Balancing parts from PC

[luboss23]

Hi, I have a problem with balancing parts from PC (Apec). One cavity is full filled and the second about 90%. I thought it is easy. I will increase the temperature of the hot-runner. But when I did it, there was no change at all. So I started to decrease the temperature of the cavity Nr.1. The steps were 5°C, but from 310°C to 255°C there was not any effect - the cavities were filled stil the same. When I change the temperature to 250°C the hot-runner was "frozen" - no melt at all. I have no experience with PC so I would like to ask: Is it standard behavior of the PC, or it could be caused by the hot-runner?

Thanks for any ideas.

Lubos

P.S.: I apologize for my English

[brentb]

Have you performed a Cavity balance study?

KOM

brent

[Jendalf]

Hi Lubos,

pictures illustrating the problem are always appreciated :)

J

[joeprocess]

Check fill only cavity balance as suggested. Also, can the lagging part be packed out or does the flow front just freeze off?

[luboss23]

Yes, I have. And it is clear, that one cavity fills better than the other one. The second one is lighter. When I set the hold pressure on and both cavities are full filed the measurements are different. I think, there is some differencies between the "tunnel gates"(I don´t know if it is the right word in english). Now we must produce, because we are in lates, but when the productions stops, I will let check the gates in tool shop. But I still do not understand the behavior of the melt, when I decrease the temperature and nothing´s hapened... :-/ Normaly when I set the temperature on HR lower I can see it on the parts. But here... Nothing. And then - it is "frozen" :-(

[luboss23]

Hi Jendalf,

ok - as soon as I will be at work (On monday) I will make some... ;-)

[luboss23]

Check fill only cavity balance as suggested. Also, can the lagging part be packed out or does the flow front just freeze off?

When I set the same temperature on both HR and switch the hold pressure off, one part is filled to about 98% and the second one about 90%. And when I decrease the better filed cavity HR it is still the same. When I reache the temperature of about 250°C it freeze off - neither cold sprue is filled...

[rickbatey]

I think you need to measure the part dimensions because I'll bet one is thicker than the other based on the hot runner temps not affecting the filling of the cavities. It could be an issue inside the hot runner tips, manifold or even in the heating of the assembly. How many zones, the layout and temps, please?
Rick.

[luboss23]

I think you need to measure the part dimensions because I'll bet one is thicker than the other based on the hot runner temps not affecting the filling of the cavities. It could be an issue inside the hot runner tips, manifold or even in the heating of the assembly. How many zones, the layout and temps, please?
Rick.

Ok I will organize the measuring of the parts. Till now we measured only the lenght and it is different.
There are four zones: Input, manifold and two runners. It injects to the cold sprues (quite small) and then there are tunnel gates to part. Temp: 320, 320, 310, 310 °C.
On monday I will take some pictures and publish them here.

[Josue]

How about the gates diameters , Did you already mesure and compare?, how many injection gates do you have, are all same dimensions?

Best regards