Four precautions for maintaining pressure in dual color mold injection molding:

1、 During the pressure maintaining process, the back pressure is high because the mold cavity is already filled with plastic. During the pressure maintaining compaction process, the screw of the injection molding machine can only move slightly forward slowly, and the flow rate of plastic is also relatively slow. At this time, the flow is called pressure maintaining flow. Because during the pressure maintaining stage, the plastic solidifies faster due to the cooling of the mold wall, and the viscosity of the melt increases quickly, the resistance inside the mold cavity is very high.

2、 In the later stage of pressure maintaining, the material density continues to increase, and the plastic parts are gradually injection molded. The pressure maintaining stage should continue until the gate is cured and sealed, at which point the mold cavity pressure during the pressure maintaining stage reaches a higher value.

3、 During the pressure holding stage, plastic exhibits partially compressible properties due to the relatively high pressure. In areas with high pressure, plastic is relatively dense and has a higher density; In the area with low pressure, the plastic is loose and the density is low, so the density distribution changes with location and time.

4、 During the pressure maintaining process, the plastic flow rate is extremely low, and the flow no longer plays a dominant role; Pressure is the main factor affecting the pressure holding process. During the pressure maintaining process, the plastic has already filled the mold cavity, and the gradually solidified melt serves as the medium for transmitting pressure. The pressure in the mold cavity is transmitted to the surface of the mold wall through plastic, which tends to support the mold. Therefore, appropriate locking force is required for mold locking. Under normal circumstances, the expanding force will slightly expand the mold, which is helpful for the exhaust of the dual color mold; But if the expansion force is too large, it can easily lead to rough edges, overflow, and even open the mold of the dual color mold.