TL;DR
Flute crush at the single facer is caused by excessive nip pressure or dull corrugating rolls. Check nip load settings, corrugating roll surface condition, and paper temperature before adjusting.
What you might see
- flat or crushed flutes visible on single-face web
- corrugating roll gap alarm
- flute height measuring below specification
- paper web wrinkling just after the single facer
Likely causes
Corrugating roll nip pressure set too high for the medium weight
Corrugating rolls worn or damaged, reducing effective flute height
Medium paper entering the single facer below the minimum temperature for forming
Starch application rate too high causing the medium to soften and crush
Required tools
- Flute height gauge
- IR thermometer for paper temperature
- Starch rate meter or flow gauge
Safety first
- Corrugating rolls operate at high temperature. Use heat-resistant gloves when near roll surfaces.
- Web breaks on the corrugator release hot steam. Maintain clear distance from the single facer web path during break events.
Procedure
- 1
Measure flute height on the single-face web with a flute height gauge at multiple CD positions. Identify whether crush is uniform or concentrated in a zone.[1]
- 2
Check the corrugating roll nip load setpoint. Reduce in 5% increments and measure flute height after each change.
- 3
Verify the medium paper preheating temperature. Temperature below the minimum for the medium weight reduces formability and increases crush risk.[1]
- 4
Check the starch application rate. Excess starch softens the medium and contributes to crush. Reduce starch to the minimum for bond strength.
- 5
Inspect the corrugating roll surfaces for wear, scoring, or buildup. Roll surface contamination reduces grip and effective flute height.
- 6
If flute height remains below specification after all adjustments, inspect corrugating rolls for measured wear at the next planned outage.
Warning: Corrugating rolls operate at high temperature. Do not touch roll surfaces without heat-resistant gloves and confirmed cool-down. - 7
Schedule corrugating roll regrinding if roll wear is confirmed.
Sources
BHS Corrugated BHS Modular Corrugator general technical documentation, BHS Corrugated
Corrugator single facer flute formation and nip control, general corrugated board manufacturing practice (general)
More guides for BHS Corrugated BHS Modular
How to diagnose glue bond failure on a BHS Modular Corrugator
Poor glue bond shows as low pin adhesion scores and delamination under flex. Check starch viscosity, gel temperature, and double backer heat before adjusting application rate.
How to reduce warp in corrugated board from a BHS Modular Corrugator
Board warp is caused by a moisture differential between the two liner facings. Check the moisture profiles of both liners, the double backer heat setting, and starch gel point consistency.
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