What can we do when the injected product in shink?

There is a dent in the accumulation area of ??the plastic surface material. Shrinkage occurs mainly in areas where the walls of the plastic part are thick or where the wall thickness changes.
Physical cause
When the product cools, shrinkage (volume reduction, shrinkage) occurs, at which point the outer layer of the mold wall freezes first, forming internal stresses in the center of the product. If the stress is too high, it will cause plastic deformation of the outer plastic. In other words, the outer layer will sink inward. If the shrinkage occurs and the deformation of the outer wall is not stabilized (because there is no cooling), the hold-up does not replenish the melt into the mold, and a settling is formed between the mold wall and the outer layer of the solidified product.
These settlements are usually seen as shrinkage. If the product has a thick cross section, such shrinkage may occur after demolding. This is because there is still heat inside, it will pass through the outer layer and heat the outer layer. The tensile stress generated in the article causes the outer layer of the heat to settle inwardly, forming a shrinkage during this process.
The reasons and improvement measures related to the processing parameters are as follows:
1, the pressure is too low, increase the pressure
2, the pressure holding time is too short, extend the pressure holding time
3, the mold wall temperature is too high, reduce the mold wall temperature
4, the melt temperature is too high, reduce the melt temperature, reduce the barrel temperature
The reasons and improvements related to the design are shown in the following table:
1. The cross section of the material head is too small.
2, the material head is too long, shorten the material head
3. The nozzle hole is too small. Increase the nozzle aperture.
4. The material head is opened at the thin wall. The material head is positioned at the thick wall.
5, excessive material accumulation to avoid material accumulation
6. The section of the wall/rib is not reasonable. Provide a reasonable proportion of the wall/rib section.
In summary, in terms of processing parameters, we first consider the pressure holding of the injection molding machine.

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