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How to deal with dents in plastic products

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Update time : 2021-07-15 11:41:12

The reason of dent
1, The thickness of each part of the product is different
2, The pressure is insufficient in the mold
3, Mold colling are not sufficient
4. Deformation due to insufficient cooling time
 
Knowledge
 
1.During the production of the product,the dent is the highest frequency, the plastic injected into the mold occurs in the incompatibility of the mold,and the surface is hardened in avance,and the inside will generate bubbles.It is so called dent. The slow portion prominent concave surface in the direction of bubble contraction
2. Materials with large shrinkage are also prone to dents. When it is necessary to change the forming conditions to eliminate the dents, the setting condition should be set to the direction of receding. It means the mold temperature, the tube temperature is lowered, and the injection pressure is increased, but it should be noted that the residual internal stress may be caused.
 
  1. he dents are good if not obvious ,so  if it does not affect the appearance, it is intentionally processed into corrosion on the mold, such as a stripe and granular. What’s more , if the molding material is HIPS, it also has an effect with reducing the smooth of molding. However, once there is a dent, it is difficult to repair the polishing product.
 Solution
  1.  : Improve the injection pressure, extend the injection pressure time, reduce the tube temperature and the mold temperature, and forced cooling in the place where the dent is generated.
2, Short term:Fill the dent according to the samll aisle on the depressed area.
3.Long-term: It should be completely avoided the difference in the thickness of the design. It is easy to generate a reinforcing ribs of the dent, and the narrow shape should be as short as possible.
 
. The difference in materials
 
 The material with large formation of shrinkage,the dent also big.
For example, PE, PP, even if a slightly reinforcing rib is slightly reinforced, the shape with neguli should be short.
Material forming shrinkage
PS0.002 ~ 0.006
PP0.01 ~ 0.02
PE0.02 ~ 0.05
 
V. References:
 
  • When lower the temperature to the no dent, if there is pressure in the mold cavity, it should be considered that there is no dent. The pressure around the mold is static in the mold, no matter where it is not necessarily.The pressure on the gate is high, if the side of the material is wide, since the pressure on every corners, the pressure the near gate compare with the pressure on the whole part is small,there is no dents. Therefore, you can get products that do not residual internal stress. Some materials are high pressure in this place where there is a difficult place, and the pressure reduction in other places will generate dents. This part of the residual residue is that the internal stress of the article is also large. In the ideal state, the material temperature is rising with the temperature of the mold, and the material is well fluid, and is shot in the static pressure state.
 
b.When changing the molding conditions, the combination of temperature, pressure, and time should be prepared in advance, and the results can be known in order. The first time the time has become very long, it is easy to know the minute changes. It should be noted that the result of obtaining temperature changes should be obtained after the injection material, the like temperature is lowered after production. What should I do if my plastic product dent?