Gentlemen and fellow Lithographers,
Being the "devil's advocate ....." I posit that the Lithographic Printing Process IS a Stochastic Model.
Deterministic Model vs Stochastic Model
1) In deterministic models, the output of the model is fully determined by the parameter values and the initial conditions.
2) Stochasstic models possess some inherent randomness. The same set of parameter values and initial conditions will lead to an ensemble of
different outputs.
Regards, Alois
What ever one thinks the process is, it still must comply with a number of scientific principles. Conservation of Mass is one of them. At a stead state condition, the output of ink must equal the input of ink on average. This is independent on the substrate, water, roller settings, etc.
So why is this simple and reliable concept based not on a theory but a principle of science so hard for the printing industry to understand and accept? It is due to ignorance or stupidity. One can be corrected while the other can't.
As I said before, if one wants to innovate, it is important to understand things. If there is no interest in innovation, it does not matter what one thinks or says.
Also models are not processes. Models might try to represent a process but if the model is not correct, it has little value. In engineering and in science, the use of models is problematic. Models tend to be too simplistic relative to the physics of the problem. Models are helpful to show how some process might perform for educational purposes, but are not always so good at accurately predicting performance.
If one wanted to develop a model for the offset printing process, most certainly it would be too simplistic and not useful. The physical issues are so numerous and difficult for modelling. But this is the great thing about the offset process. The offset process MUST follow the principle of Conservation of Mass. That means, no matter how complicated the physics is in the transport of ink to the substrate, the amount of ink output on the substrate MUST equal the amount of ink fed into the roller train on average. So one looks for the reason why the ink feed is not consistent and one finds it is a simple problem to correct.
I am not against using models. I have done many ones for specific issues but they were mainly for understanding how things worked and most would not be useful as a technical solution. They do help to direct one to what would be a potential solution but judgement is required and so is testing.
There is a long history of testing the printing process on commercial presses. Unfortunately, for about a 100 years, none of these tests are tests of the science, relative to density control, because they were done on presses that did not control the ink variable. In my 1997 TAGA paper I also mentioned this problem doing tests on presses that were not positively controlling this critical variable.
To get valid knowledge, one needs to do valid testing. This has not been done to date and so far there seems to be no effort in understanding this important factor required to innovate. And it has always surprised me to see that managers in this industry see no connection between valid knowledge and competitive advantage.