What is Open-End Yarn?

Open-end yarn is yarn made by the rotor spinning system. The sliver is separated into individual fibers; the fibers are collected in the groove of a fast-spinning rotor and twisted there into yarn (Cotton Incorporated, ISP 1006). Compared with ring yarn it is more even and cheaper; on the other hand it is harder in handle, weaker and suited to coarser counts. Open-end spinning is also called rotor spinning.

How open-end yarn is made

1. Feeding: Sliver, not roving, is used. A feed roller delivers the sliver to a fast-spinning opening roller, which separates the fibers one by one from the end of the sliver and removes trash.
2. Transport to the rotor: The separated fibers pass through a conical channel into the rotor groove. According to ISP 1006 (2003), the rotor spins at up to 150,000 rpm. The fibers lay on top of one another in the groove, and the mass needed for the desired yarn count accumulates.
3. Twisting: As the rotor turns, the fibers are twisted together, and the resulting yarn is drawn out of the spinning box. The ratio of the delivery roller speed to the feed roller speed sets the yarn count; the ratio of rotor speed to delivery roller speed sets the amount of twist.
4. Cleaning and winding: The yarn passes through a clearer that removes faulty places and is wound onto a large package for knitting or weaving.

According to Cotton Incorporated (ISP 1006, 2003), the output of an open-end spinning position is about 8–10 times that of a typical ring position. The roving step that ring spinning requires does not exist in the open-end flow.

Yarn structure: wrapper fibers

In the rotor, some fibers are wrapped around the “belt” of the yarn instead of being twisted together. These wrapper fibers do not contribute to strength and are unique to open-end yarn (ISP 1006). NPTEL’s course questions, on the other hand, attribute the lower strength of open-end yarn to less fiber migration inside the yarn.

Comparison with ring yarn

Cotton Incorporated compares the two systems as general tendencies (ISP 1006, p. 7). The hairiness information in the open-end column is supported by NPTEL’s course questions and the torque information by ISP 1009. The sources give no numerical values; the difference varies with fiber, count and machine settings.

Uses

In application examples prepared for its rotor machines, Rieter gives these yarn counts: Ne 20–Ne 30 in 100% cotton for T-shirts, Ne 18–Ne 20 for sweatshirts, Ne 16 for denim weft, Ne 17 for towel ground warp, and Ne 40 in a cotton/polyester 70/30 blend for shirting. These are brochure examples from a machine manufacturer, not a market standard.

In fabric, open-end yarn gives lengthwise shrinkage similar to ring yarn; fabric and garment torque is lower, and the fabric tends to come out wider (ISP 1009). Open-end yarn from recycled cotton fibers has also been studied in the literature; for example, Kertmen et al. produced Ne 20/1 open-end yarn from blends containing 5% and 10% recycled cotton (cited in Doba Kadem and Sevgi, 2022).

How it differs from similar terms

• Ring yarn: Another spinning system, at the same level as open-end; the two systems are compared in the table above.
• Carded and combed: These describe fiber preparation, not the spinning system. In Cotton Incorporated’s flow table there is no combing step for open-end, so the usual open-end yarn is carded. Even so, the use of combed cotton sliver in rotor spinning has been studied (Rowe, 1993). So there is no rule that “open-end = carded”.
• Vortex and air-jet yarn: These are separate systems from open-end; ISP 1006 describes them under separate headings.

In a quote, ask for the yarn type and count together, for example “Ne 20/1 open-end, 100% cotton”. You can find yarn suppliers in the yarn companies category. To convert yarn counts, see the yarn count conversion guide.

Frequently asked questions

Is open-end yarn worse than ring yarn?

No; it offers different properties. According to Cotton Incorporated, ring yarn is stronger and softer and can be spun to the finest counts, but it costs more; open-end yarn is more even, cheaper and produced with higher productivity, but it is weaker and harder in handle. The end use decides which suits better (denim weft and towel ground warp are among Rieter’s rotor application examples).

Can open-end yarn be combed?

It can, but it is not the usual route. In Cotton Incorporated’s flow table there is no combing step for open-end; rotor spinning with combed cotton sliver is a practice described by Rowe (1993). In a quote, ask about “open-end” and “combed” separately.

What counts is open-end yarn made in?

Cotton Incorporated states that open-end yarn suits a limited range of counts that are coarser than ring yarn. NPTEL’s course questions also state that fine counts are not possible in the rotor system. In Rieter’s application examples the counts range from Ne 16 to Ne 40. These sources give no general upper limit; the examples only show one machine manufacturer’s applications.