Primary Motion of Loom
There are many mechanisms on a modern weaving machine for various purposes. There are five basic mechanisms that are essential for continuous weaving. They are as follows:
- Warp let-off
- Fabric take-up
Warp let-off mechanism releases the warp yarn from the warp beam as the warp yarn is woven into the fabric. The let-off mechanism applies tension to the warp yarns by controlling the rate of flow of warp yarns. The mechanism should keep the proper tension on the warp yarns which controls the crimp rates of warp and weft yarns. Uniform tension is essential in weaving.
Shedding is the movement of some warp yarns up and comes down to make an angled opening for the weft yarn to be inserted through. This opening is called a shed. The warp sheet has to be rearranged according to the fabric design before the insertion of the next weft yarn to produce the required fabric structure.
Picking/ Weft Insertion
The weft yarn is inserted through the shed after each changing of the shed. It is possible to select and insert different weft yarns one after another. These weft yarns can be of a different color, weight, etc and a selection mechanism is used for this purpose. Depending on the machine type, several different weft yarns can be used in the same fabrics.
When the weft yarn is inserted through the shed, it lies relatively far from its final position. The newly inserted weft yarn needs to be brought to its final position by pushing through the warp sheet. Beat-up is the process of pushing the last inserted weft yarn to the cloth fell by using a device called reed as shown in the above figure.
As the fabric is woven, it should be removed from the weaving area. This is achieved by the take-up motion. The fabric take-up removes cloth at a rate that controls weft density.