Bad scumming on edges of plates y,m,c,

Hi all first time post,i am operating a 4-col cd 74 2004 , and having continuos probs with scumming on the plate edges of all cols except black, roller settings are all good ,increase in water tends to wash out the print , alchohol is at 9% ,roller temp at 23 , conductivity at 1540 . I am in Japan and cant commincate with the other guys to well but they make roller adjustments on a daily basis and it doesnt fix the problem. all 4 other presses in the factory are o.k. another issue on the press is having to adjust the sweep % of a newly loaded job sometimes by as much as 7% it seems to always have to be adjusted down,again all other presses do not encounter the same issues. Any advice would be great .

Cheers

Dave Ross

 

if you swap the inks in the units does it do the same thing? check the rider rollers in the ink train and the stripes of the forms to the oscillators.
try a little binding varnish to stiffen the ink and see if this helps. this will change your tack some so watch out for how the ink lay downs on the following units.

 

Had a similar problom...turned out to be the helper mixed the fountain solution wrong.

 

Also, sometimes depending on the ink or etch when you get running the inks start to run "hot"....thats just the ink catching up to the water from the make ready. Happens less as bad if you run the water in non integrated for every job, and use integrated for metallics or heavy PMS colors.

 

Check your rollers for flare/core separation at the ends. Turn roller end over end and re-install and see if the the problems worsens from one side to the other. Reset your rollers (water/ink) going 1mm tighter to the ossicilator and 1mm less to the plate. This technique is presented in some roller diagrams that Heidelberg has on their website in publication #3 Profitips

 

Does it still happen if you put the Black in one of the units where you are having the problem?

Please also just check if the crown is correct on the affected water pan rollers. You could maybe have to much squeeze on the end causing the scumming.

 

if all the roller settings seem fine and your crown is correct I may try a different set of inks.....seems odd that 3 units have the same prob and everything is set correctley....

 

You may need some new dampers and it looks like you may need to change the characteristic curves to alter the amount of ink loaded from the pre-press link.

 

Thanks all for your feedback, at present i am on a weeks leave but will put forward some of the ideas when i return and let you know how i go, on the charecteristic curves i am not a 100% sure on them i have read the manuals ,but anymore info on them would be helpful as from what i read i to think it maybe causing color issues .