The rapid development of science and technology, especially when the existing resources and environment cannot be overly optimistic, pose serious challenges to metal stamping processing and even the entire plastic processing industry. Reducing weight, saving materials, reducing energy consumption, and pioneering and innovating have become an extremely important issue facing the plastic processing industry.
It is undeniable that in metal stamping processing, stamping is one of the processing methods with the highest forming efficiency and material utilization, and it has its own unique advantages and characteristics.
Facing serious challenges, Shenzhen Be-Cu Technology Co., Ltd. is taking a new attitude to develop into the fields of extrusion, fine blanking and machining, such as gear stamping, stamping engine housing, stamping rocker arm, stamping rocker arm seat, Stamped exhaust pipes, stamped and welded centrifugal pumps, stamped brackets, stamped and welded car rear shells, stamped clutch housings, stamped gearbox housings, stamped pulleys, etc., all of which not only change the workpiece from casting , The clumsy appearance presented by welding production, the precision of many stamping parts is not inferior to cnc machined products, and its structural rationality even exceeds that of some machined products, especially its productivity is far from machining.
High-tech such as compound stamping, micro stamping, intelligent stamping, and green stamping have shown us the attractive new fields of stamping processing. It can be said that stamping processing has great achievements in terms of depth and breadth, and has a bright future.
Compound Stamping
The composite stamping involved in this article does not refer to the composite of blanking, stretching, punching and other stamping processes, but refers to the composite of stamping process and other processing technologies, such as the composite of stamping and electromagnetic forming, stamping and cold forging. Combination, stamping and machining composite, etc.
1.Composite process of stamping and electromagnetic forming◆◆
Materials are milestones in the progress of human society. From the Stone Age to the Bronze Age, to the Iron Age, to the current era of new material design and preparation and processing technology, it can be said that every leap forward in human society is closely related to the development of materials and material technology. The research, development and application of new materials reflect the level of science, technology and industrialization of a country. Microelectronics technology represented by large-scale integrated circuits, communication technology represented by optical fiber communication, superconducting technology represented by applications such as nuclear magnetic resonance imaging systems and magnetic levitation technology, and aerospace represented by manned spacecraft or space shuttles The development and progress of almost all high and new technologies, such as aviation technology, are premised on the development and breakthrough of new materials and new materials. The application of new material technology in stamping processing is also an extremely important aspect of the development of stamping processing, and stamping experts have always attached great importance to it.
Existing research and practice have shown that stamping forming is actually limited by two aspects of material deformation: one is the problem of necking and rupture, and the other is the problem of buckling and wrinkling under compression. Performance. The yield point, neck point and failure point of metal materials have important practical significance for stamping. The yield point is not only the end point of structural design, but also the starting point of plastic deformation, while the neck point is the end point of structural design. Material forming limits. Therefore, the stamping range is only a small stress range from the yield point to the neck point on the tensile stress-strain curve of the material, and the stress range of difficult-to-form materials is even narrower, so the limited range of stamping is often It hinders the application of many difficult-to-form material parts, and some properties of these difficult-to-form materials are often necessary to make some important parts.
For example, in the forming of automobile panels, if the aluminum alloy is used instead of steel, the weight can be reduced.30%Therefore, the use of aluminum alloy car covers is very meaningful to reduce the weight of the car. Especially in a world full of cars, its impact on resources and the environment cannot be underestimated.However, as a difficult-to-form material, the forming range of aluminum alloy is extremely limited, and people feel helpless because it cannot be used normally due to stamping instability. Now the composite process of stamping and electromagnetic forming can solve the problem of difficult forming of aluminum alloy cover parts. Although the mechanism is not yet clear, one thing is certain, that is, electromagnetic forming is high-speed forming, and high-speed forming can not only expand the forming range of aluminum alloys, but also improve its formability.
The specific method of forming aluminum alloy covers by composite stamping is: use a set of convex and concave molds to install electromagnetic coils at the sharp corners and difficult-to-form contours of aluminum alloy covers, form them by electromagnetic methods, and then use a pair of molds. The easy-to-form part of the cover is formed on a press, and the preform is then subjected to high-speed deformation with an electromagnetic coil to complete the final forming. Facts have proved that with such a composite forming method, an aluminum alloy cover that is difficult to obtain with a single stamping method can be obtained.
