Melt usually flows from nozzle into gate, but for some molds, nozzle is part of mold because it extends to bottom of mold. There are two main types of nozzles: open-ended and closed-ended. In injection molding production, open-ended nozzles should be used because they are cheaper and less likely to stay. If injection moulding machine is equipped with a pressure relief device, then even lower viscosity melts can use this nozzle. Sometimes it is necessary to use a closed-end nozzle, which acts as a check valve, blocking plastic in injection cylinder. Make sure that nozzle is properly inserted into nozzle sleeve, top hole is slightly smaller than nozzle sleeve, which makes it easier for nozzle to withdraw from mold. Nozzle sleeve hole is 1mm larger than shooting nozzle, that is, nozzle radius is 0.5mm thinner than nozzle sleeve radius.
Structural form and processing quality of injection moulding directly affect quality and production efficiency of plastic parts. There are many various injection moulding defects in injection molding production process and following are several common fault solutions.