The most important process conditions in the plastic injection process are the temperature, pressure, velocity and corresponding action time of plasticizing flow and cooling. These factors influence and restrict each other, such as increasing melt temperature and mold temperature, the injection pressure and speed can be reduced, otherwise the plastic injection pressure and speed can be increased.
The core of the influence of various process conditions is the viscosity change of plastics, which is very important for the reasonable selection of injection parameters and the mutual influence.
Improving the flow of plastic is conducive to the molding of thin-walled parts;
Improving the surface gloss of the products;
Improving the strength of the welding line, making the weld lines not obvious;
Preventing cooling deformation, etc.
Preventing the flash of molding products;
Preventing the occurrence of spray and flow patterns;
Preventing the occurrence of combustion printing;
Preventing the occurrence of gas inclusion in the plastic melt;
Preventing the formation of molecular orientation deformation.
The advantages of high-speed injection are also the disadvantages of low-speed injection, and vice versa. Therefore, the respective advantages and disadvantages of low-speed plastic injection process can be fully utilized in the injection process, which can make full use of their advantages and avoid their disadvantages, so as to ensure the quality of the plastic injection products and the cost-saving of the process.
It is commonly referred to as multi-stage plastic injection technology, which has been widely used in modern plastic injection molding machines. At present, most of the medium-sized and above injection molding machines have five to six levels of injection pressure and speed changes and three to four levels of packing pressure changes (because the melt has filled the cavity in the packing stage, the feeding material of the melt flowing into the cavity through the packing pressure is limited, so the effect of packing speed is not great).