TL;DR
Warp tension inconsistency is usually a let-off brake drag, a damaged tension sensor, or uneven back-rest roller wear. Check the let-off torque setting and sensor calibration first.
What you might see
- warp tension alarm on the control panel
- lengthwise streaks in the fabric
- warp end breaks increasing
- fabric pick count variation within the beam
Likely causes
Let-off brake dragging from contamination or wear, causing tension surges
Warp tension sensor zero drift or damage giving incorrect feedback to the controller
Back-rest roller bearing wear causing uneven warp sheet movement
Warp beam winding taper mismatch with the let-off motor profile
Required tools
- Warp tension meter
- Brake pad inspection kit
- Bearing puller for back-rest roller
- Loom controller access for sensor calibration
Safety first
- The warp beam holds high potential energy from the warp tension. Never stand directly behind the beam end when adjusting the brake.
- Lock out the loom before working on the back-rest roller bearing. The roller can rotate unexpectedly when warp tension is released.
Procedure
- 1
Read the tension monitoring trend from the loom controller over the last 100 meters of warp. Identify whether tension rises steadily, fluctuates, or spikes.
- 2
Calibrate the warp tension sensor at zero load and compare the reading to the controller reference. Replace the sensor if calibration cannot be achieved.[1]
- 3
Check the let-off brake pad surface for oil contamination or wear. Clean or replace the brake pad if contamination is present.
- 4
Verify the let-off motor torque profile setting against the setup sheet for the warp beam diameter and yarn count.[1]
- 5
Rotate the back-rest roller by hand and check for rough bearing spots or radial runout. Replace the bearing if roughness is felt.
- 6
Adjust the tension set-point on the controller to the correct value for the article and monitor the first 10 meters of weaving.
Sources
Picanol Picanol OmniPlus 800 Loom (Air-Jet / Rapier) general technical documentation, Picanol
Picanol OmniPlus loom general warp let-off and tension control procedures (general)
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