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Why there is welding mark on plastic injection products?

Jan. 18, 2017

I: Causes: 1-1 the cooling solidification of the front part of molten material

1-2 the volatilized material is sealed

1-3 there is mold release agents in cavity

II: Links:

2-1 using one sprue gate, there is no welding mark as the molten material does not come from two directions. Besides, if want to avoid marks, there needs to change gate position which can make welding mark appear in an inconspicuous place

2-2 generally the marks occur on the mold pin holes (i.e. the hole on the products)

2-3 the welding mark occurs due to the air is closed, so it has to make sure the air completely escape

2-4 this method is taken sometimes: make the marks occur on the surplus flake of the plastic products, and then cut the flake off

2-5 the mold release agent is used too much which lead to molten material bubble to flow into cavity, the welding marks certainly occur

III: Solutions:

3-1 timely method: to improve the injection speed, increase mold temperature, raise the barrel temperature and increase injection pressure

3-2 short-term: to add air escape groove

3-3 long-term: to change the sprue gate position

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