Reasons and measures to deal with bad exhaust of injection moulds

Reasons for gas in the manufacture of products

1. The material in the feeding system has gas or there is air in the cavity, and the gas in the runner and cavity is not discharged in time during the molding process.

2. Insufficient drying of resin, which contains water and becomes water vapor by evaporation at injection temperature.

3. The injection temperature is high, and the plastic decomposes and produces gas.

4. Some additives in the resin, volatile or chemical reaction to generate gas (such as thermosetting plastic molding, not only the plastic itself contains water and volatile components, but also in the curing process condensation reaction, resulting in condensation of water and low-molecular volatile gas).

5. residual gas in the resin.

Consequences of poor mold exhaust.

1. the gas is subjected to large compression and generates backpressure, and this back pressure increases the resistance of the molten material to the flow of the mold filling, preventing the molten plastic from filling the mold normally and quickly, so that the mold cavity cannot be filled, resulting in unclear plastic edges.

2. The products show obvious flow marks and fusion seams, and the mechanical properties of the products are reduced.

3. After the gas is compressed, it will penetrate into the inner layer of the plastic, causing the plastic to produce silver lines, pores, loose tissue, peeling, and other surface quality defects.

4. The gas in the cavity will be compressed and generate heat to make the local temperature of plastic rise, and the plastic melt will be decomposed and discolored and even scorched and carbonized.

5. poor exhaust, reduce the filling speed, increase the cycle time of forming the parts (especially high-speed injection molding), seriously affects productivity.