What should I do if I can't vent the air in the injection molding tool?

1. There is often gas in the injection mold, why is this?

(1) The air in the casting system and mold cavity.

(2) Some raw materials contain water that has not been dried out, they will vaporize into water vapor at high temperature.

(3) Due to the high temperature in the injection molding, some unstable plastic will decompose and produce gas.

(4) Some additives in the plastic raw materials volatilization or mutual chemical reaction generated by the gas.

2. Also the cause of poor exhaust needs to be found as soon as possible. The poor exhaust of the injection mold will bring a series of hazards to the quality of plastic parts and many other aspects.

The main performance is as follows. 

(1) In the injection process, the melt will replace the gas in the cavity, if the gas is not discharged in time will cause difficulties in filling the melt, resulting in insufficient injection volume and can not fill the cavity.

(2) The gas that is not removed properly will form high pressure in the cavity and penetrate into the interior of the plastic under a certain degree of compression, causing quality defects such as cavities, porosity, tissue sparseness, and silver lines.

(3) As the gas is highly compressed, the temperature inside the cavity rises sharply, which causes the surrounding melt to decompose and burn, causing local carbonization and scorching of the plastic part. It mainly occurs at the merging of two melt streams and at the flange of the gate.

(4) Poor gas removal makes the melting speed into each cavity different, so it is easy to form flow marks and fusion marks and make the mechanical properties of the plastic parts lower. 

(5) Due to the obstruction of gas in the cavity, it will reduce the mold filling speed, affect the molding cycle and reduce the efficiency of taxation.

3. Distribution of air bubbles in plastic parts

(1)The vapor bubbles generated by the accumulation of air in the mold cavity are often distributed on the part opposite the gate.

(2)The bubbles generated by the decomposition or chemical reaction in the plastic material are distributed along with the thickness of the plastic part.

(3) The bubbles generated by the vaporization of residual water in the plastic material are irregularly distributed on the whole plastic part.