uncontrollable water.. catchup and emulsifying

[spigot]

Hello knowledgeable people.

When running a shinohara, i seem to have issues keeping consistent density, particularly on yellow. Its worst in the middle of the sheet, and then sometimes catchup on the edges. Its so sensitive, that an increase of 1 decimal on the water feed roller will wash it out by 50%. I can only adjust skew so far before it stops having an effect.
So naturally i run, adjust, increase the ink feed to hold density, until stack change.
At that time it is mega heavy in the flood area, which goes back to light after a hundred sheets or so. To maintain density in the fllod area the duct key openeing would be for example, 5 5 5 25 25 25 5 5 5. So it needs a crap load of ink to stay ok when running.

After a while, the stripping will work its way up to the duct so there is absolutely no ink on the rollers all the way down, about an inch wide, starting at the roller that recieves ink from the duct vibrator.

I suspect the dampening forme roller itself is to blame. There has been alot of water issues lately, with the doser playing up and the press just not running well at all. At the moment the other units seem to have settled down, just the yellow is really bad.

So.... what suggestions could it be? the yellow ink/fount mix incompatible or at least not ideal? Bad forme dampener? Metering roller?

Its difficult because its a shift machine and it seems everyone has a different idea, and makes different adjustments so its hard to find consistency. There is also a hierachy as well, to add to the fun.

Also... it is pretty bad for banding. the only way to get a nice print off the black unit is to run the water in only one position, and to lower the ink until it is only just black. Like 1.4 or so on the denso, like a heavy grey almost. Any more ink and the banding happens badly. How can i adress that issue as well? The bands are in the middle 2/3 of the sheet, sometimes with a definate nip mark, or other times just bands of what looks like the screens are getting more, less more etc.

 

[Al Ferrari]

Were you running this press at some earlier time when these problems did not occur? If so, then the obvious question is what has changed? Has there been a change to new brand or type of plate or chemistry when these problems began?

No disrespect intended, but your exasperated description of the problems make it sound as though you (and/or the others) don't have much experience. Why not take the time to do a complete resetting of all the roller pressures, both ink and water. Not doing so is getting nowhere fast, and producing substandard work.

Al Ferrari

 

[GazKL440]

I agree with Al on this one, start with doing a full set on your rollers, and eliminate them from the equation as an issue. I would guess at undersize or poorly set rollers in both the water and inking train, and there is simply no way you will get a consistent run out of it.

I recently had very similar issues with unit 2 on my Komori, for example an even set profile that should be spot on when matched to the image would end up with a 30% range on the keys to get an even *looking* print. Stability was damn near impossible, and even after a very careful setting of the meter/forme/pan etc in the dampening train, emulsion of the ink was clearly visible in the roller train, duct and on the print. We replaced every roller in the inking train and found that most of the very undersize rollers were barely contacting...if at all. Not one of the forme rollers were actually touching the oscillator or transfer, with ink transfer being achieved by ink "bridging" the gap, and from the plate itself!

It gave us hell scott, and for some time we were simply pushing shit up hill. New rollers=problem solved

 

[Cornishpastythighs]

I'm not familiar with a Shinohara press but Litho is Litho and yours sounds like its gone off the rails.
Time to get back to basics I would think and check out your entire printing system.
Dampening system- Temp, pH, Conductivity, dosage, condition and settings of metering rollers.
Rollers -Durometers, Temperatures, settings, wash up procedures, type of wash up solvent
Ink-Quality, water pick ups
Plates- Are they being processed correctly.
Plate/blanket squeezes.
Most important of all develop Standard operating procedures amonst your group, If you cannot set this press up consistantly you will never truly solve the issues.

 

[spigot]

cheers for the replies guys, all useful. There isnt a lack of experience as such, all operators have been printing for 7-10 years if not more. I find it frustrating when every time i make a change thats necessary to get a result for one job, one of 2 things happens - either it will be back to poor again the next day, or another operator will have a problem and report upstairs that the settings that were changed in the prior job are the reason its playing up.
It seems to me the goal posts are constantly moving and thats not helping. It hasnt always been bad, but it has always had banding issues, an inconsistent doser and variable behaviour.

As it stands now, the rollers have been reset, and pressures are all good, yet the unit is a dog to run.

