Making of Woven Fabrics
Woven fabric is normally much longer in the warp direction than it is wide, that is, in the weft direction. Warp yarns are fed from large reels called creels or beams. Typically, these hold about 4500 separate pieces of yarn, each about 500 yards (450 m) long. The filling yarns are fed from bobbins, called quills, carried in shuttles (hollow projectiles) that are moved back and forth across the warp yarns, passing over some and under others. The shuttle is designed so that the yarn it carries can unwind freely as the shuttle moves. Each length of yarn, fed from the shuttle as it moves across the loom, is called a pick. The yarn folds over itself at the end of each pick and forms another pick as the shuttle returns. When the yarn in a particular shuttle is exhausted, current production looms have automatic devices that exchange the empty quill with a full one.
A typical loom in operation (weaving)
a) shedding, raising some warp yarns to make room for the shuttle
b) picking, laying the weft (filler) yarn across and between warp yarns
c) beating in, pushing the reed against the last filler yarn against the woven cloth.
- Raising selected warp yarns, or ends, with suitable harnesses, consisting of frames of heddles, with taut vertical wires and eyelets, or strips with openings in the middle. There is one heddle for each end that is threaded through the eyelet. The heddles guide and separate the warp yarns, raising some of them to make room for the shuttle during the pick. This action is called, shedding, and the space between the warp yarns is called the shed. Simple weaves require only two harnesses; complex weave patterns may require as many as 403.
- Picking, laying a length of the filling or weft yarn between warp yarns from the shuttle (a hollow projectile that holds weft yarn inside) as it moves across the shed.
- Battening or beating in, forcing the filling yarn from the pick against the just-formed cloth next to the previous pick. This step is necessary because the shuttle requires some space in its movement across the loom and it is not possible to deposit the pick closely against the previous picks. Battening is done with the reed, which is a grating of parallel vertical wires between the warp yarns.
- Taking up, winding the cloth, as it is formed, onto a take up reel, the cloth beam.
- As the cloth is taken up, warp yarn is released from the warp beam. This action is called letting off.
The warp yarns may be coated with a temporary sizing for protection against damage during the operation. The process of applying this coating by taking yarn from a large rack, called a creel, passing it through comb guides and through a bath of starch, and winding it on a warp beam, is called beaming or slashing.