- WHAT: Cross-direction crushing of a corrugated board. ECT is a measure of the edgewise compressive strength of corrugated board. It is measured by compressing a predefined section of board on its edge between two rigid platens.
- WHY: To test material quality, stacking strength, pallet shipping endurance
One of the most popular methods to test the stacking strength of corrugated boxes is the Edge Crush Test or ECT. Every side of a corrugated box is made up of sheets that have three or more layers. Generally, a thin sheet with grooves and ridges is sandwiched between two flat sheets. These grooves and ridges, also known as flutes, provide anisotropic strength to a box. This means the boxes can bear a greater amount of force from one direction. Edge crush test, right test, or flat crush test helps determine this.
In the Edge Crush test, force is applied to one side of the box, perpendicular to the ridges, until the box gets crushed. In the Ring Crush test, a ring cut out from the box is used to test the same. While in the flat crush test, excessive force is applied on one side.
The results of the Edge Crush test are measured in pounds per lineal inch ( LBS) of load-bearing edge but represented as ECT and in our today test we measure in KN/m unit ( KILONEWTON METER – 1 kilonewton meter [kN·m] = 101.9716212978 kilogram-force meter [kgf·m]. 25 kN means 25,000 Newtons or 5,620.225 pounds of force or 2,549 Kilograms Force (kgf).
Repeat this test for 5 samples and record the values.
ECT gives you an accurate idea of a box’s strength when they are stacked and shipped by pallets. Also, an ECT rated corrugated box uses less material than its equivalent Burst Test rated box, to provide an equivalent level of strength. This means it’s cheaper and less wasteful to purchase ECT rated boxes in bulk.
However, it is important to know that the above results (overall strength of a box) may vary based on the makeup of each corrugated sheet. Hence, knowing the type of corrugation is important before you make a decision.
International standards for measuring crush force in the Edge Crust Test (ECT)
There are a number of international standards from various standards authorities, which address the subject of measuring the crush force by the Edge Crush Test.
A variety of methods are in use in different parts of the world. These can be classified into three groups as follows:
- Those in which a carefully cut rectangular test piece is tested without any special treatment or modification (eg ISO 3037 “Corrugated fibreboard — Determination of edgewise crush resistance -unwaxed edge method”).
- Those in which the edges of the test piece to which the force is applied are waxed, to prevent the test result being influenced by “edge effects“ (eg ISO 13821 “Corrugated fibreboard — Determination of edgewise crush resistance — waxed edge method”).
- Those in which the test piece edges are not waxed but the shape of the test piece is such that the length is substantially reduced at a point midway between the loaded edges, in order to induce the failure to occur away from those edges (eg FEFCO 8, TAPPI T838 and TAPPI T839)
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