Injection Molding: Controlled Production Shutdown For PET Preform Molding
Netstal machine uses stored braking energy to maintain power during brief outages and allow controlled shutdown without short shots.
In harsh industrial environments, even brief power failures or fluctuations in the grid lasting milliseconds can interrupt the molding cycle, which cannot always be restarted immediately because of the potential presence of short shots in one or more cavities. In PET preform molds with many cavities, removal of short shots can be laborious and carries the risk of damage to the mold.
Consequently, Netstal (U.S. office in Florence, Ky.) is offering a new option for its PET-Line preform molding systems. Called CPP, for Controlled Production shutdown during a Power outage, it will provide enough power to complete the current cycle. (This power comes from braking energy recovered by the drive system.) And if the outage lasts longer, then sufficient power is provided to reliably and controllable shut down the process.
After the previous shot is fully injected and demolded, metering of the next shot is stopped and the entire system is brought to a halt. All axes are returned to their end position. As soon as the power returns, production can be started up again.
Producing plastics parts with undercuts presents distinct challenges for molders.
If you were buying an injection molding machine 20 years ago, you had to decide between a toggle or fully hydraulic clamp and that was pretty much it.
Modifications to the common core pin can be a simple solution, but don’t expect all resins to behave the same. Gas assist is also worth a try.