In order to achieve the technique of fabric manufacturing as described above briefly, the working of a loom has been divided into three basic motions:-
(i) Shedding: This is the operation that helps in opening up the warp sheet creating the gaps through which the weft yarns will pass. In order to do this operation, primitive looms had the wooden shafts that were lifted by hand or by leg-driven pedals, as in handlooms. In power looms, this is done with the help of electricity, and the shafts were cam-driven initially. But this hampered the loom productivity as well as the design size was limited. So, later on, developments have evolved the dobby and then the jacquard mechanisms for shedding. In dobby, the design size is larger, giving the weaver or designer an increased scope for design exploration. The productivity is also higher. In jacquard, the design size is virtually unlimited and productivity even higher. But jacquard designs are more complicated to be set up on a loom and hence, dobby looms are preferred in most cases, owing to comparative simplicity and lesser cost.
(ii) Picking: This is the operation in which the weft or the pick, also referred as the fill, passes through the open warp sheet. There are various methods of carrying the weft across the full width of the loom. In the most primitive way, a shuttle was used, which a wooden missile-like structure with a weft pirn would carry the weft yarn inside it. The shuttle was mechanically thrown from one side to the other. Low productivity and associated health hazards caused it to be replaced with other improved devices like the projectile, the rapier, the air-jet and the water-jet looms.
(iii) Beat-up: This is a very important operation of the loom. After shedding and picking, the beat-up action is to ensure that the newly introduced weft is closely packed in the body of the fabric, and hence, a mechanical force or thrust is exerted on the new weft by a device called the reed to embed it into the main fabric already woven, closely with the prior weft yarns.
