Can't calibrate alcolor dampening unit

[m_alatorre]

I'm working first time an alcolor GTOZ. Took all the alcolor rollers away and put them back together trying to do it acording to manual. Only in my dreams it was easy. I can't get it to distibute water evenly in the plate, but my biggest problem is that i have a 3" water stripe coming from cylinder edges to the inside and that makes it impossible to print anything. So my question is:

1. Wrong adjustment at certain (or several) point of dampening unit? (ex. too much pressure between plate dampener and metering roller, etc)

2. Water pan and/or water form rollers are worn and need to be replaced?

3. Something else that i'm not considering?

All help very apreciated

Moe

 

[NotAGooner]

Make sure your inking rollers are set to spec, that's just as important as the Alcolor train in keeping the plate clean

 

[mrheidelberg]

Hi,

Settings should be:-

Plate damper to matt chrome 4 to 5mm
Z roller to plate damper 3mm
Plate damper to plate 4mm
Pan roller to metering roller ... just remove water from ends and + 1/2 turn
Metering roller to plate damper 5mm

Regards.

 

[m_alatorre]

Hello,

Checked ink form rollers and seem good.
Calibrated alcolor rollers acording to specs kindly given me and got closer to good result... but.......

Still get too much water at operator side of machine(2 or 3" from plate edge)

I uploaded a picture of my result. Hope you can see it.

There you can see how i've got a lot of water on edges, then scumming and then again too much water in the center of the page.(wierd, isn't it?)

I saw that water damp roller is a little "wider" at edges.(a very common efect in rubber rollers) Could that be the reason why i get more water there? Contamination in the rollers?

Another thing...
When calibrating the metering roller against the pan... i did it when press was operating and both ink and water rollers were on. But didn't lock the bolts made for secure the mechanism because when i do so, calibration goes wrong....Could that show pan roller worn?

Help! Help!

Thanks!!!

 

[mrheidelberg]

Hi,

If you can, just check if there is a crown in the center of the pan roller, it should be slightly bigger in the middle than the ends.
Locking the pan roller up should not alter the setting.
It looks like there is is a roller issue somewhere.
Take the rollers out and give them a clean by hand using a mild pummice abrasive like Jif bathroom cleaner and also use a strong plate cleaner on the matte chrome.

Regards.

 

[m_alatorre]

Hi,

Took rollers out.
Pan roller seems to be equal in diameter(or ever a little bit shorter in the middle)

Tried to take plate damp roller out and could not do it. I loosen the bolt that holds it at OS and thats it... does not move nor to OS or to DS... Do i need to loosen something else or put it in certain position?

Thanks

 

[mrheidelberg]

Hi,

I would back the setting off between the plate damper and matte chrome by a couple of turns anticlockwise as probably the friction is not allowing it to move.
The roller should pull over to the operators side and lift out on the drive side.

You may have a problem with the pan roller dimensions.

Regards.

 

[m_alatorre]

Hi,

Took rollers out. Good cleaning. Put them back together.... quite same problem. But this time i could see what i think to be the problem.

When i see the ink stripe water damp leaves in the plate(when calibrating), i see not an even line but a line that "grows" as it approaches the edge. same efect against distributor roller.

If i calibrate according to specs, it will only clean the inked plate where damp roller is wider(edges). I can add more contact between metering and damp but then i get too much water even if i put pan roller at minimum speed.

My best guess?

Damp roller needs to be replaced.
Does it sound like it could be?
I just don't want to ask for a $300(?) roller with out beeing sure.

Thanks again!

 

[mrheidelberg]

Hi,

From what you have described above it sounds like there is an issue with that roller. It sounds swollen at the ends.

Regards.

 

[socrates]

I had the same problem and forced to replace all rubber rollers. Problems now are kind of adjustment corrections. But in general now situation is near perfect.

 

[RIVAO-MAD]

Hi,

Settings should be:-

Plate damper to matt chrome 4 to 5mm
Z roller to plate damper 3mm
Plate damper to plate 4mm
Pan roller to metering roller ... just remove water from ends and + 1/2 turn
Metering roller to plate damper 5mm

Regards.

Hello.
I did all the adjustments as indicated and with all the new rollers.
When printing, it generates a mark at approximately 5.5 inches, from the entrance of the sheet from end to end of the format, it is a mark of about 10 mm, as if it had excess water
Can you think of what could be the cause?
That mark is noticeable that it reappears more tenuously towards the back of the sheet.
in two units he makes the marks at the same distance.

Thank you very much who can give me some advice

 

[asem alsafady]

Some types of IPA alcohol are not valid and cause the same problem.
Test your IPA quality.
Send us feedback please.

 

[turbotom1052]

Hi,

If you can, just check if there is a crown in the center of the pan roller, it should be slightly bigger in the middle than the ends.
Locking the pan roller up should not alter the setting.
It looks like there is is a roller issue somewhere.
Take the rollers out and give them a clean by hand using a mild pummice abrasive like Jif bathroom cleaner and also use a strong plate cleaner on the matte chrome.

Regards.

Does Heidelberg even put a crown in the pan roller on GTO format presses from the factory? I would almost think it would be not needed on that width press. I know that on the 72cm format presses I would purchase our pan rollers ground without a crown.

 

[turbotom1052]

I'm going to use some terminology that I hope you're familiar with. I only know the words in English so if you're not fluent in English then I suggest you find someone to translate. The best way, in my opinion, to know when you have the correct amount of water feed, is to look at the very "gripper" or "lead edge" of the plate cylinder. Right where plate makes its bend coming out of the gripper clamp is what you will be wanting to look at. If your water feed is set correctly, you should notice what I refer to as a "scum line", right at the bend of the plate where it transitions on to the round cylinder. This "scum line" should be fairly even across the plates bend, and NOT extend more that a couple of millimeters beyond the bend. Assuming that all your rollers are in decent shape and set correctly, it would be correct to say that if that "scum line" is not visible at all, that you need to turn down the speed of your pan roller, or tighten the squeeze to the metering roller. Which one you choose would depend on how fast your current speed of the water system is running at. If your speed is running down below around 40% I would tighten up the metering roller. If your damp speed is running up past around 70% I would slow down the speed of the pan roller. Adjust the water feed in this manner until you see that "scum line" I refer to. If that scum line is uneven across the plate, then you will need to either loosen, or tighten the metering roller until the scum line is even across the sheet. If you find that the scum line only shows on the edges of the plate bend, and is not visible in the middle, then it would require you to tighten the metering roller and speed up the dampener drive motor. If the scum line is visible in the middle but does not show on the plates edges then I would suggest working with your air curtain to manage the excess water. You should NEVER pass on an opportunity to observe this "scum line" If you are in the unit, for ANY reason at all, with the gate up, either during a make ready, or during the course of a run, you should be looking for this. The advice I offer is with the assumption that the press is mechanically sound, and that the rollers are in good shape, and set correctly. It also assumes that your chemistry is clean and correct.

 

[Cdel]

If you're running a 102 and the job is on a 20x26 sheet, will the scum lines still be visible on the whole plate or will the scum line be lighter on the ends since there's no image out there?

 

[turbotom1052]

You may find it less pronounced or even absent outside of the sheets dimensions. This would be the best time to utilize your air curtains!!!

 

[Printing Fox]

Yes, talk about scum line is super.