File Combined Board Properties

When you sit down with your sheet supplier(s) to begin the process of establishing combined board properties consider the following as guidelines for the properties listed below:

Edge Crush Test: You need 20% more vertical compression coming in the front door to overcome the rigors of the normal converting processes so that you can be comfortable that the grade you stamp on the bottom of the box is actually what is provided.

Flat Crush Test:  Ask for 35 psi.

Warp:  No more than 1/8 inch per foot.

Pin Adhesion:  Seek 60 pounds per linear floor of glue line.

Caliper: Inquire into the ranges for each board combination.

Flexural Stiffness or Four Point Bending:  This is a test which only a few labs can perform, but it is critical to the performance to the displays and graphics you produce. 
      200# Mullen test should have a MD average of 112 and a CD average of 52
      275# Mullen test should have a MD average of 157 and a CD average of 79
      32# ECT should have a MD average of 85 and a CD average of 41
      44# ECT should have a MD average of 132 and a CD average of 65

MEMBER: While I know there should be many ways to get there, could you suggest a reasonable paper combination to start with to achieve EC29 B flute board?
RALPH YOUNG: Thank you for a good question. Allow me to give you the engineering answer first and then the more practical answer after that.

MEMBER: What is the standard/normal board grade combination for 48 ECT single wall? The issue is that we have a new potential customer and his current vendor is telling that customer that they can provide them with a 48 ECT S/W with a board grade comb. of either a 55/33/52 or 52/36/52; I know that you can very well get ECT values of 48 but you are correct there is no 48# ECT that I was aware of either, I just wanted to see what your opinion was and maybe I was not aware of something.

MEMBER:  We have a customer that says they are receiving a 200# test box from an other box maker, but our testing indicates that the board combination consists of 36# liners and 26# medium.  How can this be valid?

RALPH YOUNG: You raise a good question and one that has been asked for almost twenty years.  Rule 41 and Item 222 require any box that carries a circular 200# test stamp to be comprised of 42# liners and 26# medium.
Period.

You have described your customer as placing boxes in a refrigerated environment and that they sometime experience box failures.  Where a box described as 32# ECT may have sometimes performed in the past, the customer is now demanding boxes with a 200# test construction.

Every corrugated construction has weight, caliper, flat crush, pin adhesion, edge crush, Mullen, and flexural stiffness.  These physical properties are common to all  structures.  So even a 200# test box may have low ECT and low box compression and still fail your customer shipping environment.  There are many reasons for box failures.  Very little has to do with the basis weights of the components.

All that maybe needed is to change to a water resistance adhesive.  The more you can tell me about temperatures, relative humidity, storage times, pallet design, pallet layers,  box dimensions, content weights.  I would be available to coordinate with your testing facility to engineer the best solutions for you and the end user.

MEMBER:Can you tell me about the ECT potential of combined boards made with 23# and lighter mediums?