Prepared by Ibrahim Wageh — Fluting & Testliner (112–175 gsm)
| Property | 112 gsm | 120 gsm | 125 gsm | 140 gsm | 145 gsm | 150 gsm | 160 gsm | 175 gsm |
|---|---|---|---|---|---|---|---|---|
| Burst Strength (kPa) | (310–280) | (330–295) | (340–310) | (340–300) | (360–320) | (370–340) | (390–360) | (410–380) |
| SCTCD (kN/m) | (1.3–1.8) | (2.0–1.85) | (2.1–2.0) | (2.5–2.1) | (2.5–2.3) | (2.6–2.4) | (2.7–2.5) | (3.1–2.7) |
| Nominal Moisture (%) | (7% ±1%) | (7% ±1%) | (7% ±1%) | (7% ±1%) | (7% ±1%) | (7% ±1%) | (7% ±1%) | (7% ±1%) |
| COBB 60 (Top) g/m² | (30–60) | (30–60) | (30–60) | (30–60) | (30–60) | (30–60) | (30–60) | (30–60) |
| COBB 60 (Bottom) | (≥100) | (≥100) | (≥100) | (≥100) | (≥100) | (≥100) | (≥100) | (≥100) |
| Property | 112 gsm | 120 gsm | 125 gsm | 140 gsm | 145 gsm | 150 gsm | 160 gsm | 175 gsm |
|---|---|---|---|---|---|---|---|---|
| SCTCD (kN/m) | (1.9–1.8) | (2.0–1.85) | (2.1–2.0) | (2.5–2.1) | (2.5–2.3) | (2.6–2.4) | (2.7–2.5) | (3.1–2.7) |
| CMT 30 (N) | (210–170) | (220–185) | (230–200) | (240–210) | (250–220) | (280–240) | (300–260) | — |
| Nominal Moisture (%) | (7% ±1%) | (7% ±1%) | (7% ±1%) | (7% ±1%) | (7% ±1%) | (7% ±1%) | (7% ±1%) | (7% ±1%) |
| Water Drop Test (sec) | (5–10) | (5–10) | (5–10) | (5–10) | (5–10) | (5–10) | (5–10) | (5–10) |
| Property | If Value Low — Actions | If Value High — Actions | Reason / Explanation |
|---|---|---|---|
| Burst | Increase long fiber %; raise press nip load; reduce wire vacuum if drainage too high; add dry-strength aids. | Reduce refining intensity; lower nip pressure; temper calender load. | Burst is governed by fiber length distribution and inter-fiber bonding. Excess drainage or low long-fiber fraction reduces bond area and Z-strength. |
| RCT | Increase refining (target freeness ↓); tune jet-to-wire for better MD alignment; add dry-strength aids. | Reduce over-refining; lighten calender load if sheet too dense. | Ring crush reflects MD compression strength & rises with bonding and MD orientation. |
| CMT | Increase semi-chemical pulp %; improve MD orientation; reduce speed if bonding weak. | Reduce sheet stiffness slightly (refining/calender down-adjust). | Concora depends on flute stability & network stiffness; too dense sheet cracks on forming. |
| Moisture | Reduce dryer steam/hood temp; increase speed; use re-wet shower if available. | Increase dryer steam/hood temp; reduce speed; verify traps/condensate and hood balance. | Moisture controls bonding/flexibility. Low moisture → brittle; high moisture → weak bonding & winding issues. |
| Formation | Increase headbox turbulence; reduce consistency; tune shake; balance vacuum profile. | Reduce headbox energy; raise consistency slightly; lower vacuum where wash-out occurs. | Uniform formation requires enough micro-mixing to prevent flocs without washing fines. |
| Cobb 60 | Add surface sizing (starch/AKD); increase dryer steam to cure sizing. | Reduce sizing agent; reduce calender pressure; avoid over-drying that closes the surface. | Cobb indicates surface porosity/sizing. Calender pressure & drying affect surface closure. |
| Property | Too Low — Actions | Too High — Actions | Reason / Explanation |
|---|---|---|---|
| Burst | Raise long-fiber %; increase press nip; reduce over-drainage on wire; add dry-strength aids. | Reduce refining intensity; optimize calender load/temperature. | Burst rises with bonded area and fiber network integrity; over-refining can embrittle. |
| Tear | Increase semi-chemical %; improve bonding; avoid excessive fiber cutting in refining. | Improve formation (turbulence/shake); balance fiber mix if overly long fibers hurt uniformity. | Tear is energy to propagate a crack; formation and fiber length distribution are critical. |
| Tensile | Increase refining to target; adjust jet-to-wire for MD orientation; add starch/strength aids. | Reduce refining; lower calender pressure/temperature. | Tensile depends on bond strength & fiber alignment; over-refining reduces elongation. |
| Property | Too Low — Actions | Too High — Actions | Reason / Explanation |
|---|---|---|---|
| Porosity | Reduce refining; improve drainage on wire/press; lower fines carryover. | Increase refining; optimize drying; consider surface sizing to close surface. | Porosity reflects network openness; fines and refining control pore structure. |
| Brightness | Increase OBA dosage; improve furnish cleanliness & washing. | Reduce OBA; temper calender gloss/temperature if brittleness appears. | Brightness is an optical response; excessive OBA can change shade/ductility. |
| Smoothness | Increase calender load/temperature; improve formation upstream. | Reduce calender pressure/temperature to avoid crushing. | Smoothness comes from surface leveling at the calender; too much crushes bulk. |
| Property | Too Low — Actions | Too High — Actions | Reason / Explanation |
|---|---|---|---|
| Formation | Increase headbox turbulence; reduce consistency; tune shake; smooth vacuum gradients. | Reduce turbulence; increase consistency slightly; reduce vacuum where wash-out occurs. | Uniform formation balances micro-turbulence and retention. |
| Cobb (Absorption) | Add surface sizing (starch/AKD); increase dryer steam for proper cure. | Reduce sizing dosage; reduce calender pressure to reopen surface. | Cobb gauges water uptake: sizing & calendering set surface closure. |
| RCT | Increase refining to target; adjust jet-to-wire (MD); add strength aids. | Reduce refining; reduce calender densification if sheet too stiff/dense. | RCT relies on MD strength & bonding; over-densification limits buckling. |
| CMT | Raise semi-chemical %; improve bonding/orientation; manage speed. | Reduce stiffness slightly if flute crashes post-forming. | CMT measures corrugating performance: bulk/resilience vs densification trade-off. |
| Test | Frequency | Reason / Explanation |
|---|---|---|
| Cobb | Hourly | Tracks sizing/drying drift affecting printability and converting glue performance. |
| Burst | Hourly | Early indicator of bonding loss through drainage/press or stock prep shifts. |
| RCT | Every 2 hours | Compression strength control for stacking/corrugating performance. |
| CMT | Every 4 hours | Corrugating behavior varies slower; verify after furnish/speed changes. |
| Moisture | Hourly | Affects strength and winding/converting stability directly. |
| Tensile | Every 4 hours | Confirms bonding/orientation trends complementing burst/RCT results. |