The reason and treat method poor exhaust of injection mold
The reason and treat method poor exhaust of injection mold
Causes of gas generation in the manufacture of products
1. The gas entrained in the material feeding system or the air in the mold cavity was not discharged in time during the forming process.2. The resin is not dry enough and contains water, which evaporates into water vapor at injection temperature.
3. When the injection temperature is high, the plastic will decompose and produce gas.
4. Some additives in the resin will volatilize or react to generate gas (for example, when thermosetting plastics are formed, not only the plastic itself contains moisture and volatile components, but also polycondensation reaction occurs during the curing process to produce condensed water and low molecular volatile gas).
5. Residual gas in resin.
Consequences of poor die exhaust:
The results show that: 1. The gas undergoes large compression and produces back pressure, which increases the resistance of the molten material filling flow, prevents the normal and rapid filling of the molten plastic, and makes the mold cavity unable to be filled, resulting in the unclear edge of the plastic.
2. There are obvious flow marks and fusion seams on the products, and the mechanical properties of the products decrease.
3. After the gas is compressed, it will seep into the inner layer of the plastic, resulting in surface quality defects such as craze, air hole, loose tissue and peeling layer.
4. After the gas in the cavity is compressed, heat will be produced, which will cause the local temperature of the plastic to rise, the plastic melt will decompose and discolor, and even be charred and carbonized.
5. Poor exhaust reduces the filling speed and increases the forming cycle (especially high-speed injection molding), which seriously affects the production efficiency.
