Why the elimination of gas is not smooth inside the hot runner plastic mould

Why the elimination of gas is not smooth inside the hot runner injection mould?

Injection molds often have gas, may be related to the following points: 

-  There are air in the Gating system and the mold cavity 

-  Some raw materials contain moisture that is not removed by drying, and they vaporize at high temperatures

   into water vapor

-  Due to the injection molding temperature is too high, some properties of unstable plastic will produce 

   decomposition of gas

-  Some of the additives in the plastic material volatilize or chemically react with each other to produce gas.
Injection mold of the exhaust is also bad to bring plastic parts:

-  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 be filled cavity.

-  Elimination of poor gas in the cavity in the formation of high pressure, and in a certain degree of compression

   to infiltrate into the plastic inside, resulting in holes, pores, tissue and silver and other quality defects.

-  As the gas is highly compressed, making the cavity temperature rises sharply, and then cause the surrounding

   melt decomposition, burning, the plastic parts of the carbonation and charring phenomenon. It mainly occurs             in the confluence of the two melt, the gate flange.

-  The elimination of gas is not smooth, so that the melt into the cavity of different speeds, it is easy to form flow 

    marks and weld marks, and to reduce the mechanical properties of plastic parts.

-  Due to the cavity of gas obstruction, will reduce the filling speed, affect the molding cycle, reduce tax efficiency.
 The distribution of bubbles in plastic parts:
-  Bubble generated by the accumulation of air cavity, and often located in the gate relative to the site.

-  Plastic materials in the decomposition or chemical reaction of bubbles along the thickness of the plastic 

   parts  distribution.

-  Residual water vaporization of plastic raw materials in the bubble, the irregularly distributed throughout the plastic parts

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