In the process of injection mold, because the heat is easy to produce hot gas, once there is gas and it is not discharged, it is easy to cause problems in the mold, especially in the rapid prototyping process, once there is excess gas, the mold will bulge, so exhaust is a very important work.
1、 The source of gas in the injection mold.
1. There is air in the casting system and mold cavity.
2. Some enterprise raw materials mainly contain a moisture that can be removed without drying, and they are gasified into steam at high temperature.
3. Because the injection molding temperature is too high, the gas generated by the decomposition of some unstable plastics occurs.
2、 Hazards of poor exhaust
Poor exhaust of injection mold will bring a series of hazards to the quality of plastic parts. The main results are as follows:
1. In the process of injection molding, the melt will replace the gas in the cavity. If the gas is not discharged in time, it will be difficult for the melt to fill, resulting in insufficient injection and failure to fill the cavity.
2. The compressed to a certain extent will be excluded, formed in the high-pressure differential gas cavity, and penetrate into the plastic, quality defect holes, voids, loose structures, cracks, etc.
4. Eliminate the gas difference into the melt, so that the speed in each different cavity can easily form flow marks and fusion lines, and reduce the mechanical properties of plastic parts.
3、 Distribution of bubbles in plastic parts
1. Bubbles in the cavity are usually located opposite the gate.
2. The decomposition of plastic materials or the chemical reaction of bubbles are distributed along the thickness of plastic parts.
3. If there are residual bubbles generated by water gasification technology in plastic raw materials, they are irregularly distributed on the whole plastic parts.
Link to this article：Exhaust facilities must be set up in the process of injection mold
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