[Misc] Drum Screen Life Span?

[mixedfeelings]

Hello All,
I am curious about the lifespan of a drum screen. I have a few drums (some with about 200k impressions on them) that give a very mottled impression no matter how much I clean / soak them in solvent. When I clean them, they remain really bright for about 20 prints and then quickly revert to a fill quality with the a similar consistency as blue jeans: a really noticeable texture.

Last night I took apart and thoroughly cleaned a drum and replaced it's dented drum body with a new one. Everything is cleaned or new apart from the screen and I am still getting a terrible impression so I have isolated the problem to that.

I have also noticed that this seems to happen disproportionately to darker colors: federal blue, burgundy, hunter green all have more difficulty than brighter colors. I will need to double check the impression count on those drums

Can screens go bad?

Thanks

[Iowatech]

Re: Drum Screen Life Span?

From what I've seen, as long as the screen doen't get physically damaged it should be good for the life of the drum.
What does the ink bead look like in the drums having problems? Are you sure the squeegee rollers in those drums are operating correctly? Those are far more likely to be causing the print defects you are encountering.

[jermyth]

Re: Drum Screen Life Span?

Also how old is the ink? I've seen bad ink act very similar.

[mixedfeelings]

Re: Drum Screen Life Span?

The ink is brand new - made this year (a special order of Orchid)

As part of my drum body replacement, I also soaked the screen in solvent to see if i could free up any issues. There is some damage on the spot where the old body was damaged:
Photo Dec 20, 4 46 50 PM.jpg

Ironically - that area is the only part that is giving a proper impression. The "good" part is garbage.

Photo Dec 23, 4 53 47 AM.jpg

[Iowatech]

Re: Drum Screen Life Span?

How many prints did you run on that drum after you cleaned it out? Riso recommends running a ream of paper through the machine to properly ink up "inkless" drums, although I've found that 150-200 prints will do the trick most of the time.

[mixedfeelings]

Re: Drum Screen Life Span?

I thought it might just be slow to ink at first, but ran easily 1000 copies at 5 density.

I'll have to open it back up to double check the bead next...

[Iowatech]

Re: Drum Screen Life Span?

Just curious, what model Riso do you have?

[mixedfeelings]

Re: Drum Screen Life Span?

This is on an RP3700

[Iowatech]

Re: Drum Screen Life Span?

Any luck?

[mixedfeelings]

Re: Drum Screen Life Span?

Some great success!

I took it apart again, and while the bead seemed fine, I widened the gap by a notch just to be safe (though, it is only 2 notches from the end so i am not sure if "safe" is the word). I also replaced the screen with a cheap non-OEM screen that I had lying around.

The fill quality is MUCH better - though I am not sure if it was the gap widening or the screen replacement that did it in the end - i should have tested it with the old screen after making the gap adjustment.

I will say that these white (rather than silver) non-OEM screens are worthless, though. While the fill is generally much, much better, the screen itself has a "wood grain" texture that definitely leaves its mark on the impression. it's particularly distracting to have these wavy lines on photos. At least I can use it for text until I find a source for OEM screens. Does anyone have any?

Thanks for the gap suggestion, i am sure that was part of the puzzle.

[Iowatech]

Re: Drum Screen Life Span?

As for the screens, you might check here:

http://www.copytechnet.com/forums/for-sale-trade-or-wanted/