Spots on Sheet Lithrone 28

[Kaoticor]

Machine: Lithrone 28
Problem Description: Getting what appears to be oil spots on the sheet.

Already did the usual thorough cleaning, checked the bearers for flinging oil, checked blanket wash cloths to make sure no rubbing. This is not a problem that is all the time and not always on the same job. It comes and goes and sometimes we won't notice it for quite a while then it will appear. Attached is a digital microscope picture. Any comments or thoughts as to what this might be?

After some investigating, you can definitely see these spots on the unit 1 impression cylinder, like it is being sprayed or flung. We brought it up to full speed then stopped, and the spots were visible on the sheets through unit 1. They seem to be visible on the unit 1 transfer cylinder as well. They are not visible on any others. Can't really seem to find the source. What is wierd though, is when the spots appear on the sheet, they will appear at the same spot for several revolutions. So it looks like a spraying, with the consistency of a print problem.

One other detail is after a morning startup, we didn't notice anything. About 2 hours in to the run, we had to shut down to make a small delivery adjustment. We were down 5 minutes, went right back up without changing anything else, and this problem was present immediately. Not sure if related but definitely seems a possibility.

Thanks in advance,

K

 

[Lukew]

Have you checked that your fountain solution tank temp is correct and your not getting condensation under the fount pan, which could be dripping onto the sheet?

 

[Cornishpastythighs]

What chemicals do you have in your press.
Auto blanket washers (spray or cloth)
Auto wash up (solvent and water)
Oil.
ink
grease.
Fountain solution
Could you have a leaking air line that is blasting one of these chemicals onto your plate or blanket.
could you have oil that is leaking through some seals.

Without actually seeing the issue first hand its all gueswork.

 

[Kaoticor]

We checked for the condensation, but didn't seem the likely cause for this one.
I think you are right cornish, it might be one of the seals is worn on that side or an air for the forms leaking. We are going to take a look at it our next maintenance period. In the meantime, another person gave me the suggestion to spray lighty some roller wash on the side to help break down any oil or grease that might be built up and flinging. Seemed a little ghetto, but I think it did what we need it to for the time being.

 

[Al Ferrari]

<another person gave me the suggestion to spray lighty some roller wash on the side to help break down any oil or grease that might be built up and flinging.>

Using this method, can you localize the problem to one side of the press or the other? And, do not assume that it is coming down from above the cylinders. It could be coming up from bellow.

Al

 

[turbotom1052]

check to make sure your feeder pump and whatever pump delivers air to that area of the press isn't blowing oil onto the sheet either through any of the feeder blast tubes or any of the sheet guiding air blowers on the unit in question.