First, the principle of plastic mold exhaust actionIn the injection molding production of plastic molds, exhaust treatment is required. The exhaust function refers to the removal of the accumulated gas in the mold cavity to prevent the occurrence of defects such as bubbles. In the molten state, the plastic is injected into the mold, and there is a certain amount of air in the mold cavity. If there is no exhaust treatment, the air can not be completely eliminated, will form bubbles, affecting the quality of molding. Therefore, the exhaust effect of plastic mold is very important, which is directly related to the quality of product molding.

In the plastic mold injection process, the principle of exhaust includes two aspects:

1 Compression and sparsity effect of plastic melt flow:When the plastic melt is injected into the mold in the molten state, the melt will produce a high pressure on the mold cavity. In the process of plastic melt flow, because the area of different parts of the mold cavity is different, the flow speed of the melt is also different, so there will be local compression and thinning phenomenon. Local compression and thinning can cause pressure changes in the flow channel and the mold cavity, thus affecting the emission of gas in the mold cavity.

2 Expansion of plastic melt:When the plastic melt melts at high temperature, the melting volume is larger, because the plastic melt has a certain expansion. In the mold, the plastic melt is squeezed when injected into the mold cavity, forcing the gas in it to squeeze out to one side of the mold.Therefore, the principle of plastic mold exhaust action is to use the compression and sparsity effect generated during the flow of molten plastic and the expansion of plastic melt, so that the gas is discharged from the mold cavity, reduce the generation of bubbles, and improve the quality of product molding.

Second, the importance of plastic mold exhaustThe exhaust effect of plastic mold is an important factor to ensure the quality of product molding, and its role mainly has the following aspects:

1 Prevent the generation of hot bubbles and hot cracks:In the plastic mold injection process, the surface of the molded product will produce many large and small bubbles, which will affect the appearance and quality of the product. If the plastic mold can not be discharged, the long-term accumulation of gas compression force may cause the superposition of the bubbles inside the molding product and the energy inside the surface of the molding product, resulting in hot cracks and hot gas bubbles on the surface of the product.

2 Improve the service life of the mold:If the plastic mold cannot be vented, there will be compressed gas in the mold cavity for a long time, which may eventually lead to damage to the mold. Exhaust treatment can reduce the wear of the mold and improve the durability of the mold.

3 Improve product quality:Exhaust treatment can prevent the generation of bubbles, reduce the scrap rate and improve the appearance and quality of the product, thus improving the market competitiveness of the product.In summary, the exhaust effect of plastic mold is very important, which has a great impact on ensuring the quality of product molding and the service life of the mold. 

Therefore, in the plastic mold injection production must pay attention to exhaust treatment.