What to do if dents appear in plastic products

What to do if dents appear in plastic products

The thickness of each part of the product is different, the internal pressure of the mold is insufficient, the mold is not sufficiently cooled, and the deformation caused by the insufficient cooling time is related to the knowledge. In the process of producing the product, the dent is the most frequent occurrence of the bad phenomenon. The plastic shrinks when it cools. The part that is cooled early is the surface that hardens first, and air bubbles will be generated inside. The so-called dent is that the part that cools slowly produces a prominent concave surface in the direction of the bubble shrinkage.

凹 Materials with high shrinkage are also prone to dents. When changing the molding conditions to eliminate dents, the setting conditions should be set in the direction of small shrinkage. That is, the mold temperature and the barrel temperature decrease, and the injection pressure increases, but it should be noted that this may cause residual internal stress. Because the indentation is not conspicuous, if it does not affect the appearance, it is intentionally processed into a corroded pattern on the mold, such as grain, grain, etc. In addition, if the molding material is HIPS, it is also effective to reduce the smoothness by lowering the mold temperature.

However, once these methods have dents, it is difficult to repair polished products. The solution is immediate: increase the injection pressure, extend the injection dwell time, reduce the barrel temperature and the mold temperature, and force the cooling in the place where the dent is generated. Short-term: make ups where dents occur. When there is a small space in the material passing edge where the dent is generated, make this part thick. Long-term: Differences in thickness of the design product should be completely avoided. The ribs that are prone to dents should be as short as possible.

Differences in materials The molding shrinkage material is large, and the dent is also large. For example, PE, PP, dents will be produced even if the ribs are slightly reinforced. Material shrinkage rate PS0.002 ~ 0.006PP0.01 ~ 0.02PE0.02 ~ 0.05 Five reference points 1. When the temperature is reduced to not produce dents, if there is still pressure in the material in the cavity, it should be considered There are dents. The pressure of the material surrounding the mold in the mold, that is, the static pressure, is not necessarily anywhere.

The pressure near the gate is high. If the through edge of the material is wide, the pressure difference between the near gate and the place far away from the gate is small compared with the overall pressure, and no depression will occur due to the pressure transmission to all corners. It is also possible to obtain a product without any internal stress remaining. However, when some materials flow into the place where it is difficult to flow, there is high pressure in this place, and the pressure drop in other places will cause dents. This part of the high-pressure residue is the internal stress of the product is also large.

In the ideal state, the temperature of the material rises with the temperature of the mold, the material fluidity is better, and the injection also changes to the bottom in the static pressure state. When changing the molding conditions, the combination of temperature, pressure, and time should be made in advance, and the order should be performed in order to know the results early. First of all, after a long time, it is easy to know every small change in pressure. It should be noted that the results obtained when the temperature changes should be obtained after injection and after the temperature has dropped.