Alcolor unstable water-ink balance

[socrates]

I operate a GTOZS. Since day 1 I havent managed to print well because of the instability of the dampening system. I concluded to the following: I replaced all rubber rollers - inking and dampening - adjusting everything by the book. I use alcohol free solution and water no Ph additive to my fountain. This gives me a Ph of 4.8 to 5. Temperature is 15 C at the water pans. Printing room temperature is 18 C at winter to 30 at summer, usually though conditions are stable through the day. I start inking the press with the z roller in place, then I stop the press, pull the z roller off the inking contact and start printing. This gives me almost steady results. I can even change speed from 7000 to 10000 without adding water. But my problem is unpredictable. I might print prefrect 3000 sheet and then scumming begins or I might stop the press while printing perfect, talk to the phone, and when starting over again, scumming begins from the first sheet, forcing me to use more water in my printing. Moreover I have a permament drying problem with coated stock.

 

[m_alatorre]

Hi Socrates,
My GTOZ would give me headaches with water balance too! i Have the same problem of uncertanty in water response. I've come to the conclusion that relative humidity is a CRUCIAL factor when setting water in alcolor operating. My room goes frecuently below 40% and some times remains 30% or so all day. That won't work. I have a humidifier which i turn on until it raises over 40%. Any thing over that should work for me. Also keep paper away from humidity until ready for printing. Don't let room go over 50%. Temperature over 22C will also ask for more water(later hours of the day) so it's normal for me to increase 1 or 1.5 in water units(from 4 to 5.5 or so)
What i do when it starts scumming is: Let it start and print with little water even if is scumming and, as soon as paper is runnig thru 2nd unit, i acclerate to desired speed and increase water until scumming goes away. that usually works for me.

That of ink not drying might have to do with fountain solution. I'd try a diferent one(a buffered one) and, although you said you don't work with alcohol, you might want to add 1 or 2% of IPA to your fountain. (i'm currently working between 1 and 2)

Try water at 10C

Hope that helps!


Moe

 

[4 color GTO]

Do you have a problem with the EPA where you are at? I never had any luck with alcohol subs.

 

[socrates]

new data

Well, the instability of water is dealed as follows. Every day I start printing using the same values as a base setting as those values I have found them to be good ones. If the job of the humidity conditions demand so, I change the values accordingly. Values between the two printing units differ and I haven't managed to get them the same. The pressure of the z roller is critical: it leaves an ink line of 1.5 -2 mm thickness on the dampening roller. The ink dries well but I was fooled it didn't as the dust spray system was clogged at the nozzles. I use IPA-free agent to achieve 4.5-4.7 ph.
I general its difficult to get it work right but eventually you can do it and get a decent job fast ready and payed.

 

[MrRite]

Ink Water Balance

Socrates,

Your ink and water are not in balance. Your water settings are too high and thus you are setting your ink keys too heavy. It looks fine for the first couple of thousand sheets. But your ink is slowly building up in the rollers and over time will become too much for your water to handle. What happens is that the ink sits in the top of the ink train because the water is high and doesn't let it transfer down properly. You stop the press and the water system disengages. Now the ink flows down into the lower inking rollers and when you start back up there is too much ink and you get scumming. Check your plate as you are running and make sure it is not "wet", it should be dry. I have seen many a pressman run into this same problem.

I run larger presses and you can run the water system integrated or non-integrated. If you have this option you should run "non-integrated" Do not run with the bridge-roller engaged.

You mention PH, what is your conductivity? What does your manufacture say it should be at after mixing fresh water? PH is buffered in most solutions these days and therefore is not as important as conductivity.

 

[socrates]

I know exactly what you mean and you might be right. But scumming occurs not after a stop but during run. Moreover, after a stop things balance is perfect. I have the option of engaging or not the bridge roller but I see no or little difference -as I mentioned I found its critical to adjust it correctly and using strips of paper. I don't know what my conductivity is but you opened a new chapter to me. Do I have to buy a measurement device to check it? And something else, scumming may occur BEFORE I achieve a proper color tone - doesn't this mean you should add ink to achieve density?

 

[MrRite]

If you set your waters too high then you will have to set your ink keys heavy to match ink density. During the run the excess water and ink will emulsify and cause toning.

Are you using a two step fountain solution? If so you may want to increase the etch some. We run a solution that tells us to start at 3oz etch and 3oz alcohol sub per gallon. We found that we were scumming around edges so we adjusted the mix. We now run 4oz etch and 2.5oz alco sub per gallon and it is running fine. If your using a one step solution I suggest changing it.

