Press Dot Gain help please!!!!!

[Deleted member 16349]

This is an interesting statement does it have any relationship to the beta testing of the ITB? To me it would appear that anytime a different ink was used for the ITB test the data to be quantified would not have a direct relationship to the previous test.
Were they any test targets in non image areas to see the effect of ink film thickness on dot gain?

I would not consider the ITB good enough for lab testing of the process. The ITB would be good for potential commercial use and would demonstrate the relationships but is not convenient for doing the kind of work one would want in a controlled lab situation.

I consider the ITB as a transition technology. Transition technologies can last a very long time but they are not the most ideal future technology. I think about what might be the future technology for ink feed but who knows, the offset process might not be around for long to make it worth the effort. The thing about the ITB is that it can be applied to existing offset presses at very low cost and fundamentally change their performance.

Personally my interest is not to make academic studies but to develop theories and technological approaches to practical industrial problems that are relatively low cost.

For a controlled lab condition I would think that having servo driven constant displacement pumps that inject ink into the roller train at controlled and known rates would be required.

Back in 1996, I gave a seminar to the Didde Press group on the topic of the density control problem related to press design. Didde had done some interesting things and one of them was a patent related to forced ink feed with a shuttle mechanism that moved a constant displacement pump laterally across the press and injected ink into the roller train. The patent info is here:

Patent US4787313 - Printing press using shiftable inking means - Google Patents

It is an interesting patent even though it is not workable due to the shuttle action.

In discussions with the engineers there about this patent, they stated that when they tested a positive ink feed, that fed ink at just one location, they got very tight density control. As I remember, they made no effort to investigate any relationships with changes in water, temperature etc.

There are some other applications of positive ink feed that are actually used in production now. Goss is one and they market a technology called a DigiRail. This feeds ink onto the ink fountain roller using positive displacement gear pumps. Goss had many interesting technical papers years ago but as far as I know they never tested the relationships between positive ink feed and changes in other variables even though in their marketing they state that their system is consistent and it has a "set and forget" kind of performance.

Their ink feed system is reported to be very accurate and possibly could be reconfigured and used for lab type testing of relationships but I don't think they have even thought about doing that. QuadTech now has their own positive ink feed system but they also have shown no thought in testing relationships on press.

I agree that investigations of what you suggest should be done but it needs to be done when the ink feed capabilities are corrected. My opinion is that half of the material in research papers in the printing industry is either wrong or just useless. This is due to testing with uncontrolled conditions. To know which half is wrong or right, you need to already know how things work. Not so easy a thing to know. That is why I say there needs to be more studies done in the proper way under controlled conditions and not just use commercially available equipment. I stated this back in my 1997 TAGA paper.

 

[Green Printer]

You can establish values and collect data in a lab setting. The real proof is how does it perform on commercially available equipment and is it cost effective. The real world equipment will also let you know it your lab equipment has any real bearing on what you are trying to accomplish.
Commerciallly available usually will have many more variables that a lab cannot even come close to simulating.

 

[Deleted member 16349]

You can establish values and collect data in a lab setting. The real proof is how does it perform on commercially available equipment and is it cost effective. The real world equipment will also let you know it your lab equipment has any real bearing on what you are trying to accomplish.
Commerciallly available usually will have many more variables that a lab cannot even come close to simulating.

The purpose of doing controlled tests is to determine what the rules are. If the tests are done and evaluated in an intelligent way, then there is the possibility to design out the variables that seem to be having a negative effect on the performance of the process.

I would totally agree that commercial equipment gives credibility to the theoretical and lab testing efforts but only after the commercial equipment is modified based on what was learned.

One could also say that the existing commercial equipment gives credibility to the idea that the industry does not understand what it should do to make more consistent and predictable offset lithographic technology.

At any point in history, there is always the question, "How can one make the process perform better?". To just accept the view that what seems to be variables that negatively affect the process and that nothing can be done, is not a winning option but is common.

What is worse is to go down a new technology road without proper knowledge and waste time and resources only to find out near the end of the road that the assumptions that the technology was based on was faulty.

There is an example in the continuous improvement movement that tries to show the general process of improvement. It is the example of hidden rocks in the river that will sink boats. The rocks being the problems in the process that need to be corrected but are not seen clearly.

So one lowers the river. Lowering the river is related to setting a tighter tolerance for the process or other goal, such as short set ups etc. Deming says theory is required for improvement. So the river is lowered and the hidden rocks are made visible. Then one works on removing the rocks. Then one has to lower the river again to find more hidden rocks. This cycle of investigation, theory, implementation and testing is continued until one has a robust process. One that easily meets its tighter goal requirements.

The point being that a total improvement will not be done in one step but needs continued efforts to understand and correct issues that are root causes of problems in the process.