Injection molds are an indispensable part of injection molding. We introduced the number of cavities, gate location, hot runner, assembly drawing design principles of injection molds, and material selection for injection molds. Today we will continue to introduce the design of the plastic injection mold exhaust system.
In addition to the original air in the cavity, the gas in the cavity also contains low-molecular volatile gases generated by the heating or curing of the injection molding material. It is necessary to consider the sequential discharge of these gases. Generally speaking, for molds with complex structures, it is difficult to estimate the exact position of the air lock in advance. Therefore, it is usually necessary to determine its position through a trial mold, and then open the exhaust slot. The vent groove is usually opened at the position where the cavity Z is filled.
The exhaust method is to use the mold parts to match the gap and open the exhaust slot to exhaust.
Exhaust is required for molding of injection molded parts, and for ejection of injection molded parts. For deep cavity shell injection molded parts, after injection molding, the gas in the cavity is blown away. During the demolding process, a vacuum is formed between the appearance of the plastic part and the appearance of the core, which is difficult to demold. If demolding is forced, the injection molded parts are easily deformed or damaged. Therefore, it is necessary to introduce air, that is, to introduce air between the injection molded part and the core, so that the plastic injection molded part can be demolded smoothly. At the same time, several shallow grooves are machined on the parting surface to facilitate exhaust.
1. The template of the cavity and the core needs to use a tapered positioning block or a precision positioning block. The guide is installed on the four sides or around the mold.
2. The contact surface of the mold base A plate and the reset rod should use a flat pad or a round pad to avoid damage to the A plate.
3. The perforated part of the guide rail should be inclined at least 2 degrees to avoid burrs and burrs, and the perforated part must not be of thin blade structure.
4. In order to prevent dents from injection molded products, the width of the ribs should be less than 50% of the wall thickness of the appearance surface (ideal value <40%).
5. The wall thickness of the product should be an average value, and at least mutations should be considered to avoid dents.
6. If the injection molded part is an electroplated part, the movable mold also needs to be polished. The polishing requirements are second only to the mirror polishing requirements to reduce the generation of cold materials during the molding process.
7. It must be embedded in the ribs and grooves in poorly ventilated cavities and cores to avoid dissatisfaction and burn marks.
8. Inserts, inserts, etc. should be positioned and fixed firmly, and the wafer should have anti-rotation measures. It is not allowed to pad copper and iron sheets under the inserts. If the solder pad is taller, the soldered part should form a larger surface contact and be ground flat.
Post time: Dec-31-2021