Take-up Motion | Let-off Motion | Secondary Motions of Weaving Loom Mechanism

Secondary Motions:
These mechanisms are next in importance to the primary mechanisms. If weaving is to be continuous, these mechanisms are essential. So they are called the ‘secondary’ mechanisms. They are:
  1. Take-up motion
  2. Let-off motion
Let off and take-up motion
Fig: Let off and take-up motion
Take-up motion
The take-up motion withdraws the cloth from the weaving area at a constant rate so as to give the required pick-spacing (in picks/inch or picks/cm) and then winds it on to a cloth roller.

The main part of the mechanism is the take up rollers, which draws the cloth at the regular rate, and the number of picks per inch decides this rate. The take up roller is covered with emery cloth or hard rubber depending upon the type of cloth woven. The drive to the take up roller is by a train of gear wheels put into motion directly from the main shaft.

Classification of take up motion:
Take up motion can be classified in many way. They are;

According to drive:
  1. Positive take up
  2. Negative take up
According to motion of the cloth/rate of take up:
  1. Continuous
  2. Intermittent
According to drive given to the cloth roller:
  1. Direct drive
  2. Indirect drive
According to number of gear train:
  1. 5-wheel
  2. 6-wheel
  3. 7-wheel
According to brand name:
  1. Sulzer
  2. Pickanol
  3. Toyota
Functions of take up motion:
  • To wind the woven fabric on the cloth roller with continuous progress of weaving.
  • To maintain uniform picks per inch i.e. uniform texture along the length of fabric.
  • To ensure uniform pick spacing through out the fabric.
Fabric take-up motion
Fig: Fabric take-up motion.
Let-off motion
The let-off motion delivers the warp to the weaving area at the required rate and at constant tension by unwinding it from the weaver’s beam. The secondary motions are carried out simultaneously. The speed of the servo motor is transmitted to warp beam gear via reduction gear, thus driving beam.

Types of let off motion:
  1. Positive let off motion
  2. Semi-positive let off motion
  3. Negative let off motion
Functions of let off motion:
  • To maintain the necessary tension upon the warp.
  • To unwind and deliver the required amount of warp sheet from the warp beam with the simultaneous and continuously to take up motion.
  • The warp should be supplied in lengths that exactly correspond with those drawn away by the taking up roller.
  • To influence the no of picks per unit space in a fabric being subsidiary to take up motion.
  • To provide the warp and filling space during weaving.
Fabric let off motion
Fig: Fabric let off motion.

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Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia.

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