Banding Plate or Press Issue?

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Banding Plate or Press Issue?

Postby SambaFlexer » Fri Dec 29, 2017 2:03 pm

Please check out this link...

https://imgur.com/a/GU2eL

I work for a plate maker and we have a customer saying he's tried everything to get rid of the banding you see in the gradients. They said when they tried a previous version of the same Black plate it ran fine.

Both this and the previous were made at the same 175lpi and the same angle.

So can this be a plate issue?
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Re: Banding Plate or Press Issue?

Postby Gorilla Printer » Sat Dec 30, 2017 6:44 am

Hi
If that banding is travelling ,in other words ,the bands don't form exactly in the same place on the image then it's probably coming from the anilox.Have a look at the anilox's surface/sheen while job is running.You will see banding if it is there.
That's my best guess right now.

Cheers
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Re: Banding Plate or Press Issue?

Postby SambaFlexer » Sat Dec 30, 2017 11:17 am

Weird thing is that they said they Frankenstein'd the plate by using the old one and cut in the type change from the new one and it worked fine... They're a good customer so we'll give them a new plate but I'll remember your suggestion for the next time.

Thanks!
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Re: Banding Plate or Press Issue?

Postby richflexo » Fri Jan 12, 2018 2:22 pm

Still having this issue? I wrote a response but forgot to press send when you posted.

I had a customer I said to once "we only press the banding button when we make your plates".... Needless to say, we dont make plates for them anymore.

Turns out their issue was the bearings were shot and the bushings that hold them in place. I don't know too much about narrow web presses but thats what I was told. Any wear in the anilox can also cause banding.

We were selling them DPL, they wanted DPR which is harder. They wanted those plates because their previous supplier gave them those and claimed never having this issue until using us. Even when we gave them DPR, it didn't help.
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Re: Banding Plate or Press Issue?

Postby SambaFlexer » Sat Jan 13, 2018 5:47 am

I guess we'll never know what caused it this time...

Love how some customers first reaction is to blame the plates!
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Re: Banding Plate or Press Issue?

Postby barb » Wed Jan 24, 2018 12:37 am

We have this kind of issue in two situations (as far as I noticed and was informed from our press operators):

1. Older (narrow) press has some worn out format sleeves (plate cylinder) and as some of them have sligthly detached from the core it causes the cylinder to bump and cause banding
2. Both (narrow and wide) presses if the speed and pressure are too high - these types of images that have parts of full print in combination with text/blank areas cause vibrations during the press and it slams the plate as it runs

Since you said they cut the plate in to pieces maybe that helped with the vibrations or first time they screwed something up during the plate mounting.

Let us know when they rerun it with new full plate if it solved the problem!
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Re: Banding Plate or Press Issue?

Postby SambaFlexer » Wed Jan 24, 2018 8:08 am

They haven't returned the plate and I'm not going to push the issue. We pretty much just moved on. They're a good customer so we just gave them a new plate. This was the first and hopefully the last time this happened.
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Re: Banding Plate or Press Issue?

Postby flexolover » Fri Mar 23, 2018 8:03 am

Hi,
If banding line comes from same place, sure it is damaged while loading into the machine.
If it geared press, the mark may be induced by the gear damages from the particular place.
Then pl check the following if the banding line is not printing on the constant place.
1.Check the print cylinder gears and its bearings.
2.Check the tape between the plate is stuck with foreign particle.
3.Check the shaft quality is ok which engages your print cylinder and the machine.
4. If it is shaftless entry check the impression roller is free from any foreign particle.
5. Check the anilox roller gears and bearings are free rotational.
6.Check the back lash of Gears engaged to plate cylinder(Plate cylinder, anilox roller, drive gear, fountain roller gear, fountain roller swelling and impression roller gear etc)
7.Doctor blade quality and the doctor blade holder is engaged properly?
8.Doctor blade teethed?
9.Check the plate washing is ok, whether the no micro steps on the plate steps(which might caused coz of the cleaner bristles are clogged with solvent residues and the inching mechanism during washing might have residual on rollers creates in built banding -Mostly invisible)
10.Pl try it out with Thermal washed plates from dupot.
11.Change it to softer tapes which reduces the impact of bouncing.
12. Change the unit and print it and see to diagnose the same effect follows in other stations.
13. Check your pressure setting is parallel.
14.Change the material and see.
15.Calibrate your load cell if you have.
16. Call your machine guy for the inspection of the tension control system works properly.
17.Call your machine guy for the tuning of the gain values of the machine.
18. Call your machine guy for the error in mechanical syncronisation of the machine within the units.(to check or tighten the loose fits).
19.Finally if every thing is fine but if your image is random within the repeat, you may get banding coz of layout positioning..
ATB,
FL :smile:
any of the above will clear the banding !
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Re: Banding Plate or Press Issue?

Postby KF » Fri Mar 30, 2018 12:10 pm

Just a thought, in gradients/vignettes, there are only 256 "steps/transitions" if you stretch one out too far the transitions become very apparent. This is more noticeable at some line screens than others.
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