Research progress of the hottest precision injecti

2022-09-22
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Research progress of precision injection molding technology

the precision and high performance of polymer products have become an important issue of general concern in the field of polymer molding and processing all over the world. Precision injection molding technology is not only related to molding equipment, but also related to processing materials, processing technology control and other factors

technological progress of molding equipment

in recent years, in order to meet the requirements of it and other industries for plastic parts with high precision, high functionality, miniaturization, lightweight, low cost and high added value, the development of precision injection molding machines and molds is a key and difficult problem. In terms of the development of precision injection molding machines, the manufacturers representing the world's advanced level mainly include Kraus mafi, Demag and aberg from Germany, as well as Nissei, Nippon Steel, Toshiba machinery and Sumitomo heavy machinery from Japan

Germany

Klaus mafi first launched a two plate injection molding machine and attracted the attention of its peers in the world. Demag has long cooperated with Haitian, and their technical characteristics and advantages have long been known to domestic peers. Here, we will take aberg as an example to briefly introduce the characteristics of its precision injection molding machine. The clamping mechanism of aberg precision injection machine adopts box design to improve the precision of mold locking. As the front and rear plates of the three plate injection machine are fixed on the frame, when the clamping force is applied, the extension of the four pull rods is constrained by the frame, so that the pull rods tend to "arch bridge shape" and affect the clamping accuracy. The result of the box design improves the clamping accuracy from the perspective of limiting bad deformation. The two-way pressure servo control of the injection cylinder accurately positions the screw position to double the injection volume control accuracy. At present, the main development direction of using frequency converter to optimize and control the energy saving of the existing building exterior wall in our country is that the main pump motor not only improves the control accuracy of the hydraulic system, but also has a significant energy-saving effect. In addition, the abog precision injection machine also adopts a modular design. The motion systems of the injection molding machine can adopt the arbitrary combination of hydraulic and electric according to the actual production needs of users between the two extremes of full hydraulic pressure and full electric pressure. There are also a variety of options for the relative positions of the mold locking system and the injection system

characteristics of Germany's abog precision injection machine

Japan's

Toshiba machinery improves the connection between the front and rear plates and the frame from the usual bottom fixed connection to the waist hinge connection in the design of its precision injection machine's three plate clamping system, so that the pull rod when the clamping force is applied deforms and stretches freely and remains parallel all the time, and adopts the deformation dredging method to ensure the clamping accuracy. Rijing passed the comprehensive optimization of the traditional oil press, a special testing equipment manufactured by our company Jinan new era Gold Testing Instrument Co., Ltd. for the tension test of synthetic fiber lifting belts, so that its inferior situation in comparison with the all electric injection machine has been greatly improved. It adopts a new control system tact (multi language control interface to improve response speed, operational stability and LCD display), a new injection mechanism (large screw length diameter ratio to enhance the plasticizing effect, five stage temperature zone to optimize the plasticizing temperature control), and optimizes the oil pressure circuit, and develops a new oil pressure main model FN series precision injection molding machine. Taking the 110 ton mold locking force model as an example, the control response speed of the optimized precision injection molding machine is improved by 30%, the quality stability is improved by 50%, the influence of oil temperature change is reduced by 50%, and the energy saving is 30%. Recently, the company has developed a precision small electrical forming machine "eljet nex150" which is suitable for forming extremely small precision parts and has a clamping force of 15 tons. The precision injection molding machine is mainly used for molding liquid crystal polymer (LCP), polyamine (PA), polyphenylene sulfide (PPS), etc. Its typical injection molding products are key parts of digital products such as shutter of digital camera. In the injection molding process of such tiny and precise parts, the injection volume is only 0.1g-5g at a time. By adopting advanced pressure maintaining control technology, the quality stability of injection molded products has been greatly improved. Under the standard pressure maintaining condition, the change range of product weight is 0.022g, and the change range of product weight is reduced to 0.006g after the new pressure maintaining control is adopted. Japan Steel Institute has also developed j-elii-ups ultra-high speed precision injection molding machine

precision products such as compact discs have extremely high requirements for molding equipment

domestic

precision injection molding machine is also the Pearl on the crown that domestic manufacturers compete to win. In recent years, Guangdong Hongli has made a great impact in the field of precision injection molding engineering technology by producing the first optical disk injection machine in China. However, the research of precision injection molding engineering technology in China is still in the key stage of the battle, and the academic community also has a strong research interest in it. Huhaiqing, Qingdao Institute of chemical technology, discussed the main factors affecting precision injection molding, such as molding shrinkage, mold design, injection equipment and injection materials, and summarized the problems prone to occur in precision injection molding and their preventive measures; Beijing University of chemical technology has carried out a lot of theoretical analysis and experimental research from the aspects of mold locking accuracy and stiffness of injection machine clamping system, precision filling and mold optimization design, and optimization design of plasticizing system

