Injection mold is the necessary process equipment or tool of plastic parts molding. It plays an extremely important role for technology, quality and cost of plastic parts.
And the exhaust system is an important problem in mould design, especially in the rapid injection molding. It needs more strict exhaust system.
The sources of the gas in injection mold
Gating system and the mold cavity have air inside.
Some raw materials contain water. Under the high temperature, they will turn to water vapor.
Sometimes the temperature is too high, some unstable plastic will decompose into gases.
Some additives will volatilize or make chemical reaction with each other, and then produce gas.
The damage of the poor venting
The poor venting of injection mold will bring a series of harm to the quality of plastic parts. Main shows are as follows:
In the process, melt will replace the room of gas in the cavity. If the gas do not be pushed out in time, it will cause the melt filling difficult, and make the injection amount is not enough.
The poor venting will formed high pressure in the cavity, and produce a certain degree of infiltration inside of plastic. This will cause porosity, hole, organize quality problems and silver stripes.
The temperature inside will rise sharply when working. The high temperature will cause the decomposition and burning of the around melt. And then partial carbonation and plastic burning phenomenon will happen.
It will also affect the rate of melt. Different rates will be easy to form the weld mark and flow mark, and reduce the reduce
Its block to gas will also reduce the mold filling speed, and impact molding cycle, as well as to reduce the production efficiency.
So where are the bubbles in ?
The sources of gas can be divided into three main parts: the accumulated air in the cavity, the decomposition gas from the raw materials, and the water vapor. And their places are different.
The accumulated air of cavity is often in opposite place to gate area.
The second part is distributed irregularly according to the thickness of the plastic parts.
The water vapor is irregularly distributed in the entire plastic part.
According to the distribution of the bubble, we can know the nature of the bubble, and to judge security of the mold's exhaust parts. Injection molding is a delicate job, so we have to be very careful in every step. And design part is the most important,especially for plastic manufacturers.
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