The latest research shows that magnesium alloy is a metal with high specific strength, good stiffness and strong electromagnetic interface protection performance. Its application prospects in electronics, automobiles and other industries are very promising. trend. At present, the magnesium alloy parts used in automobiles include instrument bottom plates, seat frames, engine covers, etc., and magnesium alloy pipe parts are also widely used in cutting-edge industrial fields such as aircraft, missiles and spacecraft. However, the close-packed hexagonal lattice structure of magnesium alloys determines that it cannot be stamped at room temperature. Now people have developed a mold that combines heating and forming to stamp and form magnesium alloy products. The forming process of the product is as follows: when the slider of the punch press is lowered, the upper die and the lower die are clamped to heat the material, and then the material is formed in an appropriate motion mode. This method is also suitable for the connection of formed products and the composite forming of various products in the punch. Many difficult-to-form materials, such as magnesium alloys, titanium alloys and other products, can be stamped and formed by this method. Since this kind of punching requires the punching block to have a pause function during the descending process to provide time for the heating of the material, a new concept of punching machine “NC crankshaft servo motor punching machine” has been developed, which can also be used in the stamping die. The composite processing including tapping, riveting and other processes is realized, which effectively expands the scope of stamping processing and lays a solid foundation for the wide application of magnesium alloys in the plastic processing industry.
2.Stamping combined with cold forging (continuous cold extrusion technology, i.e.CFPtechnology)
Generally, sheet metal stamping can only form parts with equal wall thickness, and thick-bottomed and thin-walled parts can be obtained at most by thinning and stretching. The limitations of stamping and forming limit its application range. In the production of auto parts, some thin-walled but unequal thickness parts are often encountered (Figure 1). It is very easy to form by a composite plastic forming method combining a single stamping and cold forging. Therefore, stamping and cold forging are used. The combined method of forging can expand the range of sheet metal processing. The method is to first use the stamping method to preform, and then use the cold forging method to finalize.
The advantages of composite plastic forming by stamping cold forging are: first, raw materials are easy to be purchased cheaply, which can reduce production costs; second, the large forming force required for single cold forging is reduced, which is beneficial to improve the life of the die.
Micro Punching
The micromachining we are talking about now refers to the technology of micro-part machining.The definition of a micropart usually means that the dimension in at least one direction is smaller than100μm, it has unparalleled application prospects than conventional manufacturing technology. Micro-robots, micro-planes, micro-satellites, satellite gyroscopes, micro-chestnuts, micro-instruments, micro-sensors, integrated circuits, etc. made with this technology have excellent applications in many fields of modern science and technology, and they can bring many benefits to many fields. The new expansion and breakthrough will undoubtedly have a profound impact on my country’s future science and technology and national defense, and its role in promoting the development of world science and technology is incalculable. For example, micro-robots can complete complex operations such as lead, bonding, and docking of optical fibers, as well as detection of small pipes and circuits, and can also perform integrated chip production and assembly.
Developed industrial countries attach great importance to the research and development of microfabrication, and have invested a lot of human, material and financial resources, and some far-sighted famous universities and companies have also joined this ranks.my country has also done a lot of research work in this area, and it is reasonable to think thattwenty oneIn the 20th century, microfabrication will definitely bring huge changes and profound influence to the whole world just like microelectronics technology. For the mold industry, due to the miniaturization of stamping parts and the continuous improvement of precision requirements, higher requirements are put forward for mold technology. The reason is that microparts are much more difficult to form than traditional parts for the following reasons:
- The smaller the part, the faster the surface area to volume ratio;
- The adhesive force and surface tension between the workpiece and the tool increase significantly;
- The influence of grain size is significant, and it is no longer an isotropic uniform continuum;
- It is relatively difficult to store lubricant on the surface of the workpiece.
An important aspect of micro punching is punching small holes. For example, there are many small holes that need punching in micro-machines and micro-instruments. Therefore, the study of small hole punching should be an extremely important issue in micro punching. The research on punching small holes focuses on: one is how to reduce the size of the punch; the other is how to increase the strength and rigidity of the tiny punches Guiding and protection of punches, etc.). Although there are still many problems to be studied in punching small holes, many gratifying results have been achieved.Some data show that the micro-stamping machine tools that have been developed abroad are long111mm,width62mm,high170mmequipped with an AC servo motor that produces3KNpressure. The press machine is equipped with continuous stamping die, which can realize blanking and bending.The University of Tokyo in Japan utilizes a gastricWFDGTechnology has produced punches and dies for micro-stamping processing. Using this die for micro-stamping, it can be50μmThe polyamide plastic sheet is punched out to a width of40μmof non-circular cross-section micropores.
