ISO 16945:2014

Corrugating medium — Determination of the edge crush resistance after laboratory fluting

ISO 16945:2014 specifies two methods for the determination of the edge crush resistance of a corrugating medium after laboratory fluting. The procedures are applicable to any corrugating medium to be used after fluting in the manufacture of corrugated fibreboard.

Papier cannelure pour carton ondulé — Détermination de la résistance à la compression sur chant après cannelage en laboratoire

General Information

• Status: Published
• Publication Date: 20-Feb-2014
• ICS: 85.060 - Paper and board
• Technical Committee: ISO/TC 6/SC 2 - Test methods and quality specifications for paper and board
• Drafting Committee: ISO/TC 6/SC 2 - Test methods and quality specifications for paper and board
• Current Stage: 9093 - International Standard confirmed
• Start Date: 13-Dec-2024
• Completion Date: 12-Feb-2026

Overview

ISO 16945:2014 - "Corrugating medium - Determination of the edge crush resistance after laboratory fluting" defines laboratory procedures to measure the edge crush resistance (CCT) of a corrugating medium after it has been fluted. The standard is intended for corrugating mediums used in the manufacture of corrugated fibreboard and describes two widely used test methods: immediate testing after fluting (20–25 s) and testing after reconditioning (30–35 min). Results are reported as edge crush resistance (kN/m) and optionally as an edge crush resistance index (Nm/g) normalized by grammage.

Key topics and technical requirements

• Test principle: Pass paper between heated corrugating rolls (laboratory fluting), mount the fluted strip with flutes vertical, apply compressive load and record maximum force per unit length.
• Two methods:
  • Immediate test (CCT0): compress 20–25 s after fluting.
  • Reconditioned test (CCT30): recondition 30–35 min under standard atmosphere before test.
• Specimen preparation: Cut at least 10 test pieces, nominally 12.7 mm ± 0.1 mm wide and 152 mm ± 0.5 mm long (length in machine direction), edges parallel within 0.01 mm.
• Fluter and fluting conditions: Rolls heated to 175 °C ± 8 °C; typical roll speed 4.5 r/min ± 1.0 r/min and specified inter-roll force (documented specification). Roll geometry and matching are specified to ensure reproducible flute profiles.
• Apparatus: Matched corrugating rolls (fluter), a holder that grips 6.35 mm width of specimen with flutes vertical, and a motor-driven fixed-platen compression tester conforming to ISO 13820.
• Conditioning and sampling: Conditioning per ISO 187 and sampling per ISO 186.
• Calculations & reporting:
  • Edge crush resistance CCT = F / l (report to 0.01 kN/m).
  • Edge crush resistance index Y = 1000 × CCT / grammage (report to 0.1 Nm/g; grammage per ISO 536).
  • Test report must include method used (CCT0 or CCT30), mean, standard deviation, number of valid tests and any deviations from the standard.
• Precision: Annex A summarizes round-robin precision data and repeatability/reproducibility guidance.

Practical applications and users

ISO 16945:2014 is used for:

• Quality control at paper mills and corrugating medium suppliers to verify edgewise compression performance after fluting.
• Incoming inspection by corrugated-board manufacturers and converters to accept or qualify medium lots.
• R&D for developing flute profiles, adhesive/process settings and new medium formulations.
• Failure analysis and box design validation where edgewise strength of the medium influences the compression strength of corrugated boxes.

Primary users: test laboratories, packaging engineers, quality managers, material suppliers and standards/technical committees.

Related standards

• ISO 186 - Sampling to determine average quality
• ISO 187 - Standard atmosphere for conditioning and testing
• ISO 536 - Determination of grammage
• ISO 13820 - Calibration/description of compression-testing equipment
• ISO 7263 - (related fluting equipment specification)
• Relevant TAPPI methods and ISO technical reports referenced in Annex A for precision data