Will try and get everything looked at properly soon, and the standard operating procedures is a good call, leaving nothing to chance.
Anyone got any sales positions available haha

 

[GazKL440]

If your doser is giving you some issues, try taking it out of the loop if possible and manually mix your fount for a week or so, that will either give you a solution or eliminate a possibility. However, if the doser was the source of the problem all units, more than just one unit would be creating problems.

How are your dampeners driven on a shino? Is it possible the drive is giving you issues and a variable result? May be worth just watchin them on that unit and look for inconsistent speeds... How are the bearings on the pan/meter/etc?? shagged bearings on your roller shafts can give the symptoms you mentioned in the OP.

As for sales reps... we have been thru several over the last few months, just had another bright and shiny start......will get back to you next week

 

[cincyinkslinger]

This sounds like you also might have calcium deposited in the ink train rollers. A vinegar wash is cheap and will get a lot of it out to see if this gets you in the right direction

 

[turbotom1052]

ditton on the calcium rinse. do you run much alkaline based papers? these days if your running uncoatd paper your probably running an alkaline based product. the only thing that would sway me from thinkin it may be a calcium buildup is that you report it happening on the yellow unit. does it happen when you print a color other than yellow on that unit? others have mentioned going over the entire press and setting eveything to factory specs. this would be a good start.
the fact that youve got multiple shifts running on this press complicates things a bit. all it takes is 1 of the press operators to throw a wrench in the works. ive encountered press operators that always seem to have a wrench in their hands. if the press has been set to factory specs and your confident that its been done correctly then there shouldnt be a need to make further adjustments so soon after.
Perhaps its time to bring in outside help. When i say outside help im talkin more of a really seasoned crackerjack pressman as opposed to a press mechanic. Press mechanics are good when it comes to looking for mechanical problems but to find problems in operating procedures id suggest a pressroom consultant. you mentioned how your guys have been printing for 7 to 10 years but its been my personal experience that when i was 10 years in the printing industry i thought i knew everything needed to be succesfull. truth be told im in my 32nd year of printing and i can still learn something new.

 

[Dan Roll]

I am going to assume you have the three roller dampener. Many of these presses have a bracket design that tightens the pressure from the chrome roller to the form roller when the dampener is engaged. Try adjusting the chrome to form pressure with the dampener engaged. I have seen one of these that when set in this manner, the chrome was completely out of contact with the form when in the disengaged position. Ran good though....

 

[vik la luna]

all good replies to this issue
i have only one thing to add to this
have you checked you metering roller? does the roller have the correct duro?
is it out of round? does it have low spots?
try swapping the meter with another unit and see if the problem moves with it

 

[acacia print]

Spigot, The combined help on this page is excellent. Most sugestions above are what I was thinking. this sounds like emulsification due to rollers or roller settings. Check their shaw (shore...spelling?) hardness as well. Normally when I had this sort of thing it came down to old rollers that were past their use by date and were also set poorly. As you ahve shifts there will be guys adjusting things and you wont know then wonder why the goal posts are changing. It sounds like a factory meeting to brain storm as to who has tried what may help but if there are "Personalities": involved it may become a blame game. This is the sort of problem thatmanagment need to get a grip on or they will loose experienced staff. The roller company's rep should have a meter for checking the rollers hardness. Best of luck. PS I have been in the game 25+ years and I lernt something today from the above comments. So keep an open mind.

 

[RJ Litho]

RJ Litho

RJ Litho

One thing you can check if your metering rolller is orange peal or alligator skin looking. Normally it takes a little while for this to happen but when it does it will happen progressively more often.If you pull the roller an let it rest is will help but not the cure. Certain etches are the culprit one being Prisco 3451U. I have had a rubber roller made to combat this issue . It seems odd that I would make a roller fro this etch but it runs so well .We have four press running 3451U & Alkaless 3000 from 20'' TO 73''. Hope you have sorted out your issue running a press some days is enough of a challenge without adding problems.

RJ

 

[1Pressman]

These tips will help!

These tips will help!

Classic symptems of CONTAMINATION! Or Chemistry
Yes, Do the calcium rinse. Vineger rinse will eliminate Surfactents.
Avoid step 1 wash or other detergents. Finish all washes with some water.
Make sure fountain solution is clean-Throw out and start fresh. Be sure dosing is correct.
If problems persist, you have chemistry problem (incompatable fountion solution and ink.)
Use different foutain solution, avoid high dosses of alchohol sub's with ethinol like ingreadiants. 1-3 oz per gal. max.
Finally try heavier bodied Ink.
Good luck,
John