Tsinghua University has made a good start in the deep drawing of ultra-thin-walled metal cylindrical parts. The key to ultra-thin wall drawing technology is to have a high-precision forming machine.They have a wall thickness of0.001mm~0.1mmIn the forming of ultra-thin-walled metal cylinders, a precision forming testing machine with microcomputer control function was developed, so that the centering accuracy of the punch and the die during the processing reached1μm, so as to effectively solve the problem of wrinkling and fracture in ultra-thin-wall drawing and cannot operate normally.Using this machine, the initial wall thickness is03mmA series of thinning and deep drawing of brass and pure aluminum are processed to produce an inner diameter of16mmthe wall thickness is0.015mm~0.08mm,length is30mmseries of ultra-thin-walled metal cylinders.After testing, the wall thickness difference of the formed ultra-thin-walled cylinder is less than2μmthe surface roughness scale30.057μmthereby greatly improving the accuracy of the application of the ultra-thin-walled cylindrical instrument, and correspondingly improving the performance of the whole machine for installing the instrument.
Intelligent Stamping
Sheet metal stamping from manual operation to semi-mechanized, mechanized, and automated operation is the symbol of stamping development to each stage. Now sheet metal stamping has entered the intelligent stage. Therefore, it can be said that intelligent stamping is the development of sheet metal stamping technology. inevitable trend.The intelligent research of sheet metal forming originated from20century80In the United States in the early 1990s, after that, the Japanese plastic processing industry also began to study sheet metal intelligence.For more than ten years at the beginning of this technology research, all efforts were concentrated on the forming control of bending springback, until1990Years later, the research on this technology was extended to the deep drawing and deformation of cylindrical parts, and then to the forming of automobile panels and the intelligent forming of progressive dies.
The so-called intelligent stamping is a comprehensive technology produced by the organic combination of cybernetics, information theory, mathematical logic, optimization theory, computer science and sheet metal forming theory. Sheet metal intelligence is a higher stage of new technologies such as stamping and forming process automation and flexible processing systems. What is amazing is that it can identify the performance parameters of the material online and predict the optimal process parameters according to the characteristics of the object to be processed, using the physical quantities that are easy to monitor, and automatically complete the stamping of the sheet with the optimal process parameters. These are the four elements of a typical intelligent control of sheet metal forming: real-time monitoring, online identification, online prediction, and real-time control of processing. In a sense, intelligent stamping is actually a revolution in people’s understanding of the nature of stamping. It eschews the endless search for the principle of stamping in the past, and instead simulates the human brain to process what actually happens in stamping. It does not proceed from basic principles, but on the basis of facts and data, to achieve optimal control of the process.
Of course, the intelligent control is the optimal process parameters, so the determination of the optimal process parameters is the key to the intelligent control. The so-called optimal process parameters are the most reasonable process parameters that can be adopted under the premise of satisfying various critical conditions. In order to realize the online prediction of the optimal process parameters, it is necessary to have a clear understanding of various critical conditions of the forming process, and to be able to give a quantitative and accurate description, and only on this basis can intelligent control be determined. The accuracy of quantitative description determines the recognition accuracy and prediction accuracy of the intelligent system.This shows that the recognition accuracy, prediction accuracy and control accuracy of the system all depend on the improvement of the quantitative description accuracy, so it should be constantly revised and improved.
And the detection accuracy, recognition accuracy, prediction accuracy and monitoring accuracy system itself should be constantly improved. In this way, intelligent stamping can reach its due level.
Relevant studies show that in the intelligent control of the deep drawing process, the prediction of the optimal process parameters ultimately boils down to the determination of the change law of the blank holder force, and the control of the blank holder force is based on the prediction of the blank holder force. There are two main traditional methods for predicting the blank holder force in deep drawing: experimental method and theoretical calculation method. In recent years, artificial neural network and fuzzy theory and other artificial intelligence theories have been introduced into the prediction research of the optimal control curve of blank holder force. At present, the variable blank holder force control technology has become a research hotspot in academia and industry. The theoretical basis of the change law of blank holder force is to determine the critical condition of wrinkling or rupture. It can be seen that the correct determination of the critical condition of flange wrinkling and rupture in deep drawing cannot be ignored. Further research also shows that for the deep drawing of conical parts, the flange wrinkling area is almost surrounded by the side wall wrinkling area, so the side wall wrinkling is overcome and the flange wrinkling is also overcome, so the conical wrinkling area is also overcome. In terms of workpiece deep drawing, the main contradiction is focused on workpiece cracking and sidewall wrinkling. Therefore, the size of the blank holder force should be controlled between the side wall without wrinkling (minimum limit) and the side wall without rupture (maximum limit).
