The conventional spinning process

The conventional spinning process is as follows: 

dry chips→ melt extrusion → mixing → metering → filtering → spinning → cooling and shaping → oiling → winding → UDY bobbin.

01 Melt extrusion

The pellets enter the screw extruder through the feed inlet by gravity. Due to the rotation of the screw, the pellets move forward along the screw channel. Heating elements are installed on the outer side of the screw barrel, transferring heat to the pellets through the barrel. Meanwhile, friction and compression among the pellets inside the extruder generate additional heat. The pellets are heated and melted, and as they are compressed by the extruder, they acquire a certain melt pressure.

02 Mixing

A static mixer is used to uniformly blend the melt at the outlet, enhancing the homogeneity of the melt and reducing the temperature and residence time differences between the pipe wall and the center of the pipe as the melt passes through the bend. If the melt is already uniform, a static mixer may not be necessary.

03 Metering

The melt output from the screw extruder is distributed through a distribution pipe to metering pumps at each spinning location. This ensures consistent linear density and uniformity of the filaments. Additionally, the metering pumps can pressurize the melt to meet the requirements for high-pressure spinning.

04 Filtering

Before spinning, filtering materials such as silica sand are used to remove impurities from the melt. The filtering materials can include garnet, sea sand, ultrafine glass beads, and filter screens. In high-pressure spinning, the filtering layer generates significant resistance, causing frictional heating of the melt and raising its temperature, which improves the melt's rheological properties.05 Spinning

After filtration, the melt is distributed by a distribution plate to each spinneret hole on the spinneret plate, where it is extruded through the holes, forming fine streams of melt.

06  Cooling and shaping

The process in which the fine streams of melt are cooled and solidified into filaments is called cooling and shaping. Simultaneously, due to the stretching effect of the spinneret, the fine streams gradually thin before solidification. Cooling and shaping occur within the spinning window, where the forced cooling air blown from the upper end of the spinning duct ensures uniform cooling conditions.

07 Oiling

Due to the dry nature of the freshly spun fibers, they are prone to static electricity, have poor cohesion between filaments, and are loosely bundled with a high coefficient of friction, making further processing difficult. Therefore, oiling is necessary during spinning. Although the location for oiling varies with different spinning processes, the purpose remains the same: to aid in bundling the filaments, reduce static electricity, and improve smoothness. In conventional spinning, an oil wheel is used for oiling. The cooled and shaped filaments contact the oil wheel before reaching the winding machine, completing the oiling process.

08 Winding

Winding is accomplished through the cooperation of upper and lower guiding discs, a cross guide, and friction rollers. The oiled filaments change direction and adjust tension as they pass through the upper and lower guiding discs, then wind onto the tube via the cross guide. The tube contacts the friction rollers on the winding head with a certain pressure, and through friction transmission, maintains a consistent linear speed, which is the spinning speed. Winding tension affects both the formation of the bobbin and the relaxation tension. Winding tension, overfeed rate, and oiling agent are three important factors in the winding process.