Weaving, loom

Weaving slide.

1. weaving Fabric Manufturing II

2. Loom: Loom is machine or device which is used to produce woven fabric. It is the central point of whole process of cloth production. It is a device used to weave cloth. The basic purpose of any loom is to hold the warp threads under tension to facilitate the interweaving of the weft threads. The precise shape of the loom and its mechanics may vary, but the basic function is the same.

3. Chronological/ Historical development of loom 1. Vertical loom: Damask, Tapestry. 2. Pit loom. 3. Frame loom. 4. Chittarangan / Semi-automatic loom:Take up automatic but let off manually. 5. Hattersley loom. 6. Natural Source/ Ordinary power loom: a) Water wheel was until 195 b) Steam engine c) Diesel engine 7. Electric power loom: 1st power loom 1784 1st weaving mill with power loom 1789 a) Large single motor b) Large group motor c) Individual motor with 1930 8. Modern loom: a) Projectile b) Rapier c) Air Jet d) Water Jet e) Multiphase

4. Primitive or Vertical loom:

5. Pit loom: Weaving has a long tradition in Egypt going back as far as 6,000BC during which time methods have changed enormously. This simple pit loom is the kind that is frequently found in farms and villages operated by men and women who make carpets, chair covers, shawls, blankets and bed covers The weaver sits with his or her legs in the pit where there are two pedals which open the warp threads allowing the weft shuttle to pass through freely. This type of loom leaves the weavers' hands free to pass the weft shuttle through from side to side and to compress the weaving as they go.

6. Pit loom

7. Frame loom Simple and effective - wonderful introduction to weaving - very quick to warp and weave - strong - compact Create wall hangings, cushions, tablemats and coasters. The loom is ideal for students or any weaver wanting a simple way to be creative. Made from solid Silver Beech hard wood the frames are strong and robust for a variety of warps and tensions. Small and compact, the weaving frame is ideal for taking on holiday. The finished piece can be left in the frame and hung on the wall

8. Frame loom

9. Loom motions: There are three types of loom motions:- 1. Primary 2. Secondary. 3. Tertiary. Primary motions are: a) Shedding b) Picking c) Beating. Secondary motions are: a) Take-up b) Let-off Tertiary motions are: a) Warp stop b) Weft stop c) Reed stop. Drafting: The process of passing yarn through the drop wire is called drafting. Drawing: The process of passing yarn through the heald eye is called drawing. Denting: The process of passing yarn through the reed is called denting.

10. Power development of loom drive Hand loom: Human power drive Power loom: Water wheel Steam wheel Diesel Wheel Electric wheel Large common motor (200loom/ motor) Group motor ( 200 loom/ motor) Individual motor invented at 1930 Direct drive Indirect drive Multiple motor : for each modern loom

11. Group motor Disadvantage: Absenteeism of warker Shortage of raw materials Shortage of worker Style change Shortage of spare parts Natural calamities Political issue Power loss Advantages: Less man power required Minimum cable required Less initial cost Less electric complexity

12. Individual motor Advantage: Randomly power supply Power saving Simple driving system Least amount of production loss Disadvantage: Higher initial cost More cable required More possibility of fire hazard Maximum electric personnel required Distribution and sub distribution board required High manpower

13. Methods of power drive in weaving loom: Direct drive Loom driven directly by on-off system of motor High initial torque is required Saves energy No side way thrust is required High initial cost Used in jute loom No use of clutch Indirect drive Clutch declutch system Low initial torque Apply undesirable side way thrust Low initial cost

14. Shedding: Dividation of warp threads into two parts for insertion of weft threads is called shed and mechanism of shed is called shedding.it is the first primary motion of weaving. Types of shed: Bottom close shed Centre close shed Semi open shed Open shed

15. 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 in the bottom line. Hence in A  Bottom line of warp order to form a top shed B  Rising and falling line it is necessary to move C  An arrow showing the space some threads through a passed through space equal to twice the depth of a shed. A B C

16. Advantage: Used in hand loom Alternate tightening and slacking the warp threads produce a covered cloth DISADVANTAGE: More stress or tension on top warp line Different tension on the warp threads Low speed Not possible to produce compact fabric Poor quality fabric More chance of breakage on top warp line More power consumption

