Types of weaving loom motion
In order to interlace wrap and weft threads to produce a fabric, the following motions are necessary on any type of loom:
1. Primary motions
2. Secondary motions
3. Tertiary motions
1. Primary Motions:
These are fundamental 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 layers or divisions to form a tunnel known as ‘shed’. The shed provides room for passage of the shuttle. A shed may be formed by means of tappets, dobby and jacquard.
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Fig: Shedding motions. |
Types of Tappet Shedding Mechanism:
Generally there are two types of shedding
1. Negative tappet shedding
2. Positive tappet shedding
Negative Tappet Shedding:
In a tappet shedding mechanism, if the tappet controls only one movement, either an upward or downward movement of the healed shafts, then the shedding is known as “negative tappet shedding”. The healed shafts are returned by some external devices like springs, dead weights, rollers, etc.
Positive Tappet Shedding:
In a tappet shedding mechanism, if the tappet controls both upward and downward movements of the healed shafts, then the shedding is known as positive tappet shedding.
(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”.
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Picture: Picking Mechanism |
(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.
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Picture: Beating mechanism with sley |
2. Secondary Motions:
These mechanisms are next in importance to the primary mechanisms. If weaving is to be continuous, these mechanisms are essential. So they are called the ‘secondary’ mechanisms. They are:
- Take-up motion
- 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. The main part of the mechanism is the take up rollers, which draws the cloth at the regular rate, and the number of picks per inch decides this rate. The take up roller is covered with emery cloth or hard rubber depending upon the type of cloth woven. The drive to the take up roller is by a train of gear wheels put into motion directly from the main shaft.
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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. The speed of the servo motor is transmitted to warp beam gear via reduction gear, thus driving beam.
3. Tertiary Motions:
To get high productivity and good quality of fabric, additional mechanisms, called auxiliary mechanisms, are added to a loom. The auxiliary mechanisms are useful but not absolutely essential. This is why they are called the ‘auxiliary’ mechanisms. These are listed below.
a. Weft stop motion
b. Warp stop motion
c. Warp protector mechanism
d. Weft replenishment / Warp mixing motion
e. Cutter
f. Temples
g. Brake
h. Selvedge
1 comments:
Is it possible to have some small pictures of weaving motions like shedding and beat-up motions? I need them for my forthcomming book on textile.
Thank you. Akhil Ashdhir.
P.S. Please have a look at my other published book "HISTORY OF TEXTILE DESIGN" AT www.lulu.com
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