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How to properly set the exhaust groove in the injection mold


During the injection molding process, a large amount of melt will not seep out of the vent hole, because the melt will cool and solidify there, thereby blocking the channel, and the opening position of the vent port must not face the operator to avoid accidental The molten material sprayed hurts people.

1. The role of the exhaust groove

The main function of the exhaust groove is to discharge the air in the mold cavity and various gases generated during the heating of the material during the injection molding process of the molten material. The thinner the product is, the farther it is from the gate, the opening of the exhaust groove is particularly important. For small parts or precision parts, attention should also be paid to the opening of the exhaust groove, which can not only avoid surface burns and insufficient injection molding, but also eliminate the various defects of the product. kinds of defects and reduce mold contamination. In general, if the melt is injected at the highest injection rate and no focal points are left on the product, then the venting of the cavity can be considered adequate.

2. Exhaust method

There are many ways to vent the mold cavity, but each method must ensure that the size of the vent groove should be designed to prevent material from overflowing into the groove when venting, thereby preventing clogging. Too many venting grooves is harmful, because if the clamping pressure acting on the parting surface part without venting grooves is high, it is easy to cause cold flow or cracking of the cavity material, which is very dangerous. The cavity can be discharged by setting the vent groove at the end of the material flow of the gating system and leaving a gap around the ejector pin, because the selection of the depth, width and position of the vent groove will affect the aesthetics and accuracy of the product , so the size of the gap is limited to prevent flash around the ejector rod.

3. Design method

For product molds with complex geometric shapes, it is best to determine the opening of the exhaust groove after several mold tests, but the biggest disadvantage of the entire structure in the design of the mold structure is that the exhaust is not smooth. For the entire cavity core, there are several The exhaust method, such as using the groove of the cavity or the mounting part of the insert, using the insert joint on the side, partially making it into a spiral shape, installing the slotted slat core in the longitudinal position, and opening the process hole.

If it is difficult to open the exhaust grooves in some dead corners of the mold, when the exhaust is extremely difficult, the use of inlaid structure, etc., the proper opening of the exhaust grooves can greatly reduce the injection pressure, injection time, pressure holding time and clamping pressure, so that the plastic Molding is changed from difficult to easy, thereby improving production efficiency, reducing production costs and reducing machine energy consumption.

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