Glossary
Hot chamber and cold chamber — definition
Two die casting machine types: hot chamber has the pump submerged in the melt and is used for zinc, cold chamber doses the melt for each shot and is used for aluminium.
In a hot chamber machine the injection system sits submerged in the melt. That gives very short cycles, but requires a metal that does not attack the steel of the pump — which is why it is used for zinc and other low-melting alloys.
In a cold chamber machine the melt is dosed into a separate shot sleeve for each shot and injected from there. That is slower, but necessary for aluminium, which would dissolve a submerged pump system.
This explains a practical difference: zinc parts generally have shorter cycle times than comparable aluminium parts.