DPM 2340 Scratches on Plates - Can't figure it out.

[jpfulton248]

I'm getting vertical scratches on my plates. They are very fine, tend to be near the bottom of the plates and are so numerous they can't be counted. The problem seems to come and go in terms of severity but when it comes we'll see them on maybe 30 plates in a row before we start to notice that the problem has gotten better. The scratches are not identical on every single plate but tend to be quite similar to one another. I'm going to outline the diagnosis steps we've taken and the our experience trying to get rid of them.

Diagnosis:
1. Ran a plate with exit conveyor thing removed and guided the plate out of the unit by hand so that it wouldn't touch anything past the stabilizer squeegee rollers. Scratches seen on plate. (not the exit conveyor)
2. Removed stabilizer rack and ran plate. Plate drops into stabilizer bath. Check plate and find scratches on plate. (not the stabilizer rack)
3. Removed activator rack, flipped entrance thing with segmented rollers forward, opened doors to DPM (and shoved cardboard into the "doors open detecting switches"), turned off all lights in the room, ran plate. Plate comes down the vertical conveyor I grab the plate and gently guide it down into the activator. Let it sit in activator bath for a few minutes. Pull it out, turn lights on, check plate. NO SCRATCHES ON PLATE!!! So the determination is that the problem is the entrance thing or the activator rack.

Fix attempts:
1. Thoroughly clean everything. Never really got a good training on this so any input much appreciated. Drained chemicals, filled with a little water, drain, wipe down with paper towel. Disassemble racks. Rinse with water. Use CLR on anything that is submerged in chemicals. Rinse. Dry. Apply polishing compound (purchased at O'Reilly's) with damp applicator pad. Buff with lint free towel. Re-assemble racks. Fill chemicals. Done.
2. After above cleaning scratches still persist but are ever so slightly less severe.
3. Problem becomes less severe for a little while for seemingly no reason.
4. Problem becomes very bad again and I try just cleaning/polishing the activator rack and the entrance assembly without replacing chemicals and without cleaning stabilizer rack.
5. Scratches ever so slightly improved but mostly appear unaffected.
6. Desperate post on printplanet.

Thank you. Really hope someone can help.

 

[gregbatch]

JP, you don't say what material you are running in the DPM, but we recently had to return several rolls of SilverMaster because they had winding scratches on them. Came and went like you said. So, it may not be your machine at all.

 

[jpfulton248]

We are using Silvermaster 12 inch 7mil paper instead of the poly which I think is probably what most people use.

Our scratches aren't really noticeable in the non image area of the place even when looking under a loupe. It seems that the image is getting scratched off but it's possible they are scratched before the activator and it's just that the plates are damaged in those places so the image won't "stick". Also, ours appear to only or primarily occurred in the bottom half of the plates (18" long).

Describe your scratches...

 

[VladCanada]

You have to inspect the whole plate track from the Imagesetter to Processor. Dried activator on some places (after splashes) works like sand particles.
Wet rug plus water should help you.

 

[gregbatch]

Barely noticeable super fine and showing up as voids in the image area. Drove us crazy looking for the cause. Then we finally had to load another roll of material and the scratches instantly vanished. The next roll had scratches and we immediately replaced. No scratches. Not only that but we've had rolls that were light struck at various points throughout the roll. But if you have scratches that don't seem to change position it is your machine. Lightly buff every surface the plates touch with a Scotchbrite pad.

 

[jpfulton248]

Barely noticeable super fine and showing up as voids in the image area. Drove us crazy looking for the cause. Then we finally had to load another roll of material and the scratches instantly vanished. The next roll had scratches and we immediately replaced. No scratches. Not only that but we've had rolls that were light struck at various points throughout the roll. But if you have scratches that don't seem to change position it is your machine. Lightly buff every surface the plates touch with a Scotchbrite pad.

Wow. Thanks for the info. Was your problem on poly or paper? We just reloaded plate material 2 days after I started this post and we are dealing with the same thing but these plates were probably ordered around the same time as the last couple rolls we just went through (we don't go through plates very fast).

 

[gregbatch]

We use poly, but I can't imagine the winding practices being much different. We had, I think, 3 rolls in a box of 6 that were affected. The original roll, and two after that. You should have an emulsion number on the packaging that would tell you if they are from the same lot.

 

[jpfulton248]

Were your scratches showing up the entire length of the plates?

 

[gregbatch]

It varied. Generally, no. The first roll they appeared toward the end. The second roll they were more middle to top. I think it's just where you happen to hit it and then it moves a bit as you go through the material. It also depends on what plate lengths you run.

 

[jpfulton248]

Well, we swapped in the new plate material that we just received yesterday and no difference in terms of scratches. I'm thinking it's something in our machine causing the problem.

 

[gregbatch]

Yep. Sounds like it. I had to bring up the possibility because I know we were beyond crazy trying to figure out where the scratches were coming from. Something that has worked for us in the past to kill scratches in the machine is to run several wash-up sheets from the press through the machine. We filled the stations with hot water (distilled is best) and ran the sheets through. They are thick and rough and often will knock down anything that is contacting the plate.

 

[jpfulton248]

Thank you very much for mentioning it though.

 

[Lee Ornati]

Some times there can be a build up of silver crystals, which are very sharp, on textured metal turnarounds and guides. Sometimes you can not see it but it is there. This can be cleaned with auto polishing paste. This comes in a hockey puck shaped can. This polish has grit in it so it has to be washed out completely and rinsed. You can use this with a rag and some strong scrubbing and it will come clean. Also look at activator temperature. if this is too high it can soften the emulsion. It should be about 86f degrees. If it goes over 90f it can be a problem. Check it with a thermometer, as the probe in the machine may have wandered.

 

[jpfulton248]

Thanks for the tips. We actually already have been using polishing compound (which we got at an auto parts store). We only use it on parts that are submerged in activator or stabilizer. Have not checked temperature yet.

 

[jpfulton248]

For anyone that might come to this thread also looking for a solution: We solved the problem. It was stupid. We were too cheap to buy the replacement segmented rollers for the processor entrance assembly (that leads into the processor). Instead we took the shafts off, cut the old rubber tires off, cut up a rubber hose into segments to create "tires" and glued those makeshift tires to the old shaft. Did that on both shafts. It worked for a while. There were two problems. 1) The epoxy we used stopped holding on some of the tires so they were slipping, 2) The hose we used had a very minor flat side so as the two roller shafts would turn they would kind of bounce in and out. I finally noticed when I was watching the machine and I noticed that the metal guide on the processor entrance assembly was ever so gently moving in and out. We bought the real rollers from Presstek and all has been peachy for 6 months.