In order to interlace warp yarn and weft yarn to produce fabric on any type of weaving machine, three operations are necessary. Shedding separating the warp yarn which run down the fabric, into two layers to from a tunnel known as the shed. Picking passing the weft yarn, this traverses across the fabric, through the shed. Beating up pushing the newly yarn insert length of weft, known as the pick, into the already woven fabric at a point known as the fell.
These three operations are often called the primary motion of weaving. These
motions must occur in a given sequence, but their precise timing in a relation
to one another is also of extreme importance on a power loom. Two additional
operations are essential if weaving is to be continuous Warp control let of this motion delivers warp to the weaving area
at the required rate and at a suitable constant tension by unwinding if from a
flanged tube known as the weavers beam. Cloth
control this motion withdraws fabric from the weaving area at the constant
rate that will give the required pick spacing and then winds it onto a roller.
After these operations took place a weaving cycle is completed. Weaving cycle
is repeated over and over again until the cloth reaches the desired length.
The warp unwound from the weaver’s beam passes round the
back rest and comes to the held frames which are responsible for separating the
warp sheet for the purpose of shed formation. It then passes through the reed,
which holds the threads at uniform spacing and is also responsible for
beating-up the last inserted pick. All this yarn unites again in the fabric at
the point of cloth fell. The cloth then passes over the front rest, round the
take up roller, and is wound onto the cloth roller. A drop wire signals the
loom to stop immediately after a warp end breaks off.
Bottom closed shed this
kind of shed is produced by giving motion only to yarn that are to from the
under the upper line. Under this condition the warp is level on the bottom
line. Hence in order to from a top shed, it is necessary to move some threads
through a space equal to twice the depth of a shed, once up and one down before
a frees selection is made.
Centre closed shed is
produced by imparting an upward movement to those yarn which are to form the
top line and a downward movement to the threads which are two forms the bottom
line. Then after insert a pick, both the lines meet at the centre between the
highest and lowest line of a divided warp.
Open shed in this
types of shed, the ward threads from two stationary lines, one at the top and
another at the bottom. After inserting a pick change are made by carrying yarn
from one fixed line to the other. So some yarn are lowered from the top line
and some are raise from the bottom line during the change, raising and lowering
of the yarn occurred simultaneously.
Semi open shed this
is formed under both open and closed principles. Here a stationary bottom line
is retained, but yarn from the top line either passes to the bottom at one
movement, or are arrested midway and again carried to the top.
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