Assembled Corrugated Blank Tolerances

February 23, 2018

Kevin asks,

Is there an industry-standard tolerance that would be applied to the assembled dimensions (Length, Width, Depth) of a 2pc carton?  I would question whether multiple processes should lead to alternate tolerances when compared to a single process 1-piece carton.  I would also wonder how carton size would play into the tolerance and if there are any steadfast rules and/or guidelines throughout the industry.

The particular carton I am trying to apply tolerance to is a 2pc Partial Overlap Top, HSC bottom where the width panels are die cut and the other scoring off of a press and then offset stitched within the length panel for reference.  I am trying to hold +/- 1/8” on all dimensions now.  These tend to be around 76 x 32 x 50” with 2” POL.

According to the Joint PMMI/FBA publication PMMI B155-TR2.2-2011,  the tolerance of a RSC panels are +/- 1/16 inch per panel with an overall blank tolerance of +/- 1/8 inch for both length and width.

Slot depth should be within 1/8 inch from the center line of the corrugator score. Slots should also be centered within 1/16 inch of the aligning scores.

No allowance is given for carton size, caliper, substrate or complexity of design in this specification.

I haven’t found any reference to multiple piece cartons which would lead me to believe that there would be an additional allowance for a multi-piece carton.

So, based in this information, it would make sense that the overall assembled dimensions (interior and exterior) should be within, and controlled by, the +/- 1/8 inch overall tolerance of the RSC or die-cut blank.

— Ralph

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Bake a cake in a box

January 31, 2018

Stan asks,

We have a customer who wants to bake a cake in our corrugated box. We use recycled paper from XXXXXXXXXX Mill in XXXXXXX. We also have a letter of ‘No Objection’ from Health Canada. Do you foresee any problem or restriction on this method of cake preparation?

Assuming you have some type of suitable and accepted barrier coating the only other concern would be heat. I assume that they are planning to bake in a conventional or convection oven. Since cakes typically bake at 350 degrees F you shouldn’t have to worry about the 451 degree combustion point of the paper.

If a microwave oven is to be used then there may be a few concerns about the paper and what comes into direct contact with it. A mass resting against paper in a microwave can cause temperatures to reach a point significant enough to cause scorching and even combustion of the paper. (I’ve ruined enough bags of pop corn to prove this point)

I’m not sure how the AIB may play into this if the products are to ship into the United States.

Let’s toss this one out to the readers and see what knowledge they have to share.

– Ralph

Manufacturer’s joint tolerance

January 31, 2018

Kenny asks,

I am new to the AICC family and I have a question I hope you can help me with. I have a customer that is asking questions about the tolerances on an RSC box, specifically the glue joint gap dimension. As I understand from the FBA Handbook, a box maker has 1 board thickness of tolerance after machining. To be even more clear, for a C flute box, a box maker has approximately 3/16” total, that a gap can deviate from where it is designed from (3/32” from Center on both sides).

Well welcome to the family Kenny.

The tolerance as I have always understood it (for fishtail) is no more than 3/16 variance overall from the score line to the end of the flap regardless of the thickness of the sheet. Nor should the gap width at any point of the manufacturer’s joint be less than 1/16 inch in width, again regardless of substrate thickness.

However, with automated packing lines, customers may require a tighter or more consistent tolerance.

This is a battle that has been going on since Hector was a pup and always seems to be a topic for discussion.

– Ralph

Calculating ink coverage based on weight

January 31, 2018

Ed asks,

“We are creating a program to quote customer requirements as quickly and accurately as possible but we are stuck with ink / printing issues.

Is there a conversion that may help us translate grams of ink to square centimeters / inches of printing?”

Your ink supplier should be able to tell you how many sq. in. or sq. cm. a pound or gram of ink will cover. This will change depending on the viscosity, substrate, anilox roll volume, ink manufacturer and ink type. So in your calculator (estimator) you may want to provide the option to select from a pre-programmed list of inks, or allow the estimator to enter a pounds per inch or grams per centimeter variable.

Then of course you’ll need to know the sq inches of coverage for each color. You could simply calculate the area of the sheet and then assign a light, medium, or heavy coverage variable to simplify the calculation of inches of coverage.

– Ralph