Experiment name:
Study on Jacquard shedding mechanism.
Introduction:
In weaving if we want to make any design in our fabric we have to separate the warp yarn according to our weave plan. In tappet or dobby shedding we have some limitations in shedding for a critical design. But in jacquard shedding it can be done easily. Jacquard is a shedding device placed on the top of the loom to produce large no of patterns by using a very large no of warp threads separately by means of harness cords, hooks and needles. The figuring capacity of a jacquard is 1800+. It means it can produce design with more than 1800 warp threads by controlling them individually, which is far beyond the capacity of a dobby or tappet loom. Many specialized types of jacquard machine have been developed for weaving particular kinds of fabric, such as terry towels, damasks and carpets.
Jacquard consists of upright hooks and horizontal needles. Needle board is a perforated board through which the needles pass. Now electronic jacquards are available that are controlled by computers and there is no need for preparing laborious punching cards and pattern chains. With punching card system, each weft insertion needs one punched card, and hence the number of cards in a large design used to be several thousands and several days were required to develop one design. With electronic system, a design can be developed and sample produced within 20 to 30 minutes. The speed of a jacquard loom is much less compared to a tappet loom or a dobby loom.
Main parts of jacquard shedding:
- Pattern chain.
- Motor.
- Pattern cylinder.
- Needle.
- Knife.
- Harness cord.
- Neck cord.
- Comber board.
- Top board
- Hook.
- Grid bar
- Dead weight.
- Spring board.
- Needle board.
Jacquard Shedding mechanism:
For jacquard shedding mechanism here punched card are used which is made according to design. One pattern card is used for one pick. With these pattern cards pattern chain is made which is placed on the pattern cylinder. On each pick pattern cylinder rotates 1/4th of the full rotation in clockwise direction. At the same time it oscillates to and fro forming an arc.
Here,
- Hooks
- Knife
- Knife frame
- Neck cord
- Rod
- Grade
- Horizontal needle
- Needle broad
- Cylinder
- Spring box
- Spring
- Card
With every 1/4th rotation a new card comes front of the cylinder in the hook side and for the two and fro movement the needles enter inside the holes of the punch card. This selection of entrance inside the punches of the needles is actually done according to design.
If a needle enters in the hole of the card the needle remains stationary in its position. So the needle crank also remains stationary in its position. So for the upward movement of the knife the hooks also goes upward along with the warp threads to form the top line.
But if needle gets no perforation to enter, the hook is pushed to the right and as result the needle crank takes away the hook along with it. So when the corresponding knife goes upward it cannot lift the hook with it. Thus the warp ends of those hook remains fixed in its position and form the bottom line.
After certain time the knife releases two hooks which is lifted to form the top line and due to wrap tension and dead weight the heald eye comes down. Its downward movement is controlled by grid bar. Each needle has a spring push at its right and that spring pushes back the needle when the next card comes.
Conclusion:
By this experiment we learned about the jacquard shedding and how it works. It is the finest of all machines for making the designed woven fabrics that have been invented and far superior in capacity to a dobby or tappet loom.
You may also like:
- Differences between Tappet Shedding, Dobby Shedding and Jacquard Shedding Mechanism
- Dobby Shedding Mechanism | Scope of a Dobby
- Construction of Shedding Tappet for Plain Weave
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
