In plastic extrusion equipment, the plastic extruder is typically referred to as the main machine, while the downstream equipment that works in conjunction with it—known as the plastic extrusion molding machine—is called the auxiliary machine. After Over more than a century of development, plastic extruders have evolved from their earliest single-screw, multi-screw, and even screwless designs. These machines can be paired with a wide range of auxiliary equipment for plastic molding to form diverse extrusion production lines, enabling the manufacture of various plastic products. Consequently, whether today or in the future, plastic extrusion machinery remains one of the most widely used types of equipment in the plastics processing industry.

The main unit of a plastic extruder is the extrusion machine, which consists of an extrusion system, a drive system, and a heating–cooling system.

The extrusion system comprises a screw, a barrel, a hopper, a die head, and a die. The plastic is plasticized into a uniform melt by the extrusion system and, under the pressure generated during this process, is continuously extruded through the die by the screw.

⑴ Screw: is Plastic extruder An important component, which is directly related to Plastic extruder Its application scope and productivity are ensured by its construction from high-strength, corrosion-resistant alloy steel.

⑵ Barrel: Typically made of heat‑resistant, high‑pressure‑rated, robust, wear‑resistant, and corrosion‑resistant alloy steel or composite steel tubing. The barrel works in conjunction with the screw to crush, soften, melt, plasticize, degas, and compact the plastic, continuously and uniformly conveying the material to the molding system. In general, the barrel length is 15–30 times its diameter, with the aim of ensuring thorough heating and complete plasticization of the polymer.

⑶ Hopper: The bottom of the hopper is equipped with a shut-off device that allows adjustment and interruption of the material flow. The side of the hopper is fitted with an inspection port and a calibrated metering device.

⑷ The Die Head and Mold: The die head consists of an alloy‑steel inner sleeve and a carbon‑steel outer jacket. It is fitted with a forming mold. Its function is to convert the rotating plastic melt into a parallel linear flow, introduce it into the mold uniformly and smoothly, and impart the necessary molding pressure. Within the barrel, the plastic is plasticized and compacted, then flows through the die head neck along a defined flow path into the forming mold. The core and the die sleeve are properly matched to create an annular gap whose cross‑section gradually narrows, enabling the molten plastic to form a continuous, dense tubular coating around the core wire. To ensure a well‑designed flow channel inside the die head and eliminate dead zones where plastic might accumulate, a 分流套筒 (diverter sleeve) is often installed. Additionally, a pressure‑equalizing ring may be provided to mitigate pressure fluctuations during extrusion. The die head is also equipped with mechanisms for mold alignment and adjustment, facilitating precise centering of the core and die sleeve.

Extruders are classified into angled dies and straight dies based on the angle between the die flow direction and the screw’s central axis. The nose fairing is bolted to the fuselage. The mold inside the die head features a core holder, which is secured to the die head’s wire-in port with a nut. The front of the core holder is fitted with a core, and both the core and the core holder feature central holes for passing the core wire through. A pressure-equalizing ring is installed at the forward section of the nose to balance the pressure. The extrusion molding section consists of a die holder and a die. The position of the die sleeve can be adjusted via bolts and supports, enabling precise alignment between the die sleeve and the die core and facilitating uniform control of the extrusion layer thickness. The nose section is equipped with a heating device and a temperature-measuring instrument.