Research status and development trend of fine blanking technology

Precision blanking technology (referred to as fine blanking) is a kind of plastic processing technology developed based on common blanking technology. It uses gear ring blank holder, introduces blank holder force and back pressure to restrain the tearing of raw materials in blanking process, so as to keep plastic deformation basically before separation, so as to obtain fine blanking parts with low surface roughness, high dimensional accuracy and good section quality. Fine blanking technology is widely used in automobile industry, aviation industry, military machinery, electrical equipment and other fields because of its high processing efficiency, short processing cycle and green energy saving.
In this paper, aiming at the practical problems in the production of fine blanking technology, the research status of precision blanking technology is summarized, and the development trend of fine blanking technology is analyzed and prospected.
Research status of fine blanking technology
In 1920s, German Fritz Schiess Forrer invented the fine blanking method through experimental research and obtained the fine blanking technology patent. Through continuous improvement of process method and mold manufacturing technology, it entered the practical application stage in Europe in the 1950s. So far, the number of fine blanking machines in the world has exceeded 4500, and the types of parts are close to 10000.
After entering the new century, with the continuous development of manufacturing industry, the technical requirements of parts are higher and higher. In order to meet the production requirements of automatic, intelligent and standardized fine blanking, and to produce parts with high precision, large size and complex structure, relevant scholars have carried out comprehensive research on fine blanking mechanism, fine blanking process, fine blanking equipment and die.
Research status of fine blanking mechanism
Different from the ordinary stamping process, the transverse flow of the material is restrained by the ring gear pressure plate, and the deformation zone is subjected to three-dimensional compressive stress, which makes the workpiece and raw material remain as a whole when the fine blanking is nearly completed. Therefore, the deformation process of the material in the fine blanking process is plastic deformation, and there is no tearing before separation.
At present, the main research methods of fine blanking mechanism are finite element analysis and experimental means. The research object mainly aims at the change of material flow and processing effect in the process of fine blanking, and analyzes the influence of processing parameters such as blank holder force, back pressure and die gap on the quality of different materials and fine blanking parts. The development of finite element simulation technology provides conditions for further understanding of fine blanking mechanism. Through the finite element method, the distribution of shear stress and plastic strain in the material and die can be obtained, which is convenient to establish the relationship between fine blanking force, die and parts. Combined with the test, the fine blanking process can be analyzed, and different boundary conditions can be set to analyze the material flow and stress-strain distribution under different conditions.
It is found that increasing blank holder force and reverse jacking force can effectively improve the surface quality of parts. Changing the clearance between punch and die and fillet radius mainly affects the quality of the cutting surface. The results show that the relationship between the height of the workpiece and the thickness of the V-ring can be well combined with the thickness of the workpiece.
At present, the theory of fine blanking mechanism for thin plate materials has become mature, but some special parts such as tooth surface and thick plate still need to be studied.
Research status of fine blanking technology
Fine blanking process is proposed mainly because of the new product requirements. In the face of high requirements of parts, the old fine blanking process can not meet the product requirements, so it is necessary to develop targeted process methods.
The closed extrusion fine blanking process uses the pre extrusion to make the material flow radially, and the scrap area is extruded and deformed before the blanking process, so as to close the die cavity. In the process of closing, the plastic failure will occur in the waste area in advance, and the radial deformation will not be produced in the fine blanking process. The deformation area will be in the state of maximum three-dimensional compressive stress, and the material plasticity will be improved. There is no burr in the fine blanking parts produced by closed extrusion fine blanking process, so the deburring process can be omitted. The development of closed extrusion fine blanking technology reduces the difficulty of fine blanking for gears and sprockets, and solves the problem of insufficient material flow in the process of fine blanking for thick plates and low plasticity materials.
Fine blanking technology has high production efficiency and low production cost, but it is difficult to complete the processing of some complex parts. In order to solve this problem, the research on the combination of fine blanking technology and other processes was carried out. Under the ideal boundary conditions, the fine blanking deformation and extrusion deformation are independent of each other, and there is no interaction between them. It can complete the boss, counterbore and other processing tasks well.
Research status of fine blanking equipment and die
Fine blanking equipment is one of the important factors to determine the fine blanking ability. Since the first fine blanking machine was manufactured by Schmid company in Switzerland in 1956, the fine blanking equipment has been developing and progressing continuously. China’s fine blanking machine is developed by combining import with independent research and development, adding hydraulic die base on ordinary stamping machine for transformation. Through continuous improvement, great progress has been made in automation and large-scale.
Fine blanking die is one of the most important parts in fine blanking production. In recent years, many researches have been done on the failure analysis and life prediction of fine blanking die. Figure 1 shows a typical fine blanking die.
Figure 1 typical fine blanking die
The research direction of fine blanking die is mainly divided into three categories: the first is to reduce wear and improve the life of die. The working environment of fine blanking die is very bad, and it is inevitable to be worn. In order to prolong the service life of the die, a series of related researches have been carried out, mainly using finite element simulation to improve the die parameters and reduce the die loss in the process of processing. The second is to improve the intelligence of the mold, through the detection of various parameters in the process of using the mold and the residual situation of the mold working area