What are the benefits of high and low injection speeds?
The core of the influence in various process conditions is the viscosity change of the plastic, which is very important for the rational selection of parameters in the injection process and their mutual influence.
Using high-speed injection during the injection process has the following advantages:
Improve the flow of plastics, which is conducive to the molding of thin-walled parts;
Improve the surface gloss of the product;
It can improve the strength of the welding line, so that the welding lines are not obvious;
Prevent cooling deformation, etc.
Using low-speed injection during the injection process has the following advantages:
Prevent flashing of molded products;
Prevent jet pattern and flow pattern;
Prevent burning marks;
Prevent the phenomenon of air inclusion in the plastic melt;
Prevent molecular orientation deformation, etc.
The advantages of high-speed injection are also the disadvantages of low-speed injection, and vice versa. Therefore, using a combination of high speed and low speed in the injection process can make full use of their respective advantages and avoid their respective disadvantages, thereby ensuring the quality of the product and the economy of the process.
This is what we usually refer to as multi-stage injection technology, which is commonly used on modern injection molding machines. At present, most of the injection molding machines above medium size have five to six levels of injection pressure, speed changes, and three to four levels of holding pressure changes (due to the pressure holding stage, the melt has filled the cavity, and the melt flows into the mold after the holding pressure. The feeding material of the cavity is already limited, so the influence of the pressure holding speed is not large).