Analysis of reasons for Warpage of Plastic Injection Molding Products-3
2).In the design of cooling system, uneven cooling speed of plastic injection parts will also leads to uneven shrinkage of plastic injected parts. Such difference in shrinkage will lead to the generation of bending moment and the warping of injected plastic parts.
If the temperature difference between the mold cavity and core used in the injection molding of the plastic injection part is too large, the melt close to the cold mold cavity will cool down quickly, while the material layer close to the hot mold cavity will continue to shrink, and the uneven shrinkage will make the injected plastic part warp. Therefore,plastic injection mold cooling should pay attention to the cavity, core temperature tends to balance, the temperature difference between them can not be too large.
In addition to considering the plastic injected parts of the internal and external surface temperature tends to balance, should also consider the plastic parts of the same temperature on all sides, that is, when the mold cooling to try to keep the cavity, core temperature uniform throughout, so that the plastic parts of the cooling speed balance, so that the contraction of all more uniform, effectively prevent the generation of deformation. Therefore, the arrangement of cooling water holes on the die is very important. After the distance between the pipe wall and the cavity surface is determined, the distance between the cooling water holes should be kept as small as possible to ensure the uniform temperature of the cavity wall. At the same time, as the temperature of the cooling medium increases with the length of the cooling channel, the temperature difference of the mold cavity and core along the channel occurs. Therefore, the waterway length of each cooling loop is required to be less than 2m. Several cooling loops shall be provided in large molds, with the inlet of one loop located near the outlet of the other loop. For long plastic parts, the length of the cooling loop should be reduced, that is, to reduce the temperature difference between the mold, so as to maintain uniform cooling injected plastic parts.
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