Press Problem not matching G7 Proofs

[Chasfinch]

Hello

the last few weeks the presses ( we have 2 KOM lithrone 28s 5 color) are having problems matching out G7 proofs. Beginning of the year we had each press curved and are using the correct curves. I checked the plates and the 21Step is fine. The blue and red are causing the most problems the blue they have to run densities way up and hold one the red. The dot on plates looks nice and clean but the printed piece the dot looks a bit rough. Still creates a rosette. I did read a test chart with my verifier on my fiery XF. I see some strange readings. its all over the map. The Cyan did show out of spec but overall dot and trapping seemed fine. What is interesting we do have a small Ryobi press for BCs 2 color we generally do not have dot on this press BUT there happened to be a sheet with dot and the same rough look is there also. Not only are the dots rough but dot gain can be all over the place. Then last the plates are only lasting maybe 10000 impressions or so before starting to fade dot.
I have my own ideas on where to check. But I am looking for other balance.

 

[Cornishpastythighs]

Common denominators.

Ink Contact the supplier to see if any changes have been made.

Fountain solution. Do you have a regular FS maintenance cleaning and monitoring program?

Paper/stock.
Press temperatures.
Rollers
Blankets
Have any of these been changed/modified lately?

 

[Chasfinch]

Common denominators.

Ink Contact the supplier to see if any changes have been made.

Fountain solution. Do you have a regular FS maintenance cleaning and monitoring program?

Paper/stock.
Press temperatures.
Rollers
Blankets
Have any of these been changed/modified lately?

thank you we have no set maintence program. kinda what the pressman feel it has been over several stocks. Blankets where recently changed on one press.

 

[QualityPrint]

Tough to point at one thing with so many variables. So I suggest starting to eliminate them one by one. My gut says the issue is stemming from the Fountain solution. But that is assuming you run the same solution on each press... Since you are having plate wear (blinding) I believe calcium carbonate has claimed another victim. That has to be proven though. So pick a press and try something different. I suggest to wait until you see the plate wear, then wipe the plate down with vinegar. If it is calcium building up on the plate the dot should clean up for a period of time. (usually only 1000 sheets or so). Not a fix, but it will tell you part of the story, eliminate some variables and guide you in a direction. Or pick a press and do a full system clean of the fountain solution paired with a calcium roller rinse and see if that changes the look of the dot.

The key to sustainable color matches is to have a known state to go back to when things change. We use a characterization folder with everything that is involved in the profiling process. I.e. Ink Lab's for each color that we measure for each batch, Conductivity, pH, refractometer reading, and TDS reading for a fresh batch of Fountain solution, Bearer height readings for blankets, Paper Lab readings, dot readings from the plate, temp & humidity readings from the environment in the pressroom....etc.. We record each of these things when ever we are characterizing a stock.

These readings help us determine the cause rather quickly of why we are having an issue. Since we measure them often it helps us anticipate some reoccurring issues. It is a bit of a lab mentality but it works for us. With the workforce changing we try to build a system that is easy to follow. The days of the employees that can "feel" issues and know how to fix them are going away unfortunately.

If you need any more info let me know.... hope this helps

 

[aqazi81]

Conductivity, pH, refractometer reading

Refractometer for what?

 

[ponnapati123]

As above posts suggesting we need to rectify the problem one after one that is always great full idea. So you can start verifying from prepress, check the plate dots using plate scope to verify the dot reproduction, then raw materials, consumables, machine settings and so on. If you start checking all these processes somewhere you can get the possible solution.

 

[Chasfinch]

thanks all

Prepress is fine. I got my box of half tone dots and checked them to the plate all is well upto imaging the plate ( has been a long weekend needed some humor)

 

[QualityPrint]

Refractometer for what?

We use this measurement to ensure our wetness is always around the same. 1.5 seems to be the sweet spot for us. When we see that number dip down to 1 we are more apt to have plate blinding. Most Fountain Solution companies will measure this upon the initial setup of a new fountain solution. So we measure it simply to ensure there is no sway.

 

[aqazi81]

That sounds interesting.
Is 1.5 the specific gravity? On which scale?

 

[Dan Roll]

Uhhh, refractometry is of dubious value for measuring fountain solution. Reading the Brix value of a solution is good if you are measuring sugar, alcohol, or carbohydrate content (wine making is where this technology came from) but fountain solutions contain combinations of ingredients (gums, solvents, glycerine, etc) that may affect a refractometer reading and can not be depended on to reflect any particular property with any level of accuracy at all. To say most fountain solution companies use this measurement is a bit of a stretch, although some fountain solution companies like to sell refractometers.
Stick with conductivity to monitor concentration and pH to monitor contamination.

 

[QualityPrint]

We choose to utilize any measurement we can to ensure consistency. Dan does probably know best about the technical side of the F.S. with his background in it. With the increasing amounts of contaminants in the paper, we have seen that there are sways that are very unpredictable. The calcium carbonate in paper isn't consistent from paper brand to paper brand... for that matter it isn't consistent from lot to lot within the same paper brand. We have seen this in the last 5 years change quite a bit. We have seen instances where our dosing has been off. (we have automatic dosers that require maintenance periodically) For instance, our dosing was low due to an o-ring in the doser being worn. Looking at the spreadsheet we keep, the conductivity only raised 300 points over the course of 3 days. pH held stable at 3.8. Everything seems normal. However, our Brix % fell to 1 from 1.5 and our TDS had risen 300 points. So based on the tds, contamination was present. However the pH didn't change.... Seeing that the Brix % fell we knew immediately that we were not at our zero point. We checked a fresh dosed sample at the doser and it read that the conductivity was lower than the set point by 400 points. We did not see that with the running solution because the contaminants present had raised the conductivity up enough to compensate for the lack of conductivity cause by the bad doser.

