Analysis and solutions for ejection defects in online injection molding services

Ejection, also known as ejection marks or ejection drool, refers to the phenomenon of fibrous streamlines at the gate of plastic products, which usually occurs when the mold uses a side gate. When the plastic melt flows through narrow areas such as nozzles, runners and gates at high speed, it suddenly enters an open, relatively wide area. The molten material will bend forward like a snake along the flow direction and cool rapidly after contacting the mold surface. Because this part of the material is not well integrated with the resin that enters the cavity later, obvious ejection lines appear on the surface of the product.

Under certain conditions, the resin is ejected from the nozzle at a relatively low temperature at the beginning. Before contacting the cavity surface, the viscosity of the resin will increase significantly, resulting in a serpentine flow. As the higher temperature melt continues to enter the cavity, the initial material is squeezed to a deeper position in the mold, leaving ejection marks.

Nozzle drooling failure analysis and troubleshooting methods

1. Improper operation of process conditions

– The local temperature at the nozzle is too high: the nozzle temperature should be appropriately reduced.
– The melt temperature is too high: the barrel temperature should be lowered or the molding cycle should be shortened, and a filter screen should be set in the nozzle.
– The residual pressure in the barrel is too high: the injection pressure should be appropriately reduced, the residual pressure time should be reduced, and the injection time should be shortened.
– The nozzle aperture is too large: it should be replaced with a small aperture nozzle, or a spring needle valve nozzle and an inverted slope nozzle should be used.

2. The raw material is wet and does not meet the use requirements

– Excessive moisture content in the molding raw material can also cause nozzle drooling. For this, the raw material should be pre-dried or a hopper dryer should be used.

3. The hot runner mold design is unreasonable

– In the hot runner mold, in order to prevent nozzle drooling, a device that can release the residual stress in the manifold should be set.

Through the analysis and solution of injection defects, online injection molding service providers can effectively improve product quality, reduce defects, and ensure the smooth progress of the molding process.