To measure or not to measure that’s the question.


If you don’t measure, you can’t control
If you don’t control, you can’t improve

This quote is still not common use at a lot of corrugator plants I, am visiting all over the globe.

At 70% of the plants I visit I see a lot of experienced people and they really know how to produce good board without measuring anything, no temperatures and no moisture levels. Often there is even no temperature gun at the plant. I see Process temperatures over 100 °C at the MF and up to 10 bars steam pressure at the DF when producing single wall. Do we really need all that heat?? Not in my opinion.

The crew has often over 40 years experience in the industry and they are, so to say, pro`s. and as we know, when we talk about to change a process “it is hard to learn an old dog to sit”. Other plants have a young crew and it is easier to change some old habits. There are also plants where they already use less wrap and steam settings without using temperature guns and produce good board and a good production speed, but I my opinion these plants are rare and they still can gain progress when starting to measure process temperatures and moisture to improve their process.

Sometimes the corrugator is in such a bad condition that I really have respect for the crew how they still manage to produce relative good board. They work around all the problems and I am impressed about the (visual) board quality they produce. The production speed is also comparatively low.

The strange thing however is that this experienced crew don’t have any idea about the ongoing process. They know exactly how to produce relatively good board and what to do when problems occur, but if I ask them: “why are you doing this?” the same reply I hear over and over again: “well, that´s what I always do”.

Sometimes they see me “shortly” as a kind of a threat and they ask me how many years I, am in he business. I tell them that I have over 50 year experience with card board and show them this picture. Apparently this is an important issue.

corrugating junior

After some laughs I explain them some of the philosophies and theories, I am working with.

99% of the crews are willing to test the proposed theories, although they are quite sceptic at the beginning and see the suggested ideas only as more work.

Together we measure the temperatures and lower the temperature step by step at f.e. the DF or MF. After every single change we make, we go to the stacker and look at the produced board quality and they tell me if the board is better, worse or the same. If the board is better or the same we go on to the next step. Of course the board is better otherwise I did not make any of these suggestions to change some parameters at the first place. Only when they see that what they do, measuring temperatures and act accordingly, have visual results on the board quality they are willing to take the next step. Often they are quite enthusiastic and I have to fight to get my temperature gun back. Within some days the plant organises some temperature guns and they see the benefit of measuring temperatures. Together we also ask converting if they noticed any differences lately and in most cases they noticed positive changes. These positive changes, by using just enough temperature, changes also the use of glue in a positive way.

This is the next (hard) step they have to make: reduce glue. I like to change the up going spiral “more heat – more glue”, towards a down going spiral “less heat – less glue”. This is only possible when you start measuring process temperatures. It is not the purpose to use as less as possible heat, but just enough to produce good board.

At the beginning it is logical that, when something goes wrong, for what reason ever, they directly jump back to their old habits “more heat and more glue”. But when they have more experience and feeling comfortable using temperature guns or work with temperature sensors, they don’t want to change back. When they reach this point I, am feeling content.

The trainer job is a hard but challenging job, and because this challenge, to visit new plants, meet every week new people, all over the word and learn them to improve their corrugating process, makes the job worthwhile.

 

Something about myself:

Harre MedemblikMy name is Harre Medemblik (1958) and I am from Holland. I Started my own consulting company in March 2015 after working for BHS since 2006. I worked at BHS as a process trainer and since 2007 as a specialised trainer for the WCS system (warp control system). Together with the BHS “TE” depart we installed and improved more than 35 WCS systems in Europe and overseas.

Now I started my own Company my key customers are Savon Salu (Powerflute), BHS and BRICQ.

Before I started as a process trainer, I worked for the Dutch government as a Process analyser at the environment safety department. My job was to analyse all kind of processes at all kind of factories to determine the possible way to produce with less energy, pollution, noise and smell according the Dutch and European environment law and to write a permittance according this law. Often I see that there is still a lot to gain in the word at corrugator plants, when I see through the eyes of my former occupation.

Harre Medemblik
Pro-Corr

harre.medemblik@pro-corr.com

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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

 

Cross company cooperation at customer


I recently had the honour to work together at a customer to do trial runs and operator process training. We teamed up with two specialists Mr H. Medemblik from BHS corrugated and with Mr D. Murfitt from Crespel & Deiters (starch specialists).

This resulted in a very successful cooperation and very good light weight board production in different combinations. This also gave us the possibility to give a joint training pointing out several things to the operators and management. With as main topic, less heat, less starch.

The corrugator we used was not the youngest one and could be described as a middle aged lady with a couple of face lifts and all the other cosmetic stuff. A steam system that is not always very reliable and E flute corrugator rollers that are also due for a full cosmetic rebuild 🙂

We focused in getting flat E flute board, with no post-warp and no wash boarding neither honeycomb.

The papers used where Modo Northern light  Flexo 120 as coated fully bleached (100 percent fresh fibre), combined with 80 gsm Modo Northern Light / 100 MNL and as inner liner we used 100 MNL

2014-09-03 11.03.03 This pictures shows 120/80/100 combination. Nice board and no postwarp.

