Meaning
Compact gas-driven piston used in an injection mould controls the movement of valve gates or ejector pins to regulate the flow of polymer or to assist in part release. This pneumatic pin actuator provides a clean and reliable mechanical movement that does not risk hydraulic fluid contamination within the moulding area.
Mechanical Drive
Pressurized air enters the cylinder to drive the pin forward to block the gate, or backward to allow the molten polymer to fill the mould cavity. Unlike spring-returned pins that can lose force over time, the dual-action pneumatic pin actuator utilizes positive air pressure for both the forward and reverse strokes to ensure positive shut-off. This consistent operation is necessary for multi-cavity hot runner systems where synchronised gating prevents unbalanced filling.
Defect Prevention
Valve gating with these actuators eliminates the gate stub or vestige that typically remains on the surface of the moulded part. By closing the gate mechanically while the resin is still molten, the system produces a clean, cosmetic finish that requires no secondary trimming. This clean gate is particularly important for medical devices where surface protrusions or loose plastic debris cannot be tolerated.
Operational Limit
High ambient temperatures within the hot runner manifold can degrade the elastomeric seals of the cylinder, leading to pressure loss and sluggish action. To maintain reliability, the system requires filtered, regulated, and lubricated air supplies, alongside thermal isolation from the heated manifold plates.
