What are the respective benefits of high or low injection speeds?

The most important process conditions in the injection process are the temperature, pressure, speed, and the corresponding individual action time that affect the plasticizing flow and cooling. These factors, in turn, influence and constrain each other, such as increasing the melt and mold temperature, which can reduce the injection pressure and speed, etc., and vice versa, which requires increasing the injection pressure and speed.

The core of the influence of various process conditions lies in the change of plastic viscosity, which is crucial for the reasonable selection of parameters in the injection process and the influence of each other.


The following advantages exist for the use of high-speed injection in the injection process:

Improving the flow of the plastic, which facilitates the molding of thin-walled parts.

Improving the surface gloss of the product.

The possibility of improving the strength of the fusion line, making the fusion pattern less obvious.

Preventing the generation of cooling deformation, etc.


The advantages of using a low-speed injection in the injection process include:

Preventing the formation of flying edges on molded products.

Preventing the generation of jet lines and flow lines.

Preventing the production of burn marks.

Prevention of air entrapment in the plastic melt.

Prevention of molecular orientation deformation, etc.

The advantages of high-speed injection are also the disadvantages of low-speed injection and vice versa. Therefore, the combination of high speed and low speed in the injection process can make full use of their respective advantages and avoid their respective disadvantages, thus 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 has been commonly used in modern injection molding machines. At present, most of the medium-sized injection molding machines have five to six injection pressure, speed changes, and three to four pressure-holding pressure changes (because the pressure-holding stage, the melt has filled the cavity, the melt through the pressure-holding pressure into the cavity of the complementary shrinkage material has been limited, so the impact of pressure-holding speed is not significant).