The process of producing a fabric by interlacing warp and
weft threads is known as weaving. The machine used for weaving is known as
weaving machine or loom. Weaving is a skill that has been practiced for
thousands of years. The initial application of weaving dates back to the
Egyptian civilization. Over the years, both the process as well as the machine
has undergone phenomenal changes. As of today, there is a wide range of looms
being used, right from the simplest hand loom to the most sophisticated loom.
In this rang, the most widely prevalent loom, especially
with reference to India, is the ubiquitous “plain power loom”. In this and in
the chapters that follow, the various mechanisms associated with the plain
power loom are discussed in elaborate detail.
Different mechanisms of a Plain Power Loom
In order to interlace wrap and weft threads to produce a
fabric, the following mechanisms are necessary on any type of loom. There are
three mechanisms involve they are
1. Primary mechanisms
2. Secondary mechanisms
3. Auxiliary mechanisms
1. Primary
Mechanisms
These are primary or essential mechanisms. Without these
mechanisms, it is practically impossible to produce a fabric. It is for this
reason that these mechanisms are called ‘primary’ mechanisms. The primary
mechanisms are three in number.
a. Shedding mechanism
b. Picking mechanism
c. Beat-up mechanism
a.
Shedding mechanism
The shedding mechanism separates the warp threads into two
or more layers according to design or divisions to form a tunnel known as
‘shed’
b. Picking mechanism
The picking mechanism passes weft thread from one selvedge
of the fabric to the other through the shed by means of a shuttle, a
projectile, a rapier, a needle, an air-jet or a water-jet. The inserted weft
thread is known as “pick”.
c. Beat-up mechanism
The beat-up mechanism beats or pushes the newly inserted
length of weft thread (pick) into the already woven fabric at a point known as
“fell of the cloth”. These three mechanisms namely shedding, picking and then
beat-up are done in sequence.
2. Secondary Mechanisms
These mechanisms are next in significance to the primary
mechanisms. If weaving is to be continuous, these mechanisms are essential. So
they are called the ‘secondary’ mechanisms. They are:
a) Take-up motion
b) Let-off motion.
a) Take-up motion
The take-up motion withdraws the cloth from the weaving area
at a constant rate so as to give the required pick-spacing (in picks/inch or
picks/cm) and then winds it on to a cloth roller.
b) Let-off motion
The let-off motion delivers the warp to the weaving area at
the required rate and at constant tension by unwinding it from the weaver’s
beam. The secondary motions are carried out simultaneously.
3. Auxiliary Mechanisms
To get high productivity and good quality of fabric,
additional mechanisms, called auxiliary mechanisms, are added to a plain power
loom. The auxiliary mechanisms are useful but not absolutely essential. This is
why they are called the ‘auxiliary’ mechanisms. These are listed below.
a. Warp protector mechanism
b. Weft stop motion
c. Temples
d. Brake
e. Warp stop motion (Predominantly found in automatic looms)
a. Warp protector mechanism
The warp protector mechanism will stop the loom if the
shuttle gets trapped between the top and bottom layers of the shed. It thus
prevents excessive damage to the warp threads, reed wires and shuttle.
b. Weft stop motion
The object of the weft stop motion is to stop the loom when
a weft thread breaks or gets exhausted. This motion helps to avoid cracks in a
fabric.
c. Temples
The function of the temples is to grip the cloth and hold it
at the same width as the warp in the reed, before it is taken up.
d. Brake
The brake stops the loom immediately whenever required. The
weaver uses it to stop the loom to repair broken ends and picks.
e. Warp stop motion
The object of the warp stop motion is to stop the loom
immediately when a warp thread breaks during the weaving process.
