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.

Hazmat Labeling, Flammable, Consumer Commodity, UN?

August 10, 2018

Jeff asks –

I have a question regarding the correct markings for a customer of ours that sells marine paints and coatings. Can you please help clarify which markings are required? It is our understanding that the box can have either the Flammable Liquids placard or the Consumer Commodity placard but not both. Also, if using the Flammable Liquids placard are additional UN markings required?

For your first question you are correct. Only one placard can be used, either Flammable Liquids, or Consumer Commodity as long as it falls under the guidelines for Consumer Commodity.

For your second question regarding UN markings, according to phmsa.dot.gov it would appear that yes, the UN markings should be used in addition to the Flammable Liquids placard.

If anyone has any additional information or insight on this topic, please feel free to share it with us.

— Ralph

Could Starch Lines Be Culprit to Metal in Boxes?

May 29, 2018

Ray asks,

 Since April of this year we’ve been fighting with major metal detection rejections with one of our customer that has a stringent HACCP/SOP in place.

We feel we may have finally found the source of our metal contamination. We believe that it may be our metal starch lines and perhaps rust form the lines is mixing with the starch and being transferred to the products. We’re waiting for metal chemical analysis results to come back to confirm my suspicions.

While we are awaiting the results of the test we have come up with a few more questions and hope that you can help provide an answer.

Best Practices:

How often should starch lines be flushed?

Should straight bleach used?

What types of strainers are being used in the industry and what are considered the best systems?

Is anyone using inline magnets in their glue systems?

How often should the schedule 80 pipe lines be replaced, and is there anyone out in the industry using Predictive Maintenance to replace lines?

Is PVC piping a viable alternative for starch lines?

Thank you and your readers for any insight that can be provided.

Just a couple thoughts. Have you ruled out the chance of contamination from sources outside of the manufacturing process? Do the conveyors pass a maintenance shop grinders could be in use? Are there any RFID tags used in any of your processes?

For input on the starch lines I reached out to Wayne Porell at Harper Love Adhesives to see what experience he may have with such issues.­­­

First, I don’t have any plants having this issue. There may be more going on here than what we typically see.  Most well-run plants flush their starch lines at the end of every week by at least running water through the system after they shut down. Some plants also use Clean Tank HP™ from Walla Walla Chemical. Others just use bleach. However, bleach only disinfects the lines to help control bacteria. It doesn’t help remove any build up starch in the lines.

Some plants have strainers in place but remove the filter because they get clogged and cause the pan to over flow. These filters need to be cleaned, but can only be cleaned when there is no starch in the lines and the machine is down. You also want to make sure the filters are in place and are not damaged.

I don’t know of anyone using inline magnets to catch metal parts. If the plant is getting enough metal inside their boxes to set off alarms, then I would, as obviously they are, be looking where the metal is coming from. There shouldn’t be enough metal from mechanical pumps or bearings causing this issue. If there was, I would certainly think they would be seeing mechanical failures by now.

Over time schedule 80 iron pipes rust inside and create areas where starch can build up and harbor bacteria. This shouldn’t cause enough metal to come off to trigger an alarm. If anything, they rust through and cause leaks or the starch builds up inside the lines and creates flow issues at higher speeds.

The timeline for replacing these metal lines depends on the house keeping over the life of the lines. Like anything in the plant, the better that is taken, typically the longer it will last. The chemicals used to clean the lines can affect the longevity of the lines as well.

Schedule 80 PVC can be used and is used in some plants. The issue with these lines is you need to have hanger braces every four feet to keep them from sagging. If they sag, then you have areas where starch could build up in the lines. However, they are easier to clean if you keep them flushed on a weekly basis.

PVC lines also have to be braced well, especially if using pneumatic pumps for starch supply and return which tend to cause a pulsating action. PVC doesn’t allow bacteria to build up since it doesn’t have cavities like those caused by rust as in metal lines.

I have seen some plants switch to stainless steel lines. These are probably the best, but also cost the most.

 Again, if the plant is getting that many rejections due to metal they should review their whole process. Small specs of metal should set off alarms at their customers. Are they using any types of foil tape in their process?

— Ralph