What are the types of injection molding defects

What Are Injection Molding Defects

During the molding process of plastic products, due to varying processing equipment, differing molding performances, and a wide variety of raw materials, coupled with the operating conditions of the equipment, the cavity structure of the molds, and the rheological properties of the materials, the intrinsic and external quality of the parts often exhibit various defects.

Types Of Injection Molding Defects

1. Bubbles
Description: Bubbles refer to bubbles or voids formed when the gas generated in the plastic fails to be discharged in time during the injection molding process.
reason:
-The material contains moisture or volatile substances.
-The mold design is unreasonable and the exhaust is poor.
-The injection temperature is too high, causing the material to decompose.
2. Short Shot
Description: Short shot refers to the failure of the molten plastic to completely fill the mold cavity during the injection molding process, resulting in missing parts of the molded part.
reason:
-Injection pressure is insufficient or injection speed is too slow.
-The mold temperature is too low, resulting in poor plastic fluidity.
-The flow channel design is unreasonable, resulting in excessive flow resistance.
3. Shrinkage marks
Description: Shrinkage marks are depressions or uneven lines on the surface of a molded part, usually caused by the cooling process.
reason:
-The shrinkage of the material is high.
-The mold design is unreasonable and the cooling channel layout is uneven.
-Improper setting of injection molding parameters, such as insufficient holding time.
4. Surface Defects
Description: Surface defects include scratches, dents, bubbles, etc., which affect the appearance quality of the product.
reason:
-The mold surface is poorly treated and has scratches or dirt.
-Uneven material flow during the injection molding process, resulting in an uneven surface.
-Improper design of ejector pins or other mold components, causing damage to the product surface.
5. Transformation
Description: Deformation refers to the change in shape of the molded part after cooling or demolding, which cannot meet the design requirements.
reason:
-Improper mold design leads to uneven force on the molded parts.
-Insufficient cooling time, the plastic did not fully solidify.
-Improper temperature control during the injection molding process leads to material stress concentration.
6. Gate marks
Description: Gate marks refer to the obvious marks left on the molded parts due to the gate position, which affects the appearance.
reason:
-The gate design is unreasonable and the location is inappropriate.
-The gate size is too large, resulting in surface defects on the molded part.
-Using cold runner system failed to effectively reduce gate marks.
7. Warpage
Description: Warpage refers to the distortion of the shape of a molded part due to uneven shrinkage during the cooling process.
reason:
-The mold design is unreasonable and the cooling channel layout is uneven.
-The shrinkage of materials varies greatly.
-Improper setting of injection molding parameters leads to uneven cooling rate.

Conclusion

We cannot say that we can do it completely without defects, because defects are almost inevitable in all injection molding production. But the really good injection molding companies are those that can respond quickly to defects and solve problems effectively, and we have been working towards that.