The cure to all corrugator diseases


Élixir d'AnversWhen I was young, every time I felt a bit under the weather, my mom gave me “Elixir d’Anvers”. It was the cure to all illnesses. If it was a flu or an indigestion or whatever… “Elexir d’Anvers” took away the pain. I even heard that farmers where giving it to their horses when they had some stomach problems. (image courtesy Wikipedia)

It was nothing more than a herbal short alcoholic drink that was invented by a medical doctor as a simple and effective cure in 80 percent of the cases (and the alcohol in it was an additional advantage).

http://www.elixir-danvers.be/en/150-years-of-tradition

In exactly the simular way that “Elixir d’Anvers” was a cure to all illnesses, a cure to all Illnesses in the corrugating process is ‘less heat and less starch’

Let us some up some corrugating diseases and there cure:

Symptons:

  • Washboarding
  • Slinging (glue splashing)
  • Blisters
  • Honneycomb
  • Brittle bond
  • Steam bubbles opening layers (secret blowing)
  • Post warp
  • Bad slitting/ bad cut off
  • (and others)

Cure:

  • Less starch, less heat

For my job I do a lot of troubleshooting and problem solving and it is amazing how simple my job sometimes is (please do not tell this to my boss).

The very first thing I suggest, when confronted with a problem, is to reduce heat and starch to the minimum required, and in 80 percent of the cases the problem disappears, just like using Elixir d’Anvers.

I make it sound very easy, but to convince someone that is already using 30 years too much heat and too much starch is quite a challenge.

Some time ago I was at a company making heavy combinations for the fruit and vegetable market: the typical BC semi-chemical coated kraftliner and heavy paraffined brown kraft. They were complaining about honeycomb, wash boarding and bad bonding of the coated kraftliner.

Observing the double backer, I noticed that every time a certain combination came up with coated kraftliner, the operator put a 100% wrap around a small preheater just before the hotplates. I asked him: “Why do you put so much heat in this coated kraftliner?”. The answer I got was:  “Because someone told me to do so, and if I do not do it then we have a bad bond.”

I enquired if he understood the physics behind what he was doing, but even when explaining it to him; he didn’t want to change this behavior. It was just an automatism based on the trigger word “CKL” coated kraftliner. This resulted in a not so good looking board, I would even dear to call it plain waste.

I had to be in the same plant the next day. I was a bit devious and closed the valve at the drive side that fed the steam in to this small preheater. After a while it was around 40 degrees Celsius and was only brought to this temperature because of the preheating of the liner in the triple stack big preheaters. Nobody noticed me doing this.

The next day when the same “challenging” combination came up the same operator again put a 100 percent wrap around the small preheater. The board was looking better today then yesterday and the operator called me and explained to me that having that 100 percent wrap around is essential for having nice board. Proudly he showed me the 100 percent wrap around and the board that looked a lot better compared to yesterday.

I listened to his story and nodded from time to time. Then I took out my IR camera and showed him the fact that the small preheater was completely cold ( as I had closed the valve the day before). He panicked first a bit and then he suddenly made the link to the better board and the less heat combination. In the coming runs he even put the wrap around on 10 % since he realized that someone had given him the wrong explanation.

It was probably a lucky shot, thirty years ago, but the quality standards for making board have also changed drastically during that time.

I would like to challenge all of you that are running with a lot of starch and heat to try the following.

Let us say that you are running with the first hotplate on 6 bar (single wall, just to keep it simple).

Reduce it to 3 bar and see what happens. Most probably nothing… Reduce it to 1 bar. Remember that with thick hotplates it takes about 12 to 15 minutes before temperatures go down.

If it changes nothing to the final board, then the question is: “Why are you running with those high temperatures in the first section?”

Give your corrugator some “Elixir d Anvers”, less starch and heat, and you will be amazed how many problems it solves.

Koen

 

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It all starts with parallelism.


The ideal we want to get in corrugating are  flat sheets, no delamination, no wash-boarding and no honeycomb.

