Is UN retesting necessary for overpack?

March 27, 2014

Randy asks:

If our customer has small cartons that have already passed UN testing individually and my customer wishes to put 10 or less of these into a larger carton, would the larger carton need to be UN tested as well or would it be considered an overpack box since the smaller cartons have already passed UN testing? If an overpack box, what information needs to be on the outside of that carton?

It appears that you are going to a combination or composite type package. Since this is a deviation from the original design qualification, the entire unit should be retested. It is best to ask this question of the specific testing facility that did the last testing validation. You can certainly make the call on behalf of your customer. Your customer and lab can provide you with the proper labeling.
— Ralph

UN HazMat Packaging Update

March 25, 2014

The Pipeline and Hazardous Material Safety Administration of the Department of Transportation has finally ruled on the basis weight variation in the outer liners at +/- 5 percent. There was a proposal before them with comments from 36 converters to allow for a ten percent variation. Since the PHMSA did not have enough historical data to support the ten percent range they adopted the five percent deviation. In other words the PHSMA has adopted the terms of Competent Authority 20051120010 as proposed in the Hazardous Material Regulation 178.516(b)(7). This has become official language in the Federal Register as of March 18, 2014. Here is a link if you wish to review the details yourself www.gpo.gov/fdsys/pkg/FR-2014-03-18/pdf/2014-05630.pdf

Because this allowance is included in the HMR we should no longer need our CA. However, we need to know for certain that this is the case. We will be sending our more information when we know that this is true.

— Ralph

Corrugated crush data collection

March 3, 2014

Vincent asks:

I was just part of the webinar on crush you hosted January 30th and our GM wants my division to focus on minimizing crush throughout our facility. He wants to do a problem solving analysis on the issue. Can you help point me in the right direction for tackling a big project like this?

Where will we be most likely to experience crush on the corrugator and what are the best places to measure or take readings? I have the same question for the converting side as well. I know some of the obvious places, but I wanted to draw on your experience to identify places I may not have considered and also what you consider to be the most likely cause and therefore the best place to start.

Also, do you know if TAPPI has an Industry Standard for Caliper? If so where can I find it?

Since it is difficult at best to measure crush at each of the points on the corrugator mentioned below, you may want to focus your research on the area just before the cut-off knife and at the bottom of the stacks at the exit gates.

If you are considering using the DST method to collect your data, then you’ll need to measure five points on the corrugator, across the corrugator roll width, at each of the places listed below. Try to be consistent with the position of the five points as well. Let’s just say you select to record caliper (from the edge of the sheet) at 5″, 24″, 48″, 72″ and 91″. Then maintain those distances throughout your data collection process. Just a word of warning to keep everybody safe and happy, these measurements should only be taken with the machine stopped and/or with product off line from the machine.

  • the nip of the corrugator roll (not able to actually measure the compaction of the medium in the fluting operation)
  • the exit of the glue machine (entire machine would have to be stopped)
  • the entrance to the double backer (entire machine would have to be stopped)
  • the exit of the hot plates
  • at the slitters
  • exiting the scorer
  • after the rotary knife
  • measure the finished sheets in the down-stacker. Again check at five positions across the corrugating roll width.

With the converting machines it is a little easier to pull samples from various stages of the process, perhaps even more so with fixed architecture (non-opening) machines.

First, make sure your sheets aren’t crushed before they go on to the feed table. Many things can happen to a sheet between the corrugator and the converting machine. Units that are stacked beyond proper height/weight specification, strappers and unitizers, fork truck operators doubling-up for fewer trips, or somebody deciding to sit down and take a break on a stack can all contribute to board crush.
On the converting side of the equation, again determine from where you are going to take your measurements, just like you did for the corrugator, and maintain those locations throughout your sampling process. Again we stress… For safety reasons do not attempt to take these readings while the machine is running. Collect your samples, from each of these areas if possible, and then take the readings off-line from the machine.

Take readings,

  • Before the sheet enters the feed roll on the feed section
  • After the feed roll
  • After each print station
  • After the creaser and slotter (if you have an FFG)
  • After the diecutter
  • After the beater section of the stacker
  • After the counter-ejector (FFG, the pull rolls and compression sections can cause crush)
  • Anywhere else you have rollers or nip points.

If your operation uses bundle breakers/separators take readings after the breaking process. Improper adjustments can result in excessive pressure on the blanks. Improperly nicked bundles can require additional pressure to break the bundles and result in crush as well.

Crush can be speed sensitive. So as you’re collecting your data, you’ll want to record machine speed for further evaluation.

There is a TAPPI Test Method for measuring caliper, but it only measures “springback” caliper and not the minimum point of caliper during the thickness reduction that occurs at the various nip points.

These measurements can only properly be performed with the super sensitive DST equipment. Conventional caliper tools will not measure the amount of degradation in the corrugated sheets.

— Ralph

Die cut blank size variation

February 20, 2014

Stan asks:

We are having an issue with board shrinkage (C flute).
The sheet length off the die cutter is approximately 58” (direction of corrugation).
This overall length shrinks by approx 0.125” to .375” making the inside dimension too small for the product.
Have you encountered this phenomenon in your corrugated experiences? If so, is there a remedy and what is the cause?

I will assume that we are talking about a rotary diecutter operation.

This is not unusual. Check the sheet transfer system, bearings, ink drying, plates, die cylinders and ejection rubber compatibility. Has the liner changed? I also discussed this with my friend Dwayne Shrader who used to work for a diecutter OEM and he offered these additional thoughts.

  • Anvil covers/blankets. Are they excessively worn? Also, covers can come in different thicknesses, make sure you have the correct ones. Worn covers cause a change in the sheet speed as is moves through the diecutter section. As little as .125 difference in diameter can be problematic.
  • Verify the knife and rule height on your cutting die. The proper knife/rule height should be listed on the OEM nameplate of the machine. It should be either on the feed section and/or be on the die-cut section. Incorrect rule height can change the speed of the board as it moves through the machine too.
  • Check the impression setting on the diecutter. Operators like to crank the impression down to compensate for worn anvils. Over impression causes the surface speed at the sheet to change and this leads to size variations.
  • Is the cutting die properly secured to the cylinder? Is there a bolt in every hole as it should be, or has the operator skipped holes for the sake of a quick set-up?
  • As Ralph said, make sure your rubber is the correct height and in good condition too.
  • Is your machine servo driven or does it have a gear train? A worn and sloppy gear train can cause the speed of the diecutter to float(variable change). If it’s a servo machine, is the servo functioning properly? You’ll probably need to contact your OEM to have that checked out.
  • And here’s one that is often overlooked. If it’s an open/close (modular) machine is the machine lock adjusted properly? If the lock isn’t holding the sections tightly closed, it’s the same as having a worn gear train. Look at the frame splitlines of the sections (Where the frames come together). If you see them “breathing” (opening and closing with each feed, or just while the machine is running), check to make sure the lock is properly adjusted.
  • Has your board had sufficient time to cure off of the corrugator, or are you running hot board? If your diecutting before the board cures you’ll have a hard time predicting shrinkage and controlling finished blank size.
  • There are many other variables that can affect die-cut blank size stability, but we hope this helps you resolve your issue or at least gives you a place to start.

    Let us know what you find and please come back to us if you have more questions. Also, if anyone else out there has any ideas they’d like to share, please feel free to leave a comment.

    —Ralph


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