Keywords: ISO 16945:2014, edge crush resistance, CCT, corrugating medium, laboratory fluting, corrugated fibreboard, edge crush resistance index, compression tester, grammage, conditioning.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 16945
First edition
2014-03-01
Corrugating medium — Determination
of the edge crush resistance after
laboratory fluting
Papier cannelure pour carton ondulé — Détermination de la
résistance à la compression sur chant après cannelage en laboratoire
Reference number
©
ISO 2014
© ISO 2014
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Published in Switzerland
ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Sampling . 4
7 Conditioning . 4
8 Preparation of test pieces . 4
9 Procedure. 4
9.1 General . 4
9.2 Testing immediately after fluting . 4
9.3 Testing after 30 min of reconditioning . 4
9.4 Fluting and testing . 4
10 Calculation . 5
10.1 Edge crush resistance . 5
10.2 Edge crush resistance index . 5
11 Test report . 5
Annex A (informative) Precision . 7
Annex B (informative) Maintenance of fluting rolls (horizontal type) . 9
Bibliography .10
Foreword
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The committee responsible for this document is ISO/TC 6, Paper, board and pulps, Subcommittee SC 2,
Test methods and quality specifications for paper and board.
iv © ISO 2014 – All rights reserved

Introduction
This International Standard evaluates the ability of corrugating medium to contribute to the compression
strength of a corrugated box. It is a procedure for measuring the edgewise compression strength of a
laboratory-fluted strip of corrugating medium. The corrugated medium is fluted by passing it between
heated rollers. Two different test procedures are then widely used.
a) The fluted corrugating medium is compressed immediately after fluting (i.e 20 s to 25 s after
fluting).
b) The fluted corrugating medium is conditioned for 30 min to 35 min after fluting under standard
laboratory test conditions before being compressed.
Procedure a) generally gives considerably higher results than those obtained with procedure b). The
differences in results are claimed to be caused by the lower moisture content (and thus higher stiffness)
of the unconditioned fluted corrugating medium.
Since considerable advantages are claimed for both procedures and both are widely used, this
International Standard describes both procedures.
Test values and failure modes in this approach are expected to be different than those for ring crush
method and short span compression test (SCT).
NOTE This test is sometimes referred to as CCT (corrugated crush test) or CFC (corrugated fluted crush test).
INTERNATIONAL STANDARD ISO 16945:2014(E)
Corrugating medium — Determination of the edge crush
resistance after laboratory fluting
1 Scope
This International Standard specifies two methods for the determination of the edge crush resistance
of a corrugating medium after laboratory fluting. The procedures are applicable to any corrugating
medium to be used after fluting in the manufacture of corrugated fibreboard.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 186, Paper and board — Sampling to determine average quality
ISO 187, Paper, board and pulps — Standard atmosphere for conditioning and testing and procedure for
monitoring the atmosphere and conditioning of samples
ISO 536, Paper and board — Determination of grammage
ISO 13820, Paper, board and corrugated fibreboard — Description and calibration of compression-testing
equipment
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
edge crush resistance
CCT
maximum edgewise compression force per unit length that a laboratory fluted test piece will withstand
before onset of break under the test conditions specified in this International Standard
Note 1 to entry: Edge crush resistance is expressed in kilonewtons per metre (kN/m).
3.2
edge crush resistance index
edge crush resistance divided by the grammage
Note 1 to entry: The result is expressed in newton metres per gram (Nm/g).
4 Principle
The principle is as follows:
a) fluting of the paper by passing it between heated rollers and mounting in a holder with the flutes
placed vertically;
b) application of a compressive force and determination of the maximum force per unit length.
5 Apparatus
5.1 Cutting device, for cutting the test pieces to the required specifications, see Clause 8.
5.2 Fluter, consisting of a pair of matched steel corrugating rolls. The rolls shall be capable of being
maintained at a temperature of 175 °C ± 8 °C. The temperature is controlled by any suitable method.
Check the temperature when the rolls are in motion.
One roll is motor-driven at 4,5 r/min ± 1,0 r/min and the rolls are held in mesh by a force of (100 ± 10) N
exerted between the rolls and distributed evenly across the teeth, under test conditions. In some
instruments, the force between the rolls is applied by a spring acting in a slide. In such instruments,
friction in this device can result in the force which acts upon the test piece being considerably less than
the force required to displace the rolls initially. When verifying that an instrument conforms to the
requirements given in this subclause, it is therefore necessary to measure the force required to prevent
the undriven roll from moving towards the driven roll, from a position about 200 μm away.
The essential characteristics of each roll are the following (see also Figure 1):
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