Twisting is the process which applies turns to one or multiple strands of yarns.
Turns can be in S-Direction and they can be in Z-direction.
Depending on the intended following production process, the amount of turns/ inch or turns / m can vary.
For better visibility, following is an example of a twisted cotton strand:
You can now count how many turns/ inch or per cm have been applied.
In general, the larger the amount of turns / inch, the higher the cost, as it takes the machine longer to manufacture the required count.
While Rovings have almost no or even zero twist, fine yarns usually will only be available with a low twist count. A converter will then apply higher twist counts.
Reasons to twist Yarns:
- protection of the fiber
increase tensile strength
creating hybrid fibers with various properties
There are two main twisting processes:
a) Ring twisting
b) Direct Cabling or “false twisting”
Glass Fibers have a “recall” effect, they tend to twist or turn back into the original form. Therefore, when twisting two strands together, this needs to be taken into account.
Ring twisting consist of two production processes:
Individual strands will be first twisted in one direction, in most cases Z-Direction.
In the second conversion process, two or more single strands will be put together while twisting them now in the opposite direction, in this case in the S-Direction.
This way, 2 up to 12 or even more strands can be twisted together and they are not effected by the “recall”-effect when twisted right.
The cones the materials are twisted on are called “milk bottle” bobbins, due to the shape.
Direct cabling process is only one production step. While one strand of yarn stays in the original direction, the second strand of yarn will be wrapped around the other.
Due to only one required production process, this method is considered to be more cost effective.
The cones the materials are twisted on are cylindrical.
Currently, direct cabling can only be done with two strands, while ring twisting is more flexible and can be many fold.