The main unit of a knotless‑net extruder is an extrusion machine, which comprises an extrusion system, a drive system, and a heating–cooling system. The extrusion system consists of a screw, a barrel, a hopper, a die, and a mold. As the plastic passes through the extrusion system, it is plasticized into a uniform melt and, under the pressure generated during this process, is continuously forced through the die by the screw.

Screw: It is the primary component of an extruder, directly influencing the machine’s application scope and productivity, and is manufactured from high-strength, corrosion-resistant alloy steel.

Barrel: A metallic cylindrical component, typically fabricated from heat‑resistant, high‑pressure‑strength, robust, and corrosion‑resistant alloy steel, or from a composite steel pipe with an alloy‑steel liner. The barrel works in conjunction with the screw to crush, melt, plasticize, degas, and compact the polymer, while continuously and uniformly feeding the molten material into the molding system. Generally, the barrel length is 15 to 30 times its diameter, with the design principle being to ensure thorough heating and complete plasticization of the polymer.

Hopper: The bottom of the hopper is equipped with a shut-off device for adjusting and stopping the material flow, while the side of the hopper features an inspection port and a calibrated metering device.

Die Head and Die: The die head consists of an alloy‑steel inner sleeve and a carbon‑steel outer jacket, with a forming die mounted inside. Its function is to convert the rotational motion of the plastic melt into a parallel linear motion, guide it smoothly and uniformly into the die sleeve, and impart the necessary molding pressure. Within the barrel, the plastic is plasticized and compacted; it then passes through a porous filter plate and along the flow channel, entering the die head via the die neck. The core and die sleeve are properly matched, creating an annular gap whose cross‑section continuously decreases, thereby forming a continuous, dense tubular sheath around the core.

An extruder is a common piece of plastic-processing equipment. During routine operation, extruders can experience a wide range of malfunctions that disrupt normal production. To extend the machine’s service life and boost productivity, it is essential to perform regular maintenance and operate the equipment correctly.

The following outlines the daily maintenance and care of extruders: Routine maintenance is a regular, scheduled task that does not consume equipment operating time and is typically performed during machine operation. Key activities include cleaning the extruder, lubricating all moving parts, tightening any loose threaded fasteners, and promptly inspecting and adjusting the motor, control instruments, working components, and piping systems.

Regular maintenance is typically performed after the extruder has been running continuously for 2,500 to 5,000 hours; at this point, the machine should be shut down for disassembly and inspection, with measurements taken and the wear condition of key components assessed. Components that have reached their specified wear limits must be replaced, and any damaged parts repaired. Running the machine empty is prohibited to prevent scoring of the screw and barrel. If abnormal noises occur during operation, the machine should be stopped immediately for inspection or repair. Care should be taken to prevent metal or other foreign objects from entering the hopper, as these can damage the screw and barrel. To keep ferrous contaminants out of the barrel, magnetic devices or magnetic racks may be installed at the feed inlet, and materials should be screened beforehand. Maintain a clean production environment; do not allow debris to mix with the material, as this can clog the filter plate, reduce product output and quality, and increase head resistance. When the extruder is to remain idle for an extended period, anti‑rust lubricant should be applied to the working surfaces of the screw, barrel, and die. Small screws should be suspended in mid‑air or stored in wooden crates, with wooden blocks used to level them, to prevent deformation or impact damage. Temperature control instruments should be calibrated regularly, and their adjustment accuracy and control sensitivity verified.