Thermal Gating

Thermal gating or hot tip gating generally represents a more economic mold investment compared to valve gating, however hot tips have a tighter processing window and are more sensitive to operate.

The cyclical function of a thermal gate hot runner is much more complex than that of a valve gate because it does not have the benefit of positive shut-off pins that can open and close the gate orifice. The thermal gate forms a small, solidified, cold plastic slug inside the gate bore during the cooling time of the plastic part. This slug remains in the gate during the mold open phase, part ejection and mold close motion. With the next injection the pressurized melt flushes the cold slug into the melt stream that fills the empty cavity. While all molding parameters (pressure, temperature and time) are still focused on producing a quality plastic part, they are also responsible for the formation of the thermal gate at every cycle to avoid drooling and stringing of the gate. If gate quality is a critical factor, valve gated hot runner systems are generally recommended as they offer more processing control.