The compression ratio of the screw of the injection molding machine refers to the ratio of the volume of one screw groove of the feeding section of the screw to the volume of the last screw groove of the homogenization section, which is directly proportional to the plasticization degree of the plastic.

The screw can be divided into: feeding section (50% screw length), compression section (25%), homogenizing section (metering section) (25%). The ratio of the three plastic segments differs.

Feeding section-the bottom diameter is small, the main role is to convey raw materials to the rear section, so it is mainly a problem of conveying capacity, parameter (L1, h1), h1 = (0.12-0.14) D.

Compression section——The change of the bottom diameter is mainly used for compacting and melting materials and establishing pressure. Parameter compression ratio ε = h1 / h3 and L2. Accuracy should be based on the gradient A = (h1-h3) / L2.

Homogenization section (metering section)-quantitatively squeeze the molten material in the compression section to the forefront of the screw at a constant temperature, with parameters (L3, h3), h3 = (0.05-0.07) D.

The screw compression ratio refers to the ratio of the volume of one screw groove in the feeding section of the screw to the volume of the last screw groove in the homogenization section (metering section). Its value is 2 ~ 4.

In contrast, the larger the compression ratio, the more uniform the plasticization of the plastic.