Bridge roller: if you run with it "on" (engaged) then you are introducing water into the ink train during the run and will have to increase your ink. This causes you to run a heavy ink film which increases dot gain. If it is off you will run less ink to achieve the same ink density and print a sharper dot.

Conductivity: Your fountain solution should be a buffered solution with the PH about 4.5. Starting Conductivity will differ with the mix. Each product is different so you should check with the salesman or a technician from the company you buy your solution from. Ours starts at 2400 and we will change it if it reaches 3400 during the week otherwise we change it every Friday. As the conductivity rises and you get up to around 800 you will find yourself pushing a little more water to keep the print clean. If I find my conductivity to be high during a run I'll try to finish the job then immediately change it so I don't have problems on the next job. A conductivity meter can be purchased from most print vendors. Check the Conductivity of the water you are using before you mix. If the water has a conductivity of 200 and your vendor says the mix should be 2000 then your starting point would be 2200.

 

[The Heidelberg Guy]

Hello!

Try your pH at 4.3, and set the stripe to your intermediate (bridge) at 2mm.

Set your machine up to run in segragated (dampening and ink seperate) as follows;

-Stop machine
-Unlock barrel screws from the spring rods and screw them down until they just touch the blocks
-Tighten slotted screw.

 

[socrates]

I attach a picture showing what is usually but not always happening. I dont think I used to much water and/or ink to obtain balance. Press printed almost good in the rest of its width, but at the edge water was excessive.
Bridge roller is set to 2mm stripe. Maybe I should mention the proccess method I use. I ink the press with the bridge connecting dampening and inking rollers, then stop, disengage the bridge as it has on/off devices (without the need of using tools), then start printing. In order to wash, I re-engage the bridge and wash the dampening system along with the rest of the press. To be honest, I forgot the other day to disengage the bridge and I printed the job with the damp connected to inking, but I havent noticed any difference in the whole printing process (and problems).

 

[Grant B]

Hi Socrates,

I agree with both posts made by MrRight. You are emulsifying. I too run a larger press and have the option of running using Vario. If you have that option I would suggest you try it. You will be able to run with less water. If not, I would avoid integrating damps as it requires more water. No need to ink up integrated.

Our Heidelberg instructor set our water temperature at 12C (we have roller chillers too, set at 18C). I'd suggest turning your water temp. down, 15C seems high.

Every technician I have spoken to has said the same thing regarding alcohol subs-get PH at 4.1

 

[socrates]

Problem solved

Thank you all for your answers. The problem was solved by using a different ph agent and alcohol as well. Or else I should change my damp rollers to a different shore grade. Frankly, the worst of all was and still is, the chemical suppliers do not know much (or anything at all!) about the use of the stuff they sell. End of story though.

 

[ims1985]

from the manual

Hello!

Try your pH at 4.3, and set the stripe to your intermediate (bridge) at 2mm.
-Tighten slotted screw.

hi
i work on GTOZPS and the stripe of intermediate mast be (4 to 5 mm) by the book not 2 mm

 

[The Heidelberg Guy]

That is way to0 heavy of a stripe for the intermediate roller IMO, I have never set up any machine with Alcolor (GTO, SM52,SM/CD102) with that heavy of a stripe. Try the 2mm (+ 0.5mm), then write back on the forum saying thanks!!

 

[ims1985]

Thank you for your attention..(The Heidelberg Guy)
I hope u r right
I'm not an expert
but this photo from the operating manual HEIDELBERG GTO Stream feeder Edition 2006.11 .00999.1226

 

[The Heidelberg Guy]

Thats the Alcolor form roller to the distributor cylinder (matte chrome roller) should be 4mm.

I was refering to the intermediate roller (bridge roller) to the Alcolor form 2mm (+0.5mm).

I'm attaching a roller stripe chart you can use.

 

[ims1985]

I write this from the photo
(between the plate damping roller and the intermediate roller is correct,you will see a roller mark of 4 to 5 mm)
is this has another meaning?

 

[gazman]

I tend to agree with The Heidelberg Guy the intermedite (z roller) should be set @ 2mm to the water form not 4 to 5 mm this is far too heavy

 

[ims1985]

I understood that 5 mm strip from your reply as too heavy. Agree with you but can some one till me what is the difference when make this strip 2 mm. in another word is it affecting printing efficiency?

 

[ims1985]

Is a difficult question?
What is the expected affect if I change the intermedite set from (4 to 5 mm) to (2 mm) in printing?

 

[ims1985]

I tried to adjustment the intermedite roller at (2 mm) to day
the result is much easier water-ink balance.
thanks The Heidelberg Guy
but how manual dose not be correct :0