Page 47 - Shawl Weaving Artisan - TT

Auxiliary motions Interrelationship and synchronization
These motions are crucial for efficient operation and The power loom operation hinges on the precise timing
quality control: and synchronization of all these motions. A central
crankshaft, driven by an electric motor, typically powers
1 Warp stop motion
the primary motions. Cams, gears, linkages, and
• Theory: To prevent weaving defects and increasingly, electronic controls and servo motors, are
unnecessary fabric waste when a warp thread used to translate this rotary motion into the specific
breaks. reciprocating and oscillating movements required for
• Mechanism: Each warp thread passes through a shedding, picking, and beating-up.
drop wire. If a warp thread breaks, the corresponding For example
drop wire falls, completing an electrical circuit and • Shedding must occur before picking. The shed must
immediately stopping the loom.
be fully open for the weft insertion device to pass
2 Weft stop motion through cleanly.
• Theory: To detect the absence or breakage of the • Picking occurs when the shed is at its widest point.
weft yarn and stop the loom, preventing missing
picks or faulty fabric. • Battening occurs after picking, once the weft yarn is in
its desired position within the shed, and as the shed
• Mechanism: This can be mechanical (e.g., a begins to close or is fully closed.
weft fork that feels for the yarn) or electronic • Take-up and let-off motions are continuous, but their
(using optical or capacitive sensors). If no weft is rates are synchronized with the loom speed and pick
detected, the loom stops.
density.
3 Weft replenishment (Automatic weft changing)
Modern power looms incorporate sophisticated electronic
• Theory: To allow continuous weaving without control systems, sensors, and computer numerical control
manual intervention when the weft pirn (in shuttle (CNC) to achieve higher speeds, greater precision,
looms) or weft package (in shuttleless looms) runs versatility in weaving complex patterns, and minimized
out. downtime due to breakages. The drive systems are
• Mechanism: In shuttle looms, a full pirn is often optimized for energy efficiency, and features like
automatically ejected into the shuttle, or the shuttle automatic fault detection and self-correction are common.
itself is automatically replaced. In shuttleless
looms, this involves automatic splicing or knotting
of a new weft package.

Textile & Handloom: Shawl Weaving Artisan : (NSQF - 2024) R.T. Ex.No 1.3.26 37