scum/catch up

Hi
I run a 3304ha about 4 years old I've always had a scum/catchup problem on the yellow deck. I've done the obvious and checked the roller settings, the water form and metering roller are new. I run about 8-10% alcohol and Varn Aquarius font which I've tried at 2-5% to get my PH to 4-5, the conductivity reads about 13000-14000. Yet the yellow (I've tried different brands and Aquacheck binding varnish) scums and catches up after a few hours of running, increasing the damping only leads to water dripping and water streaking, the other colours/decks do it but to a much lesser/ managable degree.
Any thoughts Mike

printer@bigpond.net.au

 

Are you running the yellow in the last unit/4th unit?
It could be that the heat from your dryer is having a scumming effect on that unit.

 

Thanks yes I am running the yellow on deck 4 but I don't have a dryer fitted. As soon as the damper hits the plate it inks up (metal plates) and after about 50 revolutions it cleans up but by then water is dripping off the cylinder. no problems with other colours. I 'm running 8% alcohol and upped the PH to 5.5/6 today with a small improvement. It's got me beat, it gets worse as the day heats up.
Thanks for the input though.

Mike

 

It sounds like somewhere the roller pressure are off on the damps.
Check to see if the stripe to the plate is good.
You said you put in new rollers. Did you back off all the adjustments first before putting in the rollers?

Don't know what kind of damps you have. If it isn't hard to do. You might want to swap the rollers with another unit and see if anything changes.

Also, are the damps run by air pressure? Maybe the 4th unit doesn't have enough air to it??

 

Increase the % amount of fount solution you mix. We recently had the same problem due to increase in temp. within the factory. All roller settings were spot on. Even tried new rollers. Checked all chemistry in platesetter. Our symptoms were exactly the same - yellow catching/scumming up, less so on the other units. I would run a minimum of 10% fount.

 

yellow catch up

Just crossed my mind is the unit damp water warmer than the 1st three. or water level in the tray low due to poor flow?

 

you mightwant to change color rotation,k,c,m,y, to cmyk and if your dampner is taking 50 rev to clean up you got a mechinal setting(s) out of adjustment

 

Does the yellow look emulsified on the rollers while your running? Even though the metering is new, I would check the durometer and make sure it meets specs. On my Akiyama it is around 25d. It sounds like the settings are out or the water isn't dropping to the plate correctly. I would make sure the water form is hitting the vibrator. Sounds like your not putting water to the plate until the water get's into the roller train, and when the ink forms drop it starts to clean up. Also make sure the metering is being driven by the motor and there is no slipping going on, ex.gear on metering roller. Make sure water form is engaging to the chrome properly as well as dropping to the plate. I'm surprised your running alcohol, I would try a alcohol substitute which EPA wants you to run anyway. If you spend some time in that unit I'm sure that you will locate the problem.

Good Luck
jtdoonz