Functional Features of the Exhaust Screw
Release Date:
2026-01-04
The venting screw is a specialized component used in extruders, vacuum pumps, and other equipment, with the primary function of efficiently removing volatiles, moisture, or entrapped air from the material to enhance product quality and process stability.
The functional features of the exhaust screw are mainly reflected in the following aspects:
Efficient Venting and Pressure Control: The venting screw achieves pressure-gradient control through a specially designed screw section—such as the venting section—ensuring that the pressure at the vent port is close to zero, thereby preventing melt escape. At the same time, the groove depth in the venting section is significantly greater than that in the metering section (typically at least three times), and this is complemented by the pumping section, where the groove-depth ratio is 1.5 to 2.0, to maintain stable material conveyance.
Temperature and Sealing Optimization: The polymer must be fully melted above its melting point to enhance the diffusion rate of volatiles. Prior to the venting section, melt sealing must be ensured to prevent vacuum leakage between the feed inlet and the vent ports, thereby improving venting efficiency.
Structural Adaptability: A typical venting screw comprises a feeding section, a compression section, a metering section, a venting section, and a pumping section, among others; although its structure is complex, it can accommodate various material properties. In twin-screw extruders, the position of the venting section, the screw elements, and the temperature must be optimized to strike a balance between devolatilization efficiency and energy consumption.
Application Scalability: Degassing screws are not only used for devolatilization in plastic extrusion but also in screw-type vacuum pumps, which achieve rapid gas evacuation through screw rotation. These pumps feature high vacuum levels, corrosion resistance, and low noise, making them well suited for applications with stringent vacuum requirements, such as semiconductor manufacturing and chemical processing.
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