UV offset production

[Deleted member 16349]

"

It is not a question of "missing ink" it is a fact of "watered down" ink.

Whaddya think?

I don't want to give the explanation right away. I really want people to think about this.

So, are you thinking that watering down the same amount of ink printed on the paper, is going to have a lower density?

If so, when the water evaporates from the printed ink (after it is printed), will the density increase?

 

[Lukew]

Erik. Increasing water dial levels above what’s needed can cause the water to travel up to the ink ducter & ink duct which certainly does stop the ink from transferring from ink duct to roller train correctly. I can see that a system that has the ability to force ink into the roller train regardless of the amount of water run could be beneficial at keeping density at a more constant level and perhaps yes the point of ink / water level could be pushed further outside of the normal operating window before issues arise.
But, that is one part of the equation.
In all your testing have you run any tests with polyester plates?
The image area of a polyester plate isn’t very ink receptive. Depending on the type of fountain solution used you can actually wash the ink dot off the plate and fails to transfer and likewise with a solid ink patch.
Likewise running a water dual too high to the point the plate is overly wet the ink simply fails to transfer. You can test this with a very small amount of paper which takes the whole ink duct/forced ink feed system out of the equation.
Not to mention ink drying.
An opinion is just that, someone’s thoughts.
Reading most of your posts referring to the ITB for the most part your trying to sell the idea of your invention based on forced ink feed controlling ink density irrespective of water levels. One might wonder if it may have been better to push the invention based on given proven facts that a system such as the ITB is superior at delivering ink into the roller train at all occasions when compared to a standard ink duct.

 

[Deleted member 16349]

In all your testing have you run any tests with polyester plates?
The image area of a polyester plate isn’t very ink receptive. Depending on the type of fountain solution used you can actually wash the ink dot off the plate and fails to transfer and likewise with a solid ink patch.


Likewise running a water dual too high to the point the plate is overly wet the ink simply fails to transfer. You can test this with a very small amount of paper which takes the whole ink duct/forced ink feed system out of the equation.

In all the tests done with the ITB running EB, UV and conventional inks on coated, uncoated and plastic coated papers, it was not possible to wash out the print when going to extremely high water settings. Very waterlogged ink still transferred. Print quality was surprisingly good except for printing on plastic at those water levels. One would never run production at those water levels and these tests just showed that the water window would be huge relatively. The patents on the ITB have expired.

I don't have any experience with running tests with polyester plates so I can't comment on what might happen but it would be interesting. The problem you bring up might be more complicated than just the image area not being very receptive to ink. There might be an issue with the non image area not being able to transfer a lot of water out of the roller train to the paper. This is one of those things that should be tested to find out. Possibly polyester type plates, which are less expensive, might be more useful if the other conditions are corrected.

 

[Alois Senefelder]

In all the tests done with the ITB running EB, UV and conventional inks on coated, uncoated and plastic coated papers, it was not possible to wash out the print when going to extremely high water settings. Very waterlogged ink still transferred. Print quality was surprisingly good except for printing on plastic at those water levels. One would never run production at those water levels and these tests just showed that the water window would be huge relatively. The patents on the ITB have expired.

I don't have any experience with running tests with polyester plates so I can't comment on what might happen but it would be interesting. The problem you bring up might be more complicated than just the image area not being very receptive to ink. There might be an issue with the non image area not being able to transfer a lot of water out of the roller train to the paper. This is one of those things that should be tested to find out. Possibly polyester type plates, which are less expensive, might be more useful if the other conditions are corrected.

Erik,


Why would we want to transfer ALL the water from the Roller Train into the Paper ??


Regards, Alois

 

[Deleted member 16349]

Erik,


Why would we want to transfer ALL the water from the Roller Train into the Paper ??


Regards, Alois

I never said "ALL" of the water in the roller train should be transferred.

 

[robb]

I don't want to give the explanation right away. I really want people to think about this.

So, are you thinking that watering down the same amount of ink printed on the paper, is going to have a lower density?

If so, when the water evaporates from the printed ink (after it is printed), will the density increase?

Good question-maybe this is a better explanation, from the Sun Chemical PDF:

When an ink over-emulsifies, or takes up too much water, it changes its flow properties, with the effect that transference is adversely affected. This leads to the need to run with an excessive ink film (just to achieve somewhere near the correct density) and all the problems which are associated with that.

 

[Alois Senefelder]

Gentlemen and fellow Lithographers,


The WATER from over emulsified Ink (water-logged) does not evaporate BUT is absorbed into the paper fibres ! with the result paper changes its dimensions.

Regards, Alois

 

[Deleted member 16349]

Gentlemen and fellow Lithographers,


The WATER from over emulsified Ink (water-logged) does not evaporate BUT is absorbed into the paper fibres ! with the result paper changes its dimensions.

Regards, Alois

Duh.. Evaporation of water is happening all the time. Water is evaporated off the surface of the rollers, off the paper after it is printed and out of the printed ink. The rate of evaporation depends on the relative conditions in the environment in which the press and paper are situated. If a moist printed paper sits in a dry room, it will evaporate water to the room. If dry paper sits in a high humidity room, it will pick up moisture (water). Yes and dimensions will change.

