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        來源:http://www.lasagnafarm.com/ 日期:2021-09-25

        With the rapid development of injection molding industry, people have higher and higher requirements for the surface quality and dimensional accuracy of various plastic products, especially the plastic products used as pure structural parts in different engineering technologies. In order to meet their different physical and mechanical properties, the main requirements are dense structure, firm fusion High strength and low internal stress.
        But in the process of injection mold testing, and then adjust the parameters of injection molding process, the products often appear various phenomena, such as insufficient filling, high internal stress and surface streamline, which is mainly due to the problem of the exhaust of the mold. During the injection molding process of the mold, various gases generated in the mold mainly come from the following sources: there is air in the mold cavity and gating system; Water vapor formed by evaporation of water contained in plastic raw materials at injection temperature; Gas produced by plastic decomposition at high temperature;
        During injection molding, the gas generated by cross-linking reaction after some additives in plastics volatilize or during the forming of thermosetting plastics. At the same time, in order to ensure the complete demoulding in the process of injection molding and reduce the forming defects of products, we must not only consider how to improve the injection processing technology of its quality, but also pay attention to the design of the system for discharging excess gas from its mold.
        In the process of injection mold, if the mold exhaust is poor and the gas in the mold cavity is compressed, it will produce a great back pressure, which greatly hinders the normal and rapid filling of plastic melt and makes injection molding difficult; At the same time, it will force the continuous increase of pressure during injection, the increase of pressure holding time, the extension of forming cycle, and the continuous reduction of efficiency in the production of injection molded parts. Sometimes corrosive gas forms scale on the surface of the cavity, which reduces the service life of the die under normal use.
        During the plastic filling process of the injection molding machine, in order to maintain the fluidity of the molten plastic in a good state, it is necessary to increase the temperature and injection pressure of the molten plastic, but also because the residual stress of the product will increase with the pressure, and the possibility of warpage and plastic cracking around the product will also increase.
        For example, under normal conditions, the injection speed can be improved, and the filling and pressure holding can easily reach a good state without increasing the temperature of the barrel and nozzle. In this way, the residual stress of the product is small and the warpage deformation is small. During injection molding, we should also consider how to exhaust. A good exhaust system will submit the quality of plastic parts.

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