Getting ink on paper: rebuilding the science of offset starts with density control
Robinson, Jon
Advances in traditional offset presses have stalled as digital technologies and toners continue to be driven by research and development. PrintAction talked with Erik Nikkanen, president of Fountech and a mechanical engineer, about his radical ideas on redesigning the offset press. He believes the science behind controlling ink transfer can unlock a potential that the industry just refuses to see.
Where does the industry have it wrong when it comes to density control on the offset printing press?
People have been saying variation is inherent in the process or that it is a chemical process and this doesn’t really describe what is happening. It also leads the industry into dealing with density control by measuring and then correcting. This is a common approach to the industry’s solution to process control, that they measure and then correct. Traditionally, they’ve done it by having the operator look at it with densitometers, and now they use a closed-loop system, which is an expensive way to do it.
[Graph Not Transcribed]Is closed-loop an effective way to do it?
It works but you are paying twice. You pay for a press that is supposed to give you consistent colour density and when it doesn’t you have to pay again. The idea of process control in this industry is that you can’t control something unless you measure it. Well, this isn’t quite true.
You can calibrate something and if it’s consistent you don’t have to measure it any more. You make the process predetermined so that you have everything under control so that when [the press] starts up it goes directly to the density that you want, without any need for adjustment. Instead, the whole industry is based on measuring and adjusting.
Then what is the main issue of getting proper ink/water balance?
The heart of the matter is that the press is broken as a process and so the industry has compensated by having to take these steps to get things under control. But they are not looking at the source of the variation, which is the ink feed. People think density control has hundreds of variables when it actually only has this one variable. What I’m talking about is steady-state average density, which is what the printer wants. When they are running, they want the density to be the same sheet after sheet.
Why are these issues being ignored?
They aren’t ignored, but it’s in how you deal with the problem. If you don’t know of a better way, you deal with it in the way you have – you measure it and when it changes you make an adjustment. A closed-loop system measures it and looks for the error between what it reads and what it should be, the target, and it makes a correction.
This is continuous inspection, which is not a popular manufacturing philosophy. A modern manufacturing philosophy is that you make a system that doesn’t vary, not one that you constantly correct.
Can you give me an example of such a manufacturing philosophy?
I read this stuff back in the early 1980s about Toyota getting rid of waste. I’m not sure if it’s from the book The Machine that Changed the World, but the concept called SMED, which refers to Single Minute Exchange of Die, was said to have made all the lean concepts possible. Toyota’s idea was that you redesign a changeover so that it’s as fast as possible. If you have a one-minute changeover, as your goal, that makes you think past continuous improvement. It makes you think in radical ways. To do that you have to actually understand the process, you can’t do it by a shotgun approach. You do it by lean manufacturing.
Is Computer Integrated Manufacturing not an effective manufacturing philosophy?
It is only icing on the cake after you make everything work very well. CIM is a very marginal improvement. I read that the former director of CIMS [Center for Integrated Manufacturing Studies] at RIT, Dr. William J. Sheeran, in speeches he made at Digital Smart Factory and Seybold, didn’t agree with CIM as being a big benefit. He argued that it’s a minor benefit. You have to fix up all of these islands first and he was trying to tell them that, but they don’t really listen.
He said a lot of modern manufacturing places are reducing their IT, taking it out because they are finding it is causing problems and he’s actually saying they are taking automation out in some areas. His approach was more that you should use the right technology and you solve the problem with the appropriate approach and not just throw automation at everything. If you look at the Digital Smart Factory events over the years, they are moving away from the factory and they are moving toward IT for the customer and the frontend, because I think they don’t know how to help the factory with IT.
What about presetting ink keys through CIM?
It’s good in concept but the information to preset keys should be correct and the equipment should be capable of consistent ink delivery. Now the information to preset ink keys is not correctly calculated because the effects of wet trapping and other factors are not accounted for. The equipment is also not capable.
The amount of ink that is fed into the press, into the roller train, varies, even though you have your ink key settings set exactly and your ink fountain rollers set exactly, the actual amount of ink that goes into the press can vary. It is not related to the mechanical settings of these components.
Your major variable for density is ink. And your major variable for ink feed into the press is not positively controlled on any offset press that is built today. Positively and properly controlled. It’s a design fault. Ink/water balance is only related to a design fault for ink feed control.
How does wet trapping effect ink key settings?
It throws off the calculation of what the ink key should be. If you are printing ink onto wet ink that is already down it won’t take the same amount of ink because of wet trapping. The difference can be 40 per cent. If the presetting calculation is only based on dry trapping, the error can be large in those areas.