Odd ball issue, but we learned from it and solved it impressively quickly. As Dan implied, pH and conductivity tells you the story on a fresh batch. But introduce contaminants and deal with it at a real world, printing everyday level, you take whatever you can get.

Dan- maybe I'm too sensitive but your response is an example of why I don't like to post on these forums. Your response implies that you are frustrated with my response and has a implication that what we are doing is ridiculous. If you came to our shop on a technical level I know that you would love the data we could present. In over 5 years we have seen, based on data, that the Brix % helps tell the story. It helps ensure we are at our zero point thus allowing us to match our proofs consistently. It also helps us trouble shoot quickly when problems arise by eliminating variables right away.

I hope the OP finds this info helpful. For credibility purposes, I reached out to 7 different press operators and 5 pressroom managers from different companies that are very successful with matching their proofs and they have mimicked our approach based on our consistency. Yes we do share this info and is very helpful to us all.

 

[aqazi81]

QualityPrint If this is working for you then its good, but again as Dan also said that during printing there are contaminants from paper and ink and you get the wrong reading.

I also work for a FS supplier company and we measure pH and Conductivity to monitor the FS behavior on press.
My recent experience was with one of our clients who were complaining that our FS is not maintaining pH. When I visited the customer and saw there newly installed Technotrance Beta d and it was showing pH at 7.
I asked them to check their dosser that if it is dosing properly but they said that this is a brand new Technotrance and it cannot be wrong.
Anyways they contacted Technotrance and their tech found that the pressure at the intake valve was not sufficient for the dosser to work properly and when they corrected that, everything was fine again.

We all are here to learn from each others experiences and posting on this forum has always helped me to correct my mistakes.

 

[Dan Roll]

I'm sorry, I didn't mean to tread on anyones feelings, I'll try to be more sensitive in the future. My lovely wife will agree with you, I am a jerk sometimes. I will admit to a level of frustration at the widespread use of refractometers in the FS and silicone business and while the use QualityPrint describes is valid, there are a lot of printers under the impression they are measuring something specific in fountain solutions with their refractometers when the chances of this are slim. In QualityPrints case, measuring the conductivity of the FS delivered to the tank (before it came in contact with circulated FS) would have indicated the mixer was malfunctioning with a higher degree of accuracy than the refractometer. If you were to titrate (meaning in this case to take measurements at a steady increasing of concentration of fresh solution and make a chart at one half ounce or one half percent intervals) fresh fountain solution taking Brix readings you might be able to use this information under certain conditions. Most fountain solution contaminants are both non-ionic and non carbohydrate and unlikely to effect a refractometer reading much one way or another.
Aquazi81 referring to TechnoTrans as TechnoTrance is hysterical. I have had many run-ins with this fine company in the past, mostly centered on the differences between the European and North American printing markets and how what is well accepted in Europe occasionally doesn't work well here.

 

[Chasfinch]

Thanks everyone. Fuji said they will be sending out someone this week to go over what is going on. I will update what Fuji tells us as well as anything else the pressmen says. Hope all is going well for a Monday

 

[Chasfinch]

just had bay digital in and they checked the laser, it actually was a little to strong backed it off and refocused.

 

[Chasfinch]

had fuji come out. looking at rollers a couple of plates fuji thinks it maybe blinding. calcium looks like it has put its evil hooks in and we need to have some sort of maintenance schudule to help with calcium which we do not even treat for right now.

 

[aqazi81]

There are some great products by Boettcher for calcium build up.

 

[Chasfinch]

Fuji said it looks like EVIL CALCIUM

 

[Dan Roll]

Evil calcium is the worst kind! Be careful with calcium removers, they are pretty strong and can damage your rollers if you are not careful.

I am curious though, calcium problems usually involve stripping in the ink rollers and your original complaint doesn't mention stripping. Calcium ions bonding, usually with acid ions forms what is referred to as 'scale' a water attracting, oil repelling material, preventing ink from sticking to surfaces and the rollers stay in the press a lot longer than the plates do. in the absence of roller stripping that can not be traced to some other cause I would think calcium being the problem is unlikely. There will be no shortage of people happy to sell you expensive calcium 'solutions' though...

 

[Chasfinch]

Hi Dan the pressmen did not complain about stripping. But looking back especially in solids I think that has been an issue here. I should also say this has been an ongoing problem here for years; the variation in dot and color. Stripping has in the past been an issue. One of the major factors is the maintainence program or lack there of out with the presses. We are kind of shooting at the hip. Fuji looked at all the data I had built up and came to at this time calcium is the most likely suspect. As for calcium removers we are not tied to any one item. Production will look at all options and go from there. Most of our work is under 10 K sheeting so the problem can or cannot show its head. So we are at this time going to leave it to the pressroom and managers to come up with a game plan. My hands are really tied until they start maintaining the presses with some consistency.