Is there a mathematical formula to calculate the ECT value using liner combinations?

Josh Asks Ralph…

I have a customer who is buying a 200 C box with a liner combination of 42/40/42, I am not sure but I am pretty sure this is not the normal liner combination. Is there a mathematical formula to calculate the ECT value using liner combinations also what is the usual liner combination of 200 C?

Josh –

Thank you for contacting us again with a very good, but complex question.

A “normal” 200 C linerboard and medium combination must include 42# linerboards with any grade of fluting. Mullen is based on the burst strength of the combined board. Burst strength is a contribution by the liners alone without regards to the medium. So 200# test board can be engineered with 18# to 47# medium. NOW, THE ECT VALUES ARE VERY DIFFERENT!

Predicting ECT for different combinations requires knowing the cross direction ring crush strength or STFI of the components. This then needs to be factored by the corrugator efficiency factor which ranges from +15% to -25 percent. Then that result must be factor by the deterioration factors of the converting equipment which ranges from zero to – 35 percent.

The ECT formula you asked for can be shown as:
ECT greater than 32 = 0.212 (sum of the CDRC values) minus 6 OR 1.27 (RC liners/6) + (RC medium x take-up Factor)/6 -6

The predicted range of potential ECT values off the corrugator operation at 100% efficiency would be 31-48# for a 42/26C/42 and 46-60# for a 42/40C/42 combination.

One Response to “Is there a mathematical formula to calculate the ECT value using liner combinations?”

  1. texomacyclist Says:

    Hi Ralph,
    I’m trying to do this very thing, but I don’t understand what CDRC is or how you got to .212. The combination I’m veing asked to calculate is 42-36-56.

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