in weaving different types of shed are produced. here i give short note on shed

1. SHORT NOTE ON
SHED

2. SHED:
 In weaving shed is the temporary separation between upper and
lower warp yarns through which the weft is woven
 The shed is created to make it easy to interlace the weft into the
warp and thus create the woven fabric
 Shed is produced by means of healds or harness

3. CONDITION FOR GOOD SHED:
 It should be as small as possible
 Heald are to be placed at right angle to warp thread
 Perfect leveling of healds are to be obtained
 The velocity of the upward and downward movements of the healds
must be variable to correspond, as far as possible with the tension
upon the warp
 Smooth movement of the heald frames

4. TYPES OF SHED:
SHED
CLOSED
SHED
BOTTOM
CLOSED
SHED
CENTRE
CLOSED
SHED
OPEN SHED
SEMI OPEN
SHED
OPEN SHED

5. CLOSE SHED:
BOTTOM CLOSED SHED:
 This kind of shed 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 shed, once up & once down,
before a fresh section is made.
 A shed of this kind is known as a stationary bottom with a rising & falling top

6.  A bottom line of warp
 B rising and falling line
 C an arrow showing the space passed through

7. ADVANTAGES:
 Alternate tightening and slackening the warp threads produce a covered cloth
 It is suitable for fine fabric particularly in silk fabric
 Produce fine fabric
DISADVANTAGES:
 It takes long time to produce a shed
 Not suitable for high speed loom
 More chance of breakage of top warp line
 It requires more power
 Unequal warp tension
 Low production
 More tension on yarn
 Not possible to produce compact fabric

8. USES:
 Tappet loom
 Single loom dobby
 Jacquard loom

9. CENTRE 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.
 Upper and lower lines of a divided warp respectively

10. In the figure
 A is the closed warp line,
 B and C are respectively the upper and lower lines of a divided
warp
 D and E are arrows which show the movement of each thread to
equal the depth of a shed, namely half the distance in an upward
and half in a downward direction.

11. MERITS:
 Equal tension on the top and bottom warp line
 Less time required so high production
 Less wear and tear of the m/c
 Less power consumption
 Less tear of the threads
DEMERITS:
 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
 Since every thread is moved to form each shed, strain on yarn is
more
 Possibility of yarn breakage due to rubbing

12. USES:
 Tappet loom
 Single lift jacquard loom
 Dobby loom
 Wood crafts tappers
 Hand loom

13. OPEN SHED:
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.
 They all reach the top together but the strain upon them is not
equally distributed.
 Upper and lower lines of a divided warp respectively
 In this shed close and open shed occurred simultaneously.
 This shed is formed under both open and closed principal

14.  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

15. MERITS:
 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 and jacquard loom
 For fancy fabric,
 Less power consumption
 Less tear of threads
 Required minimum time
 Strain upon warp is low

16. DEMERITS:
 Strain on yarn is not equally distributed
 Difficult to find breakage yarn
 Levelling the heald is difficult
 Unusable movement
uses:
 Double lift jacquard
 Double lift dobbies

17. OPEN SHED:
 In this types of shed, the warp threads form 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 the other.
 Some threads are lowered from the top line and some are raised
from the bottom line during the change raising and lowering of the
threads occurred simultaneously.

18. Here,
 A & B two stationary lines of warp
 C & D arrows which show the movement of rising and falling warp to
equal the distance between A & B
 The fell of cloth E & lease F from two ends of the open shed

19. MERITS:
 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 and tear of the weaving m/c
 More production
 Strain upon the warp is less

20. DEMERITS:
 High breakage rate
 If higher no of healds are used then the warp in back healds are
more strained than the front ones
 Problem in knotting, so some effective apparatus known as
“Leveling apparatus” should be added to open shed to place the
headls in one plane.
USES:
 Ordinary tappet loom
 Jacquard loom