A hot runner

A hot runner mould is similar to the three plate mould apart from that the sprue and
runners are kept in a molten state by electrical heaters, so the runner system does
not have to be discharged with the part. In accession to eliminating regrind, hot
runner systems eliminate runner system cooling, time is eliminated from the
production cycle, and the shot size is decreased by the size of the sprue and
runners.