Definition

"Concora" flat crush refers to the crushing resistance of a laboratory-fluted strip of corrugating medium.

Influence

Rigidity of the fluted structure is one of the key characteristics of corrugated board. The Concora test provides a laboratory procedure to predict the flat crush resistance of combined board from the Concora value obtained in the laboratory on the corrugating medium.

Potential Problems

Mediums of very low "Concora" values result in the combined board with resistance to crushing of the fluted structure below that necessary to avoid deterioration from the effects of rider rolls, feed rolls, pull rolls, and other downstream processing forces, even if those nip point forces are carefully controlled. Mediums of very high Concora values may cause fluted formation problems or score cracking problems on downstream equipment.

Source
McGrattan, W. "Key characteristics of linerboard, corrugating medium, and roll stock mechanical condition and their influence on the manufacture of corrugated products, part 1." Tappi Journal (1990): 99-108.

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