PS product is very easy to crack and has poor impact resistance. Many customers have the problem with their moulds to manufacture PS product. There is a little crack or something like that, not smooth of surface. Then how to effectively avoid PS cracking during mould injecting? Then how to solve this problem?

Many customers will reduce cooling time, or reducing water from both side of the mould. This method is not completely acceptable because demolding the part with high temperature causing warping and this is undesirable for assembling of the part. Or faster injection speed to inject more speed is creating more flash. These can work to aviod PS crack, but not everythingtime. Crack of PS material is occuring from cycle to cycle. Then what can we do about this problem?

At first, you need to check draft and tool finish in this area. Too little draft and the part will be cracked while opening the mould. Check the steel temperature, poor or too much cooling could cause this as moulded in stress from different cooling. You may have a poor knit line to improve air venting of this area. Check how much radius is on the inside and outside of the part, the thickness and the radius is important.

And if it is crack when the mould is opened, before ejection, it could be from sticking in the stationary half of the mould. This maybe caused by uncorrectly moving of the inserts. You need to adjust the timing or polish.
Sino Holdings has rich experiences in molding field, we have successfully manufactured glass moulds, PS petri dish moulds, PS airline cup moulds, PS tableware moulds, etc.

If you have any question or comment, please feel free to contact with me.

Miss Diana

dkm@dakumar.com

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