Cold runner

Where it comes up

• Plastic injection moldingMolten thermoplastic injected into a steel or aluminum mold. Lowest piece price for plastic parts at 5,000+ a year.

Related terms

Hot runner

A hot runner is a heated manifold and nozzle system inside an injection mold that keeps plastic molten all the way to the gates. It eliminates runner scrap and often shortens cycle time, but it adds several thousand to tens of thousands of dollars to the mold, plus controller maintenance.

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.

Shot size

Shot size is the volume or weight of material injected into a mold in one cycle, including parts and runners. Molders typically want a shot to use about 20–80% of a press's barrel capacity to avoid degraded resin or inconsistent fill. In die casting, shot size drives machine and shot sleeve selection.