Filling stage
Filling is the first step in the entire injection molding cycle, from the time the mold is closed to the injection, until the mold cavity is filled to approximately 95%. In theory, the shorter the filling time, the higher the molding efficiency; but in actual production, the molding time (or injection speed) is subject to many conditions.
Pressure holding stage
The role of the packing phase is to continuously apply pressure, compact the melt, and increase the density (densification) of the plastic to compensate for the shrinkage behavior of the plastic. During the pressure holding process, the back pressure is high because the cavity is filled with plastic. During the pressure-preserving compaction process, the screw of the injection molding machine can only slowly move forward slightly, and the flow speed of the plastic is also slow. The flow at this time is called pressure-holding flow. Since the plastic is accelerated and solidified by the mold wall during the pressure holding stage, the melt viscosity is also increased rapidly, so the resistance in the mold cavity is large. In the later stage of pressure keeping, the material density continues to increase, and the plastic parts are gradually formed. The pressure holding stage is continued until the gate is cured and sealed. At this time, the cavity pressure in the pressure holding stage reaches the highest value.
Cooling stage
In injection molding dies, the design of the cooling system is very important. This is because the molded plastic product can only be cooled and solidified to a certain rigidity, and the plastic product can be prevented from being deformed by external force after demolding. Since the cooling time accounts for about 70% to 80% of the entire molding cycle, a well-designed cooling system can significantly reduce molding time, increase injection productivity, and reduce costs. Improperly designed cooling systems can lengthen the molding time and increase the cost; uneven cooling will further cause warpage of plastic products.
Demoulding stage
Demolding is the last step in an injection molding cycle. Although the product has been cold-formed, the demoulding has a very important influence on the quality of the product. Improper demolding may result in uneven force during demolding and deformation of the product when it is ejected. There are two main ways of demolding: demolding of the ejector and demolding of the stripper. When designing the mold, choose the appropriate release method according to the structural characteristics of the product to ensure the product quality.
