Shed: Deviation of warp threads into two parts for insertion of weft threads is called shed. Shedding: the mechanism of shed is called shedding. It is the first primary motion of weaving.

1. Welcome to our Presentation
Fabric Manufacturing-II (Shed geometry)

2. 2
SHAMIM SARKAR SAMIUL
Presented By:
Department of Textile Engineering
Dhaka University of engineering & Technology,
Gazipur

3. Our presentation topic:
SHED
GEOMETRY

4. Shed and Shedding:
Shed: Devidation of warp threads into two parts for
insertion of weft threads is called shed.
Shedding: the mechanism of shed is called
shedding.
It is the first primary motion of weaving.

5. Types of shed:
1.Bottom close
shed
2.Centre close
shed
3.Semi-open shed
4.Open shed

6. TYPES OF SHED:
There are four types of shedding.
Center close shed
After inserting a pick, both the lines meet at the center
between the highest and lowest line of a divided warp.
Bottom close shed
This kind of shed is known as a stationary bottom
with a rising and falling top.
Semi open shed
A stationary bottom line is refined, but threads from
the top line either pass to the bottom at one movement
or carried out to the top. The remaining threads move
down.
Open shed
In this types of shed, the warp threads from two
stationary lines, one at the top and another at the
bottom. After inserting a pick change are made by
carrying threads from one fixed line to other.
6

7. A→ Bottom line of warp
B→ Rising and falling line
C→ An arrow showing
the space passed
through
1.Bottom close shed:
This type of shedding is produced by
giving motion only to threads that are to
form the upper line. Under this condition,
the warp is level on the bottom line.
Hence in order to form a top shed, it is
necessary to move some threads
through a space equal to twice the depth
of a shed, once up and down, before a
fresh selection is made. A shed of this
kind is known as stationary bottom with
a rising and falling top.

8. Advantages:
 Alternate tightening and slackening the warp threads produce a
covered cloth
 Produce fire fabric (silk)
 Used in hand loom
Disadvantages:
 More stress or tension on the top warp line and less tension on the bottom
warp line.
 More chance of breakage on top warp line
 Unequal warp tension produces poor quality fabric
 Loom speed/ waving speed is slower
 Not possible to produce compact fabric
 More power consumption
 More time required

9. 2. Center close shed:
This type of shed is produced by imparting an upward movement
to those threads which are to form the top line and the downward
movement to the threads which are to form the bottom line. Then
after inserting a pick, both the lines meet at the center between the
highest and lowest lines of a divided warp.
A→ Closed warp line
B, C→ Upper and lower lines of a divided warp respectively
D→ Arrow showing the half distance of a shed in an upward direction
E→ Arrow showing the half distance of a shed in a downward direction

10. Advantages:
 Equal tension on the top and bottom warp
line
 Less time required so high production
 Less wear of the m/c
 Less power consumption
 Less tear of the threads
Disadvantages:
 Beat up takes place in the closed shed
condition
 There is chance of weft being moved
backward
 Compact fabric can not be produced by this
shed

11. 3. Semi-open shed:
In this shed, the stationary bottom is retained but threads for the top line either passes to
bottom at one movement and again carried to the top mid way and again carried to top. In this
shed close and open shed occurred simultaneously. In it the stationary bottom line is retained,
but threads for the top line either pass to the bottom at one movement, or are arrested midway
and again carried to the top. Such a shed can be formed as expeditiously as an open shed, for
the upward movement begins and ends with the downward through movement, and the
arrested downward movement is converted into an upward movement immediately the falling
threads are in the same plane as the rising ones. They all reach the top together but the strain
upon them is not equally distributed.
A→ Stationary bottom line
B→ Top point
C→ The point where downward movement ceases in threads
D, E→ Showing the movement of through healds
F→ Arrow showing the threads which are to lift for the next pick

12. Advantages:
 Equal tension on the top and bottom warp
line
 All the warp yarns are not required to move
up and down in every pick
 Beat up takes places in the cross-shed
condition
 The loom can run at a faster speed
 Possible to produce compact fabric
 Less complexity or disturbance in the
shedding mechanism
 Used in power, dobby & jacquard loom
 For fancy fabric
 Less power consumption
 Less tear of threads
Disadvantages:
 Unusable movement

13. 4. Open shed:
In open shed, the warp threads form two stationary
lines, the top line and the bottom line and changes are
made by carrying the threads from one fixed line to the
other without any interval.
A, B→ Stationary warp line
C, D→ Arrows which show the movement of rising
and falling warp to equal the distance between A & B

14. Advantages:
 Beat up takes place in cross-shed condition
 Equal tension on the top and bottom warp line
 The loom can run at a fastest speed
 Extensively used in tappet shedding mechanism
 Basic fabric (twill, sateen, plain) can be produced.
 Less power consumption
 Less wear of the weaving m/c
Disadvantages:
 High breakage rate
 If higher no of healds are used then the warp in back healds
are more strained than the front ones
 Leveling apparatus should be added to open shed to place
the headls in one plane

15. Thanks you All for being keep with us