What Are The Problems Of High Back Pressure In Plastic Injection Molding?

Plastic injection processing

What are the main injection process parameters of plastic injection processing technology? Flow of materials. Changes in the process of melt flow / shrinkage / hardening. The master at this stage must have perspective in order to see through the changes of the melting material in the machine / mold. How? Where will stress occur after shrinkage? How to transfer heat? Why is there internal pressure? What will happen? This ability is where this realm is higher than the previous realm. If the third area appears with fewer indicators on multiple indicators from the outside to the inside, the area from the inside to the outside, in which the defect corresponding to the fishbone diagram is meaningless, and the parameters become very simple. When processing plastic molds, excessive back pressure may cause the following problems:

The melting pressure at the front of the barrel is too high, the material temperature is high, the viscosity decreases, the molten material flows back in the screw groove, the water leakage flow between the barrel and the screw gap increases, and the plasticizing efficiency (the amount of material that can be plasticized per unit time) decreases.

For plastics with low thermal stability (such as PVC, POM, etc.) or colorants, the melt temperature increases and the barrel heating time increases, resulting in an increase in thermal decomposition or colorant discoloration, and a decrease in the color / gloss of the product surface.

The back pressure is too high, the screw retreats, the pre plastic recharging time is long, the cycle time increases, and the productivity decreases. 


Plastic mold processing

The back pressure is high and the pressure of molten material is high. The nozzle is prone to molten drool after injection. When the adhesive is injected next time, the cold material in the nozzle channel will appear cold material spots on the nozzle or product.

In the process of beer plastic, the back pressure is too large, the nozzle leaks, wastes raw materials, and the heating ring near the inlet burns a lot.

When processing plastic molds, excessive back pressure will increase the mechanical wear of pre plastic mechanism and screw barrel.

Post time: Apr-10-2022