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.
) Sounds like a primer, however it's 365 pages of heavy slogging with lots of serious mathematics – not my strength for sure :-(
