Xl106 scum line issues

Hi all.
I am currently running a 2022 heidelberg xl 106 one over one. Running primarily black ink. We run alcohol free with chameleon sub and etch. All the roller to roller and roller to plate stripes are set correctly. We are having problems with a lot of ink building up on the tail edge of the plate when the press runs with vario on. Vario off, we do not have this problem. This only happens on uncoated stock. Coated stock we have no issues. We primarily run uncoated off this machine though. I have exhausted all of my ideas and the demonstrator has never seen this before.

Any help will be greatly appreciated

Thanks

 

Almost forgot. We have a xl106 that is 18 months old pretty much the exact same press. Same chemistry paper rollers ect. We do not have this problem on this press

 

There is too much ink on the rollers, or you need to reduce the overall ink supply or add compensation zones to the plate to increase ink on paper.
Look at the rollers while working, you may have "paint hiss on the rollers."
It is also worth changing the ink profile, you have a very small area of the printed element, and judging by the photo, the water and ink settings for printing the maximum poster format with 300% ink overlay.

 

Are you running with the Vario on when just running plain black type ?

 

Our KBA also has a "bridge shaft" to connect water and paint.
We receive ink profiles by zones from the prepress department.
BUT! The adjustment of the feed and transfer shafts remains with the print operator.
The operator pointed out to me that the problem was not in the technical condition of the machine, but in the adjustments made by the operator.
You can do like this:
1) wash off the colorful apparatus
2) leave the rotation of the ductors as is
3) reduce water and paint to 2-5%
4) gradually add paint-water-paint-water in turn until the desired result is obtained
5) write down the settings when you get the optimal density

Regarding your question, our operators can print black text, pantone, posters on 15-20 grades of paper in 12 hours. No quality loss. Maybe that's why they don't have this problem.

 

Yes vario Is on.

 

Nick

Very puzzling.

Same symptoms on both units?
Been happening since installation?
Running integrated roller set-up?
Running standard inking or short inking unit settings on light coverage?
Is it equipped with colour control? If so what calculated densi is it showing for uncoated stock, if not, what densi do you run black at on uncoated stock?
Who set the rollers, especially the dampers? Setting the dampers is (to me atleast...) on these presses, quite protracted and there are a number of prerequisites that must be followed carefully.

Having said all that, struggling with the fact running coated stock shows no problem.
Whenever I've seen vertical repeating lines like those, upping the dampening removes them, but that may just be the dampening masking the underlying condition???
The build up at the back edge is what I'd only expect to see when running longer runs with (dreaded) metallic inks.
I'm not familiar with the latest version of Prinect you'll be using on your press, could there be something in the pre-press file being sent over, with regard to printing material properties, that your older XL press has been setup to disregard?

Steve.

 

@Nick201
What number of printed sheets leads to this result? Are you using non-stop paper feed?
With very long print runs there is a "small numbers" effect when an excess of 0.01 leads to a serious change in the parameters.

 

Can i ask why ?

 

A further thought.

In job-prep when you've selected printing material as uncoated, measured the paper white and then confirmed the job onto the press, just double check the uncoated setting is actually being sent to the press, and it isn't showing coated in the printing material tab.
As this would lead the Inpress to put too much ink on the sheet trying to see what it would expect to see for coated stock.

Inpress running too much ink coupled with the vario effect on the dampening roller could quite easily lead to a build up of excess ink along the back edge.

As you said, with vario turned off you don't see the effect. Although it would still be running with too much ink.
This would also explain why you would have no problems when running on coated stock, as it would match up to the stock type entered in the printing material menu, and run at the correct ink weight.

Steve

 

Looks to me like you're running a little washed out on both ends. The scum line should be even across the entire width of the plate even when printing on smaller side to side sheet sizes. Generically speaking.... either the metering roller needs to be run more parallel if your press is equipped with a skewing adjustment, or.... the crown of your roller needs to be changed, or.... you need to use your air curtains if so equipped to control dampening on the ends.

 

Reduced # 1 ink forum on both units and the scum lines instantly returned to normal. Set the roller at a 3 instead of a 4.

Two more issues to fix and and she will be like a normal press!

Thanks for all the ideas!!!

Nick

 

Form rollers bouncing too much in the gap will cause that issue, but what puzzles me is "why is the hard line not extending all the way to the edges???" Might want to check the diameters of form rollers on the edges compared to the diameters closer to the middle. What you would more often see is form rollers with swollen edges as opposed to shrunk edges, just because the oscillating action of the vibrators coming into contact with the rollers often build enough heat to cause swelling.

 

@Nick201
Good work!