Hot runners often have multiple low or zero-flow areas, so it is good practice to remove any heat sensitive resin from the hot runner prior to extended shutdown, or mold storage. First, clean the hot runner using either the open or closed mold method. Then, at low screw speed, extrude a sealing grade purging compound through the mold. Finally, turn off the hot runner temps and follow standard mold storage procedures.

Upon startup, turn on heats in the mold, and allow the purge to become completely melted and ready to flow. Purge the mold with a small amount of purging compound to make sure there is no degraded material present. Then, flush with next production resin. Once the parts are free of purging agent, begin production.