(3) The diameter of nozzle inner hole is too large or too small. If it is too small, the specific volume of the strip increases due to the small flow diameter, which is easy to cool, block the feed channel or consume the injection pressure;

If it is too large, the flow cross-sectional area is large, and the pressure per unit area of plastic molding is low, resulting in a small injection force. At the same time, non-Newtonian plastics such as ABS can not reduce the viscosity because they do not obtain large shear heat, which makes it difficult to fill the mold.

The nozzle is poorly matched with the inlet of the main flow channel, which often leads to overflow outside the mold and insufficient filling in the mold. The nozzle itself has great flow resistance or is blocked by foreign matters, plastic carbonization deposits, etc; The spherical surface at the inlet of nozzle or sprue is damaged and deformed, which affects the good cooperation with each other;
The mechanical failure or deviation of the injection seat causes the tilting displacement of the nozzle and the axis of the main flow channel or the separation of the axial compression surface; The nozzle ball diameter is larger than the inlet ball diameter of the main flow channel. Due to the gap at the edge, the axial pushing force of the nozzle will gradually increase under the pressure of overflow, which will cause dissatisfaction of the product injection.