What is hot runner
Hot runner system is an assembly of heated components—hot halves, nozzles and gates and—that inject plastic into the cavities of an injection mold. The system usually includes a heated manifold and a number of heated nozzles. The manifold distributes the plastic entering the mold to the nozzles, which then meter it precisely to the injection points in the cavities. The hot runner is equipped with its own temperature control system.
It has several advantage
· Save raw material and reduct the cost
· Shorter cycle time and improve the machine efficiency.
· Improve product surface quality and mechanical properties
· Do not need to use three plate mould can direct use spot gate
· Easier to start: Without runners to remove, and auto cycle occurs faster and more frequently
· Fewer sink marks and under-filled parts: Unlike when plastic flows through a cold runner and loses heat to mold plates
· Design flexibility: Can locate the gate at many points on the part
· Balanced melt flow: Separate melt channels are in externally heated manifolds that are insulated from mold plates surrounding them
Compared with cold runner
Cold runner is simply a channel formed between the two halves of the mold, for the purpose of carrying plastic from the injection molding machine nozzle to the cavities. Each time the mold opens to eject the newly formed plastic parts, the material in the runner is ejected as well, resulting in waste. A hot runner system usually includes a heated manifold and a number of heated nozzles. The main task of the manifold is to distribute the plastic entering the mold to the various nozzles which then meter it precisely to the injection points in the cavities