Roller life - Specifically Soft duro type

[Dan Roll]

If your dampening system is the one illustrated in the previously referenced Oliver_Sakurai_72.pdf, what does the manufacturer suggest for the pressure between Q and S? Is the form roller (Q) gear driven or is the roller identified as U gear driven? I am suspicious of the need for,or the utility of, the roller U if the form roller (Q) is gear driven. I doubt very seriously the ink form roller (A) and the water form roller (Q) turn at the same surface speed, even if it was the design engineers intention to have it so. Unless the bridge roller (T) is being used to drive the water form roller (Q), it will turn with the ink form roller (A) and scrape against the water form roller (Q).

[Green Printer]

If your dampening system is the one illustrated in the previously referenced Oliver_Sakurai_72.pdf, what does the manufacturer suggest for the pressure between Q and S? Is the form roller (Q) gear driven or is the roller identified as U gear driven? I am suspicious of the need for,or the utility of, the roller U if the form roller (Q) is gear driven. I doubt very seriously the ink form roller (A) and the water form roller (Q) turn at the same surface speed, even if it was the design engineers intention to have it so. Unless the bridge roller (T) is being used to drive the water form roller (Q), it will turn with the ink form roller (A) and scrape against the water form roller (Q).

The U roller is the oscillating chrome. The roller Q is a differential speed water form gear driven. The T roller is just a rider that oscillates and can be bridged or unbridged between the water form Q and the ink form A. The S is chrome water fountain pan roller, R is the water meter.

[Dan Roll]

I suspect the roller (U) in the diagram is only there to prevent patent issues with the Epic people. Since the form roller is gear driven, there is no reason to have a roller between the water supply (S) and the plate cylinder, this roller is more likely to cause mischief than contribute anything, I would remove it. You did not mention the recommended pressure between (S) and (Q).....

[Lukew]

Dan,
The U roller is important. It is on all the larger shinohara's as well, but not the 52 size.
My understanding it is there to help rid any imperfections in the damp transfer (IE circumferential comb cording) and any other imperfections that may form on the water form roller.

I wish the 52 size shinohara had this, as a lot of founts have issues with circumferential comb cording.

One issue we still have is water beading between the chrome and water form on start up or if the damp is left on and machine idles..
I'm positive a 22 duro water form roller would stop this problem, but how long that duro roller would last in the water form position is a bit of a gamble

[Green Printer]

Lukew

When the press was installed 8 years ago I did try backing off the U roller in a unit to see what ramifications would occur. Almost instantaneous circumficial lines randomly dancing across the plate. I was expecting this but not to the extent that it occurred and so quickly. Without the U roller engaged this dampner is totally worthless.

[Dan Roll]

Well, if the form roller is gear driven in contact with the plate (at a speed that does not match the plate speed), run in contact with the bridge roller, and in contact with a driven occilator (U) I would expect a soft roller would wear out pretty quickly under these circumstances. Three friction points are a lot to expect a roller to endure.
By 'circumferential comb cording' do you mean streaks appearing in the work in the direction of sheet travel? If so, these are usually caused by the chrome roller being set too tightly to the form roller causing the chrome roller to scrape against the form instead of slipping. This is why I have asked several times what the manufacturer recommends for pressure at this point. Do you have any information from the manufacturer explaining the role of the (U) roller? I would be interested to hear it.
Many years ago (and maybe still) the brackets on these presses dampening systems were designed in a manner causing the pressure between the chrome and form roller to increase significantly when the unit went on impression. These were difficult to run and streaked badly. When the chrome to form pressure was lessened while the press was running (this took a lot of lessening, it was really tight) to the point the streaking stopped and the dial speeds were reduced, there was no contact between the chrome and form at all when the press came off impression. It may be the (U) roller was/is an attempt to cover this problem up.
If water is beading up on the chrome roller, the contact between the chrome and the other two rollers is certainly too tight.

