Analysis of why the injection mold has an exhaust system!


Author: MULAN -Plastic Molding Manufacturer

Injection mold venting is an important issue in mold design, especially in rapid injection molding. Today, the injection mold processing manufacturer will introduce to you why the injection mold has an exhaust system! 1. The source of gas in the injection mold 1. The air in the gating system and the mold cavity. 2. Some raw materials contain water that is not removed by drying.

They gasify into water vapor at high temperatures. 3. Due to the high temperature during the mold injection molding process, the gas generated by the decomposition of some unstable plastics. 4. The gas produced by volatilization or mutual chemical reaction of some additives in plastic raw materials.

Second, the harm of poor exhaust The poor exhaust of injection molds will bring a series of hazards to the quality of plastic parts and many other aspects. The main performance is as follows: 1. During the injection molding process, the melt will replace the gas in the cavity. If the gas is not discharged in time, it will make it difficult to fill the melt, resulting in insufficient injection volume to fill the cavity.

2. Poor gas removal will form high pressure in the mold cavity, and penetrate into the plastic under a certain degree of compression, resulting in quality defects such as pores, cavity, loose tissue, and cracks. 3. As the gas is highly compressed, the temperature in the mold cavity rises sharply, causing the surrounding melt to decompose and burn, resulting in local carbonization and carbonization of plastic parts. It mainly occurs at the confluence of two melts, the insert and the sprue mold.

4. Poor gas removal makes the speed of melt entering each cavity different, and it is easy to form flow marks and melt marks, which reduces the mechanical properties of plastic parts. 5. Due to the blockage of gas in the cavity, the filling speed will be reduced, the molding cycle will be affected, and the production efficiency will be reduced. 3. The distribution of bubbles in plastic parts There are three main sources of gas in the cavity: air accumulated in the cavity; gas generated by the decomposition of raw materials; due to different sources, the position of the bubbles generated by the evaporation of residual water in the raw materials is also different.

1. The air bubbles generated by the accumulated air in the mold cavity are usually distributed on the opposite side of the gate. 2. Bubbles generated by decomposition or chemical reaction in the plastic raw material are distributed along the thickness of the plastic part. 3. Bubbles generated by gasification of residual water in plastic raw materials are irregularly distributed on the entire plastic part. From the distribution of bubbles in the above plastic parts, not only the nature of the bubbles can be judged, but also whether the venting part of the mold is correct and reliable.

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