Twist is the measurement of the spiral turns gives to a yarn in order to hold the constituent fibre or together. Twist may defined as the rotation about the yarn axis of any line drawn on the yarn which was originally that is before twisting parallel to the yarn axis.

1. LETS COME TO THE TOPIC
YARN TWIST
By:
Foysal Ahmed

2.  WHAT IS TWIST?
Twist: Twist is the measurement of the spiral turns
gives to a yarn in order to hold the constituent fibre
or together. Twist may defined as the rotation about
the yarn axis of any line drawn on the yarn which
was originally that is before twisting parallel to the
yarn axis.

3. Types of Twist
 S-twist
Z-twist

4. Z-TWIST
A single yarn has Z twist if, when it is held
in the vertical position, the fibres inclined to
the axis of the yarn conform in the direction of
the slope to the central portion of the letter Z.

5. S-TWIST
A single yarn has S twist if, when it is held
in the vertical position, the fibres inclined to
the axis of the yarn conform in the direction of
the slope to the central portion of the letter S.

6. Twist and Yarn strength:
Fig: Relation between yarn strength & twist

7. An increase in the amount of twist
produces an increase in the yarn strength.
This effect holds only up to a certain
point beyond which further increase in
twist causes the yarn to become weaker &
finally breakage of yarn.

8. THE TWIST CONTRACTION
METHOD
One of the effects of putting into a strand of fibre or filament is to
cause the strand to contract in length. Suppose a yarn is twisted Z way
and has a length, h. Let the twist be completely removed to produce an
untwisted strand of length h+c, c being the contraction due to twist. If
the strand is now twisted S way with a number due to turns equal to
those removed, we would expect that the strand will again contract to
the original length, h .Several twist testers are based upon this concept.

10. Thank You.