Standard ink densities?

[Deleted member 16349]

i am talking about the vibrator which moves laterally ofcourse

OK thanks for the clarification.

The problem I have is that I do not see how adjusting the lateral oscillation helps reduce density variation from the gripper to the tail, say in line with an ink key.

 

[Deleted member 16349]

is there a relationship between the ink film thickness and density? is it true that by using a high pigmented inks you will be able to print with a thinner ink film and this helps in printing with less water therby avoiding all problems associated with ink water balance.can anybody throw some light pl

The problem may actually get worse. Is it easier to control low coverage or high coverage print? As far a I know, most would say that low coverage is more difficult to control on press because it is harder to maintain low ink feeds.

Similarly when you print with high pigment inks, this means less ink for the same coverage and controlling less ink can be more of a problem.

There may be some advantages to high pigment inks that are not clear to me. Pat Berger, I think has some experience and opinions on higher pigmented inks and maybe he can comment.

 

[gordo]

[SNIP]There may be some advantages to high pigment inks that are not clear to me. Pat Berger, I think has some experience and opinions on higher pigmented inks and maybe he can comment.

High pigment load inks are sometimes/historically used in newspaper work as a way to reduce dot gain. It is sometimes the path that press operators take who don't realize that dot gain can be managed with plate curves. It is also sometimes used intuitively to fix on press problems unrelated to ink film thickness.

In my experience the use of these types of inks are problematic on press and certainly not the optimal method for reducing dot gain.

What I believe is the goal for press stability is to have an ink formulation that results in the correct measured SID at an ink film thickness of about 1 micron on the sheet of paper. That ink film thickness is about 1.75 microns on the blanket and about 3 microns thick on the plate – thick enough to emulsify molecules of water/fount solution without breaking down as well as allowing for a sufficient film of water/fount solution to avoid plate scumming. Not so thick as to result in misting, tailing and the like and not so thin as to cause picking or piling.

best, gordon p

My print blog here: Quality In Print
Current topic: Ink savings using solid screening - part 1

 

[Deleted member 16349]

What I believe is the goal for press stability is to have an ink formulation that results in the correct measured SID at an ink film thickness of about 1 micron on the sheet of paper. That ink film thickness is about 1.75 microns on the blanket and about 3 microns thick on the plate –

Gordo,

When I model ink films I use 3 on the plate (after the form rollers), 2 on the blanket (after the plate/blanket nip) and 1 on the substrate.

Is your 1.75 micron value on the blanket coming form some experimental results or some other method. Just curious what the source for that value is.

Thanks.

Erik

 

[gordo]

Gordo,
When I model ink films I use 3 on the plate (after the form rollers), 2 on the blanket (after the plate/blanket nip) and 1 on the substrate.
Is your 1.75 micron value on the blanket coming form some experimental results or some other method. Just curious what the source for that value is.
Thanks. Erik

The target is 1 micron ink film thickness on the substrate – a value that as far as I'm aware of is the generally accepted target value (and you use it too!). The micron thickness at the blanket and plates are...not absolute/fixed values. There is a range, there is some uncertaintly and it changes with the percent ink coverage – which is why I used the qualifier "about." In the end, you're only .25 microns (0.0000098425") different on the blanket from what I suggested – but with plate and substrate values the same as what you suggest.
The numbers I quoted come from the very excellent "Fundamentals of Lithographic Printing" Volume 1 (the only volume) by John MacPhee, GATF press ISBN 0-88362-214-9. It's a pretty darned good book (considering its publisher) Sounds like a primer, however it's 365 pages of heavy slogging with lots of serious mathematics – not my strength for sure :-(

best, gordon p

 

[Deleted member 16349]

The target is 1 micron ink film thickness on the substrate – a value that as far as I'm aware of is the generally accepted target value (and you use it too!). The micron thickness at the blanket and plates are...not absolute/fixed values. There is a range, there is some uncertaintly and it changes with the percent ink coverage –

Thanks Gordon,

Actually I do not use 1 micron for my modeling. I use 1T where T can be any ink film thickness. Then other locations on the press would be 2T or 3T or 4.6T etc. When modeling the ink films in the roller train they all are proportional to the final printed T on the substrate.

According to the models, from the plate to the substrate the ink films are not related to coverage but up in the roller train they are.

The models use an ink film split of 50%-50% for convenience but actual ink film splits can be different depending on roller material, roller curvature, temperatures and water content etc. Therefore I would not be surprised that actual ink films have variability due to changes in conditions.

One can do complicated mathematical analysis of the process but most of that does not lead to solutions and also does not describe properly the complicated physical conditions. Models help to provide some understanding but one needs to understand the limitations of models.

One has to step back and ask what is needed to solve the problem. The goal is to solve the problem and not analyze it.

