Common problems with nozzles

During the injection molding process, the phenomenon that the melt cannot enter the mold runner is called nozzle clogging. The causes and improvement methods of this phenomenon are shown in the table.

Reduce melt temperature or nozzle temperature

Reduce back pressure or screw speed

Increase the amount of glue (pump glue before or after melting)

Use a nozzle with a small aperture or a self-locking nozzle

Switch to plastic with higher viscosity

Change to injection molding with movable injection molding

When plasticizing plastics, the phenomenon of melt flowing out of the nozzle is called nozzle casting. In contact injection molding production, if the nozzle is cast and the melt flows into the main runner, the cooled plastic will affect the smooth progress of injection molding (blocking the gate or runner) or cause appearance defects on the surface of the plastic part (such as cold spots, shrinkage, Lack of material, etc.), especially for plastics with good flow properties, such as PA materials, which are prone to nozzle casting. The causes and improvement methods of nozzle casting are shown in the table.

Reduce melt temperature or nozzle temperature

Reduce back pressure or screw speed

Increase the amount of glue (pump glue before or after melting)

Use a nozzle with a small aperture or a self-locking nozzle

Switch to plastic with higher viscosity

Change to injection molding with movable injection molding

During the injection molding process, the phenomenon that hot plastic melt flows out of the nozzle head or the connection between the nozzle thread and the barrel is called nozzle leakage. Glue leakage in the nozzle will affect the normal production of injection molding. The lighter ones will cause the product weight or quality to be unstable, and the heavy ones will cause the plastic parts to shrink, lack of material, burn out the heating coil and other undesirable phenomena, thereby affecting the appearance of the product. The reasons and improvement methods for nozzle leakage are shown in the table.

Re-align the nozzle or check the matching of the nozzle head and the mold

Tighten the nozzle thread or replace the nozzle

Reduce back pressure or screw speed

Reduce nozzle and barrel temperature

Appropriately increase the distance of pulling glue

Switch to plastics with low melt index (FMI)