Bob asks:
I have a carton that has a board combo of 69/23/90 (90 is the inside liner). I am trying to find the ECT value ?
I appreciate your expertise on this. I’m figuring about 65. In my 20+ years I had never seen that combo. What complicated it even more was the 69# is White Top. With the unbalanced liners as they were and the lightweight 23# med, in my opinion it was a valiant attempt to strengthen the carton but the end results fell short. Had they invested in a heavier medium the effect would have been much better. What it comes down to is overkill for what they are trying to accomplish.
I can’t recall ever seeing that combination either. The direct answer to your question is that the ECT value should range between 64 and 90 pli when combined properly at the corrugator. However, having said that, I am concerned about the fit for use of this board combination in a corrugated box. There is too much compression strength carried in the external flanges and too little in the web (medium) of the corrugated structure. We obtain the best delivery of performance in engineering the corrugated design when placing 50% of the strength in the two liners and 50% in the fluted medium. The flexural stiffness or budging resistance of your current structure would be considered flimsy.
If you want to provide some more information of the dimensions of the box and the intended end use, we could develop a more cost effective alternative.
— Ralph
askralph 