The ITB is based not on a model or theory but on a principle. The principle of conservation of mass. The beauty of this approach is that one looks at the process as a "black box" and the mass flow of ink into and out of this black box at steady state conditions. This is a common method of analysis used in Thermodynamics.

At steady state conditions, you do not have to consider the process inside the black box. All that is important is the input and output. Due to conservation of mass the output of ink onto the substrate MUST equal the input of ink into the black box. The percentages of ink film splitting is not important.

If one changes the input ink feed rate to a known value, then after the transient when steady stated conditions have returned, then you will know exactly how much ink is being outputted to the printed. This makes the system predictable.

This was understood before the ITB was invented.

Transients are different. The transient will be the time it takes to go from one steady state condition to another. To deal with this problem one does have to know what is in the black box since transients are related to how the ink is stored on the roller train. This is where simple models help. Models do not solve problems but they give one insight into how a roller train should be designed to reduce transients. They also provide some insight to know how to reduce variations in ink film being applied to the plate from side to side and from top to bottom.

It is not the models themselves that solve the problems. It is the effort of a person to see the problem in a holistic way based on a physical rule based approach that will result in improved performance.

The problem with much of the existing literature, that seems to be scientific, is that it can not really describe the physical conditions and that it does not lead to solutions.

Much of the existing so called science related to press performance is garbage. So don't worry about not being able to follow the complicated math, it is probably not right or useful.

When you see this kind of scientific literature in the industry, ask your self, has this person actually discovered anything or solved any fundamental problem. If they have only been technologists, don't take their work too seriously. Maybe it can be a source of interesting observations and material but if they have not solved a problem then they don't understand the problem.

 

[Al Ferrari]

It would have been better to rotate that pdf before posting it, than having hundreds, perhaps thousands of recipients do the rotating.

 

[gordo]

Hi Erik,

I was trying to answer vaithi47's question regarding the relationship between the ink film thickness and density and his thoughts about the possible benefit of thinner ink films rather than commenting on your ITB.

I am mathematically challenged - always have been. My artsy type mind seems to be challenged by numbers

The book that I referenced was published in 1998. Its author, John MacPhee was at the time an engineer, working at Baldwin Technology (Baldwin Printer Accessory and Control Equipment for the Printing Industry) first as Vice President of Engineering, then VP Research & Technology and finally as Senior Scientist. He has some 20 inventions in the nuclear, industrial robot, and graphic arts industries with over 100 patents worldwide.


best, gordon p

 

[Alois Senefelder]

re Lateral Vibrator Oscillation

re Lateral Vibrator Oscillation

Gentlemen, posted some Pdfs regarding the the " Grip to Tail Density Variation"


Regards, Alois

 

[Alois Senefelder]

Vibrator Oscillation # 2

Vibrator Oscillation # 2

Gentlemen - Continuation of PDFs


Regards, Alois

 

[Deleted member 16349]

Hi Erik,

I was trying to answer vaithi47's question regarding the relationship between the ink film thickness and density and his thoughts about the possible benefit of thinner ink films rather than commenting on your ITB.

I am mathematically challenged - always have been. My artsy type mind seems to be challenged by numbers

The book that I referenced was published in 1998. Its author, John MacPhee was at the time an engineer, working at Baldwin Technology (Baldwin Printer Accessory and Control Equipment for the Printing Industry) first as Vice President of Engineering, then VP Research & Technology and finally as Senior Scientist. He has some 20 inventions in the nuclear, industrial robot, and graphic arts industries with over 100 patents worldwide.


best, gordon p

Yes I am aware of John MacPhee. A good engineer is not necessarily a good scientist. A good inventor is not necessarily a good scientist also. He missed the important issues even though he has been working in the field for a long time. Technology and science are different. One could have developed a thousand patents but not introduced any new science into a field.

You can not move a field of knowledge forward with just good engineering and technical improvement. You need new science that leads to new knowledge. Piles and piles of data and observations are not knowledge.

It is great to have good engineers in an industry but most engineers do not develop science. They rely on the science that has been done before or they rely on past practice. If the science that has been developed is faulty, the results the engineers will get will be faulty. This industry disparately needs better science.

 

[Deleted member 16349]

Gentlemen - Continuation of PDFs


Regards, Alois

Alois,

Thanks for all the PDFs. I think some of the info is myth and I still can not see how the timing of the oscillators can affect density variations from top to bottom. Sorry. There may be some phenomena that I am not aware of and I will keep my mind open about it but just now I can not see it being a factor.

Besides the fact that oscillation tries to move ink laterally across the roller train it only does this with different ink films on the rollers in line with the ink keys. On many presses the oscillating rollers are not all started at the same time but there lateral movements are done out of phase with each other. It would not be good press design to start them all at the same time for other reasons. Also oscillators do not cycle once for each plate cylinder cycle, especially on fast presses.

