How Does a Single Screw Extruder Work? – A Technical Overview

Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with over 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.

The single screw extruder is one of the most widely used machines in the plastic processing industry. It plays a critical role in the production of a variety of piping systems, including PP-R pipes, PE gas pipes, PEX cross-linked pipes, aluminum-plastic composite pipes, ABS pipes, PVC pipes, HDPE silicon core pipes, and various co-extruded composite pipes. Its robust design and operational flexibility make it an indispensable asset in modern extrusion lines.

To fully understand its functionality, it is essential to examine the working principle of the single screw extruder, which is typically divided into three distinct zones along the screw length. These zones—conveying, compression, and metering—are defined based on screw diameter, pitch, and channel depth, and are generally proportioned to occupy approximately one-third of the total screw length each.

1. Conveying Section (Feed Zone)

Starting from the first thread near the hopper, this section is responsible for transporting the raw material forward. In this zone, the material is not yet plasticized; instead, it is preheated and compacted under pressure. Earlier extrusion theories assumed the material remained loose in this area, but subsequent studies have shown that it actually forms a solid plug—a dense, cohesive mass—due to the compaction force. The primary function of this section is therefore to efficiently convey the material toward the next stage.

2. Compression Section (Transition Zone)

In this zone, the screw channel volume gradually decreases, compressing the material as it moves forward. The temperature is raised to initiate melting and achieve proper plasticization. The reduction in channel volume creates the screw's compression ratio—typically 3:1 (i.e., the channel depth decreases from three units in the feed zone to one unit here), although this ratio may vary depending on the machine design. By the end of this section, the material has reached a fully plasticized state and is ready for the final metering stage.

3. Metering Section (Feed Zone)

The metering section maintains the material at the required plasticizing temperature and ensures a consistent, pulsation-free flow of melt to the die. Acting similarly to a metering pump, this zone precisely regulates the output volume, with the temperature typically kept slightly above the plasticization point to guarantee stable melt delivery and optimal extrusion performance.

Advanced Design for High-Performance Extrusion

Modern single screw extruders often feature a two-stage, integrated design that enhances plasticizing efficiency and supports high-speed, high-output extrusion while maintaining process stability. The incorporation of advanced mixing elements ensures thorough homogenization of the melt, while the combination of high shear rates and controlled low melting temperatures enables superior low-temperature, low-pressure metered extrusion—resulting in excellent product quality and energy efficiency.

Whether for standard pipe production or complex co-extrusion applications, the single screw extruder continues to be a reliable, versatile, and high-performance solution for the plastics industry.

If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.