"Scratches" on plates?

[ssutton503]

We are a commercial print shop running Goss Community presses. In the last 3 months we have been experiencing what I will call "scratches" that print on the finished product. On a newspaper page, the scratches run top to bottom and are hairline thickness. I have attached 4 photos we took with a magnifying camera. Sometimes it looks like an actual scratch from top to bottom and other times it looks like the plate was beat with a piece of chain. We have only seen these scratches on cyan and magenta units but they have appeared on multiple towers. I have now seen scratches on plates from 2 different manufacturers (our regular plate is processed and the new plate was "No-Process"). The scratch will not be on the plate at the beginning of a run but develops as the run goes along. It might show as early as 1000 impressions or it might take longer.

Anybody seen anything like this? Any guesses as to the cause?

 

[Cornishpastythighs]

As you say only the cyan and magenta units are affected I would hazzard a guess that you have some damaged inking rollers in those units. I have seen pieces if metal imbedded in rubber rollers causing scratches in the machine direction. Your platemaking process doesnt care about cyan or magenta just plates so first I would do some roller maintenance on press in those two print units.

 

[Alois Senefelder]

Hello ssutton503,


1)First step do as "Cornish" suggested. 2) Are the Scratches in the same place on the Magenta/Cyan plates, do these Scratches appear repeated "X mm" apart on the same Plate?


3) When you remove the Plate Inkers check for any Debris Build-up on the Cross Tie Bar in the Inking Roller Train.

Regards, Alois

 

[ssutton503]

Thanks for the responses so far. I forgot to mention that this issue has (for the most part) been sporadic. You might get scratches on this job but not necessarily the next. I do have a unit that has put these marks on a plate on 4 consecutive jobs (with some marks being in the same location) but other units that have created the marks will not show again for quite a while.

Rollers was an early guess for us as well and the pressroom has changed rollers but we got the marks showing even after changing rollers. And, if it is rollers, how notable that we only put the damaged rollers on the cyan and magenta units.

My best guess (and I work in the prepress so what do I know! ;-O ) is we received a batch of contaminated cyan and magenta ink. This ink damaged the rollers (pieces of metal getting embedded??) and even after we changed the first damaged rollers, the pressroom didn't dip out the contaminated ink (not knowing it might be contaminated) or continued to use the bad ink from the buckets we use to transfer ink from the large totes to the press.

Thanks again for your suggestions.

 

[CSF]

For the plates you put through the processor, try Tuff Stuff, a scratch resistant finishing gum from Applied Chemistries. Works exceptionally well. https://appliedchemistries.com/plate-finisher/
Determining and fixing the root cause is best, of course, but this product provides proven results.

 

[Alois Senefelder]

Hello ssutton503,


Have you checked the plates before mounting on the press? Your pictures show damage to the "Anodizing Layer" exposing the Aluminium, Ink would not cause this.

Obviously, the damage caused on the Press.


Regards, Alois

 

[ssutton503]

Alois,

Yes, plates are checked before leaving the plating area - have not seen scratches. Scratches develop while press run progresses since we have seen no scratch printing at beginning of run but later in run you have a scratch printing.

 

[Cornishpastythighs]

So ssutton did you solve this problem by changing inks, have you involved the ink supplier and requested they do a full analysis of your Magenta and Cyan inks. This should result in a claim for downtime caused by their products. Keep us up to date. Cheers

 

[ssutton503]

"Changing inks" would be up to our pressroom manager but I don't think we have switched. We may have received a new tote but I can't say for sure nor do I know if an ink analysis was ever requested. Our current plan (since the problem is not solved) is to put the cleanup trays on the units, give all the rollers a good cleaning and do what we can to keep the ink supply clean - i.e. - dip out old ink, clean ink trays, get new buckets for transport and see what happens. I have a feeling this will be one of those issues that quietly goes away and you never really know what was the root of the problem.

