What are the requirements for injection mold design? Th […]
What are the requirements for injection mold design?
The characteristics of the injection mold are determined by the characteristics of the raw materials. There are two main points: one is the filling flow characteristics of the plastic melt during injection, and the other is the shrinkage position of the plastic in the cavity during cooling and solidification. These two points determine the injection mold. Particularity and difficulty of injection mold design. Since the plastic melt is a viscoelastic body, the viscosity of the melt changes with the shear stress and the shear rate when the melt flows. During the flow process, the macromolecules are oriented along the flow direction. After the cavity is filled, the melt is partially compressed and cooled and solidified. The shrinkage of plastics is very complicated. The shrinkage rates of plastics in various parts and directions in the mold cavity are different. The shrinkage rates of different types and grades of plastics are very different. When the resin or plastic of the same grade is processed, due to the different formulations, its filling flow Sex and shrinkage are also different. Based on the above characteristics, it is necessary to fully understand the characteristics of the processed plastic raw materials when designing the injection mold, so that the designed injection mold is used reasonably, and the characteristics of the plastic are effectively used in the design process. Therefore, the following issues need to be considered in the injection mold design process.
1. In-depth analysis of the structure of plastic parts and its technical requirements. The structure of the plastic part determines the complexity of the injection mold structure, and the technical requirements of the plastic part (dimensional accuracy, surface roughness, etc.) determine the difficulty of the injection mold manufacturing and molding process, so there is no special requirement for plastic injection molding. , Unreasonable structural shapes, etc., should be proposed to improve the design of injection molded parts, otherwise it will increase the difficulty of injection mold design and manufacturing and injection molding process.
2. Familiar with the technical specifications of injection molding machines. The technical specifications of the injection molding machine restrict the size of the injection mold and the range of injection products that can be molded.
3. Understand the processing performance and process performance of plastics. Including the flow position of the plastic melt, the larger the flow distance ratio that the melt can achieve: analyze the flow resistance of the runner and the cavity, the original air discharge in the mold cavity, and the plastic may occur in the injection mold Crystallization, orientation and the internal stress caused by it, plastic cooling shrinkage and compensation problems, plastics' requirements for injection mold temperature, etc.