Shedding mechanism is set according to the picking and Beat-up motions. Timing of shedding is set with respect to crank shaft position.
In general Shedding is Classified into three categories:
Normal Shedding
Early Shedding
Late Shedding.
Normal Shedding:
In case of normal shedding all the heald shafts comes to equal level when the crank shaft is at top center position, i.e., 0 degree or 360degrees.
Early Shedding:
In case of early shedding all the heald shafts come to equal level when the crank shaft is at 5 degrees before top center i.e., 355 degrees.
Advantages of Early Shedding:
Fabric cover is improved, because during beat-up, the warp yarns are evenly distributed.
It assists in clearing the shed while weaving fibrous warp like woolen and worsted. So, entanglements are avoided.
Heavy weft yarn can be easily inserted. So hard weaves like corkscrew weaves can be woven.
Disadvantages of Early Shedding:
Strain on Warp yarn is high as the warp yarns are widely opened during beat-up.
High end breakages as chuffing of warp yarn (yarn abrasion) during Early Shedding.
Late Shedding:
In case of late shedding all the heald shafts come to equal level when the crank comes to 5 degrees after top center.
Advantages of Late Shedding:
Late shedding can be used for weak warp yarn.
It allows greater time for shuttle passage, so it is suitable for synthetic yarns.
It is useful if pick of low strength is used.
Disadvantages of Late Shedding:
It causes a very weak fell of the cloth because the weft may roll back.
It causes less distribution of yarn. So, it is not suitable for fibrous warp.
As the warp yarns are not distributed evenly during beat-up, fabric cover is low.