 

[engin]

Duh.. Evaporation of water is happening all the time. Water is evaporated off the surface of the rollers, off the paper after it is printed and out of the printed ink. The rate of evaporation depends on the relative conditions in the environment in which the press and paper are situated. If a moist printed paper sits in a dry room, it will evaporate water to the room. If dry paper sits in a high humidity room, it will pick up moisture (water). Yes and dimensions will change.

This phenomenon is called as "mass transfer" in which the flow ( of anything mass, heat,light,etc) always from the high concentration to the low concentration and this concentration difference is also called as "driving force" which creates this flow to occur . But the flow rate depends on many conditions and always happens.

 

[Deleted member 16349]

Good question-maybe this is a better explanation, from the Sun Chemical PDF:

When an ink over-emulsifies, or takes up too much water, it changes its flow properties, with the effect that transference is adversely affected. This leads to the need to run with an excessive ink film (just to achieve somewhere near the correct density) and all the problems which are associated with that.

Robb, the purpose of my questions was for people to think about the problem. Going to find a PDF is not thinking for yourself. Look at Lukew's post. He described the issue quite well and basically clearly described that the loss of ink was due to the reduction of ink transfer at the Ductor.

Sun's PDF is just BS and it does not help to understand the problem. It is unfortunate that Sun and other large companies do not have the ability to understand the problem.

Flow properties have nothing to do with the fundamental problem of ink transport down the roller train. Ink is transported down a roller train to the paper by means of ink splitting. It does not flow like a river. No one in physics would say that the ratio of ink splitting will change due to ink properties.

The problem people have is that they do not think in terms of the context of how something is being used. Lab tests with ink on IGT testing machines do not test in conditions that represent how things work on a particular press.

To understand the general problem of ink transfer in a printing process, one needs to look at the whole process from ink feed to ink printed on substrate. This can be applied to any printing process and the general rules are common.

I am not going to go into more details on this but I suggest that more thinking about the issue is useful. Common sense and some logic can go a long way.

 

[engin]

This phenomenon is called as "mass transfer" in which the flow ( of anything mass, heat,light,etc) always from the high concentration to the low concentration and this concentration difference is also called as "driving force" which creates this flow to occur . But the flow rate depends on many conditions and always happens.

There is a saturation point ( or equilibrium stage) where the mass transfer occurs at which the concentartion difference of the two systems is zero, means ,there is no driving force to flow the concentration any more ( in this case water evaporation from paper to the environment of the printing room).

May be, one reason of the poor drying in winter is that, if a moist paper is used in printing and picked extra water from the over-emulsified ink then the water in the paper did not have enough conditions ( temperature, time, humidity in the environment etc,) to evaporate within the desired finishing time of the printed job.

In humid environment, since there are existing water vapors in the environment which slows down the water to evaporate ( the driving force magnitude is lower) from the paper and care should be taken in post finishing stages of the print. May be this is one reason for conditioning of the printing room..

 

[Deleted member 16349]

This phenomenon is called as "mass transfer" in which the flow ( of anything mass, heat,light,etc) always from the high concentration to the low concentration and this concentration difference is also called as "driving force" which creates this flow to occur . But the flow rate depends on many conditions and always happens.

This is so bad I can't respond.

 

[PricelineNegotiator]

This is so bad I can't respond.

Is it because he used the wrong term? The concept is right, but it's called diffusion. Nothing else he said is wrong.

 

[Alois Senefelder]

Erik - FORGET the Duh..... I'm talking about the moment WHEN the emulsified ink MEETS the paper at Impression NIPS via the Desensitised Areas and the INKED IN IMAGE AREAS !!!!!

 

[engin]

Is it because he used the wrong term? The concept is right, but it's called diffusion. Nothing else he said is wrong.

In engineering ( Mechanical and Chemical), Mass transfer and Heat transfer are the fundamental concepts ( breakdowns called as diffusion, conduction, convection, radiation, etc) and, for the engineers all the designs of the equipments for any process based on mass and heat transfer calculations.

Dry paper will take water from the humid environment, but can anyone tell us how much quantity and how long will it get the water from the environment and when it will stop getting the water from the environment, and this is the matter of calculation (s) of the mass transfer concept in Engineering.

This the general equation ( studied in engineering) and is applicable to everything in the world :

"something entering into the system" - "something going out from from the system" + "something generated by the system" = "Accumulation in the system"

I just wanted to explain some definitions from the engineering point of the view.

 

[Deleted member 16349]

Is it because he used the wrong term? The concept is right, but it's called diffusion. Nothing else he said is wrong.

It would have been fine to use diffusion. My reaction was related to his other comments, which IMO are wrong.

If you think that heat is driven from higher concentrations to lower concentrations, you would be wrong. Heat is driven by temperature differences. Heat and temperature are not the same thing.

One can have a lower concentration of heat with a higher temperature that will drive heat to a higher concentration of heat which as a lower temperature.

How does one have a concentration of light? Light is not a substance. Light is generated at the atomic level by a very specific process which is not related to the output of other light sources.

