Cold shut

Where it comes up

• Zinc and aluminum die castingMolten zinc or aluminum injected into steel dies at high pressure. Thin walls and net shape at 2,500+ parts a year.

Related terms

Porosity

Porosity is voids inside a cast or sintered part, caused by trapped gas or by shrinkage as metal solidifies. In die castings it can cause leaks and weaken machined surfaces. It is controlled with gating, venting, and vacuum assist, and pressure-tight parts are sealed by vacuum impregnation.

Knit line

A knit line is a visible line and potential weak spot where two flow fronts of molten plastic meet and fuse inside a mold, usually around holes or bosses. In glass-filled resins, knit line strength can drop to half of the base material or less. Gate location controls where knit lines fall.

Gate

A gate is the opening where molten plastic or metal enters the mold cavity from the runner. Gate type, size, and location affect fill, knit lines, sink, and the mark left on the part. Common types include edge, submarine, pin point, and valve gates.