Archive for the ‘Finishing/Converting’ Category

Measuring Force to Break PDQ Perforation

April 10, 2019

Pete asks,

We have been working with several different perf styles to provide ease of opening for retail ready PDQ style trays. There is a variety of different sizes and the majority of the items are earmarked for Walmart stores. While our execution has been successful we do not have an effective process to measure the force required to open the boxes to ensure consistency. Are there any tests to can recommend or any laboratories capable of testing the variables we are trying to measure?

Very good question Pete! You might review TAPPI T-813 which discusses the tensile test for the manufacturer’s joint. There are also jigs for compression testers that will measure the force necessary to bend a crease through a certain distance, usually to a 90 degree angle.  Also check TAPPI 577 and 829 for ideas.

Another option may be to use a burst test at the point of the perf. TAPPI T-810 describes the burst testing method. The question would be whether conventional equipment would have a satisfactory range of operation/measure or would the bursting strength of the perforation be below the recommended operating range of the equipment.

Now let’s toss this one out to our readers to see what their thoughts and experience may be. Has anyone done this type of testing, or is anyone aware of a specific method for testing the force necessary to break a perf?

– Ralph

Tuck Top vs Tuck with Locking Tab, or Friction Tuck

March 1, 2019

Rich asks,

I have a customer who orders a lock bottom box with a tuck top from us. It ends up at distribution in Walmart and Walmart is having issues with the top flap coming open. It does not get taped closed. They are asking if we have packaging engineers that can provide documented test results or studies on performance changing it to a tuck top with a locking tab, or friction lock tuck top tab, or extending the tuck on the top tuck. Have you seen anything like that or are you aware of any hard documentation that says how much it changes the function of the top tuck? Thanks for your help with this.

I would start by checking with your sheet supplier and/or their containerboard provider to see if they have any information regarding the information you are looking for. Often integrated companies do these types of studies. Some will be willing to share and others are not as open to sharing their results. I have an associate in Canada that may want to weigh in on this issue. I’ll touch base with him and then update this post with any input he may have. I also searched through my George Maltenforts’ books, but found no discussions or reported research in this area.

However I do believe that a friction fit is the best way to go short of some type of press applied coating.

— Ralph

Student Question about Corrugated Use in North America

November 15, 2018

Christoph asks,

Hi Ralph, I was wondering if you may help me with a few questions. I am a German Master Student studying Printing Technology at CalPoly State University. The topic is about the corrugated packaging market and the most common used papers and purpose of the boards.

Therefore, I would like to ask you if you can provide me with information for the following questions:

  1. Which are the three most produced board qualities (e.g. Brown Kraftliner 35# – recycled fluting 30# – Brown Kraftliner 35#: C-flute) in the Northern American market?
  2. What is the most common purposes for corrugated boxes? (shipping, shelf-ready packaging, …)
  3. On average how many colors are printed on the above requested corrugated board qualities?

I am very thankful for any information you can provide.


Hi Christoph, happy to share a little information with a student of the industry.

  1. The most common combined board grade is 33/35 test liner / 23# test medium / 33# test liner.  While virgin kraft linerboard is still present, the US is about 50/50 new verses used fibre.  In Europe this is very different.  Mills that use the newest papermaking technology can use 28/26/23 C flute constructions.  We make heavier boxes here than you do in Europe.
  2. We ship durable and nondurable goods in corrugated packaging.  If you want this broken down by manufacturing segment I can provide that.  The biggest market is food.  Yes there is shelf ready packaging and displays.
  3. On average we probably print three colors via flexo. There is a great deal of four-color work done, but there is still a significant amount of two-color and one-color work being done (think Amazon, Home Shopping Network, etc.). Digital is gaining ground quickly, but it is not the ideal process for most boxes. It has its niche and its popularity is growing especially in the graphic market. However, digital has yet to reach the speeds necessary to make it ideal for high throughput orders. You’ll want to keep your eye on it though as the technology is continually evolving.

— Ralph

Skip Feed Repeat and Max Print Area

November 15, 2018

Chuck asks,

My question, is there a formula that determines how long of a print area (thru the machine) can be printed without being printed a second time when running skip feed. We have a 66” rotary diecutter with skip feed. We did a test on a sheet size of 79-1/4, mounted a 28″ plate, centered and it did not reprint.

I reached out to a few of my industry contacts. My colleague Dwayne Shrader put together some info for this post.

Max Sheet Length Before Print Repeat

On a 66 inch machine the print is going to repeat every 66 inches from the lead edge of the plate. That’s the key to determining the length of the sheet before repeat… ‘from the lead edge of the plate’.

To determine the maximum sheet before print repeat where …

Cylinder Circumference with plate installed = CC
Lead Edge Offset = LEO
Max sheet Before print Repeat = MBR

Then…CC + LEO = MBR

You say you mounted it in the center, I assume you mean you centered it around the cylinder. So the lead edge of the plate would have been at 19 inches behind zero register… (66 – 28)/2=19. This being true, then CC + LEO = MBR, or 66 + 19 = 85. Therefore, you could run a sheet just under 85 inches before the print would repeat.

Maximum Print Length

Now, determining the maximum print length, is just a little different because the cylinder circumference is not the maximum machine print length. Keep in mind that the lead and trail edge lockup takes up some of the circumference (or print area). On the typical 66 inch cylinder your maximum machine print length is going to be between 61 and 64 inches depending on machine design, lockup type, etc. Your machine manufacturer should be able to provide the maximum through machine print length.

To determine the maximum print length where …

Maximum Machine Print Length = MMPL
Lead Edge Offset of printing plate = LEO
Maximum Printable Length through machine = MPL

Then… MMPL – LEO = MPL.

For example, let’s say the maximum machine print length is 62 inches and the lead edge is offset by 5 inches… 62 – 5 = 57 inches of available print length. Consequently the maximum sheet before repeat would be 71 inches in this case.

Sometimes a converter may have a plate that is made for a normal feed job, but they want to use it to print a larger skip feed job. In this case the plate is mounted in the normal position and then the register is retarded to offset the distance from the lead edge to the start of the print. The same formula for maximum print length is used here as well just substituting the register offset from zero register.

To determine the maximum print length where …

Maximum Machine Print Length = MMPL
Register Offset from Zero = ROZ
Maximum Printable Length through machine = MPL

Then… MMPL – ROZ = MPL.

Hope this is helpful.