[Green Printer]

Q to S stripe 2mm to 5mm depending on Q roller durometer. Dan contact Sakurai directly for the U roller function. They can be reached at (847) 490-9400.

[Dan Roll]

Many years ago I visited some plants in OZ that had this problem (Walmac, Heaney's, Printing Place, Bayfield, and CT Graphis to name a few) when I was working with an engineer working for Curries (they were the Shinohara/Sakurai dealer in Australia at the time) who had been trained in Japan. This was before the adaptation of the (U) roller. These presses would streak like mad when the high percentage of alcohol they were running was removed (the last time I was in Australia/NZ was 1997 and interest in alcohol free printing then was not what it is today) unless we reduced the chrome to form pressure as I discussed earlier. I remember setting the chrome to form pressure carefully to the four mm recommended by Curries at the time and stopping the press while it was on impression to find the chrome roller crushed up against the form with what looked like a contact of 15 mm or more. When this pressure was reduced significantly, the press ran well until it came off impression and the chrome separated from the form completely, sometimes dripping FS onto the feeder board. I am not surprised Sakurai chose to address this with an additional roller rather than redesign the brackets. In this position a soft roller will be ruined quickly.

[Lukew]

Dan:
Thankyou for that information!!!

Although the late model shino, the water form doesnt alter its settings as you describe.

I dont beleive the water form is the cause for circumferential comb cording, as if you put a fount in that does it you can see the cording on the metering roller as it spins without you running the machine.

I always found, the higher % IPA the worse cording was, and also running alcohol with alcohol free fountain solutions.

Yes I know Bayfield had an issue for some time.
My understanding is Shinohara has altered the waterform position on our year model shino but this has caused other issues.
Also know another shop with the same year model as ours had huge dramas even getting the thing to print, would either scum up on start up or wash out..

Our water buildup between water form and chrome, happens as soon as you hit damp on, before you even feed any sheets.

I have tried previously to run it down to a 2mm stripe (water form to chrome), but I couldn't get an even transfer of fount, you would be running then all of the sudden 1/4 of the sheet would scum up. tighten the nip to the chrome again and the scumming went away.


If you could give the info on what you did, that would be great.

[Dan Roll]

The reason you see 'cording' on the metering roller is it experiences the same friction problems the form roller does. The surface speed of the metering roller and the surface speed of he pan roller are often geared to be very different and this scraping action is what causes the 'cording'. I have never heard a rational explanation for why so many dampening systems have this design 'feature' but you will find it on a surprising number of dampening systems. Heidelberg operators usually believe these streaks originate from the metering roller for the same reason, but th streaks that print are caused by scraping between your pan roller and form roller.
If I remember correctly, the Curries tech guy I was working with was able to reduce the chrome to form roller pressure while the press was running (I do not recommend anyone who wants to keep all of their fingers to try this however) and did so until the streaking stopped. The couple of times we did this it took a lot of turns to reduce the pressure adequately.
I am not surprised Sakurai chose to redesign their dampener since then as it was a pretty poor performer in those days. They would not be the first manufacturer to 'improve' their dampener without making much progress.
When reducing the chrome to form pressure I would do it with the (U) roller removed from the unit. Otherwise there will be no way to determine if you are making progress.
If you remove the bridge roller and the (U) roller, you are left with the dampener design used by Mehlie back in the day, a very good dampening system, but I am sure the gearing of the Sakurai effort is such there will be excessive friction in the unit compared to the MehlieMatic. On the old MehlieMatic, as we called it, the pan and metering rollers turned at the same speed and if the pan ran dry and the unit was left running it could go all night without damaging the metering roller. A press next to the old Super Sixty had a Dahlgrens dampener and if the pan ran dry when it was running it would ruin the metering roller in a matter of fifteen minutes. Do you have any information of the speed of the form roller? Many gear driven form rollers are driven at a speed quite different than the plate speed in an effort to 'pick hickies' but this 'Delta effect' does little to help the dampening system run well.