 

[turbotom1052]

Are your presses equipped with an auto plate feature? If so try over riding the auto plate, and mount the plates manually to see if it makes a difference. If your issue resolves itself with manual plate mounting then it sounds like your auto plate needs a bit of maintenance.

 

[ssutton503]

turbotom, Appreciate the thought but no, we do not have automatic plate hanging.

 

[turbotom1052]

have you removed and inspected the safety bar that is in the nip between the plate cylinder and blanket cylinder?

 

[ssutton503]

Ultimately the "scratching" issue turned out to be caused by either the ink transfer rollers or the waterform roller. Not sure which since we changed all rollers that touch the plate at the same time. My guess as to what happened is that little pieces of metal (from the ink perhaps?) got embedded in one of the rollers and as the press rolled around, the metal bit would create an indentation in the surface of the plate. Because the plate circumference and the roller circumferences are not the same, with each revolution the mark would be in a slightly different location around the plate. After enough revolutions, a complete line would have been formed. A small piece of metal might have taken 10,000 revolutions to make a line that printed but a larger piece of metal might have do it in 3,000 revolutions.

As always with forums like these, I want to thank everyone who contributed ideas and suggestions.

 

[Cornishpastythighs]

Good to hear you solved the problem and thanks for getting back to the people in the forum with your findings. all too often people ask for help then you dont hear hide nor hair of them again Cheers

 

[ssutton503]

In a previous post (quoted below) you stated that you changed the rollers, and the problem persisted?

Alibryan, Someone is paying attention!
Yes, rollers were changed and the problem persisted. Again, my best guess as to the why would be that the original set rollers got pieces of metal embedded in them and then the rollers were changed. The 2nd set of rollers again became embedded with metal pieces. Keep in mind that at the time we changed rollers (and in fact to this day) we did not know the cause of the scratches. Personally I think we received a batch of cyan and/or magenta inks (these were the units that showed scratching the worst) that had metal shavings in the ink. Some units we run more than others and they showed scratches worst. Even after we used all the contaminated ink from the totes, we probably still had some contaminated ink in certain fountains and/or in the buckets we use to transport ink from the totes to the press thus causing re-contamination.

I hope I am not slighting our ink supplier by believing we received contaminated ink. I certainly have no proof. It just seems like the most likely scenario to explain what we saw.

 

[ssutton503]

Hopefully the problem wasn’t/isn’t metal shavings from the plates, themselves. I think you can guess what that might mean.

Had the problem stemmed from the plates, we would have seen the problem on more than cyan and magenta units. We run more black plates than any other color and we never saw the scratches on a black unit.

 

[Alois Senefelder]

ssutton and alibryan and fellow Lithographers,



99.9% OF Aluminium (Swarf) embedded in the Inkers/Plate Dampeners originate from poorly cut Plates.


Regards, Alois

 

[ssutton503]

ssutton and alibryan and fellow Lithographers,



99.9% OF Aluminium (Swarf) embedded in the Inkers/Plate Dampeners originate from poorly cut Plates.


Regards, Alois

I won't argue your point. I can say that we buy from a reputable plate manufacturer and we remove slip sheets by hand so we would notice if edges felt rough. I can't believe that the anodized layer of the plate came of in hairline, perfectly straight lines. And again, if it were a plate issue, shouldn't we have seen it manifest itself on a black unit? I realize the cyan and magenta inks may have the highest tack and there may be a chemical in those two inks that attacked the plate surface but it still seems more likely to me that the roller contaminate came from a different source.

 

[Alois Senefelder]

Hello ssutton,


The Evidence is "Staring you in the face" and on the Plate ! ......... just scratch the plate anodizing some where by hand - IT will ink up and Print.

The scratches appear in the same place everytime when ever you change the plate


Regards, Alois

 

[Rickyo]

I would put plate on , no impression inch around have some with light watching from Back side check water forms , blankets plate bender ?