In the process of producing Ps lid, the quality of raw materials, processing factors, temperature control, and workers' technical level will all have a certain impact on the quality of PS lid, and there are some defects, such as bubbles, which will not only affect the aesthetic degree of PS lid, but also affect its use effect. So what are the factors that cause bubbles in PS lid?

1. technological factors. The injection speed is too fast, so that the molten plastic is decomposed by large shear and gas is produced; The local cooling of the product is too fast and the shrinkage is uneven, especially when the wall thickness of PS lid is large, the surface cooling speed is faster than that of the central part. During the cooling process, the plastic edge in the central part shrinks and expands to the outside, which makes the central part insufficiently filled and forms true bubbles; Insufficient injection pressure and holding pressure make the melt and cavity surface not close to each other, which is not conducive to air discharge; Back pressure is insufficient, which controls the backward speed of the screw. When the back pressure is small, the backward speed of the screw will be fast, which will easily lead to insufficient feeding. There is too much air brought into the material to be discharged from the feed inlet, resulting in a large number of bubbles.

2. Material factors. The raw materials may contain moisture.

3. Mold factors. The mold should be maintained or an exhaust groove should be added.

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