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;

在注塑的时候塑料中一些添加剂挥发掉后或者一些热固性塑料成形过程中交联反应所生成的气体。同时在要保证注射成形的过程中要完整的脱模进行，减少制品的成形缺陷，我们再考虑如何提高其质量的注射加工工艺的同时，还一定重视其模具排出多余气体的系统的设计。

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 should 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.

在注塑模具的过程中，如模具排气不好，型腔中的气体受到压缩将产生很大的背压，大的阻碍了塑料熔体的正常快速充模，使注塑变得困难；同时会迫使注射时压力不断提高，保压时间增加，成形周期延长，生产注塑件的时候效率也不停降低。有时候腐蚀性的气体在型腔表面形成积垢，降低了模具正常使用下的寿命。

In the process of injection mold, if the mold exhaust is not good, the gas in the mold cavity will be compressed, which will produce a great back pressure, which greatly hinders the normal and rapid filling of plastic melt, making 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.

在注塑机塑料充模的过程中，为了将熔融的塑料的流动性保持在好的状态，因此必须要提高在熔融塑料的温度和注射压力，但也因为这样制品的残余应力会随之压力而提高，产品四周的翘曲和塑料裂解的可能性也增加。比方模具的排气正常情况下，注射速度可提高，充填和保压可容易达到好的状态，不需额外增加料筒和喷嘴的温度。这样制品的残余应力小，翘曲变形小。注塑加工时候我们也要考虑如何排气，好的排气系统会提交塑料件的质量。

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.