The plastic mechanical reciprocating single screw system is equipped with a two-stage granulation unit, which uses an equally spaced and deep single screw extruder to transport the melt, complete plasticization and longitudinal mixing, and establish a stable extrusion pressure due to its low speed. After the outer cement mortar has finally set, inject polyurethane foam adhesive into the bolt hole from the inside. The hole can be filled or 20-30mm can be reserved on the outside for sealing with cement mortar after the foam adhesive dries and hardens. Therefore, the shearing is lower, avoiding the main shearing heat of the material, and the temperature control is better.

For some low foaming and heat sensitive products (especially PVC products), this configuration separates the mixing and pressure establishment processes. After the melt plasticization is completed, it is sent to the extrusion die for pelletizing at a fixed pressure, temperature, and quantity to prevent the degradation of heat sensitive and shear sensitive materials. It has the characteristics of high yield and stable product quality, and the mixing process can be optimized without being affected by the material making process. During the process of material entering the single screw, a vacuum exhaust device is installed. This method of exhaust has a large exhaust area and a large change in material surface area, providing sufficient exhaust time, which is better than the exhaust effect of a single stage exhaust extruder.

The pressure head loss is relatively small during the material flow of the screw injection machine

The use of screws can effectively heat and transport thermoplastic materials, so screw injection molding machines are also widely used, especially suitable for processing thermoplastic materials with thermal instability.

Screws are used in both extruders and injection machines, but the screws in injection machines are very different from those in extruders. The difference is reflected not only in the structural parameters of the screw, but also in the working condition of the screw. For example, the basic structural parameters of the 30mm diameter screw used in injection machines and extruders differ greatly.

Screw injection machine

In an injection machine, the screw works intermittently, while in an extruder, the screw works continuously, so a certain thermal balance can be established; In addition to rotational motion, the screw in the injection machine also needs to complete axial motion, while the screw in the extruder only performs rotational motion; The head of the screw used in the injection machine is specially designed, such as the installation of a check valve. Its function is: when the screw rotates, the material can freely enter the front of the barrel through the valve. During the injection stage and pressure holding period, the check valve is closed under pressure to prevent the melt from returning from the front of the barrel to the screw groove. If the geometric structure of the screw is changed, it can also be used for the molding and processing of other materials, but its strength is still PVC molding and processing.