I'll start the discussion and hope others will too.
As I mentioned in another post, doing a more accurate zero setting reduced our set up waste by about 20%. Our web press was a Chambon press and the inks were EB inks. The new procedure that was used that resulted in the savings unfortunately is not applicable to most other presses. I will go into the background of this.
The Chambon press had a continuous ductor. It was a knurled roller. When engaged there was a gap between the ink fountain roller and the continuous ductor of about 4 to 6 thou (0.004 to 0.006"). So if the ink key gap was less than this value, no ink was transferred to the ductor and no ink could return to the ink fountain. The ink fountain was a Solna ink fountain with a continuous (wavy) blade.
The original zero setting procedure was to print 20% bars across the web and adjust the ink key mechanism so that the bars printed evenly. This was not a true zero setting method but it was all that was available.
A colleague of mine, named Frank Assinck, came up with an ingenious method to zero set that ductor arrangement. There were two specific and important features to his method. They were:
Zero setting was not done by running any paper. It was all done by actions done on the print unit.
First, the roller train was cleaned of ink. With a clean roller train, it was easy to see when ink just started to transfer to the ductor roller. The software zero set position was used and then the mechanical setting of the relative position of the ink key was gradually increased until ink started to transfer. Then the mechanical setting was backed off very slightly.
As other ink keys were zeroed in this fashion, ink starts to build up on the rollers. The second important feature of this method is that the roller train clean up unit is left on press and periodically engaged to clean ink off the roller train. This ensures that all keys tend to get a more consistent zero setting.
Besides the immediate reduction in set up waste, this procedure could be done at any time, by the operators, if they thought that there was a problem. Simple, quick and effective.
Unfortunately, I don't see any way that such an effective method can be done on presses with conventional ductors. There is a point where if the ink key is more open, ink goes into the press and if the ink key is more closed, the ink returns to the ink fountain. That zero point where no net amount of ink goes to the press varies and is hard to determine.
I will be interested to see if some people have some clever ways to zero set ink keys on press with conventional ductors. I suspect most ignore this important issue since it is quite hard to do on their presses.
