Two for one twister (TFO)
At
the yarn stage, TFO renders improved evenness, strength and elongation the
material. It also enhances the lustre and abrasion resistance of the yarn. At
the fabric stage, however TFO aids in attaining higher stability, better
handle, visual characteristics and improved fabric roll.
 |
| TFO Machine |
Process parameters
TPI
|
8-28
|
Metric count
|
18-120
|
Spindle speed (rpm)
|
5000 – 8500 (practically)
|
Production (Kgs/hr)
|
52-750
|
Doffing time (min)
|
45-135 (depending on count)
|
Efficiency
|
80-90%
|
Principle
The
yarn unwound from the feed package goes to the snail wire through the tensor,
inside the spindle and outside the rotary disc. The yarn receives its first
twist between the capsule and the bending part and the second turn between the
bending part and the snail wire thus obtaining two twists with one rotation of
the spindle.
Main features
Spindle
One
spindle rotation gives the yarn two twistings, therefore the productivity in
the T.F.O. twister equals twice as much as that in the ring twister. The rotary
disc is made free from vibrations and surely balanced, because its
circumference speed reaches as high as 375 kmph in case of machines for cotton
yarns. Each guide is made of Alumina porcelain in order to maintain anti
abrasion characteristics of the rotary disc specially processed for giving a
good slide to the yarn.
Cheese Cover (Balloon
Limiter)
The
cheese cover is furnished in order to prevent the interference of unwinding
yarn with ballooning yarn. It stands still by virtue of magnetic force while
the spindle is rotating. Even a scar or scratch may damage the yarn to cause
ends down, because the yarn touches the upper edge of the cheese cover at
starting.
Cradle
Even
a little slip of the take up bobbin may cause uneven twisting. Ball bearings
are mounted at both sides of the cradle in order to ensure the smooth and light
bobbin rotating. A contact pressure of about 1.5 kg is given to the package at
the beginning of winding to enable the package driven smoothly. The pressure is
designed to be decreased in proportion to the increase in the package diameter.
Feed roller
The
circumference speed of the feed roller is rated 157 to 181% over the yarn speed
thus converting the high ballooning tension to the lower take up tension. Take
up tension can be arbitrarily adjusted by virtue of the effective usage of slip
between the feed roller and the yarn, resulted from changing the yarn contact
angle wound around the feed roller.
Antipatterning Device
This
device is built in the gearbox. It prevents ribbon winding changing the yarn
path by varying the cam speed slightly with a certain interval.
Tailing Device
Used to take off the no twist yarn at the start of
winding.
Twisting condition
When
the new yarns are taken up the following twisting conditions are examined to
ensure the smooth operation
1.
Relationship
between the spindle rotation and the yarn breakage.
2.
Relationship
between the ballooning height and the balloon shape.
3.
Relationship
between the tension and yarn-winding angle.
4.
Relationship
among the overfeeding ratio, guide roller position to adjust yarn winding.
5.
Relationship
between number of set twists and number of required twists.
Functioning of the
rotating disc
The
unwound yarn from the feed package is clung around the circumference of the
storage disc automatically through inside of the spindle and via yarn guide of
the storage disc, then it reaches to the snail wire, twisted diagonally by the
air resistance.
The
degree of winding around the storage disc is conventionally called “storage
angle” or the “winding off angle”. The storage angle is the one that the yarn
from the yarn guide makes in contact with the storage disc. If the angle is
more than 90o, the variance in unwinding will be thrown by its own centrifugal
force collapsing balloon shape, and breaking the yarn. The yarn breakage in
this case is called “breakage caused by extended winding angle”. Therefore,
twisting condition of the machine can be judged by the storage angle around the
storage disc. The storage disc is adjustable by the tensor.
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