Stripes on the printing plate

[Martin_85]

Hello,

please, do you, someone, any idea, what is wrong? We have Harlequin RIP, CTP Lüscher and dry-offset technology. These stripes are on the printing plate where we have the pattern for example from 2% to 100%.

 

[Red_Right_Arm]

Are these plates made by layering off a carbon mask?

 

[Martin_85]

Red_Right_Arm: Yes. Have you any idea what is wrong? Or it is normal?

 

[Red_Right_Arm]

Red_Right_Arm: Yes. Have you any idea what is wrong? Or it is normal?

We make CTP flexo plates that are lasered off carbon masks. We've seen something like this happen when the laser starts to lose power. It happened when the filter stopped working and the dust particles were starting to cover the laser. It happened when the laser just started wearing out. And it happened when the laser went out of focus and the energy wasn't as pinpoint as it was supposed to be. When this has happened, we slow the laser down giving it more time to put down the energy. If slowing the laser down makes the problem go away, we know that's what's causing it, and we call to have it serviced.

So, I imagine the processes might be slightly different, but this might be a good place to start looking as a cause.

 

[nelly]

Hi, when my screen CTP did something similar it turned out to be dust on the lens and dust on the spinner mirror thing. The long mirror glass lens inside the imagesetter. Engineer cleaned it all up and cleaned the mirror spinner in there too. All cleaned and was back to normal.

 

[Slammer]

A weak laser would be evenly weak or blotchy at best and, depending on the CTP of course, the machines internal settings would either adjust to compensate or at least give some form of warning, dust or other debris in the path of the laser would not be so regular and also depending on the CTP the blowback sensors would start screaming, then if any spinner was going blind it would be visible as a gradient from one side of the plate as the sintered mirror would collect dust on the edge in spin direction. As far as I can see at first glance and from the pictures it would seem more mechanical, take a look at your post imaging.