ISO 3037

What the test does

A short rectangle is cut from corrugated board so that the flutes run across its height. It is stood on edge between two flat parallel platens, flutes vertical, held upright by a guide only until the load takes over. The platens close at 12.5 ± 2.5 mm/min and crush the specimen along its loaded edge. The peak force is recorded and divided by the measured specimen width to give the edgewise crush resistance in kN/m. No wax or other reinforcement is applied to the loaded edges — the method relies instead on a clean cut and a short specimen to prevent premature edge failure and buckling.

What it measures, and why it matters

ECT is the most useful single property of corrugated board, because box compression strength follows from it. The McKee relationship estimates the compression strength of a regular slotted container from ECT together with board thickness and box perimeter, which lets a converter predict how a box will perform from a test on a piece of board rather than by making and crushing containers. That makes ECT the working basis of board specification, of supplier acceptance, and of everyday production control in a corrugating plant. It is quick, it uses very little material, and it responds directly to the liner grades and flute profile that determine board performance.

Specimen

A piece of board standing on edge is a very short column. The method exists in several variants precisely because keeping it from buckling, without reinforcing it, is the hard part.

Form

Rectangle cut with the flutes running across the heightFlutes vertical in the test. They are the columns doing the work.

Loaded edges

Cut clean and exactly parallelThis is the whole test. A crushed or ragged edge collapses first and the result describes the knife.

Non-waxed edge method

No edge reinforcementOlder methods waxed the edges to stop them crushing prematurely; this one relies on clean cutting and a short specimen instead.

Conditioning

23 ± 1 °C and 50 ± 2 % RHTighter than the usual atmosphere, because ECT falls sharply with moisture content.

Cutting

With a sharp, correctly set twin-blade cutter

Check the edges under a loupe

Before testingDakDelaminated or fuzzed edges are visible, and the specimen is cheap. Rejecting one costs seconds; testing it costs a result.

Cut across the web, not along one liner

Sample the board fairlyDak

ECT is a property of the board, not of the box. Converting it into a box compression prediction goes through the McKee relationship and needs the box perimeter and board thickness as well — the ECT figure alone predicts nothing.

Test speed

Platen speed

12.5 ± 2.5 mm/min

Result

Peak force divided by specimen width

Valid failure

Crushing across the specimen, not bucklingA specimen that bows and folds has failed as a column and is rejected.

Reject low outliers rather than averaging them in

After checking the edgeDakNearly every low ECT result has a visible edge defect behind it.

Calculations

How the test runs

1. 01Cut specimens with a sharp twin-blade cutter, flutes across the height.
2. 02Inspect both loaded edges for crushing, fuzz or delamination.
3. 03Measure the specimen width.
4. 04Condition at 23 ± 1 °C and 50 ± 2 % RH for the full period.
5. 05Check the platens are parallel and clean.
6. 06Stand the specimen on edge in the guide, flutes vertical.
7. 07Close to light contact and zero the force.
8. 08Compress at 12.5 mm/min.
9. 09Record the peak force.
10. 10Confirm the specimen crushed rather than buckled.
11. 11Divide by the measured width and report in kN/m.

Grips and fixtures for this method

5 to 400 kNTJ-125

Direct Compression Fixture

Direct compression platens. The requirement is parallelism and a clean flat face; any debris under a specimen this short becomes a local stress concentration.

Specifications

Rigidly fixedTJ-146

Compression Anvils

Hardened parallel anvils suit the low forces and small specimen, where a large platen is unnecessary.

Specifications

What the report has to contain

• Reference to ISO 3037 and the edition
• Board identification — flute type, liner grades, combined grammage
• Specimen dimensions and how they were cut
• Conditioning atmosphere and duration
• Platen speed
• Peak force and ECT for each specimen
• Number of specimens rejected, and why
• Mean, standard deviation and coefficient of variation
• Board thickness, where a box compression estimate is to be made

What the machine must be capable of

Modest force and good low-end resolution: ECT specimens commonly peak between a couple of hundred newtons and a few kilonewtons, so accuracy to ISO 7500-1 Class 1 is needed over that range rather than at the top of a large cell. The crosshead must hold 12.5 mm/min. Platens must be parallel, flat and clean — on a specimen this short, debris under an edge becomes a local stress concentration. A guide is needed to hold the specimen upright until the load takes over, without restraining it once loading begins. Above all the laboratory needs humidity control tight enough to hold ± 2 % RH, which is the real barrier to producing comparable ECT data.

What goes wrong in practice

Edge quality accounts for the overwhelming majority of poor results, and it is visible: crushed flutes, fuzzed liners or delamination at the cut. A loupe check before testing catches most of it, and rejecting a suspect specimen costs seconds. Buckling rather than crushing is the next problem and invalidates the result — the specimen has then failed as a column. Humidity drift produces a consistent bias rather than scatter, so it hides well. And the commonest misuse sits outside the laboratory: quoting an ECT value as though it predicted box compression on its own, when the McKee relationship also needs board thickness and box perimeter.

ISO 3037 or TAPPI T811

Waxed and non-waxed methods do not give the same number — waxing stiffens the loaded edges and raises the result. A specification citing one is not met by running the other, and mixed data sets show a step that looks like a board change.

Questions we are asked about this test