Valve gate systems, the alternate solution, offer injection molders increased flexibility and process opportunities that cannot be achieved with the use of thermal gate systems.

Typical valve gate systems are operated by either pneumatic or hydraulic cylinder mechanisms attached to hot runner nozzle pins that then open and close the gate area controlling the fill and pack of the injection molded part.
The automotive and electronics markets are examples where these specialized processes are necessary and include sequential, independent, and alternate fill and pack, as well as predictable gate opening and closing. The elimination of weld lines in single-cavity, multi-gated molds can only be achieved with the use of hot runner valve gate systems by cascading the filling and final pack. Backmolding—or the process of applying molten plastic to a fabric or other material—is another area where valve gate systems are necessary to achieve the cosmetic requirements of the customer.
Valve gate systems provide the optimum in cosmetic gate performance and also are necessary to stop drooling of molten plastic in vertical injection molding operation; yet, with all the advantages provided by their use, the vast majority of hot runner systems sold are still thermally operated.
Most of the time initial cost will be the determining factor for the thermal gate selection, and often the molder will forego the process benefits that can be realized with the use of valve gate designs.