Four stages of injection molding process

 Plastic products are inseparable from our lives, so the mold-opening production of plastic injection molds also becomes the most important part of the production of plastic products. A good mold will reduce the work of the assembler and increase customer satisfaction.

During the mold opening process of the injection mold. It mainly consists of four stages: filling-pressurize- cooling-demoulding. These four stages directly affect the quality of plastic parts. Good plastic parts are produced. The surface of the plastic part looks very smooth and there are no flashes on the edges of the product. But he poor plastic parts are produced with uneven coding,appeared flash, burrs and other problems.

1, mold filling stage:Mold filling is the first step in the process of producing plastic parts for all molds. The injection time is calculated from when the injection mold starts to run, until the cavity is filled to about 95%. In the case of normal mold production, the shorter of plastic filling time, the higher of product's molding efficiency.

2, maintaining pressure stage:The stage of mold pressure maintenance is also the continuous pressure application. As the pressure of the injection molding machine increases, the density of the plastic gradually increases. In the mold holding pressure process, the mold cavity is slowly filled with plastic, causing the mold back pressure to gradually increase. During the pressure holding process, the screw of the injection molding machine moves forward slowly , and the speed of the plastic is also relatively slow. In this case, the flow is called pressure maintaining flow. In the mold holding pressure stage, the plastic is cooled, resulting in faster curing, increased melt viscosity, and large resistance in the cavity. In the later stage of pressure holding, the material density continues to increase, and the plastic parts are also injection molded until the gate cures and the holding pressure phase ends. At this point the cavity pressure reaches the highest value.

3. Cooling stage:In the molding of the mold, the design and arrangement of the cooling system is also very important. Because the plastic product can only be cooled when the temperature of the injection mold cools down to a certain degree of rigidity, the plastic product can be reduced from being deformed by external forces to ensure the appearance of the product.

 4. Demoulding stage： The demolding phase is the last step in injection molding. Demoulding has a very important influence on the product. Improper demoulding may cause the surface of the product to be unbalanced during demoulding and cause defects such as product deformation when ejected. There are two common demoulding methods: stripper stripping and ejector stripping. When designing the mold, we must select the proper mold release method according to the structural characteristics of the product to ensure product quality.

Our normal production cycle of injection molds consists of mold closing time, filling time, pressure holding time, cooling time, and demolding time. The four are closely connected. If any one is missing, it will bring about waste products.