Shedding, Picking, and Beat-up are the mechanisms which are essentially required on a weaving machine for the operation to be carried out. Shedding motion is one of the basic motions in a weaving machine.
Types of shedding mechanism
There are three major types of shedding mechanism’s namely Tappet, Dobby, and Jacquard. Based on their technical and operational characteristics on should decide which shedding mechanism to be used.
Tappet Shedding System
The tapping shedding system is a motion of tappets and cams that cause shafts to be raised to form the shed. The mechanical arrangement of this system occupies so much of space that it can accommodate a maximum of eight shafts and that is why its eight shafts represent maximum size of its weave repeat. This limits to the weaving of plain weaves, simple twills and simple sateen and satin weaves. In case, the repeat of the desired design requires more than eight shafts, then a dobby loom has to be used. Fig. shows tappet shedding with roller reversing.
Dobby Shedding System
A mechanism for controlling the heald shafts of a loom. It is required when the number of heald shafts or the number of picks in a repeat of pattern or both is beyond the capacity of tappet shedding This is a shedding system capable of having up to 32 shafts. Being able to accommodate up to 32 shafts, a much greater weave repeat and complicated design is possible.
Jacquard Shedding System
This shedding system has no shafts. A harness consisting of as many cords as there are ends in the warp sheet connects each end individually to the Jacquard machine situated high above the loom. Therefore, each warp can weave independently of all the others. Since each warp yarn can be controlled individually, the greatest weave repeat is possible. This enables most intricate designs to be woven.
Standard Properties of Woven fabrics
|Very heavy||> 13 oz/yd2|
|Heavy||> 6 – 13 oz/yd2|
|Medium||> 4 – 6 oz/yd2|
|Light||> 2 – 4 oz/yd2|
|Very light||< 2 oz/yd2|
|Medium or average||45, 54, 60, 72”|
|Narrow||27 – 36”|
|Very narrow||< 12”|