How to improve the production of weld lines in injection molding

- Nov 24, 2018-


There are often many new injection molding techniques in injection molding plants, and the causes of weld lines in injection molding are caused by the fact that the fusion of plastic products from different directions is not fully integrated at the joint. During the injection process, the two resin streams at the fusion site do not mix with each other; therefore, the lower the temperature, the more pronounced the fusion mark and the lower the strength. On the contrary, the higher the temperature, the stronger the adhesion. The bonding condition at the fusion also depends on the pressure applied there. The lower the holding pressure, the worse the fusion and the lower the strength. Fusion is the junction of the resin, and may also be the flow end. In the weld mark of the plastic product, if a gas outlet is not provided at this position to discharge the gas, the appearance and strength of the fusion are deteriorated.


Improvements: 


l) increase resin temperature, increase mold temperature, increase injection pressure and speed;


2) Pay attention to the exhaust of the parting surface, and increase the insert and the thimble at the place where the weld line is generated, which is also advantageous for exhausting.


3) Select a reasonable feeding position, and mold flow analysis is best before plastic products are opened;


4) Increase the process overflow and discharge the cold material, and then cut and remove it after molding.


5) Extend the runner system as much as possible to improve the glue removal;


6) The rough surface product can choose the coarse grain surface as much as possible, which is also beneficial to improve the weld line;


Technology is developing and technology is improving. I will not list them here. Better technology is waiting for everyone to specialize!


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