Green Stamping
Environment and resources are two major issues that must be solved in the development of today’s world. In order to ensure the sustainability of human social civilization and economic development, people propose green manufacturing. The so-called green manufacturing refers to systematically considering the entire life cycle from product design, manufacturing, packaging, transportation, use to end-of-life disposal under the premise of meeting product function, quality and cost requirements, and strives to minimize the negative impact on the environment in each link. The smallest, the highest resource utilization. Green manufacturing is a modern manufacturing model that comprehensively considers environmental impact and resource efficiency, and green stamping is also the same, which is essentially the embodiment of human sustainable development strategy in china stamping. It should cover all aspects of mold design, manufacturing, maintenance and production applications.
Green Design
The so-called green design means that measures such as environmental protection and resource consumption reduction are incorporated into the product design during the mold design stage, and the disassembly, recyclability, and manufacturability are considered as design goals in parallel, and the product function, quality life and economical.For example, in the production of small batches and multiple varieties, general mold bases and combined mold structures can be used, so that one mold can be used for multiple purposes, and even one-shaped and two-sided punches can be used[Fig2]one model with many shapes[Fig3]and other methods to reduce the number of molds and save materials.picture2afor45Angle cutting punch, figure2bFor deep drawing punch, figure2cIn order to bend the punch, its characteristics are that one side is worn out, and the other side can be used continuously.
picture3For the punching and fastening die, the three punches share one die, and the die is made into one die with multiple shapes, which greatly reduces the consumption of materials and energy, and is beneficial to the environment.
With the development of the mold industry, the requirements for sheet metal forming quality and mold design efficiency are getting higher and higher, and the traditional experience-based design method has been unable to adapt to the development of modern industry. In recent years, computer numerical simulation of sheet metal forming process with finite element method is a revolution in the field of mold design. The displacement, stress and strain distribution of the workpiece during the forming process can be obtained by computer numerical simulation. The possible wrinkling can be predicted by observing the deformation shape of the workpiece after displacement; according to the position of the principal strain value at the discrete point on the sheet metal forming limit curve or by analyzing the damage mechanics model, the possible rupture during the forming process can be predicted. ;Release the external force on the workpiece or the restraint of the part to be cut off, the springback process can be simulated, and the shape and residual stress distribution of the workpiece after springback can be obtained. All of this provides a scientific basis for optimizing the stamping process and die design, which is a true green die design.
Green Manufacturing
In mold manufacturing, green manufacturing should be adopted.Now there is a laser remanufacturing technology, which is based on the appropriate alloy powder as the material, and has the original shape of the part.CAD/CAM With the support of software, the computer-controlled laser head is used to repair the mold.The specific process is that when the powder feeder and the processing machine move according to the specified space trajectory, the beam radiation is synchronized with the powder transportation.: The repair part is gradually deposited, and finally a three-dimensional body similar to the original part is generated, and its performance can reach or even exceed the level of the original base material. Since the technology is not aimed at consuming a lot of natural resources, it is called green manufacturing.
In addition, stamping process waste and structural waste should be minimized in stamping production, maximizing the use of materials and minimizing waste. Reducing process waste is solved by optimizing layout, such as using opposite layout, cross layout and other methods, and can also use less waste layout method to greatly improve the material utilization rate. The so-called optimization layout is to solve two problems: one is how to express it as a mathematical model; the other is how to find the optimal solution as soon as possible according to the mathematical model, the key is the algorithm problem. Modern optimization techniques have developed into intelligent optimization algorithms, including artificial neural networks, genetic algorithms, simulated annealing, and tabu search. It is believed that there will be a breakthrough in optimizing layout. The nesting method can be used for workpieces with a lot of structural waste, so as to achieve waste utilization and turn waste into treasure. In addition, it is not impossible to solve it by changing the product structure. For nesting, it is well known that there are large gaskets for medium gaskets, and middle gaskets for small gaskets.
The rapid development of science and technology in the world has pushed my country’s die and die industry to a new stage. We have reason to believe that the future of stamping processing is infinitely bright. The plastic processing industry will surely enrich and expand itself in the course of its great march to nature, while providing human beings with increasingly improved material products, and achieve more gratifying results.
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