A dynamic mixer and associated injection molding system for mixing a melt flow. The injection molding system includes: a hot runner assembly having a plurality of splits; an injection unit that delivers a melt flow to the plurality of splits in the hot runner assembly via a melt channel; and a dynamic mixer incorporated into the melt channel upstream from the plurality of splits, wherein the dynamic mixer includes a rotor assembly configured to be rotationally driven by the melt flow, and wherein the rotor assembly is further configured to mix the melt flow passing through the melt channel.