2. Introduction
• Weaving is the process of interlacing two or more sets of threads to create a
fabric.
• The two main sets of threads are the warp threads, which run vertically, and
the weft threads, which run horizontally.
• The process of weaving involves separating the warp threads into two layers,
or a shed, so that the weft thread can be passed through. This is called
shedding.
• Once the weft thread is in place, it is beaten up against the previous weft
threads to secure it in place. This is called beat up.
6. Shedding
Shedding is the first of the three primary
motions in weaving. The goal of shedding is to
create an opening, or shed, in the warp threads
so that the weft thread can be passed
through. There are many different ways to shed
the warp threads, but the most common methods
are dobby, tappet, and jacquard.
7. Here's a step-by-step explanation of the shedding process:
1.Warp Threads:
• The warp is the set of lengthwise yarns in a loom. These threads are
typically stronger and run parallel to each other.
• The warp threads are attached to the loom's front and back beams and are
initially in a straight, parallel arrangement.
2.Heddles:
1. Heddles are devices that hold and control the warp threads individually. They
are attached to shafts or frames.
2. Each warp thread passes through a heddle, and multiple heddles are attached
to a shaft. The shafts can be raised or lowered to create the shed.
8. 4.Insertion of Weft Yarn:
• With the shed open, the weft yarn (the crosswise thread) is inserted through the
gap created by the shedding process.
• The weft thread is usually carried by a shuttle, a small device that moves back
and forth across the loom.
3.Shed Formation:
• To create a shed, some of the heddles are raised while others are lowered. This
action creates an opening or gap between the layers of warp threads.
• The raised warp threads form the upper layer, and the lowered warp threads
form the lower layer. The space between these layers is known as the shed.
9. 5.Changing the Shed:
• After inserting the weft, the shed needs to be changed to prepare for the next
insertion of the weft.
• The heddles are manipulated again, alternating the position of the warp
threads to create a new shed.
6.Repeating the Process:
• The shedding, beating (packing the weft threads together), and advancing
the warp are repeated to build the fabric.
10. Types of shedding mechanism
1. Negative shedding
In negative shedding , the upward or downward movement of the heald frame only
controlled by shedding mechanism. The returning Action of the heald frame is assisted by
some separate mechanism namely top reversing rollers, elastic cords and springs
2. Positive shedding
In this, both up and down movement of heald frame is controlled by the shedding
meachanism itself
11. Negative Tappet Shedding
Working : As the bottom shaft rotates,
the tappet presses the bowl and hence
the treadle lever lowers. As the treadle
lever lowers, one heald shaft is
pressed and due to the top reversing
roller action the other heald frame is
raised and the warp shed is formed.
The tappet is designed in such a way
that the back heald frame will be given
higher lift than the front heald frame
8 heald frames were controlled in
tappet shedding.
12. Positive tappet shedding Working : When the tappet is rotated,
the bowl is also rotated. According to
the shape of the groove , the bowl is
moved up or down or is still.If the
bowl is moved up, the tappet lever
moves to the right through the links
the heald shaft is lowered . If the bowl
is moved down, the tappet lever
moves to the left and the heald shaft is
raised.Since the heald shaft is raised
and lowered by means of the
mechanisms, this tappet shedding is
known as positive tappet shedding
mechanism.When the bowl stands
still, the heald shaft is in the dwell
stage.
16. Jacquard shedding
Jacquard is a device used to produce large figures or patterns that are above
the capacity of the dobby. A jacquard device is located above the loom. Here no heald
frames are used. Warp threads are individually controlled by hareness cords, hooks
and needles. Jacquard is invented in the year of 1801 by a French weaver
"Joseph.M.Jacquard".
17. Types of jacquard
1. Single lift jacquard.
2. Double lift single cylinder jacquard.
3. Double lift double cylinder jacquard.
4. Double lift single cylinder single hook jacquard for high speed weaving.
5. Electronic jacquard.
6. Jacquards for special use as Cross border jacquard, Damask jacquard, Leno
jacquard, Fine pitch jacquard.
18. Picking mechanism
In a weaving loom, the picking
mechanism is a crucial component responsible
for inserting the weft yarn through the shed
created by the warp threads. The shed is the
opening formed when some warp threads are
raised and others are lowered, creating a space
through which the weft yarn can be passed to
form the fabric.
There are various types of picking
mechanisms used in different types of looms,
and the choice of mechanism depends on the
specific loom design and weaving requirements.
Here are some common types of picking
mechanisms:
19. 1.Shuttle Picking:
• In traditional shuttle looms, a shuttle containing the weft yarn is propelled
across the loom through the shed. The shuttle is typically moved by a picking
mechanism that can be driven by various methods, such as a cam, dobby, or
Jacquard mechanism.
Types of shuttle picking mechanism:
1. Cone over pick mechanism
2. Side lever under pick mechanism
22. 2. Rapier Picking:
• Rapier looms use a rigid or flexible rapier to carry the weft yarn across the
loom. The rapier is either rigid and extends across the loom or flexible and is
guided through the shed by a series of pulleys. This mechanism eliminates
the need for a shuttle and is often faster than shuttle-based systems.
23. 3.Projectile Picking:
• Projectile looms use a small metal or plastic device, known as a projectile, to
carry the weft yarn across the loom. The projectile is shot through the shed,
and once it reaches the other side, the weft yarn is released, creating a
continuous insertion of the weft.
24. 4.Air-Jet Picking:
• Air-jet looms use a jet of compressed air to carry the weft yarn across the shed.
The weft yarn is attached to a small plastic tube, and when the air jet is released,
it propels the weft through the shed. Air-jet looms are known for their high speed
and efficiency.
25. 5.Water-Jet Picking:
• Water-jet looms use a jet of water to carry the weft yarn across the shed.
The weft yarn is carried by the water stream and then pressed against the
fabric by rollers. Water-jet looms are suitable for weaving a variety of
yarns, including filament and spun yarns.
26. Beatup mechanism
The beat-up process is a critical step in
the weaving of fabric that follows the shedding
process. After the weft yarn has been inserted
through the open shed formed by the raised and
lowered warp threads, the beat-up process is
employed to tightly pack or compress the weft
threads into the woven fabric. This step ensures
that the newly inserted weft is securely
integrated with the existing fabric structure,
creating a stable and cohesive textile.
27. Here's a breakdown of the beat-up process in weaving:
1.Shed Formation:
1. The process begins after the insertion of the weft thread through the open shed
created by the shedding process. The shed is the temporary gap between the
raised and lowered warp threads.
2.Beater or Reed:
1. The beat-up process is carried out using a component called the reed or beater.
2. The reed is a comb-like structure that contains a series of closely spaced metal
or plastic strips called dents. These dents correspond to the desired density or
thickness of the fabric.
28. 3.Beating the Weft:
1. Once the weft thread is inserted through the shed, the reed is moved toward the
fell of the cloth. The fell is the point where the newly inserted weft meets the
woven fabric.
2. The reed is pushed or struck against the woven fabric, forcing the weft threads to
settle into their final position.
4.Ensuring Uniformity:
• The purpose of beating up is to ensure that the weft threads are evenly
distributed across the width of the fabric.
• The reed helps maintain the proper spacing and alignment of the weft threads,
preventing irregularities and ensuring a consistent fabric density.
29. 5.Advancing the Fabric:
• After beating up, the fabric is advanced or moved forward to expose a new
section of the warp for the next shedding and weaving cycle.
