What is Yarn Twist ? Types of Yarn Twist?

 Yarn Twist:

Twist is the number of turns per unit length (cm, m or inch).In the manufacture of staple fibre yarns, twist is inserted into the fine strand of fibres to hold the fibres together and impart the desired properties to the twisted yarns. Without twist, the fine strand of fibres would be very weak and of little practical use. A change in the level of twist also changes many yarn properties, such as strength and softness. This section discusses the nature of yarn twist, the effect of twist on yarn properties, as well as twist measurement.

Types of Yarn Twist:

There are two types of twist: 

                     1. Real twist 

                     2. False twist.

1. Real twist:

To insert a real twist into a length of yarn, one end of the yarn

Fig 1 : Real Twist

needs to be rotated relative to the other end, as indicated in Figure -1.

Spun yarns usually have real twist, which holds the fibres together in the yarn and provides strength.

2. False twist:

When inserting false twist into a length of yarn, both ends of

Fig 2 : False Twist

the yarn are clamped, usually by rollers, and twist is inserted with a false twist device between the clamping points, as indicated in Figure -2.

If the yarn is not traversing along its axis, the twist will be in opposite directions above and below the false twister. If the false twister is removed, the opposite twists will cancel out one another, leaving no real twist in the length of yarn. If the yarn is traversing along its axis, then the section of the yarn moving away from the false twister would have no net twist, as indicated in Figure -2.

False twisting is a very important phenomenon, which has considerable practical implications in yarn technology. False twisting is featured in many key processes that we will discuss later, including woollen ring spinning, open-end rotor and friction spinning, air jet spinning, and filament yarn texturing.