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How to reduce the problem of sharp corner effect when making plastic molds

2019-11-02

How to reduce the sharp corner effect when making plastic molds.


尖 The sharp corner effect often occurs when the mold manufacturer designs the mold. The so-called mid-angle effect mainly refers to the situation where the angle formed by two or three faces is less than 120 °, which will cause a concentration of stress at the sharp corner. When this stress reaches a certain level, the sharp corner Everywhere is prone to cracks. Under a continuous stress, the cracks continue to expand and eventually cause the finished product to break or crack; how to avoid the crack effect in the mold design?


Under the premise of ensuring that the mold is normally ejected, the injection molding process should be as simple and easy as possible, and try to avoid or reduce various core drawing mechanisms around the mold. This can not only greatly simplify the mold structure, but also facilitate mold injection molding. Can improve production efficiency.


Shanghai injection manufacturer


When making molds, it is necessary to avoid the concentration of round corner stress as much as possible, and to increase the strength of the product to ensure the stress concentration at the corners of the part, and to reduce the cracking that will occur when the product is stressed or impacted again. Improper molding conditions or unreasonable parts structure will cause great internal stress, which is particularly prone to stress cracking. When the fillet radius at the concentration is less than 0.3 times the wall thickness of the part, the stress concentration increases sharply, and when it is greater than 0.8 times the wall thickness, the stress concentration becomes significantly smaller.


Filling and demolding can be easily done only by using rounded corners. For some plastics with poor fluidity or plastics with fillers added, various rounded corners are particularly important in the design of parts, which can not only improve the filling performance, but also improve the parts. Use performance.


Rounded corners are conducive to the manufacture of various molds. In order to improve the strength of the molds, various rounded corners are designed for the parts. The corresponding parts of the molds should also be rounded. This increases the sturdiness of the molds of Shanghai injection molding manufacturers. When in use, it will not crack due to the concentration of stress, which also increases the strength of the mold release.


How to avoid the sharp corner effect when injection mold manufacturers design molds, rounded corners are one of the good methods.


In order to meet the different physical and mechanical properties of its machine. The main requirements are to make the product dense, weld secure, high strength, and low internal stress. However, in our daily injection molding or test mold process, even if the process parameters are adjusted, the product often shows various phenomena such as insufficient filling, high internal stress, and surface streamlines. This is mainly due to the problem of mold exhaust.


During the injection molding process of the mold, the various gases generated in the mold mainly come from the following sources and sources: there is air existing in the cavity and the pouring system; Water vapor, a gas produced by the decomposition of plastics at high temperatures. At the same time, in order to ensure the complete mold release during the forming process, reduce the molding defects of the product, we must also pay attention to the design of the system to exhaust excess gas from its mold.


During the injection mold process, if the mold exhaust is poor, the gas in the cavity is compressed, which will generate a large back pressure, which greatly hinders the normal and rapid filling of the plastic melt, making injection difficult; The pressure is continuously increased during the injection, the holding time is increased, the molding cycle is prolonged, and the efficiency is constantly reduced when producing injection molded parts. Corrosive gases sometimes form deposits on the cavity surface, reducing the life of the mold under normal use.


In the process of plastic injection molding of the injection molding machine, in order to maintain the fluidity of the molten plastic, the temperature and injection pressure of the molten plastic must be increased, but the residual stress of the product will increase with the pressure. The possibility of warping around the product and plastic cracking also increases. For example, under normal circumstances, the injection speed of the mold can be increased, and the filling and holding pressure can easily reach a good state, without the need to increase the temperature of the barrel and nozzle. In this way, the residual stress of the product is small, and the warpage deformation is small.


We also need to consider how to vent when injection molding. A good exhaust system will improve the quality of plastic parts.


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