Common Defects in Plastic Injection Mold

As we all know, some defects often occur in injection molds after forming, which seriously affects the normal use of the workpiece, and even leads to the unusable workpiece, which will seriously affect the cost and efficiency of the manufacturing workpiece. Therefore, we must do a good job of preparation before moulding, and find out the specific causes of these defects.

  1. Lack of glue.


(1) If one of the multi-mode cavities lacks glue, it may be due to the different size of the inlet point or the different length of the channel of each cavity.


(2) The bad exhaust of the die can also cause the lack of glue, but often accompanied by burning.




(1) Shrinkage caused by uneven wall thickness of products.


(2) Shrinkage caused by uniform wall thickness.


Phenomenon: There are reasons for wave phenomenon on product surface: (1) It may be that Cushion volume of injection molding machine has no or insufficient. (2) It may be countercurrent to prevent the valve from acting smoothly.


  1. 3.Charring


Suggestion: Grind the exhaust gas on the mold, or change the water level to the conducive exhaust place.



  1. 4.Black stripe


Phenomenon: The product extends from the black strip placed in the water level.


  1. The surface gloss of the product is not good, and it is cloudy.


  1. Silver stripes: A uniform line appears in the direction of the rubber flow.


  1. Flow marks: The product’s water inlet is the center of the wave.


  1. Weld marks:


Fusion line generated at the hole of the product.


(1) It is very difficult to completely eliminate the weld lines.


(2) The number of water entry points also affects the number of weld marks.


(3) Other ways to consider improvement:


A: Change the water entry method.


B: Increase the exhaust equipment.


C: Bone where the weld line appears.


  1. Jet flow: form earthworm-like lines in the water inflow part.


(1) Other improvement methods:



The obstruction needle can be added to the place where the water-entering glue is flowing in.


  1. Impurities: Mixed impurities in products


Other reasons: Runner cold slug well does not save light. To produce debris during ejection and to remain in the cold well. Make the surface of the product appear impurities.


JasonMould Industrial Company Limited, established in 2010, is a leading China mold factory. JasonMould specializes in plastic mould production for household appliances, medical equipments, electronic equipments, safety equipments as well as monitoring system.

The company has over 15000 square metres factory. With plastic injection tooling divisions possessing different machinery and expertise, JasonMould offers tools from small and precise mobile phone parts to as big as automotive parts. Our tools are mainly exported to U.S.A., Europe, Japan and UK. JasonMould’s diversification strategy and full service has won compliment from customers all over the world.

Our mission is to provide our customers high quality moulding products and services. We aim to exceed our customers’ expectations of pricing, quality and on-time delivery. To achieve our mission, JasonMould:

  • Commits to continually improve employee skills and efficiency,
  • Provides our employees a clean and safe working environment,
  • Upgrades machine technology and support equipment through a strict maintenance program, and
  • Maintains customers’ tooling to its highest peak of performance

For more about China injection molding cost,please visit

Inquiry Contact:

Contact person: James Yuan

Company name: JasonMould Industrial Company Limited

Address: LongGang Village,LongXi Town,BoLuo County,HuiZhou City,GuangDong Province, China

Telephone: 86-752-6682869

Email: [email protected]


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