As you can see these are very low grammages and these fully bleached virgin fibre liners have the tendency to pick up heat very fast and have an build in natural humidity barrier. ( so they do not like water/ starch to much).  So the risk one has poor bonding due to excess starch is there always.

When we started the corrugating we first monitored the settings and state of the equipment. We noticed relatively high amounts of starch and a bit to much preheating an about all positions (SF and DB) whilset running Flexo preprint coated liner 120gsm combined with MNL 100 as fluting and MNL 100 as inner liner.

After one day we ended up using a gap of 0,12 on the  ( in stead of 0,20 ) DF with 0% preheating so liner went in to hotplates at around 27 to 40 degrees Celcius..

Same actions were taken at the single facer where we went to minimum possible gluegap and reduced drastically the preheating of liners and fluting.

So finally we arrived to following process parameters:

      Process temperatures and glue gaps

  • 200 m/min
  • SF liner 80- 90°C
  • Fluting 75- 85°C
  • web 85-95°C
  • Glue gap on mechanical minimum.
  • Temperature liner before hotplates 27 (uncoated) 40 degrees coated
  • DF 117- 122°C Sensor  (130-130-135-135°C hotplate temps)
  • DB gluegap: 0,12 mm

before web
before: web






liner

 

before: liner

 

 

 

fluting

 

 

before: fluting

 

 

 

 

after lining

after fluting

 

after: liner

 

 

 

 

 

after: fluting

 

 

 

 

too_much_wraparound

 

 

zero wrap

 

Too much wrap around

 

 

 

 

 

 

Zero wrap

 

 

 

 

 

The very stable one bag mix from Crespel & Deiters performed very well – the parameters for this high-performance wheat starch based glue were 55-60 seconds Stein Hall viscosity (18-20 sec. Lory cup), 57 DegC gel. point and (oven) dry substance of 22.70%. Even at what we would consider a bit high temperature of the starch in the glue pan (38 degrees) it sill performed very well.

This cooperation has again taught us that using iodine pictures is so very helpful.

While running at 180 m/min making perfect board we increased the speed to 200 meters and the board started to delaminate:

Iodine pictures showed us again what was happening:

170m

 

At 170 meter

 

 

 

200m

 

 

At 200 meter

 

 

 

 

So the iodine pictures showed it why we had a bad bond at 200 meter. Too much glue and not enough heating. First reaction of operators before making iodine picture was putting even more glue…..

This irregular glue-lines on the liner where caused by an excess vibrating of the arm holding the interfic shoes.

metpijlke

 

 

 

 

 

 

After fixing this the problem disappeared and the road is open to higher speeds than 200 m/min.

So making iodines is very important, it show the soul and conscience of the corrugator and help us to take the correct decisions.
Another tool that is also very handy and I dare to say a must is an absolute humidity measuring device.
This will give us peace of mind and we will not be afraid of postwarp.

This corrugator still had some issues like a doubt on the parallelism and some irregular belt porosities but these where just some things to add to the list to be checked along the road.

I would like to thank Mr Medemblik and Mr Murfitt for their perfect help for the commen goal: GOOD BOARD!

Koen

 

Litholaminators with in line single facer.


These machines are awesome! Especially for a corraddict since these machines are so open – unlike the single facer with negative or positive pressure – that they allow you to see and measure everything.

One would expect that just because these machines are so accessible that they would be in a very good mechanical state, but I see more of the opposite in the field, not too good maintained equipment with serious maintenance issues.

 

Incoming steam pressure in the single facer at the litholaminator.

Let’s start with the incoming steam. Most cases one runs with 14 bar incoming steam. That’s in most cases just too much and the more one goes to smaller flutes the more difficult this becomes with this amount of heat. At one customer we were able to go to 9 bar without seeing a drastic change. So even going lower in pressure when running N flute is possible.

Quote:  “We cannot run with steam pressures lower than 14 bar”.

Question (me) : “Can you explain why ?”

Answer:  “Because it is so…. “

Question: “Did you try to run with lower heat/ lower starch amount?”

Answer: “ No”, or “Board will not glue” or “We will have too much warp” etc.

A most interesting answer : “We can’t  apply less heat on the single facer because then we need to use less glue and this results in too dry board that will cracks in converting.” ?!

We all know that higher temperatures /steam pressures results  automatically in a higher starch demand, ending up with at the end of the day a wetter single facer web.

And how do we get then a flat sheet after laminating with Poly Vinyl Acrylic glue (PVA glue)?

Mostly we will apply too much glue to enable us to create flat board. (The 50% water in the PVA glue will balance the sheet with the high humidity of single faced web). So then we get almost perfect flat sheets but very wet and with a huge amount of washboarding.

extreme washboarding

So one creates very wet board that one also needs to flip flop to get flatness.

An additional problem with this way of running is that through the hydrodynamic forces of the glue one tends to apply more glue in the middle then on the edges. Many mechanical solutions have been tried to overcome this, but one this phenomenon cannot completely be suppressed.

To be able to apply low amounts of glue on has to have a single facer in perfect mechanical state.

