Draw Frame
Draw frame is a machine for combining and drawing slivers of
a textile fiber (as of hemp for rope manufacture or cotton for spinning).
Drawing is the operation by which slivers are blended, doubled and levelled. In
short staple spinning the term is only applied to the process at a draw frame. In
drawing slivers are elongated when passing through a group of pair rollers,
each pair is moving faster than previous one.
Objects of drawing
· To straighten the crimped, curled and hooked
fibers.
·
To make the fiber parallel to their neighbors.
·
To improve uniformity of fibers by drafting and
doubling.
·
To reduce weight per length unit of sliver.
·
To remove dust from slivers.
·
To blend raw material of same hank perfectly.
Importance or
Necessity of Draw frame in Yarn Production
·
To parallelization of fiber and blending the
carded sliver, draw frame is needed.
·
In carded sliver, fibers are present in hook
form i.e. trailing hooks and leading hooks. To parallel these hooks raw frame
is used.
·
Majority of the fiber hooks in a carded sliver
are trailing hooks while leading hooks are comparatively less.
·
Trailing hooks are also known as major hooks,
while leading hooks are known as minor hooks.
Actions Involved in
Draw Frame
Drafting: It is
the process of increasing length per unit weight of sliver. It is mainly due to
peripheral speed of the rollers.
Doubling: The
process of combing two or more carded sliver into a single form is called
doubling. In draw frame m/c generally six slivers are fed to convert into one
i.e. six doubling.
Drawing: In the
cotton industry the term is applied exclusively to processing on the draw
frame, where the operation is one of doubling and drafting. Drawing= Drafting +
Doubling.
Tasks of Draw frame
·
Equalizing
·
Parallelizing
·
Blending
·
Dust removal
Equalizing: One
of the main tasks of draw frame is improving evenness over short, medium and
especially long terms. Carded slivers are fed to the draw frame have degree on
unevenness that cannot be tolerated in practice and slivers from the comber
contain the “infamous” piecing. It is obscured by draw frame.
Equalizing is always performed by a first process, namely
doubling and can optionally also be performed by a second process, namely auto
leveling. The draft and the doubling have the same value and lie in the range
of 6 to 8.
Parallelizing: To
obtain an optional value for strength in the yarn characteristics, the fibers
must be arranged parallel in the fiber strand. The draw frame has the tasks of
creating this parallel arrangement. It fulfills the task by way of the draft,
since every drafting step leads to straightening the fibers.
Blending: In
addition to the equalizing effect, doubling also provides a degree of
compensation of raw material variation by blending. Their results are exploited
in particular way in the production of blended yarns comprising cotton or
synthetic blends. At the draw frame metering of the individual components can
be carried out very simply be selection of the number of slivers entering the
machines.
Dust Removal:
Dust is steadily becoming a greater problem both in processing and for the
personnel involved. It is therefore important to remove dust to the greatest
practical extent at every possible point within the overall process.
Dust removal can only be carried out to a significant when
there are high levels of fiber. Since a large function the smallest particles
adhere relatively strong to the fibers. High performance draw frame is equipped
with appropriate suction removal systems; more than 80% of the incoming dust is
extracted.