I just think that engin's comments were sloppy. They would have been a problem in a high school physics class.

 

[Deleted member 16349]

Erik - FORGET the Duh..... I'm talking about the moment WHEN the emulsified ink MEETS the paper at Impression NIPS via the Desensitised Areas and the INKED IN IMAGE AREAS !!!!!

Thanks, that makes it clearer. I was commenting earlier about when the paper and its printed ink dry. The ink will lose most of the water in it. So the question was, will the ink density get higher when it loses that water due to evaporation.

This was a response to the idea that waterlogged ink, with the same amount of ink in the ink film, would print at a lower density. So if the water evaporates, does in change the density.

What do you say? Does the density increase when the water in the printed ink evaporates?

If the same amount of ink in an ink film is printed but the levels of water content in those ink films affect the print density, then there is no relationship between density and amount of ink in the printed ink film. That does not sound right to me.

With existing offset presses, IMO printing on plastic or metal makes water control more of a problem on existing presses because it is not absorbed into the substrate but only runs a thin film of water on its surface. I suggest this affects the amount of water in the roller train and that then affect the ink feed. Fix the ink feed and it would be less of a problem.

 

[Deleted member 16349]

In engineering ( Mechanical and Chemical), Mass transfer and Heat transfer are the fundamental concepts ( breakdowns called as diffusion, conduction, convection, radiation, etc) and, for the engineers all the designs of the equipments for any process based on mass and heat transfer calculations.

Dry paper will take water from the humid environment, but can anyone tell us how much quantity and how long will it get the water from the environment and when it will stop getting the water from the environment, and this is the matter of calculation (s) of the mass transfer concept in Engineering.

This the general equation ( studied in engineering) and is applicable to everything in the world :

"something entering into the system" - "something going out from from the system" + "something generated by the system" = "Accumulation in the system"

I just wanted to explain some definitions from the engineering point of the view.

OK, this is a little better. So why not apply this to printing and to offset in particular.

No ink is generated in the press roller train but it can be stored there. Therefore, the equation can be stated as:

The amount of ink printed (out) = the amount of ink fed into the roller train (in) + changes in the amount of ink stored in the roller train.

One can then say that at steady state conditions, which is the goal of the operation there are on average no changes to the amount of ink in the roller train.

Rewriting the equation gives at steady state conditions.

The amount of ink printed (out) = the amount of ink fed into the roller train (in).

So to have a constant amount of ink out, one requires a constant amount of ink to be fed into the roller train.

Simple and it is not affected by chemistry or other issues in the press. Just a mass transfer problem.

The non steady state conditions like going from one density level to another.

The amount of ink printed on the paper is closely related to the storage conditions of ink on the roller train. Higher amounts of ink storage, via thicker ink films on the rollers result in higher print densities.

So if one increases the ink feed, time is required for the ink storage to increase to the point where the higher ink film is printed on the substrate. Low coverage (less ink consumption) takes longer time than high coverage. If the ink feed is increase and it is also fed at a constant rate as with a positive ink feed, the press will go through the transient and arrive at a new steady state condition that is at the higher density level. The change in can be predicable because the ink out must equal the ink in at the new steady state condition. The time it takes is related to how the press is designed relative to how it stores ink.

I am all for a more scientific or engineering principled approach. Why does not Sun think in the same way as you suggested? That is the problem.

 

[engin]

OK, this is a little better. So why not apply this to printing and to offset in particular.

No ink is generated in the press roller train but it can be stored there. Therefore, the equation can be stated as:

The amount of ink printed (out) = the amount of ink fed into the roller train (in) + changes in the amount of ink stored in the roller train.

One can then say that at steady state conditions, which is the goal of the operation there are on average no changes to the amount of ink in the roller train.

Rewriting the equation gives at steady state conditions.

The amount of ink printed (out) = the amount of ink fed into the roller train (in).

So to have a constant amount of ink out, one requires a constant amount of ink to be fed into the roller train.

Simple and it is not affected by chemistry or other issues in the press. Just a mass transfer problem.

The non steady state conditions like going from one density level to another.

The amount of ink printed on the paper is closely related to the storage conditions of ink on the roller train. Higher amounts of ink storage, via thicker ink films on the rollers result in higher print densities.

So if one increases the ink feed, time is required for the ink storage to increase to the point where the higher ink film is printed on the substrate. Low coverage (less ink consumption) takes longer time than high coverage. If the ink feed is increase and it is also fed at a constant rate as with a positive ink feed, the press will go through the transient and arrive at a new steady state condition that is at the higher density level. The change in can be predicable because the ink out must equal the ink in at the new steady state condition. The time it takes is related to how the press is designed relative to how it stores ink.

I am all for a more scientific or engineering principled approach. Why does not Sun think in the same way as you suggested? That is the problem.

Thank you Erik for your good explained application in offset for the equation that I wrote .

 

[Deleted member 16349]

Thank you Erik for your good explained application in offset for the equation that I wrote .

You are welcome. I wrote basically the same equation in my 1997 TAGA paper.