abs injection molding
4) The density of different parts is different. The final result of shrinkage, the density of each part is different. The density of the central part or the thick glue position is small, and the density of the frozen layer is relatively large.
5) Reasons for shrinkage-concavity: When abs injection molding product cools and shrinks, the frozen layer is cooled first, forming a hard shell surrounded, which has a fast cooling rate, a small-shrinkage and a high density; and the center or thick glue The location temp is high, the cooling rate is slow, the density is low, and the amount of shrinkage-is large. Since the cooling of the central portion or the thick glue position lags behind the frozen layer, when these portions are cooled and contracted, they are not able to shrink-freely, and are restricted by the peripheral frozen layer. When the thickness of the frozen layer is large and the resistance to deformation is strong, when the shrinkage force of the thick glue position of the-product is smaller than the deformation resistance of the frozen layer, hollow bubbles are generated; when the thickness of the frozen layer is thin and the resistance to deformation is poor, When the-shrinkage force of the thick glue position is greater than the deformation resistance, the skin is pulled inward to form a shrinkage concavity limit.
There are many reasons for the shrinkage-concavity, and the solutions are different.
First, choose a plastic raw material with a small shrinkage-rate.
For raw materials of the same nature, the shrinkage-rates of different grades are different. It is necessary to select raw materials with small shrinkage as much as possible. Crystalline plastics shrink-more than amorphous plastics.
The cooling conditions are different, and the thickness of the frozen layer of the product is different. The thickness of the frozen layer is different, and the ability to resist shrinkage-deformation is different. Sometimes the temp of the front mold is lowered, and the temp of the rear-mold is increased, so that the frozen layer of the-product surface becomes thicker, the thickness of the frozen layer on the reverse side becomes thinner, and when the thick glue position-shrinks, the reverse side is concave, and the surface of abs injection molding does not have a depression.
The change and effect are also contradictory. The high mold-temperature is conducive to the flow of the melt, which is-conducive to compression and feeding; but the-mold-temperature-is-high, the cavity size is large, the-melt-temperature is-high, and the-shrinkage-rate is-increased.
Our Service It is not known that changing the thickness of the frozen layer can change the direction of the shrinkage dents, and is rarely used.
Fourth, change the structure design. Change the structural design of the product so that it is as uniform as possible. For the-mold that has been completed, it can be discussed with structure designer to solve the problem of partial reduction.
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