Reasons for the poor exhaust of injection molds and treatment measures
Causes of gas generation during the manufacture of the product
1. The material in the feed system entrains the gas or the air originally stored in the cavity. During the forming process, the gas in the flow channel and the cavity is not discharged in time.
2. The resin is not sufficiently dried, contains water, and evaporates at the injection temperature to become water vapor.
3. The injection temperature is high and the plastic decomposes to generate gas.
4. Some additives in the resin, volatilization or chemical reaction to form a gas (for example, when the thermosetting plastic is formed, not only the plastic itself contains moisture and volatile components, but also undergoes a polycondensation reaction during the curing process to produce a condensation water and a low molecular volatile gas).
5. Residual gas in the resin.
The consequences of poor mold exhaust:
1. The gas undergoes large compression to generate a back pressure, and this back pressure increases the resistance of the molten material to the mold filling flow, prevents the molten plastic from filling normally and rapidly, and the mold cavity cannot be filled, resulting in unclear edges of the plastic.
2. The visible visible flow marks and fusion joints on the product, the mechanical properties of the parts are reduced.
3. After the gas is compressed, it will infiltrate into the inner layer of the plastic, causing the plastic to produce surface quality defects such as silver streaks, pores, loose tissue, and peeling.
4. After the gas in the cavity is compressed, heat is generated to increase the local temperature of the plastic, and the plastic melt decomposes and discolors, and even burns carbonization.
5. Poor exhaust, reduce the filling speed, increase the cycle of part forming (especially high-speed injection molding), seriously affecting production efficiency.