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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

S-warp


Picture2

A while ago a customer was constantly facing s-warp on his recent corrugator (2800 mm).

In the picture you see E-flute with s-warp. The s-warp was only noticeable when running E-flute.The s-warp was so extensive that certain jobs were considered as broke. This had for sure a cost.

At the beginning we thought the paper was the cause. After turning around reels end changing positions the s-warp remained in the drive side so it became clear that the problem was caused by the corrugator.

During several weeks we verified a lot on the corrugator.

A first thing we noticed was an accumulation of dirt on the first pressure rollers on the hotplates. This accumulation was especially at the dirve side. These rollers where cleaned but still the s-warp remained.

In the picture below you see the pressure rollers. At the left hand side you see the dirt accumulation, and on the right side you clearly can see the damage on the hotplates by the grinding action of the belt.

Picture3

I was convinced that it was a parallelism issue but the question was where did it happen in the corrugator?

So a big job was done by checking everything starting from the single facers up to the belt.

Step by step the glue-machines in the SF where checked and double checked. All the preheaters, and rap arms where double checked. All preheating cylinders wherechecked, as well on parallelism as on heat distribution.

Iodine images and also absolute humidity measurements, where helpful in this process.

Many times we found a difference between operator side and drive side. After readjustment, we still had the same s-warped board. It improved a bit but the problem was still not gone.

Same action was taken on the unwinders by checking the parallelism.

After a visit of the corrugator technicians (supplier), they suspected a different porosity of the upper belt between operator side and drive side.The different porosity could also explain the faster contamination of the first pressure rollers on the belt.

A brand new belt was installed but still the problem remained.

At this time we got a bit desperate because we thought we checked everything.

The hotplate positioning in height however and the belt pressure system was not yet checked….

We asked a belt supplier who uses an acupressure system to check this up. It took a while before we could organize this but at the end we were able to get the technicians to come and perform this mapping.

A pressure sensitive material is put between the cooled down hotplates and the belt, and then step by step the whole hotplate section was checked up.

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We first tried the pressure for EB and that gave a rather equal image. However, when we gave in the E-flute settings and about 50% of pressure, we recognized a big difference between operator side and drive side.

Picture10

We decided to do the measurement based on the E flute settings. We noticed a higher pressure at the operator side compared to the drive side. The pressure was higher on the operator side on both the pressure roler and the shoes throughout the whole hotplate section.

Picture11As the images where rather similar on each row of shoes we did two tests to make sure that the measuring tool was not faulty.

I came up with a very professional test which you can see in the following picture. It is the “ISO Samsung S3 test”.

Picture6On the pressure sensitive material I had put my mobile phone and then a can of 5kg lubricating oil was put on my phone. On the picture at the right you can see the readout on the computer. One can even recognize the rounded corners of my mobile.

As a second test we turned the complete measuring device around to make sure the pressure sensitive sensors weren’t invoking a difference. But the image we got was exactly the same. So it was clear that what we could see on the screen was the reality.

So it was very clear that or the pressure system or the hotplates needed to be re-adjusted.

After that re-adjustment the problem improved drastically. To be a 100% sure one should redo the acupressure measurement.

Picture1

The before and after picture…….

Another solution would have been to install a zonal moisturizing device, but it would be a bit strange to try to correct a problem with an investment

 

 

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

 

Even heat transfer


Today it was a terrible day to travel.  Due to an autumn storm I got rebooked and delayed. This prevented me from getting some work done on the corrugator this afternoon, so I’m using the time wisely to talk about another parallelism challenge or better put ‘controlled heat transfer’.

It is very important that an equal amount of heat transfer happens as well in machine direction as in cross direction.

A corrugator (“is not an evaporator”) has plenty places where heat is transferred to the liner fluting and corrugated board.  I already talked about the parallelism challenge from reel-stand towards the next stage in the unwinding in my first blog ‘parallelism’. That type of parallelism mostly prevents the forming of creases. Irregular tensions, however, can also cause irregular heat transfer. One only has heat transfer if there is a contact between paper and preheater, or hotplates, etc.

Once it comes to preheating, irregular web tension will result in irregular heating, causing warp at OS or DS depending where the irregular heating occurs.

IR_0126With a simple pyrometer (= an infra-red thermometer) one can check this.  Even a better tool is an IR camera, this can easily show differences between OS and DS in machine direction caused by irregular tensions. The rule here is to aim for only minor differences.

Online systems can also help us but their usefulness is as good as the correctness of the measurements. When using thermometers it is necessary to understand that one needs to adapt the sensitivity of the device depending on the materials that are measured (shiny steel, mat steel, coated liners, brown liners, white liners, etc.).

So lets now go in detail in to the double-backer.  We all are aware of the fact that the more shoes we apply – or rollers we engage – the more contact we are making, the more heat we are transferring. A key question is: do you know if the heat is equally transferred at OS and DS or even in MD?

I will gladly entertain you with some terribly disappointing (shocking?) images of irregular heat transfers on the double-backer.

Psi accupressure1

For these examples I am using real images I have ‘stolen’ from Alabany which is using a system called “Accu-pressure” to check the double-backer rollers, the shoes, the Shortt-press or combinations pressure towards the corrugated board.

The identification used is the following: dark colours show high pressure areas, light and yellow shades identify low pressure areas.

A special film is put under the belt and the shoes/rollers. Once the shoes/rollers are engaged, the amount of pressure à contact à heat transfer can be visualized in an image looking like the one underneath.

Accupressure-RT Norcro(4

 
Every red square represents a shoe. You don’t have to look close to see that on drive side there is no contact and in the middle there is an area with heavy contact that can cause scratches.Accupressure-RT Norcross (3)

In this way the whole double-backer section can be mapped and in this example above, one can clearly see that there is a difference between operating side and drive side.

On top of the previously mentioned pitfalls you also should take into account the simple mechanical system of siphons, valves that transport the steam in the cylinders and hotplates. All of this has to function correctly to make sure that we have no irregularities in heat amounts. Problems can easily be caused by corrosion, damage or failure.

I know, corrugating is complicated, so many things that can go wrong…  and yet also so many things that can work perfect.

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.