This may be another of those myths that printers accept but has no basis. I am sure there will be printers that say it does help and if it does the reason for that would be interesting to know.

 

[gordo]

This industry disparately needs better science.

Sadly, so true.

gordon p

 

[tmason]

On our presses, the plate cylinder gear drives the ductor mechanism and the lateral movement runs off the same gear through an intermediate gear. We can change the lateral timing in relation to the cylinder without changing the duct timing. When we change the lateral timing, we see a shift in density from gripper to tail.

This is not myth, theory, technology or science. It is fact based on observation through trial and error.

Why do we see the density shift when we change the lateral timing? Numerous theories have been introduced but it does happen without changing the ductor timing. If the ducting motion were continuous, would the problem still occur??? If the press was "gapless" would it still happen??? If we print waterless, why is the problem much less noticeable??? Water pickup in the gap???

 

[Deleted member 16349]

On our presses, the plate cylinder gear drives the ductor mechanism and the lateral movement runs off the same gear through an intermediate gear. We can change the lateral timing in relation to the cylinder without changing the duct timing. When we change the lateral timing, we see a shift in density from gripper to tail.

This is not myth, theory, technology or science. It is fact based on observation through trial and error.

Why do we see the density shift when we change the lateral timing? Numerous theories have been introduced but it does happen without changing the ductor timing. If the ducting motion were continuous, would the problem still occur??? If the press was "gapless" would it still happen??? If we print waterless, why is the problem much less noticeable??? Water pickup in the gap???

Thanks for your feedback on this. If it is a real phenomena, then there has to be a physical reason. I will keep an open mind on this.

Now I am getting curious about this observation. The phenomena may not be so much related to the change in direction of the laterally moving oscillation rollers but to the mechanical shock on the gear train at those specific points in the cycle. That shock might then affect the quality of ink transfer at different points of the cycle.

The press that I had most experience with had a continuous ductor and a very small gap (10mm). I don't remember this problem on that press. It is new to me and therefore interesting if true.

If it is press design related, then I would expect that some presses would show this phenomena and others would not.

There's always something new to learn in the printing process. Thanks.

 

[rising]

Standard ink densities?

Hello all,

As per ISO 12647-3 the standard densities for un coated paper (for newsprint) for coldset process at Satus E are
C,M,Y - 0.90 ,Bk - 1.10 (tolerance of 0.10)

Pls refer below url
Revision of ISO 12647-3

> {quote:title=ian wrote:}{quote}
> The values you have mentioned are what we use for coated paper.
> Does anyone have the values for uncoated paper??
> We use
> C-110
> M-110
> Y-95
> K-130

Hi Ian,

Sorry to but in, but do you have values for running Matt/Satin stocks?

cheers!

dwane

 

[rising]

Ift

Ift

is there a relationship between the ink film thickness and density? is it true that by using a high pigmented inks you will be able to print with a thinner ink film and this helps in printing with less water therby avoiding all problems associated with ink water balance.can anybody throw some light pl

Hi Vaithi

Yes your write higher the pigment% lower the Ink film thick ness but aware high pigment % can create ink,pluff accumulation build up problems on inking rollers turns to increase the glazy ness of the rollers tends to disturbing ink transfer property

Reg,
Arunoday

 

[yk_chin86]

How much is the tolerance for both ISO 12647-2 paper type 1's 40% and 80% TVI? Kindly advise.

 

[turbotom1052]

Gordo,

Not exactly sure about what they would mean when they say "acceptable". Would that be from plant to plant or within a run. I would think that if they mean within a run then seeing a variation is not so good.

I thought that a difference in density of 0.05 was not easy to see within a run. A difference in density of 0.05 is about an 8% difference in ink film thickness and that can lead to visible differences due to the difference in the dot gain as more ink squeezes our more than less ink. Have two screens that are printed with solids that vary in opposite directions and the resulting shift in colour is very noticeable.

What is actually required for consistent printing of screens is to be able to print the solids at much tighter tolerances that are not visably different.

For printing within a run, the notion of basing control on such a chart is just not capable.

a difference of 0.05 when printing yellow at 100 is significantly more that that same 0.05 difference printing the black at 175 or 180. a .05 difference when printing say a single pms color may be within acceptable visual tolerance and not be noticable to most experienced eyes but when your printing 4/c process and you have one color 0.05 high and another color 0.05 low then your talking about an image that can deviate considerably from the ok sheet on color sensitive forms.

 

[vaithi47]

i am talking about the vibrator which moves laterally ofcourse

gy this adjustment the gripper to tail density variation can be adjusted