The print sequence is important. A computer program has to look at each ink layer and say if there is anything underneath. If there is nothing underneath it, it assumes dry trapping. But if there’s wet trapping you say, OK, adjust the ink amount for wet trap. So the software would say it’s only 70 per cent of the amount of ink needed.
Developing software is not that expensive, relatively. And then [together with controlled ink feed and software] you have a press that has 80 per cent of the potential improvement. And if you redesign the roller train, you can make a press that allows you to go from one job to the next to the next. And the colour comes up really fast because you have changed the way that ink is stored on the press. So that it is independent of the design you are printing.
[Graph Not Transcribed]How do you propose to fix this problem, to achieve better density control?
Let’s say you had ink keys that meter ink perfectly. That ink is metered perfectly on the ink fount roller, but as that ink moves around, some of it gets transferred into the press and here’s where the big variation of ink feed comes in. The amount of ink that goes into the press where the ductor is, the rate of ink transfer, can change very easily.
When water is changing in the roller train, it goes up and it affects this transfer of ink coming across, and when the transfer changes, it affects the storage of ink on the roller train and then you start printing at lower densities. The troubles also arise with temperature and speed changes.
When you fix the transfer problem then you get the full benefit of whatever accuracy the ink keys have, so that you can move water up and down but it won’t affect the transfer. I’m looking for printers to test this.
How does your proposed transfer happen?
It’s basically very simple, it uses something like a scraper blade, called an Ink Transfer Blade or ITB. It sits on the ink fountain roller in the ductor region of the press and the ink collects on the end of the blade. Then you have another roller that picks this up and brings it into the roller train. So if water changes it can’t change this transfer rate. And it’s dirt cheap.
There are a lot of problems that are wrong with press design. Some are expensive such as changing the roller trains…those are expensive. But the good news is 80 per cent of the potential improvement that can be done on a press is dirt cheap. And it can also be done with legacy presses, with presses that exist.
Are people then learning the right things about the printing process?
There are two aspects. There is the craft part of it and what they teach about craft is fine enough. You need craft, but there is not enough teaching of theory, partially because [educators] don’t have the theory, they don’t understand it enough themselve to teach it.
What does theory do? Theory is not pie-in-the-sky. Theory is very practical. People always say, “well, you know it works in theory but not in practice” and that is the biggest misnomer because if theory doesn’t work it is not theory. A theory explains something. It is not opinion. It is a set of rules. Theory should explain what practically happens.
Will the lack of understanding the science behind density control come back to bite an industry infatuated with software?
You can’t do anything you want. You can’t assume things are going to be alright, because you can’t fool mother nature. The idea of working outside the box is thrown up a lot, but if you are talking about engineering or science you have this other box in which nature allows you to do things. You have to recognize physical problems and then take some steps so that the results you want to get stay within the box of what nature allows you to do.
What box have press developers been working in?
Most of this technology could have been developed 50 years ago, but there wasn’t enough interest to look at problems in that way. So for 50 years or more they have been continually putting out fires. You are layering more and more problems, complexity, into the process and it’s already very hard for people to understand what’s going on now because there is no pattern to it. They have to accept it.
Are digital printing presses and toners creating a fire that traditional printers can’t handle?
Both the wet toner and the dry toner, I think those are great in a way and they will suit a certain market and be good in certain applications like personalization. But if you think the traditional printing industry is in a commodity market, companies that use digital printers will find themselves in a commodity market even faster.
As soon as they start making more presses and bring the prices of the machines down, customers will start pushing the price of what the machines produce down and down and down, because the real source of commodity is not really over-capacity but rather because nobody has any significantly different capabilities. At least with offset printing there are bigger machines, so there is a money barrier and there is a skill barrier.
Can the offset process be advanced?
The offset process is not a mature process, it is a stalled process. It is a process that has been refined for decades, but not innovated as much as other processes in other industries. If the printing industry looked at things a little more scientifically, the potential of offset for consistent density is much greater than for flexo or gravure.
With flexo and gravure, at this time, I see no way of controlling the ink transfer to the paper; there will be variation. But with offset you have the opportunity to feed ink into the press in a consistent way. If they eventually change the roller trains you will have presses that will be up to colour within 10 sheets, probably.
Why is it not being done?
The press manufactures, their markets are shrinking and they are shrinking but they refuse to do anything or look at anything. They don’t believe anybody can come out with something, but if somebody does comes out with something it will destroy the other manufacturers. The important work is to get the ink transfer problem corrected, to show that density can be stable.
But because they do not have any theory, they have no way to base any imagination. Theory takes you into the future because if you know what is physically possible you can plan things out. You can design what the future is going to be. People didn’t get to the moon because somebody else did.
Copyright Youngblood Communications Co., Ltd. Sep 2003
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