Is there any relation between the gas generated during the injection molding process and the mold?

Reasons for gas generation during product manufacturing

1). The material in the feeding system is entrained with gas or the original air in the cavity, and the gas in the runner and cavity is not discharged in time during the molding process.

2). The resin is not sufficiently dried and contains water, which evaporates and becomes water vapor at the 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 of the 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 produces backpressure, and this back pressure increases the resistance of the molten material to the flow of 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 visible flow marks and fusion seams, and the mechanical properties of the parts 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). After the gas is compressed in the cavity, it will generate heat and make the local temperature of plastic rise, and the plastic melt will decompose and change color, and even scorch and carbonize.

5). Poor venting, reduce the mold filling speed, increase the cycle time of forming the parts (especially high-speed injection molding), seriously affecting productivity.