Welcome to Spinning Processes where you will learn about “Ring Spinning”, “Rotor Spinning”, “Air Jet Spinning”, “Yarn Numbering”, “Yarn Twist” and “Yarn Plying.”
Ring spinning is the oldest type of fiber spinning still in use. The process takes a fiber mass (roving), reduces the mass through fiber drafting, inserts twist for strength, and winds the yarn onto a bobbin. Even today, ring spinning makes the widest range of yarn counts with the highest strength. However, ring spinning is slower than other modern spinning systems and requires more processing steps, including off-machine winding of the yarn into large packages.
Rotor spinning, also known as open-end spinning, was developed in the 1970s and early 1980s. The system spins yarn directly from slivers, using a spinning rotor and a withdrawal system that imparts false twist to form the fibers into a yarn. Open-end spinning requires fewer steps than ring spinning, because roving is not needed, and a full-sized package is made directly on the machine. Rotor spinning is about seven times as fast as ring spinning, but produces weaker yarn in a smaller range of yarn counts.
Air-jet spinning first appeared for production use in the early 1980s. A sliver is fed into a drafting system that feeds the yarn into a vortex created by high-speed air jets, to impart false twist. Air-jet spinning has grown in popularity because of its high productivity; it is about 20 times as fast as ring spinning. However, air-jet spinning produces weaker yarn in a smaller range of yarn counts; yarn sizes typically are above 24/1.
Yarn numbering (count) describes a yarn’s physical size — specifically, its linear density. Numbering is based on the relationship between the length and weight of the yarn. Two types of systems are used, direct (weight per unit length) and indirect (length per unit weight). Common numbering systems include English count, worsted, metric, tex, and denier.
In all yarn spinning systems, twist is used to hold the fibers together. The frictional forces created by the twist determine the yarn’s strength and elongation characteristics. “Twist multiple” is the measure of twist per unit length, and twist direction is described as “S” or “Z.”
All yarns are originally spun as single yarns, but for certain end uses, single yarns may be twisted together to produce a “ply yarn.” Most common are two-ply yarns, formed by twisting two single yarns together. The plying twist is in the opposite direction of the singles twist.