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

Tap to mark as ruled out

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

7 steps · ~45 min

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)

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