17. 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 a downward movement to the threads which are to form the bottom line. Then after inserting pick both trhe lines meet at the centre between the highest and lowest lines of a divided warp A  Closed warp line B, C  Upper and lower lines of a divided warp 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 A B C D E A

18. Advantage: Equal tension on top and bottom warp line Less time required, so high production Less wear of the machine Less power consumption Less tear of the threads DISADVANTAGE: Beat up takes place in the closed shed Compact fabric can not be produced Chance of weft being moved backward

19. 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 distribut

20. Semi-open shed: 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 C A D B F E

21. Semi-open shed: ADVANTAGE: Equal tension on the top and bottom warp line Beat up takes place in the close shed Speed faster For fency fabric Less power need Less tear of threads Possible to produce compact fabric Disadvantage: unusual movement

22. 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 C A D B

23. Open shed ADVANTAGE: Beat up takes place in cross shed condition Equal tension top and bottom warp threads Faster speed Extensively used in tappet shedding mechanism Basic fabric (twill, sateen, plain) can be produced Less power consumption Less wear of loom DISADVANTAGE: High breakage rate If higher no of heald shafts are used then warp in back healds are more stained than the front ones

24. Basic shedding mechanisms: Paddle/ treadle loom: hand loom Tappet shedding mechanism Dobby shedding mechanism Jacquard shedding mechanism Combined shedding

25. Tappet shedding A type of cam which transforms a rotary motion into a reciprocating motion in rods and levers by sliding contact is tappet. When the receives a series of lifts, with intervals of rest and thus forms a shed called tappet Scope of tappet shedding: Maximum capacity 14 heald shafts Normally produce square design Only the basic weave and small design are produced

26. Construction of tappet shedding: The figure shows a negative tappet shedding mechanism. A pair of tappets A and B are fixed to the bottom shaft C at 180 degrees to each other. Two treadle levers D and E are connected to the loom back-rail by a bracket F. The bracket acts as a fulcrum for the levers. The two treadles have teeth to carry the lamb rods G and H respectively. Two heald shafts J and K are connected to the lamb rods. A top reversing roller shaft Q carries two rollers of different diameters. The roller of small diameter N is connected to a leather strap L to which the front heald shaft J is connected. The roller P of large diameter is connected to a leather strap M to which the back heald shaft K is connected. The tappets A and B touch the anti-friction bowls or followers R and S respectively, which are fixed to the treadle levers. The heald shafts have heald eyes T and U through which the war p threads pass X is the war p sheet and Y is the cloth. The odd ends are passed through one heald shaft while the even ends are passed through the other heald shaft.

27. Working principle of tappet: When the bottom shaft is rotate as shown in the figure, the tappets also rotate. The tappet will depress the anti-friction bowl and the treadle. Being fulcrumed at one end, the front portion of the treadle moves down. This action is transferred to the lamb rod, the heald shaft and the leather strap. So one heald shaft is lowered and the threads connected to this heald shaft are lowered and form the bottom layer of the shed. The leather straps attached to the reversing rollers are connected in opposite directions, i.e. when leather strap is pulled down, it is unwound from its roller. The shaft therefore rotates in the clockwise direction and the other leather strap is wound on to its roller. The heald shaft is raised and therefore the lamb rod and treadle lever are also raised. The threads connected to the heald shaft are also raised and form the top layer of the shed. For the next shed, the other tappet works with the other set of bowl, treadle, lamb rod, heald shaft, strap and roller and the other heald shaft is lowered.

28. Types of tappet: Negative tappet: in a tappet shedding mechanism if the tappet controls only one movement either an upward or downward movement of heald shaft, then the shedding is known as negative tappet shedding. Positive tappet: : in a tappet shedding mechanism if the tappet controls both the upward and downward movement of heald shaft,then the shedding is known as positive tappet shedding.

29. Advantages of tappet shedding: Simplest Cheapest If properly used, it gives the best results within its capasity Action is certain It is capable of lifting heavy weights with less wear and tear than other shedding mechanisms Less wear and tear Consumes less power and give greater output

30. Defects of tappet shedding: Over shedding strains and breaks the warp threads Under shedding does not permit the space to pass the shuttle through the shed. Sometimes unequal shedding by lifting one end of the shaft more than the other Missed shedding May impart jerky motion Capacity is only 14 heald shaft