TL;DR
Weft insertion faults are usually a blocked main nozzle, incorrect relay nozzle timing, or yarn tension out of spec. Check the main nozzle pressure and relay nozzle sequence first.
What you might see
- weft stop alarm at the right selvage
- short pick or missing weft in fabric
- weft yarn broken in the air channel
- compressed air pressure below set-point during insertion
Likely causes
Blocked or worn main nozzle reducing air velocity and weft transport force
Relay nozzle timing shifted from cam or electronic setting drift
Weft yarn tension set too high, slowing insertion speed
Compressed air supply pressure dropping below the insertion minimum
Required tools
- Compressed air pressure gauge
- Yarn tension gauge
- Loom controller for timing review
- Nozzle cleaning brush and airline
Safety first
- The main nozzle operates at pressures up to 6 bar. Never block the nozzle outlet with your hand or face when the air is on.
- Keep fingers and tools clear of the rapier or shed area when manually cycling the loom.
Procedure
- 1
Stop the machine and read the weft detector fault code to identify the insertion zone where the weft failed.
- 2
Check the compressed air supply pressure to the loom at the main regulator. Pressure below specification requires upstream investigation.[1]
- 3
Inspect the main nozzle tip for yarn fiber buildup or clogging. Clean the nozzle with a dry brush or airline according to the maintenance schedule.
- 4
Verify relay nozzle timing on the loom controller against the setup sheet for the current article. Adjust timing if any zone is outside specification.
- 5
Check the weft accumulator (pre-winder) for correct unwinding. Verify the thread is unwinding freely and the tension ring is set correctly for the yarn count.[1]
- 6
Measure weft tension at the yarn carrier with a tension gauge. Reduce tension if it exceeds the recommended value for the count and speed.
- 7
Run 10 picks manually and monitor the weft sensor signal at each zone to confirm consistent arrival timing.
Sources
Picanol Picanol OmniPlus 800 Loom (Air-Jet / Rapier) general technical documentation, Picanol
Picanol OmniPlus air-jet loom general weft insertion and nozzle maintenance procedures (general)
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