The screw compression ratio of the injection molding machine refers to the ratio of the volume of one groove of the feeding section of the screw to the volume of the last groove of the homogenization section, which is proportional to the degree of plasticization of the plastic.
The screw can be divided into three sections: feeding section (50% screw length), compression section (25%), homogenization section (metering section) (25%). The ratio of the different plastic segments is different.
Feeding section - the bottom diameter is small, the main function is to transport the raw material to the rear section, so it is mainly the conveying capacity problem, the parameter (L1, h1), h1 = (0.12-0.14) D.
Compression section - the change in the bottom diameter, the main function is to compact, melt the material and establish pressure. The parameter compression ratio is ε=h1/h3 and L2. Accuracy should be based on the gradient A = (h1-h3) / L2.
Homogenization section (metering section) - squeezing the molten material of the compression section to the foremost end of the screw, the parameter (L3, h3), h3 = (0.05-0.07) D.
The screw compression ratio refers to the ratio of the volume of one groove of the feeding section of the screw to the volume of the last groove of the homogenization section (metering section). Its value is 2~4.
In contrast, the greater the compression ratio, the more uniform the plasticization of the plastic.