Why do plastic products produce bubbles during processing?

In general, the bubbles generated by plastic products occur at the last seam or where the product is thick. The plastic product is first surface-cooled in the model. When the exterior is cooled, the central part is still hot. The central part is shrunk when it cools, and the plastic surface is already cooled, so it can only be formed by the internal contraction itself. There are many thick parts that have no bubbles at the time of ejection, but after tens of seconds, bubbles appear in the center.
There are several cases of bubbles, the phenomenon is different, and the reasons are different. The analysis is as follows:
Thicker products, the surface is fat and bulging, there are bubbles at the sawing section, the reasons may be:
1 The injection speed is too fast, enveloping the air, can not be ruled out, forming bubbles.
2 If the amount of feed is too much or too little, and the injection pressure is too high, this phenomenon will also occur. If the feed amount is properly adjusted, this phenomenon will be improved.
3 cooling time is too short (especially thick-walled products), the solution can be cooled outside the machine with cold water and cold stamping die.
4 There is a phenomenon of black line decomposition in the product, which is formed due to excessive temperature. If the situation is not serious, the temperature can be lowered appropriately. If the entire barrel is disassembled, it must be removed by car.
6 The mold's inlet gate is too small and the exhaust is poor, which will also occur.
Solid products have holes and blackening:
When the solid product is formed, the injection pressure is low, and the injection speed is slow. Otherwise, the air is wrapped in the product by friction scorching under high pressure, so that there is black void in the product.
Therefore, the injection pressure and the injection speed are appropriately reduced, and the void phenomenon disappears. It is also possible to check if the amount of feed is too much, and it is also advantageous to appropriately reduce the amount of feed to improve this phenomenon.
When the thickness of the plastic product is different, there are small bubbles in the thick part of the product, or there are black big bubbles in the thick part of the product:
When molding several products with different shapes at the same time, it must be noted that the size of each gate should be equal to the weight of the product. Otherwise, thick products are prone to bubbles.
At the same time, it is necessary to pay attention to the exhaust of the mold, and the products often left on the front mold make the exhausting more difficult, and the above phenomenon is easily generated. This can be improved by modifying the mold or increasing the dwell time and cooling time to compensate for the lack of pressure on the thick section. More importantly, when designing products, it should be avoided to have extra thick parts.

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