Views: 0 Author: Site Editor Publish Time: 2026-03-30 Origin: Site
The single-screw extruder consists essentially of a screw that rotates in an axially fixed position within the close-fitting bore of a barrel. Extruder sizes are identified by the inside diameter of their barrel. Size range from ¼ to 24 in. diameter with the usual from 1 to 6 in. (Europe and Asia sizes range from 20 to 600 mm with the usual from 25 to 159 mm.). The screw is electrically motor driven through different devices such as a gear reduction train or belt to meet different performance and cost requirements. These gear reducers are rated in mechanical horsepower and thermal horsepower as defined by the American Gear Manufacturers (AGMA). The AGMA rating system is based on the understanding that not all gear reducers are used the same way. There are also gearless drive systems such as those using Siemens high-torque motor with an unusual low-inertia hollow shaft.
The output rate of the extruder is a function of screw speed, screw geometry, and melt viscosity. The pressure developed in the extruder system is largely a function of die resistance and dependent on die geometry and melt viscosity. Extrusion pressures are lower than those encountered in injection molding. They are typically 500 to 5000.
In extreme cases, extrusion pressures may rise as high as 10,000 psi (69 MPa). Variants on the single screw include the barrier or melt extraction screw and the vented screw.
