Fluting (Corrugated Medium Paper)

Overview

Fluting is the corrugated medium -- the paper that gets formed into the characteristic wave (flute) shape between the flat linerboard layers (wiki/entities/kraftliner or wiki/entities/testliner) in corrugated board. While linerboard provides the flat surfaces and printability, fluting provides the structural rigidity, cushioning, and stacking strength that make corrugated boxes the dominant shipping container material.

In the marketplace, fluting is classified under the fluting paper type enum. Parser configurations also recognize "CMP" (Corrugated Medium Paper) as an alias that maps to the fluting type.

Technical Specifications

Key mechanical properties for fluting:

• Ring Crush Test (RCT, kN/m): Critical for column compression (box stacking)
• Concora Medium Test (CMT): Measures fluting's resistance to flat crush
• Moisture content: Affects fluting performance during corrugation process
• Cobb value: Water absorption resistance

Flute Types

The flute profile is a critical specification stored in the Product entity's flute_type field (CHAR(1), values A/B/C/E/F):

The take-up factor indicates how much fluting medium is consumed per linear meter of corrugated board. A-flute at 1.50 means 1.5 meters of fluting medium produces 1 meter of corrugated board. This affects material consumption and therefore surplus generation.

C-flute dominates with approximately 80% market share because it provides a good balance of cushioning, stacking strength, and material efficiency for standard shipping applications.

Surplus Context

Fluting surplus is common because:

• Corrugated packaging production is massive globally
• Side trims are generated at every corrugator (width adjustment)
• Corrugator changeovers between flute types generate waste
• GSM and moisture specification deviations create off-spec lots
• Different flute types require different medium weights, creating surplus when switching

Matching Behavior

In the wiki/concepts/matching-algorithm:

• Fluting is a distinct paper type (binary gate at 30% weight)
• Never cross-matches with kraftliner or testliner
• GSM scoring follows standard tolerance bands (within range = 80-100, +/-5% = 60, +/-10% = 30)
• The flute_type field on the Product entity provides additional matching granularity, though the current algorithm scores on paper_type, GSM, and width (flute type is informational in V1)

Container Compatibility

Fluting belongs to the "packaging" group in the container assembly algorithm. It can share containers with: kraftliner, testliner, white_top_testliner, duplex, triplex, and coated_board. This makes sense logistically because these products are all consumed by corrugated packaging converters.

Relationship to Corrugated Board

A typical corrugated board structure:

Kraftliner (outer liner)  -- flat, printable surface
Fluting (medium)           -- wave-shaped for rigidity
Testliner (inner liner)    -- flat, cost-effective inner surface

Single-wall board uses one fluting layer between two liners. Double-wall (used for heavy-duty boxes) uses two fluting layers with three liners. The marketplace handles surplus for each component independently.

Sources

• raw/articles/PRD -- Appendix A (Paper Types and GSM Ranges, Corrugated Flute Types), section 5.3

Related

• wiki/entities/kraftliner -- virgin fiber linerboard (outer layer)
• wiki/entities/testliner -- recycled fiber linerboard (inner layer)
• wiki/concepts/paper-types-overview -- full paper type classification
• wiki/concepts/matching-algorithm -- paper type binary gate
• wiki/concepts/container-assembly -- packaging group compatibility
• wiki/concepts/quality-grades -- A/B/C grading for fluting