A Gate is a small area between the runner and the part cavity. The type, size and location of a Gate in an injection mold is critical to efficiently producing quality parts.
The type of gate selected depends on many factors including:
Gate witness marks,
Filler used (if any),
and the Mold Plates used among others.
Small restrictive gates are preferred. Minimal sized gates provide a small witness mark, and detaching parts from the Gate/Runner is easier.
A single gate per cavity is desired, however, part size and the material used may dictate multiple gates to be used.
Locate the gate in an inconspicuous location of the part if possible. The Gate location should be at the thickest wall of the part (flow from thick ,to thin) and the thickness of the gate should be approximately two thirds the size of the wall.
The gate location and the surrounding area is also the highest area of stress in the final part. Do not position the gate at a location that part function indicates bending or impact strength is required.
There are two general categories of gates:
1. Automatic De-gating
Automatic de-gating includes Sub gates and 3-Plate Pin gates
2. Manual De-gating
All others generally fall into the Manual de-gating category.