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Analysis of the causes of bubbles in the processing of plastic display shelf

Air bubbles often occur at the last seam of the plastic display shelf article or in the thicker portion of the article. The product is first surface cooled in the model, and when the exterior is cooled, the center portion 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 several tens of seconds, bubbles appear in the center.

There are several kinds of bubbles, the phenomenon is different, and the reasons are different. The description is as follows:

Thicker products, the surface is fat and bulging, there are bubbles at the saw section, the reasons may be:

1) The injection speed is too fast, entraps the air, cannot be eliminated, and bubbles are formed.

2) If the feeding amount is too much or too little, and the injection pressure is too high, this phenomenon will also occur. If the feeding amount is properly adjusted, this phenomenon will be improved.

3) The cooling time is too short, and the solution can be cooled by using cold water and cold stamping die outside the machine.

4) There is a phenomenon of decomposing black lines 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.

5) The phenomenon that the mold inlet is too small and the exhaust gas is poor.

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 product is different, there are small bubbles in the thick part of the product, or there is a black big bubble in the thick part of the product.

When molding several products of 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.

What is the reason for plastic foaming in PVC material injection?

1. The raw materials are damp Lonely leak

2, containing more volatiles will cause PVC edge banding to blister during the extrusion process.

3. Insufficient thermal stability leads to decomposition and foaming of PVC.

Analysis of the causes of bubbles in the processing of plastic display shelf

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