Four stages of the mold forming process
Update time:2019/8/6 09:52
The injection molding process of the plastic parts involved in the production of the mold mainly includes four stages of filling - holding pressure - cooling - demoulding, and these four stages directly determine the molding quality of the product.
1. Filling stage
Filling is the first step in the entire mold cycle production process, from the time the mold is closed and the mold cavity is filled to approximately 95%. The shorter the filling time, the higher the molding efficiency.
2. Pressure keeping stage
The role of the packing phase is to continuously apply pressure, compact the melt, and increase the density 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.
3. Cooling stage
The design of the cooling system is very important in mold forming. Because the molded plastic product only cools and solidifies to a certain rigidity, the plastic product can be prevented from being deformed by external force after demolding. The molding cycle of injection molding consists of clamping time, filling time, holding time, cooling time and demolding time.
4. Demoulding stage
Demolding is the last step in a mold forming cycle. Demolding has a very important influence on the quality of the product. Improper demolding may result in uneven force on the product during demolding, and defects such as product deformation 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.
