TL;DR
CD basis weight variation is most often caused by turbulence insert fouling or slice lip profile error. Scan the CD profile, adjust the slice lip, and inspect the turbulence insert.
What you might see
- CD basis weight profile showing periodic high or low zones
- CD moisture profile variation corresponding to BW zones
- nozzle velocity uneven across machine width
- streak visible in finished paper under raking light
Likely causes
Slice lip profile deviating from the flat setpoint due to actuator drift or fouling
Turbulence insert partially blocked by fiber or filler deposits reducing local jet velocity
Manifold flow distribution uneven across the machine width
Feed pump pressure fluctuation creating a whole-width CD variation
Required tools
- Quality control CD scanner access
- Slice actuator diagnostic tool
- Pressure gauges for manifold
- LOTO kit for insert cleaning outage
Safety first
- The headbox operates under pressure and contains hot stock. Never open inspection covers without full LOTO and depressurization.
- Slip hazard from stock spillage around the headbox. Use non-slip footwear.
Procedure
- 1
Pull the CD basis weight scan from the quality control system and map the zones of deviation against the slice actuator positions.[1]
- 2
Verify slice actuator feedback. Confirm each actuator is responding and holding its setpoint without drift.
- 3
Make small manual slice adjustments (+/- one step) at the problem zones and observe the CD scanner response after two scans.
- 4
If the CD profile does not respond to slice adjustment in one zone, suspect a blocked turbulence insert at that position.[1]
- 5
Schedule a turbulence insert cleaning at the next planned headbox outage. During outage, remove and flush each insert with clean water.
- 6
Check the manifold pressure distribution at multiple CD positions. More than 0.5% variation across the width indicates a flow distribution problem requiring manifold inspection.
- 7
After adjustments, allow at least five full scans to stabilize before committing to a new slice profile.
Sources
Voith Paper Voith MasterJet Pro Paper Machine / Headbox general technical documentation, Voith Paper
Paper machine headbox slice adjustment and CD profile control, general paper machine practice (general)
More guides for Voith Paper Voith MasterJet Pro
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How to fix a sticking slice actuator on a Voith MasterJet Pro Headbox
A sticking slice actuator creates a fixed CD basis weight hump that does not respond to control commands. Identify the stuck actuator from position feedback, lubricate or replace it at the next outage.
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