special tool for batch processing materials (metal or non-metal) into required stamping parts. Stamping die is very important in stamping. Without qualified stamping die, it is difficult to carry out mass stamping production; Without advanced die, advanced stamping process can not be realized. Stamping process and die, stamping equipment and stamping materials constitute the three elements of stamping processing. Only when they are combined with each other can stamping parts be obtained.
1.2 advantages of stamping
Compared with wire cutting, cold stamping has a series of advantages, such as high production efficiency, low processing cost, high material utilization rate, stable product dimensional accuracy, simple operation, easy mechanization and automation, and is especially suitable for mass production. As a very important processing method in modern industry, stamping die forming is used to produce various sheet metal parts, which has many unique advantages. Its formed parts have the advantages of light weight, high stiffness, high strength, good interchangeability, low cost, easy mechanization in the production process and high production efficiency, It is an advanced manufacturing technology that cannot be compared and replaced by other processing methods. It has strong competitiveness in the manufacturing industry and is widely used in the production of automobile, energy, machinery, information, aerospace, national defense industry and daily life.
After absorbing the knowledge of mechanics, mathematics, metal materials, mechanical science, control and computer technology, the basic forming theory of stamping discipline has been formed. Take stamping products as the leader, mold as the center, combined with modern advanced technology
Under the stimulation and promotion of the huge market demand for products, stamping technology plays a more and more important role in the development of national economy, the realization of modernization and the improvement of people’s living standards.
Modern stamping die production is a manufacturing mode of large-scale continuous operation. Due to the participation and intervention of high and new technology, the stamping production mode has gradually evolved from initial manual operation to integrated manufacturing. The production process has gradually realized mechanization and automation, and is developing towards intelligence and integration. Mold master wechat: mojuren realizes automatic stamping operation, which reflects the advantages of safety, efficiency and material saving. It has been the development direction of stamping mold production.
Many utensils used in daily life are made by stamping, such as stainless steel rice jar. It is made by pressing a circular metal plate on the press and pressing the circular plate with a die. It can be seen that cold stamping is a metal pressure processing method that uses a die to apply pressure on various metal (or non-metal) sheets on the press at room temperature (cold state) to separate or deform them to obtain parts with a certain shape.
In recent decades, stamping technology has developed rapidly. It is not only reflected in the wide application of many new processes and technologies in production, such as spinning forming, soft die forming, high energy rate forming, but also in the qualitative leap in people’s understanding and mastery of stamping technology.
1.3 advantages of composite mould
The mold is not affected by feeding error, so it has many advantages:
(1) The relative position of internal and external shape and the consistency of part size are very good. The surface of production parts is flat and has high precision
(2) The die structure is compact, and the requirements for the platform of the press are not high
(3) Short and surplus materials can be fully utilized
(4) Suitable for blanking thin materials and brittle or soft materials
2. Research status at home and abroad
In recent years, the level of stamping die in China has been greatly improved. Large stamping dies have been able to produce a single set of dies with a weight of more than 50 tons. The panel die supporting medium-sized cars can also be produced in China. The accuracy reaches 1 ~ 2 μ m. The multi station progressive die with a service life of about 200 million times has been produced by many domestic enterprises. The surface roughness reaches RA ≤ 1.5 μ M precision die, large size（ Φ ≥ 300mm) precision die and medium plate precision die have also reached a fairly high level in China.
2.1 technical status of mold CAD / CAM
The development of die CAD / CAM technology in China has a history of more than 20 years. The precision die CAD / CAM system jointly completed by the former Huazhong Institute of technology and Wuhan 733 factory in 1984 is the first self-developed die CAD / CAM system in China
At the beginning of the 21st century, CAD / CAM technology has been gradually popularized. Now stamping die enterprises with certain production capacity basically have CAD / CAM technology. Some key enterprises also have various CAE capabilities.
Mold CAD / CAM technology can significantly shorten the mold design and manufacturing cycle, reduce production costs and improve product quality. During the “Eighth Five Year Plan” and “Ninth Five Year Plan”, a large number of mold enterprises have popularized computer drawing technology, the utilization rate of NC machining is also higher and higher, and a considerable number of CAD / CAM systems have been introduced one after another. For example, UG of EDs in the United States, Pro / Engineer of parametric technology in the United States, cads5 of CV in the United States, doct5 of Delcam in the United Kingdom, crade and space-e of HZS in Japan and Cimatron of Israel have also introduced AutoCAD, CATIA and other software and Euclid is and other special software for automobile and panel molds of Marta daravision in France. CAD / CAM technology is widely used in domestic automobile panel die manufacturers. The design of DL drawing and die structure drawing have realized two-dimensional CAD. Most enterprises have made a transition to three-dimensional, and the general drawing production has gradually replaced the part drawing production. And the parametric design of mold also began to move towards the field of technical development of a few mold manufacturers.