research progress of processing technology

in order to meet the strong demand of users for using the purchased injection molding machine to produce the best products, suppliers can not only provide technologically advanced equipment, but also provide users with the best molding process technical support

because the polymer molding process is a complex process in which various physical and mechanical phenomena coexist, there are many urgent problems to be solved, such as the coupling between polymer molding processing conditions, morphological structure evolution and mechanical properties of products under the coupling action of multiple physical fields such as temperature and pressure, complex hydrodynamic problems of polymers, mold optimization design and product quality control theory, The research of precision injection molding process is mainly based on experimental research and computer analysis and simulation with the help of various data analysis methods

experimental research

experimental research is an important method for the research of injection molding process. Many scholars, research institutions and professional companies at home and abroad have carried out a lot of research work. These studies involve the flow behavior in the injection molding process, such as the solid bed crushing mechanism, melting behavior, the influence of molding conditions and so on. In recent years, visual experiment method has become one of the hot spots in the industry. The author studied the filling process of "sandwich" composite polymer injection molding skin core material by visual method; The mechanism of Filling Imbalance in multi-mode cavity injection molding is also studied, and an effective method to improve the flow balance from the injection process is proposed; On the basis of the injection molding visualization experimental device of Beijing University of chemical technology founded by Professor Wang Xingtian, and drawing on the beneficial experience of foreign related research, the injection molding visualization laboratory was established, and some phenomena in the injection molding filling process were successfully photographed, which created favorable conditions for the research of injection molding process optimization. In recent years, in order to optimize the injection molding process, some research has been carried out on the injection molding performance of polymer materials, and the p-V-T (pressure specific volume temperature) relationship and its test methods of materials in the process of polymer molding have been studied

numerical simulation

in the numerical simulation of injection molding process, due to the rapid development of plastic industry in the past three decades, it is also the period of rapid development of computer application. In addition, the numerical analysis technology represented by finite element analysis has achieved exciting application results in a wide range of engineering fields, thus promoting the development of the theory and application technology of simulation of injection molding process

Moldflow of Australia accounts for 75% of the global injection simulation technology market share, and has always led the development trend in this field. Its "medium-sized surface" model is still in use. The "medium plane" simulation method is more suitable for the molding analysis of thin-walled injection products, and can make more accurate predictions for the weld line, pore location, fiber orientation, etc., but for products with complex structures, it is difficult or even impossible to construct a continuous medium plane model. In recent years, a "two-sided flow" model has been developed. The main advantage of this method is that the lattice is generated directly on the surface of the product, and there is no need to extract the medium-sized surface, which is convenient for modeling. The theoretical basis of these two simulation methods is to calculate the pressure with finite element on the two-dimensional surface and the temperature with finite difference in the thickness direction, so they are often called 2.5-dimensional analysis method. Because the 2.5-dimensional analysis method ignores many physical information in the thickness direction, it will inevitably lead to the existence of analysis errors, which will be meaningless for the analysis results of thick wall or complex products. Using 3D solid model, there is no need for too many assumptions and simplifications, and it can be seamlessly integrated with cad/cam model. Now it has gradually become the mainstream analysis technology. Since the 1980s, domestic scholars have carried out relevant research work one after another. The main research groups that have concentrated and continued to carry out research are: the research groups led by zhangrongyu of Tsinghua University in Taiwan, Shen Changyu of Zhengzhou University and Li Dequn of Huazhong University of science and technology. They systematically carried out the numerical simulation of the whole process of injection molding from mold filling, pressure maintaining, to cooling and curing, and developed injection molding CAE software: moldex, z-mold and HsCAE. In recent years, major injection molding CAE software developers are competing to develop simulation and analysis functions for gas assisted injection molding. Zhang Rongyu of Tsinghua University in Taiwan started early, and the mathematical model proposed by zhouhuamin and Li Dequn of Huazhong University of science and technology has been recognized by international peers

summary

in terms of injection molding processing technology, although rich achievements have been made in experimental research and numerical analysis, these words summarize the achievements of molding technology in engineering language, which are just a plate of scattered pearls. If a set of effective molding process optimization technology can be provided for users in combination with specific equipment, this experimental machine is applicable to all kinds of waterproof coiled materials, coatings, rubber, braids and small cross-section metal filament guides, and will have a great impact on the injection molding processing industry as software makes computers play a great potential

source: Yang Weimin, School of mechanical and electrical engineering, Beijing University of Chemical Technology

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