Main runner nozzle, also calls the central nozzle . The main flow  nozzle may  direct inject to molding plastic products cavity, also does not have the divergence and the manifold. This kind of hot runner nozzle is called as the single nozzle. Because it only has a hot runner nozzle in the mold injection process, it is the standard seriation hot flow  single  nozzle. Other kind of main runner nozzle's downstream, needs to diverge the plastic melt, also has many nozzle injection cavity, this is the multi nozzle hot runner system. Has the hot runner single  nozzle inject mold to decompose structure as shown in Figure 3-1. This kind of single nozzle commonly used four kind of runner form.

Figure 3-2 is the direct gate, other three kinds are a thimble type runner. Direct gate's single nozzle permission has the long thick plastic melt channel, leaves the large diameter material handle on the plastic. The direct runner single nozzle, the runner has the taper, advantageous leaves is also long the thick material handle. It can inject the big depth molded cavity shell, like barrel, box place and so on. In the main runner nozzle passage, the melt transmission's pressure loss is small, also does not have the divergence to say. Permission of injection cavity  when sufficient mold flowing has the long flow compared to, may inject the thin wall long flow the shell. Moreover this kind of single central positive runner, the formation shell orientation is good, also does not have the melt perfect fitting of seams.