Meaning
Precise positioning of the shut-off needle within the gate orifice ensures a clean and reliable seal. Correct valve gate pin alignment prevents the pin from hitting the sides of the gate, which would cause wear and damage. It also ensures that the pin closes completely to stop the flow of plastic at the end of the injection cycle.
This alignment is critical for achieving a high-quality gate vestige on the moulded part.
Mechanical Guidance
Supporting the pin along its entire length helps maintain its position as it moves. Good valve gate pin alignment relies on tight tolerances in the nozzle and the manifold where the pin is held.
Thermal Stability
Changes in temperature can cause the components to shift and pull the pin out of centre. Designers account for this by ensuring the valve gate pin alignment is correct at the operating temperature of the hot runner. This often involves using the expansion of the manifold to bring the pin into its final position.
Part Finish
Producing a part with no visible gate mark is the main reason for using a valve gate system. When the valve gate pin alignment is perfect, the pin seats flush with the cavity wall and leaves a nearly invisible mark. If the alignment is off, the pin will leave a step or a ring on the surface of the plastic.
Misalignment also increases the risk of the pin seizing within the nozzle body. Regular inspection of the pin tip reveals the early signs of contact with the gate insert.