2.2 mold design and manufacturing capacity
Under the correct guidance of the national industrial policy, after decades of efforts, China’s stamping die design and manufacturing capacity has reached a high level. Many modern design and manufacturing technologies, including information engineering and virtual technology, have been applied in many die enterprises.
Nevertheless, there is still a big gap between China’s stamping die design and manufacturing capacity, market needs and international advanced level. These are mainly reflected in the dies and high-precision stamping dies for high-end cars and large and medium-sized automobile panels. There is a big gap in design, processing technology and capacity. The car panel die has the characteristics of great difficulty in design and manufacturing and high requirements for quality and precision, which can represent the level of panel die. Although the design and manufacturing methods and means have basically reached the international level, the mold structure and function are close to the international level, and a big step has been made in the process of car mold localization, there is still a certain gap compared with foreign countries in terms of manufacturing quality, precision and manufacturing cycle.
Multi station progressive die and multi-functional die, which mark the advanced level of die technology, are the key varieties of precision die in China. The representative is the multi-functional mould of iron core precision automatic valve plate integrating electromechanical integration, which has basically reached the international level.
However, compared with foreign multi station progressive dies, there is still a certain gap in manufacturing accuracy, service life, die structure and function.
2.3 degree of specialization and distribution
The degree of specialization of China’s mold industry is still relatively low, and the proportion of self-produced and self-made molds is too high. The proportion of self-produced and self-made molds in foreign countries is generally 30%, and the proportion of self-produced and self-made stamping molds in China is 60%. This has had many adverse effects on specialization. Now, the molds with high technical requirements and large investment have a high degree of specialization, such as panel molds, multi station progressive dies and precision dies. The degree of specialization of general die is low. Due to the high proportion of self matching, the distribution of stamping die production capacity basically follows the distribution of stamping part production capacity. However, the distribution of professional production enterprises of automobile panel dies and multi station and multi-functional precision dies with a high degree of specialization does not follow the distribution of stamping capacity, but often depends on the decision-making of major investors. For example, Sichuan has a large capacity of automobile panel die, Jiangsu has a strong capacity of precision die, and most of the die users are not local.
3. Basic stamping process and die
There are many kinds of stamping parts, and the shape, size and accuracy requirements of various parts are different, so the stamping process methods used in production are also diverse. To sum up, it can be divided into two categories: separation process and forming process; Separation process refers to the process of stamping (commonly known as blanking part) to separate the blank along a certain contour line to obtain a certain shape, size and section quality; Forming process refers to the process of making the blank produce plastic deformation without fracture to obtain a stamping part with a certain shape and size.
According to different basic deformation modes, the above two types of processes can be divided into four basic processes: blanking, bending, deep drawing and forming. Each basic process also includes a variety of single processes.
In the actual production, when the production batch of stamping parts is large, the size is small and the tolerance requirements are small, it is uneconomical or even difficult to meet the requirements if stamping with a scattered single process. public platform of molder magazine: at this time, centralized schemes are mostly adopted in the process, that is, two or more single processes are completed in one pair of molds. The combination methods are different, and they can be divided into three Compound stamping – a combined combination methods: Compound progressive and compound progressive.
method of simultaneously completing two or more different single processes at the same station of the die in one working stroke of the press.
Progressive stamping — the first mock exam of a press is a combination of two or more than two different single processes in different positions of the same mold in a certain sequence.
Compound – Progressive – a combination of compound and progressive processes on a pair of dies.
There are many types of die structures. Generally, it can be divided into blanking die, bending die, drawing die and forming die according to the nature of process; According to the combination of processes, it can be divided into single process die, composite die and progressive die. However, no matter what type of die, it can be regarded as composed of upper die and lower die. The upper die is fixed on the press workbench or backing plate, which is the fixed part of the die. During operation, the blank is positioned on the lower die surface by positioning parts, and the slider of the press drives the upper die to press down. Under the action of the working parts of the die (i.e. punch and die), the blank will produce separation or plastic deformation, so as to obtain the punch with the required shape and size. When the upper die picks up, the unloading and discharging device of the die will unload or push and eject the punching parts or waste materials from the male and female dies for the next punching cycle.