To obtain above one has to have a corrugator which is in a perfect state. And this has nothing to do with the age of a corrugator but all to do with maintenance.

People spend millions on a 2.8 or 3.3 meter corrugator, but seem to have no money left to spend on some simple and basic tools to maintain the state of their equipment. For instance, when I’m visiting corrugating plants, I often need to improvise to be able to make an iodine image. I some cases I even have to bring or buy my own iodine. A simple setup can make a big difference and allow you to save multiple thousands of Euros a month. Other affordable but indispensable tools around a corrugator are: a wet film glue metering gauche, and infrared thermometer, a device to measure absolute humidity, a tachometer, a digital microscope, etc.

In this article, and probably many times in the future, i will repeat the importance parallelism. With ‘parallelism’ I refer to both mechanical parallelism (such as reelstand splicers, incoming rollers, glue machine preheaters, etc.), thermal and glue application evenness.

Today there is the tendency to run lower board grammages compared to the past and in addition we run them on wider corrugators. This may lead to creases while unwinding.

Sometimes these creases can be invoked from the paper, either the creases are already in the reels, or the humidity and thickness profiles may cause the crease happening while unwiding. Do not forget that a mechanical chock on a reel, which makes the reel dancing (bouncing), can also be the cause of irregular tension resulting in.

thickness profile paper humidity profile paperGood profile (left: thickness, right: humidity)

A mill expert will be able to tell you based on the profiles if the paper is causing the creases. This can always be the case of course, but in most mills the paper has been wound and often been rewound, so the operators would have noticed if some PROFILES were bad. Winding and rewinding speeds in the mills are at least three times faster than on a corrugator….. the webs are also wider than on the corrugator.

Imagine you are the liner of the singlefaced C  that will end up as BC double wall board. At the start you will be unwound on the UNWINDING STAND that is furthest away of the take-off. Already here you have the option to be unwound on TWO DIFFERENT UNWINDERS.  PLENTY OF ROLLERS will guide towards the singlefacer. Some will be FORMED SPECIALLY to avoid wrinkles or creases (banana reels). You get PREHEATED a couple of time and then you MEET the C flute. Depending on the type of singlefacer you will be PRESSED to the C flute and in between there will be starch applied through the singlefacer GLUEMACHINE. Then you are pulled upstairs on the bridge and they fanfold you. Then you are put on the bridge after being fanfolded, awaiting the next stage in the process.

In the imaginary story above I placed the words in CAPITAL of the areas where parallelism is important.

I think we all agree that if you have two different UNWINDERS (let’s call them unwinder 1 and 2),   there should be no difference between the two. In reality I often see lots of difference. And when i say ‘lots’ then I refer to the fact that I see three corrugators a week by average and this for about 40 weeks (for a period of about 9 years now).  One corrugator a day keeps the doctor away 🙂

If you place your hand on a singlefacer, you will feel the vibration. This vibration is going on every second the machine is running and in the long run there is a risk that parts reposition and mess up parallelism.

The same thing happens to your equipment as to the glass of wine in the video. Centerlining or checking parallelism should be done every second year especially if you are running low grammages.

Other causes to destroy parallelism may be small accidents. For instance if one hits a reelstand with a reel truck or so. Things like this happen more often than they are revealed.

One easy trick if you have issues unwinding is to first unwind the reel on stand 1,  check where the creases are happening (OS or DS),  change the reel to stand 2 and check again.  When you change the reel to stand 2, make sure to follow the unwinding logic.  If the creases disappear it could be that there is something wrong with unwinder 1. If the creases remain in the same relative position toward the reel, then the chance that there is something wrong with the profile of the reel is big. If the creases are still there but at the same side, like when the reel was on reel unwinder 1, then most probably you need to look a bit further in the process to find the cause of the problem.

In this article I concentrated on the singlefacer and reel stands, but parallelism is important in many other area’s which I will discuss in future blogs.

It’s time for my sauna now.