Pneumatic actuated valve stem technology currently makes up over 80 percent of the market. It is the most widely used technology in the medical, technical and closures markets.
There are several reasons why pneumatic systems are so widely applied. The technology uses a medium that is readily available in molding facilities—compressed air—to move the valve system.

The use of air makes it a relatively clean technology. Even the worst-case scenario of a leak does not warrant a huge clean up as in the case of a hydraulic oil leak. Pneumatic actuated systems are also easy to maintain and some require only one seal ring to operate. In addition, pneumatic technology offers simple system integration that everyone can use, yet still provides reliable actuation.

While pneumatic systems are fast, they can be limited in performance because air is typically available for up to only 100 psi. This limits the available stem force, especially in the case of small-pitch, individually-stem-driven systems with small piston diameters.

Special attention needs to be given to the setup of air supply hoses and solenoid valves to ensure proper operation. If incorrectly assembled (e.g., air lines too long; solenoid mounted too far from hot runner), valve stems can open and close with slight delays between pistons—causing inconsistencies in cavity filling. Despite these limitations, pneumatic systems are a very effective technology for the majority of applications and continue to serve as a viable gating solution.