As an example I will show you some pictures of what can cause serious problems in a litholam line:

The problem: 2014-04-02 11.01.51

 

The result:2014-04-02 10.59.40

 

effect of scorelines

The iodine coloring of the fluting in the picture above does not look good. In the light colored area’s one could obtain a lack of glue. If that happens the operator has no other choice then to increase the glue, but then this will result in an overload of glue in the darker areas.

This is resulting in applying more PVA glue on the PVA glue station to get the board back in balance. (flat).

Another risk of  applying too much heat and starch, caused by damaged equipment, is splashing or spraying of glue in the flute valley, where there is even no contact with the liner.

exttreme splashing

So the message here is to make sure that the equipment is in good shape.

 

Running Lower grammages as fluting and inner liner

There is a tendency to use lower grammages. The prerequisites to be able to run low grammages like 70 g fluting and 60 g liner are:

  • Positive mentality of the crew to do its best, and accept change.
  • Good starches and good PVA glue (mostly not the cheapest)
  • Equipment in a perfect state:  glue rollers, blades, corrugating rollers
  • POSSIBILITY TO REDUCE THE STEAM PRESSURE IN SINGLE FACER

The same prerequisites are valid for running aereated glues. These allow you to save big time in glue consumption but also in the total drying time of your laminated sheets (less PVA glue used, less water, hence less drying time). But mostly one does not succeed because one of the four conditions above have not been met.

So one ends up using 230 g as a top sheet in order to cover up the imperfections in the laminator or the crew’s mentality. Have you ever made the calculation if you could run 160 g as top sheet?

Koen

pool car

Even glue application


 One of the hidden problems in corrugators are uneven glue application along the width and even sometimes in machine direction. Let’s concentrate here on the doublebacker glue machines.

Luckily there is such thing as a wet film glue metering gauge that helps you checking the evenness of the glue application. The instrument is simple and actually brilliant.

glue metering

The glue metering gauge is a high precision tool. Protect it well so it doesn’t get damaged. The two side metal circles are perfect circles. In the middle there is an oval where the height difference corresponds with the markings on the wheel. There where we have 100 microns, this means at that particular place there is a 100 microns difference between the two side circles and the oval.  If you put the gauge on the glue roll one will be able to read the exact glue amount you have on the glue roll. This does not tell you anything about the amount of glue that is transferred to the flute tip. Other factors that influence the amount of glue are the glue roll engraving and the amount of pressure applied with the small shoes or rider roll on the singlefaced material pushing it to the glue roll. The rheology of the glue is also a factor and for sure the capability of the flute tip to absorb the glue or at least the water.

So if you run a non-absorbing liner with a very absorbing flute, playing around with the borax can help…

At least the metering gauge learns you how much glue you have on the glue roller and you can then calibrate your digital settings. It also allows you to measure the parallelism of your glue machine.  If you have more glue OS then DS then you need to do something about it. It is normal that there will be more glue in the middle of the web then at the two sides.

When running C flute – and even B flute – with for instance 10 microns difference between OS and DS will not be catastrophic but you will end pushing more starch then needed. To have enough glue on one side you will need to open the glue machine with an extra 10 microns…..so that is a waste of money and also a risk to have warped board or excessive washboarding.

The measuring with the glue metering gauge should happen at a speed above 150 meters per minute. If you need to open the glue pan leave it a bit running before you measure so that dried starch is dissolved again.

Unfortunately more and more safety instructions and also the construction of glue machines make it more difficult to access the glue machine for measuring. So hopefully someone invents quickly a device that can measure accurately without any impact. Maybe it exists already in other industries? If you know of it, please don’t hesitate to comment on this post.

I also sometimes have the tendency to measure the upper glue machine by accident, hitting the emergency red mushroom with my fat ass 🙂 If this happens twice in 20 minutes then the operators have the tendency not to smile at me anymore and are starting to say dirty words in their communication headsets…

The doctor roll needs to stay intact and smooth as glass, otherwise uneven glue application will be a fact.  Again it maybe not be a big thing on big flutes but on N or G flute, where we are maybe talking about 80 microns of glue, then 10 microns more or less is a big difference. This is sometimes one of the reasons why people have problems running E flute or lower.

You can also understand that the scale of the metering device is important. In some places I see people use one from 0 to 500 microns or even from 0 to 1000 microns.  You can give it to your kids and let them play with it; the scale is just too big to read small differences. Use one from 0 to 200 or 250, that’s definitely working out the best.

This type of parallelism I described you can have as well in doublebacker glue machines as in the SF glue units.

Glue splashing in glue machines is another issue where one is adding unneeded glue in the valleys of the flutes that is absolutely of no use what so ever.

glue problemPlease have a look at the picture, this is what happens if maintenance did not do a good job… you can see a glue machine running without paper, it helped to see clearly where the problem  was. Guess where the board constantly opened up?

Last but not least and sometimes forgotten, the best way to check your glue application is still to make a iodine image.  The iodine reacts with the starch and gives you a pretty nice image of how the glue is applied on the flute tips and on the liners.

Please feel free to put comments or add if I forgot some things.

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.