Plastic Molding Manufacturer | China Custom Plastic Parts Services Contact@china-plasticparts.com
Author: MULAN -Plastic Molding Manufacturer
Mold precision injection molding will be affected by many related factors and environmental conditions, the most basic factors are plastic material, injection mold, injection molding process and injection molding equipment. In the early stage of plastic product design, first, select engineering plastics that may be required according to the environment. Secondly, according to the selected plastic material, the dimensional accuracy of the finished product, the weight of the part, the quality requirements and the expected mold structure, select the appropriate injection molding machine.
Among the relevant factors affecting precision injection molding, molds are the key to obtaining precision plastic products that meet quality requirements. Mold design, whether the mold design is reasonable will directly affect the quality of plastic products. Because the mold cavity size is obtained by the required plastic product size plus the shrinkage rate of the material used, and the shrinkage rate is usually within the range recommended by the plastic manufacturer or engineering plastics manual.
It is not only related to the gate shape, gate position and mold distribution, but also related to the crystal orientation (anisotropy) of engineering plastics. The shape and size of plastic products are related to the distance and position of the gate. The main factors affecting plastic shrinkage are heat shrinkage, phase change shrinkage, orientation shrinkage, compression shrinkage and elastic recovery, which are related to the molding conditions or operating conditions of precision injection molded products. Therefore, the injection mold processing designer must have rich experience in design and injection molding, and must consider the relationship between these influencing factors and injection molding conditions as well as their apparent factors, such as injection pressure, cavity pressure and filling speed, injection melt Temperature and mold temperature, mold structure, gate shape and distribution, gate cross-sectional area, product wall thickness, content of reinforcing filler in plastic material, crystallinity and orientation of plastic material.
Due to different plastic materials or other molding conditions, such as temperature, humidity, continuous crystallization, and changes in the injection molding machine after molding, the influence of the above factors is also different. Because the injection molding process is the process of converting plastic from solid (powder or granules) to liquid (melt) and solid (product). From granular material to melt, and then from melt to product, it needs to experience the effects of temperature field, flow field and density field.
Under the combined action of these fields, different plastics (thermoset or thermoplastic, crystalline or amorphous, reinforced or non-reinforced, etc.) have different polymer structures, morphologies and rheological properties. All factors affecting the above "field" will affect the physical and mechanical properties, size, shape, precision and appearance quality of plastic products. In this way, the inherent relationship between process factors and polymer properties, structural morphology and plastic products will be expressed through plastic products.
Analyzing these internal connections is of great significance for rational formulation of injection molding process, rational design of injection molds according to drawings, and even reasonable selection of injection molding equipment.