Motions of Loom

Weaving is the most basic process in which two different sets of yarns or threads are interlaced with each other to form a fabric or cloth. One of these sets is called warp which is the lengthwise yarn running from the back to the front of the loom. The other set of crosswise yarns are the filling which are called the weft or the woof.Therefore Weaving loom motions can be broadly catagorised as follows:

Primary Motions

Shedding:

The separation of warp thread by lifting and lowering of heald frames, according to pattern, to allow for weft insertion.

Picking:

The process of inserting the filling yarn through the shed while the shed is opening.

Beating-up:

The process of pushing the filling yarn into the already woven fabric at a point known as the fell and done by the reed.

Secondary Motions

Let-off motion:

This is the motion which delivers warp to the weaving area at the required rate and at a suitable constant tension by unwinding it from a flanged tube known as the weaver’s beam.

1. Positive let-off motion: A mechanism controlling the rotation of the beam on a weaving or other fabric forming machine where the beam is driven mechanically.
2. Negative let-off motion: A mechanism controlling the rotation of the beam on a weaving or other fabric forming machine where the beam is pulled round by warp against a braking force applied to beam.

Take Up motion:

This is the motion that withdraws fabric from the weaving area at a constant rate. It ensures that the required pick spacing is maintained, and then winds it onto the cloth roller.

1. Positive take up motion: It is the motion in which the take up roller is gear driven, a change wheel or variable-throw pawl and ratchet being provided to allow the required rate to be obtained, so determining the pick spacing.
2. Negative take up motion: It is the motion in which the take up roller is rotated by means of a weight or spring, this roller only rotates when the force applied by the weight or spring is greater than the warp lay tension in the fabric. The take up rate is controlled by the size of the force applied by the weight or spring and/or the warp tension.

Auxiliary Motions

To get high productivity and good quality of fabric, additional mechanisms, called auxiliary mechanisms, are added to a plain power loom.The auxiliary mechanisms are useful but not absolutely essential. That is why they are called the auxiliary mechanisms.

• Warp protector mechanism: The warp protector mechanism will stop the loom if the shuttle get strapped between the top and bottom layers of the shed. It thus prevents excessive damage to the warp threads, reed wires and shuttle.
• Weft stop motion: The object of the weft stop motion is to stop the loom when a weft thread breaks or gets exhausted. This motion helps to avoid cracks in a fabric.
• Temples: The function of the temples is to grip the cloth and hold it at the same width as the warp in the reed, before it is taken up.
• Brake: The brake stops the loom immediately whenever required. The weaver uses it to stop the loom to repair broken ends and picks.
• Warp stop motion: The object of the warp stop motion is to stop the loom immediately when a warp thread breaks during the weaving process.