Spots on printed sheet?

Hi all, first post here.

I'm running a Komori Lithrone 40" with RP.

We're getting spots completely at random, any size but never more than a full stop, anywhere on the sheet and for any amount of sheets, from 10 to 100 hundred before they gradually fade away.

We have checked everywhere, there is no visible signs of dripping (from wash up nozzles) or anything.

They appear to create white spots if they land on image area or a colour if it lands on a non printed area.

Any ideas? Thanks.

 

Could be oil from seals.

 

Hi we were getting a build up of oil on the back cylinders but that didn't solve the problem unfortunately.

 

Could it possibly be excess blanket wash solution flicked onto the the transfer cylinder?

 

I have also seen this caused from the lead edge and/or tail edge of the plate due to plate wash solutions.

 

I'll check this out when it next occurs thanks.

 

This is what I think/thought it was, and I cleaned both edges, also those of the blanket and it returned less than 1000 sheets later.

 

Could it be two different issues? White spots in the printing sounds like oil or some oily substance, but specks in the non image areas may be something else such as dust or grime... probably more of a solid substance. We've had stuff like that from slinging off of the back cylinder, leaving the white specks, but you've checked that.

 

we have a 2004 LS 640 that we started to get spots on around 2010 chased it for a year tried everything...... in 2011 we put in a LS 840 (new) and found that Komori had installed mist guards over the cam followers, then the light went on....... asked Komori about this and they said there was an up grade for the 2004 press. $25,000.00 later and no more oil spots. It seems that at the speed the bearing turns it was misting ANY oil/anything on the cam and with just a small amount air movement.......white spots on the sheet.

Bill