Glossary
Gate and runner — definition
The channel system that carries the melt from the machine into the cavity, and the point where it enters the part.
Where the gate sits determines how the cavity fills, and therefore where the porosity, the cold shuts and the weak zones end up. It is one of the most consequential decisions in the whole tool design.
A well-placed gate fills the cavity under control, pushes the air ahead of it towards the overflows, and lets the critical sections solidify under pressure.
The gate has to be removed after casting and leaves a mark. It should therefore sit on a face that is neither visible nor functionally critical.