Semi Positive Let off Mechanism

Functions of let off motion:

  1. To maintain or control the necessary tension upon the warp.
  2. To unwind and deliver the necessary amount of warp sheet from the warp beam with the simultaneous and continuous take up motion.
  3. To impact the no of picks per unit space in a fabric being subsidiary to take up motion.

Motion Transfer:

Sley sword>Driving rod/Connecting rod>Ratchet wheel>Bevel Gear>Worm Gear>Worm Wheel>Plange Gear>Warp Beam

Working Principle:

  • Sleysword is connected with connecting rod.
  • Connecting rod is attached to ratchet wheel.
  • Ratchet wheel rotates because of pawl/pushing pawl
  • Ratchet wheel transfers the motion on the bevel gear.
  • Bevel gear transfers the motion on the worm gear which is set on the top portion of the bevel gear
  • Here worm wheel is placed beside the worm gear
  • Worm wheel attach to the plange gear & transfer the motion on warp beam/weaving beam.
  • When plange gear is rotated, the warp beam/weaving beam is also rotated and let off the warp beam

One potential disadvantage of a semi-positive let-off mechanism in a weaving machine is that it can be less precise than other types of let-off mechanisms. Because the tension on the warp yarns is not completely constant, it can be more difficult to control the tension accurately and consistently throughout the weaving process.

In addition, the semi-positive let-off mechanism may not be suitable for certain types of fabrics or weaving patterns that require very precise tension control. For example, if the fabric being woven requires a perfectly uniform appearance or a very tight weave, a more precise let-off mechanism may be necessary.

Finally, the friction between the rollers and the warp yarns in a semi-positive let-off mechanism can cause wear and tear on the yarns, which can lead to breaks or other defects in the finished fabric. This means that regular maintenance and inspection of the let-off mechanism is necessary to ensure that it is functioning properly and not causing damage to the yarns.

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