Cd102 6color+coating

Sir,
I am working cd102 6+coating.I facing problem the color going light while running,sometime after 1000 or 2000 sheets.that case I increase ink a little. Then running some quantity may 2000 sheets it will happend again.increase again alittle.the same prosess repeat many time.until reach imp may be 15000 sheets.it happening some times unit 4 or5.and six.My roller adjustment was good.and looking by eye's ink fountain roller working properly.I face long time this problem ,my machine model 2005.so pls help me solve this problem
Thanks

 

You better check your fountain solution chemistry or your roller settings.

 

Lets go back a step and determine if your pre press curves are correct. If your starting out a run with pre press curves that don't include enough dot you will be forced to feed more ink to the form to compensate for the lack of dot. This increased feed of ink, that may be outside of the window of a stable emulsion, can cause problems similar to what you describe. The increased ink required to compensate for not enough dot will as the press runs require more fountain solution. This increase in fountain solution will, as the press runs tend to wash out your images making them lighter in color. Some less experienced pressman will respond to this with more ink yet. This creates a cycle of instability that will, as the press runs get worse and worse. Eventually if will become unmanageable, forcing you to stop the press out of frustration to rinse the rollers , in order to start fresh. Inconsistent color may be in this case the least of your problems. The above described scenario would certainly cause other problems to include setoff problems, excessive paper waste, trouble in the bindery as a result of a wavy printed sheet, etc. Does the scenario I mention sound familiar to you? Do have have working for you a level of competance thats capable of recognizing these sort of trends? Im not trying to be insulting here but without competent pressmanship you will likely continue to have problems like these and others. If, in fact you do have fully competent staffing on your press, and the scenario I described does not apply then I would do as Aquazi suggested. Evaluate my suggestions first, as they are earlier in the process, and if they don't offer any insight then move on to the press. My suggestion only requires a bit of introspection and soul searching. You could do that without wasting a single sheet of paper or a single hour of press time.

 

color going down

Thank you for your replay sir,
Heidelberg engineer already reset the characteristic curves and the color going down not when I increased speed,The problem same speed ,and fountain solution using a minimum level and no need to increase , the problem some times after 10000 imp,sometime 20000 imp.No more other problem like setoff and other printing problems or during binding and my pressman have 20 year experience in offset printing and he handle same model machine 2007 cd 102 with out any problem using same material.The ink fountain roller value for eg 35 starting printing after color balancing,then color going down slowly running same speed and I increase a little by little until 40 or 45 may be reach 5000 imp or more,then suddenly coming too darker,that time go back the starting level of 35 and repeat the process,and I cannot blame my operator because he is senior but cannot find the problem from where? I hope give me more suggestions.
thanks

 

Roller setting and fountain chemistry is good,because I have another on machine same model ,using same material and everything same,problem only one machine ,color going down while running with out changing speed.It happening some times reach imp 5000 or more and that time increase the ink fountain roller value eg; 35 to 45 , then suddenly color coming darker reach imp another 5000 shts or more,and go back to actual value of 35,and repeat this process until finish the job.may 10 or more time out of 100000 imp.

 

Roller setting and fountain chemistry is good,because I have another on machine same model ,using same material and everything same,problem only one machine ,color going down while running with out changing speed.It happening some times reach imp 5000 or more and that time increase the ink fountain roller value eg; 35 to 45 , then suddenly color coming darker reach imp another 5000 shts or more,and go back to actual value of 35,and repeat this process until finish the job.may 10 or more time out of 100000 imp.

 

Are you sure your fountain roller clutches aren't going bad?

 

based on your answer to my question i think I would look at junkers suggestion next. yhis may just me being super anal but when i ran a press I always wanted the ink charge handle on the gear side of the ink fountain roller pointed toward the feeder of the press on all units. This in my opinion has an effect on the clutch operation. You may also want to test the clutches by squirting a little solvent into them right around the above mentioned handle. This allows the clutches to gain a little temporary traction. It will not be a permanent fix (for that you'll have to call in Junker) but it may help you in diagnosing a failing clutch.

 

Check the ink sweep adjustment motor. I've come across these moving on their own as the press is running. Take the operator cover off and watch the ink sweep mechanism where the two white gears are. As it is running you should see the gears move by themselves. A simple solution if this is happening is to put a cable tie between the two gear shafts to put a little tension on them.

 

I was questioning the drive clutch under the OS cover , would just seem likely that should be looked at closely. Tom's suggestion re. rinsing clutch out with solvent sometimes does give life to the drive clutch,but not a long term fix.

 

When I talked about curves I was referring to PRE press curves not the characteristic curve adjustment written into the press software. So I will ask again....do you know for a fact that your PRE press curves have been properly fingerprinted to the press in question. My solution is to refine the process that occurs before the plates are even mounted on the press. Are you familiar with the term "fingerprinting" as it refers to PRE press curves? My intent was to through the process of elimination rule out any variables. In doing so it makes sense to start from the begining. Having the correct dot curve on your plates assures you that you are starting from a place that will give you the best chance of success.
I would think it should go without saying, that these correctly imaged plates, should be mounted on a press thats known to be printing with the correct pressures, both between the plate and blanket, and between the blanket and sheet. It would also be good to know that the presses mechanical soundness is up to snuff. All I mention about the press setup is to assure that there is not excessive dot gain. Properly imaged plates, mounted onto a mechanically sound press, set up with factory recommended pressures would in my opinion the best place to start. I perhaps wrongfully assumed that the press was mechanically sound and printing with correct pressures. If so then you would need to begin there as any work in adjusting pre press curves would be putting the cart before the horse. Good luck and keep us posted.