Banding/Ghosting

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Banding/Ghosting

Postby DMan » Mon Apr 12, 2021 2:48 am

Hi all
getting a typical issue of banding /ghosting during printing.
some dark areas in print appear (horizontal staright ) in every ups although the anilox visibly from outside is absolutely clean and fine.
I see it in regular ups .
I see the descriptions related to blade chatting on anilox, banding on anilox and also ghosting but cant make out which out of them is the real cause.
Not certainly gear marks . Its from the anilox because i see the same effect on a different station also.
Can you all provide some inputs for the same.
warm regards
DMan
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Re: Banding/Ghosting

Postby Frank Burgos » Mon Apr 12, 2021 9:02 am

Hi DMan,

Any chance you can upload a pic for us to see?
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Re: Banding/Ghosting

Postby DMan » Tue Apr 13, 2021 10:59 am

Pls find below the URL.
I hope it opens.

https://ibb.co/8NbgsYm

Dman
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Re: Banding/Ghosting

Postby longtimefan » Tue Apr 13, 2021 11:04 am

Hard to tell from that picture
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Re: Banding/Ghosting

Postby Frank Burgos » Tue Apr 13, 2021 11:21 am

Do the marks correspond to images elsewhere on the plate?

Ghosting is when part of the plate takes ink out of the anilox and the area of the anilox that has ink taken from it doesn't replenish completely before transferring to the solid area, so you see the ghost.

If not ghosting, you may be experiencing bounce. Are the defects horizontal bars across the solid? Difficult to see.
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Re: Banding/Ghosting

Postby DMan » Tue Apr 13, 2021 11:47 am

Yes..The bands are across the solid. From start to end.
But if its ghosting, I should get a lighter tone in that area ? Am i right ?
whereas in this case, I get a slight darker tone across the Banded area.
Could it be an anilox TIR or some sort of imbalance which hits the blade . Just a guess.
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Re: Banding/Ghosting

Postby Frank Burgos » Tue Apr 13, 2021 8:10 pm

Lighter tone, yes.

It's sounding more and more like bounce. If that's the case, running slower might clear it up, even if only a test.

Some designs introduce more bounce than others, especially large solids. Lower speeds and softer tape can help.

If you can get a clearer image, that would be great
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Re: Banding/Ghosting

Postby just Andy » Wed Apr 14, 2021 9:54 am

Hi Dman

From your pic I see a hand-cut over on the top; I assume it's a butt-joined and continuous plate and the print direction is from top to bottom. If that's the case then as Frank mentioned, that's not likely to be ghosting (ghosting in that instance would be a light image of the butt-joined clear gap).
I have only seen that sort of band once but I don't think it's your case. Ink left in the chambers without rotation, so the chambers had closed and ink remained on the one section. After starting up, the ink had left a slight band (the size of the gap between the blades). However in your case, you have two sections, not one.

In your first post, you already mentioned it occurs on different stations. My one suggestion to bounce is: if possible, move it to another station. As a machine gets older, there will certainly be stations that are worn differently to another. But if it's a continuous print, you shouldn't have too much bounce.

If you highly suspect it's the anilox TIR, have you tried putting another anilox?
Alternatively is the doctor blade tip style or thickness too thin making it flimsy?
If chambered doctor blades, is your air pressure sufficient for holding the chamber down?

I hope those can be of some help, cheers
Andy
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Re: Banding/Ghosting

Postby iteachflexo » Thu Apr 15, 2021 11:59 am

What is the material you are tinting? Film or paper? Are you using plate material wrapped around a print cylinder to tint? Why not use a tint sleeve?
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Re: Banding/Ghosting

Postby lavoie » Sat Apr 24, 2021 8:08 pm

I too see the hand cut plate. To me, it looks like an anilox rewetting issue or a backing issue.
Rewetting issues occur when the plate cylinder/sleeve and the anilox are too close in diameter and the ink laydown is heavy not allowing the cells to fill to an even capacity. If continuous print is the goal for that blue, try going up a few sizes on the plate cylinder/sleeve. Most presses allow you to run different sizes simultaneously.
If it is a backing issue, personally I prefer a mid hardness range .020 backing for solids. You could try a .060 if you have the accommodating cylinder/sleeve. I warn you though, printing on .060 is like printing on a mattress but you can go in more on the impression more than normal.
If it is a bounce issue (not as likely on a continuous print plate). When bouncing occurs, There is generally a visible low spot when the anilox bounces out and a corresponding high spot when it bounces in. Yes slowing will help that issue. So will larger diameter cylinders/sleeves. How fast are you running? Sometimes going faster will smooth out the bounce.
Zooming in on that image, that looks like a fairly straight line that is darker. Does it repeat or is it more random? Backing splices and the end of the backing roll can cause things like that.

For a better controlled resolution, I would replace the backing, change the dr. blades and seals, reset the chamber pressure and make a new plate. Then I would eliminate one issue at a time like speed, deck location, cylinder size etcetera.
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Re: Banding/Ghosting

Postby JRO » Fri May 21, 2021 10:33 am

We had this problem on solid and we minimized it by using soft sticky and run faster. It does not really go away but it lessen very significantly. the number of streaks became lesser and the distance per streak becomes far.
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Re: Banding/Ghosting

Postby DMan » Wed Jun 09, 2021 3:52 am

Hello Gentlemen

Sorry didnt update you all on the progress.

The matter turned up something else .

Attached are two pics. Kindly zoom on other one to have a view.
Ink -UV
Observations : on all speeds (slow - fast)
1.white streaks visible on anilox Dia repeat (74.8mm) . With plate dia size 64mm, visible every 235 mm, With plate dia 96mm, visible every 470mm
2.when the ink chamber blade makes a pressure contact with anilox, after a few rotation, a sound comes and i see a faint horizontal impression on the anilox. This is the same impression on the actual print.
Please note the anilox runs freely as long as it is not in contact with doctor blade.
The TIR of anilox while running on press is 6 microns.

Anyways I understand the problem is from these two aniloxes since other anilox work fine.
Can someone tell if something mechanically is wrong with the anilox or some engraving patterns ,depths to be verified. The two are new anilox and not used.

Warm regards
Dman
Attachments
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Light Area--Pls zoom
WhatsApp Image 2021-06-09 at 11.29.31.jpeg (98.29 KiB) Viewed 142 times
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