This question arrived this morning via email…
We are processing polycarbonate and are having problems with short molding as well as silver streaks. The mold design is a hot runner system with three drops.
For the silver streaks, I suggest you ensure the material is properly dried. A dewpoint meter or moisture analyzer should be incorporated to ensure the material is dry enough for processing. It is also advisable to pull the screw and clan both the screw and barrel to ensure there is no buildup contaminating the material. It is also advisable to use a temperature probe to ensure the material temperature is at the manufacturer’s recommended setting.
As for the short shots, you may need to develop a more robust process better capable of handling variation. for more on this, please consider reading the following: