Random spots showing up

[JDMFUK]

We have recently started seeing spots showing up on press sheets in random places. They are very small but often, when the show up, they are made up of multiple colors in the exact same spot on the sheet. When this happens most of the time the pressman can use plate cleaner to fix the issue but sometimes he has to use image deletion to remove the spot.

We are using Fuji LH-PJ plates in a Screen 4000 platesetter. The press is a Heidelberg SM-74.

Thanks in advance for any help.

[Erik Nikkanen]

We have recently started seeing spots showing up on press sheets in random places. They are very small but often, when the show up, they are made up of multiple colors in the exact same spot on the sheet. When this happens most of the time the pressman can use plate cleaner to fix the issue but sometimes he has to use image deletion to remove the spot.

We are using Fuji LH-PJ plates in a Screen 4000 platesetter. The press is a Heidelberg SM-74.

Thanks in advance for any help.

I have heard about something like this on this forum. It was related to static electricity in the plate making process or in handling. That is if it is not coming into your plant that way. Just a thought.

[BeauchampT]

It definitely has nothing to do with the press. For the marks to be the same plate to plate it is likely, like Erik said, either the plate making device, or processing.

However, that said, one plant I worked at kept getting a strange mark on all plates for weeks. Turned out it was something wrong at the plate providers plant that had initially caused it. I would say that if you can't figure exactly where it is coming from in your process, contact your provider and see what they can offer as a solution.

[couriergraphics]

could also be a plate bender. Can you see the plate polished in that spot or does it look like an imaged spot?

[Brer]

Are they always there from start up? Or do they show up though the run? If they are there from the start put your lupe on them. Do they look like image? If so, Its your plates. We get them some times from a dirty processor. If they show up later in the run it could be paper junk sticking to the plate on the firs unit then transferring forward. We were getting this and upped our fountain solution just a little bit and it helped.

[SHELBY]

sounds like a bad batch of plates to me! open up a new batch and try them, if that dont work call fuji and get some new ones. Kodak is famous for this problem. Its not the press if its spots. So hmmm pre press ??? trust me bad batch it happens. my 2 cents.i know you said fuji plates but about 10 years ago kodak had the same problem!. they are both gangsta's

[otherthoughts]

Load one of the plates into the platesetter rotated 180 degrees from the others in a 4 color set. If the spots rotate 180 degrees with that plate? It would suggest that the plates have a problem.

[akalaray]

We use the same plate and have experienced the same problem. The fix was in the processor, the plate was not getting gummed or finished correctly. Check the quality of the gum, the amount being applied and the pump.
Worked for us and anytime they reappear it's in the finishing.

[cmac617]

Been in the ink/paper biz since 60's....small little dupilcators to 6/c wide format...have seen/heard this lament before. #1 check water systems...any contamination from wash-ups or paper dust collecting or fungus growing in the system causes water to carry particles to ink/water ductors to plate to blanket...
Just spent the last 3 hrs cleaning water fount. trays, hoses and flushing chiller on a small ABD 4995 for this very reason.
If the dampening system be crudy so will the sheet be...

[Kaoticor]

You can try cleaning your drum on the plate maker. If the marks are consistently in the same spots, I would start there. Make sure to use the right cloth and not leave any debris, or you will have even more spots!