Yarn Twist

Yarn Twist
Yarn twist is the spiral given to the yarn standard to hold the fiber permanently according to construction. It is measured by twist per inch (TPI). If TPI increase to a certain level then the strength of the yarn will be increased and if decreased then strength will decreased. The twist of yarns and threads influences their morphology. This feature creates the thread’s properties, and at the same time is decisive regarding the processing throughput. A great amount of the literature published hitherto deals with the problem of yarn twisting, but there is a lack of sufficient information related to the twist of multi-folded threads. Technologists in the textile industry set the thread’s twist value in their ‘spinning planes’. Its actual realization on the spinning machine and ring-twisting frame is performed by selecting the spindle rotary speed and fibre stream delivery velocity. Yarn plying, i.e. twisting together some component fibre streams, causes a decrease in the linear mass irregularity (thanks to a better fibre packing in the stream), an increase in tenacity, a lowering of the bending stiffness, an increase in the abrasion resistance, and a lowering of the thread’s tendency to pilling formation. Owing to these favorable circumstances, twisting positively influences the thread’s manufacturing throughput and the barrier ability (e.g. against UV radiation) of the fabrics produced from such a yarn.

Types of yarn twist

ü  S Twist

ü  Z Twist

S twist:

A single yarn has S twist when it is held in the vertical position, the fibers inclined to the axis of the yarn conform the direction of slope to center position of the letter S.

Z twist:

A single yarn has Z twist when it is held in the vertical position, the fibers inclined to the axis of the yarn conform the direction of slope to center position of the letter Z.

Construction:

ü  This instrument has two jaws& distance of them is 1 inch.

ü  Yarn can set two jaws.

ü  That means 1 inch yarn can set two jaws.

ü  A lens is used to watch the number of revaluation properly.

Procedure

ü  At first the yarn can set two jaws.

ü  Then a weight is hung at one end of the yarn with fixed tension.

ü  The yarn led through the fixed jaw over a grid pulley & at last to the weight to maintain fixed tension.

ü  After closing the fixed jaw the turns are removed by the rotating the handle.

ü  When the twist is removed the needle is pushed through the fibers closed to the fixed jaw and gently moves towards the rotating jaw.