Analysis of factors affecting mold precision injection molding

Precision injection molding is affected by many relevant factors and environmental conditions, and the basic ones are plastic materials, injection molds, injection molding process and injection molding equipment. In the early stage of designing plastic products, the engineering plastics that can be required are selected according to their environment. Selected plastic materials, finished product dimensional accuracy, part weight, quality requirements and the expected mold structure to select the appropriate injection molding machine.
Among the factors affecting precision injection molding, the mold is the key to obtaining precision plastic products that meet quality requirements. The design of the mold, whether the mold design is reasonable will directly affect the quality of plastic products.
As the mold cavity size is required by the plastic product size plus the shrinkage of the material used, and shrinkage is often recommended by the plastic manufacturer or engineering plastics manual a range of values, it is not only with the mold of the gate form, gate location and distribution, and with the engineering plastics crystalline orientation (anisotropic), the shape of the plastic product, the size of the gate to the distance and location of the relevant.
The main factors affecting plastic shrinkage include thermal shrinkage, phase change shrinkage, orientation shrinkage, compression shrinkage and elastic recovery, etc., and these influences are related to the molding conditions or operating conditions of precision injection molded products.
Therefore, the designer of the mold must have a wealth of design and injection molding experience, must consider the relationship between these influencing factors and injection conditions and its apparent factors, such as injection pressure and cavity pressure and filling speed, injection melt temperature and mold temperature, mold structure and gate form and distribution, as well as the gate cross-sectional area, the product wall thickness, the plastic material in the content of reinforced filler, the plastic material's degree of crystallinity and orientation and so on. The influence of the above factors also depends on the plastic material.
The influence of the above factors also varies depending on the plastic material, or other molding conditions such as temperature, humidity, continued crystallization, and changes in the injection molding machine after molding.
Since the injection molding process is the process of transforming plastic from a solid state (powder or granule) to a liquid state (melt) and back to a solid state (product). From the pellet to the melt, and then from the melt to the product, in the middle of the temperature field, flow field and density field, etc.. Under the joint action of these fields, different plastics (thermosetting or thermoplastic, crystalline or non-crystalline, reinforced or non-reinforced, etc.) have different polymer structure and rheological properties.
All the factors affecting the above “field” will certainly affect the physical and mechanical properties of plastic products, size, shape, precision and appearance quality.
In this way, the intrinsic connection between process factors and polymer properties, structure and morphology and plastic products will be expressed through plastic products. Analysis of these intrinsic links, the rational formulation of injection molding process, reasonable design and manufacture of molds according to drawings, and even a reasonable choice of injection molding equipment are of great significance.