Heater Coils
Heater coils are generally the most popular heating element of any type of hot runner system due to their very low initial cost and widespread global availability. This makes them ideal for creating economical hot runner systems with easy to source spare parts. Generally speaking, heater coils are ideal for low cavitation hot runner systems producing simple cost sensitive parts and/or limited production runs or hot runner systems with extended nozzle lengths that benefit from having multiple zones (automotive). When used on longer nozzles they can be more difficult to install/remove as they can be tightly coiled around the nozzle so they don’t slide off like heater band sleeves.
Because these elements are installed directly over top of the nozzle core, they operate with a very limited contact area which restricts heat transfer efficiency and requires more energy to operate. As there is no optimization possible with standard off the shelf components, the thermal profile is often more challenging to control and have the least precise thermal profiles due to thermal inconsistencies. The gate area temperature may not be as hot as the body since the heater band cannot run the full length of the nozzle as embedded elements can.
Depending on the manufacturer, heater coils may also require larger cut-outs to accommodate their external design and sometimes larger terminal ends and clamping mechanisms. In addition, they generally have the shortest lifespan of any heater type and usually require replacement within 1-3 years so spare part and downtime costs can quickly eat up any upfront savings from an initially low system cost.
