A novel test method for predicting crushing elasticity in medium fluting with higher relevance than for instance

During the corrugated board making process the board is passing several rollers and belts, which compress the material more or less. This also happens later in the process when corrugated board sheets are printed, scored and die-cut. As a damage trouble shooting tool, thickness measurements are not sensitive enough to estimate the amount of crushing in these processes. The loss in thickness will be recovered after the crush and not measurable. The board might lose some of it functionality as packaging protecting its content when it is crushed. Of course a converter doesn’t want that. Adjustment in the converting process might work for minimize permanent damage of the corrugated board. But it is also important to have strong medium with high resistance to crushing. Testing of crush resistance of medium called CMT is very time consuming. It involves hot corrugating a small test strip of paper in a laboratory fluter, fixing it without delay on a self-adhering pressure sensitive tape and testing it immediately in a laboratory crush tester. Such test yields a final strength of the flute at the moment of total collapse, which is not a relevant value because when the board reaches this point it is already damaged. The more relevant point is when the board starts to lose its elasticity and begins to fail. Manual testing CMT is a very unpopular test and a difficult one to automate. A new test with the working name S-test can accurately predict the elasticity break point also called CMT plateau.