Molds used for injection molding can produce molded products when they are completely filled with resin.
Before the resin fills the mold, the inside of the mold is filled with air.
However, as the resin gradually flows through the gate, the percentage of air in the mold decreases rapidly. Rather than a decrease in the percentage, it would be more correct to say that the resin is compressed.
If the resin is compressed at this rate, it will ignite due to adiabatic compression and burn marks will appear on the resin.
This is called gas burning and is a molding defect.
Molds are usually designed with gas vents, which are gas (air) venting channels that allow gases generated from the resin and air in the mold to escape.
So air and gas should not ignite, but if the installed gas vent is clogged with resin or tar...
There is no way for the gas or air to escape, resulting in gas burning.
In other words, to eliminate gas burn defects
(1) Regular mold maintenance (cleaning)
(2) Installation of a gas venting receptacle is necessary.
In some cases, mold maintenance requires removing the mold from the molding machine and disassembling it for cleaning.
In addition, since the mold cannot be used during maintenance, production is stopped only during the maintenance time.
The frequency of maintenance varies greatly depending on the mold size, layout, product shape, and resin used, so there is a lot of reliance on the instincts of the people on the molding site.
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