Issues with color variations on jobs

I am having issues with color variations on full color job/2 color jobs. We are running a SM52 and QM 46-2 (Same press operator) What I think is the pressman is not paying attention. So far this year I have had 3 major jobs with swings of color. He uses a densitometer on the 4 color and I feel that if he was pulling sheets consistently, the color would not vary.
Right now I have egg on my face with one of my largest customers. When I talked to my operator he took responsibility for it------but this has happened often enough that I need to do something.
1. Do any of you have standard operating procedure for pulls, etc?
2. Since I have only one pressman, I am in a bind as far as really coming down on him.
3. Any insight(s) would be helpful
(Press is up-to-date and maintained.)
Thanks!

 

been doin this 40 years i pull sheets constantly tell him he needs to show you pulls on all jobs keep and review

 

Dear Mike
There are more than one reason which may cause the color variation during production
First you have to check your rollers adjustment and your dampening solution ph, conductivity and alcohol.
Then check up your blankets height following the manual.
Then your operator have to print with the lower water which means to achieve good ink water balance
Then your printer must recognize the image area he is printing ( low image area needs more sheets in the make ready stage) then he can achieve the stability you want.
Finally, the printer must not play with the ink zones before he is sure that the ink in the pulled sheet is really the result of the ink profile. ( the image area decides every how much sheets the printer can play with the ink profile).
Best wishes

 

The process is not a perfect one . There is such a thing as acceptable color variations,particularly when your printing 4color process in multiple passes. If your a small job shop ,which im assuming you are, and printing 4 or 5 small jobs a day then 3 bounced jobs in a years time would have your guy with a pretty good batting average. Do the math snd you will see what im talking about. Now perhaps you understated his screwups and he bounced 10 jobs in a year. Now perhaps youve got a bit more to cry about but ONLY if your giving him all he needs to succeed. Remember that crap in will equal crap out. Also remember that high quality work requires ample time to complete. If you cracking a whip real hard for him to complete too many jobs in a day he will be forced to take shortcuts. Remember the old saying.... you can have it either cheap, fast, or good. Pick any two!!!

 

Put in place a time stamp pull out sheets procedure

 

Even if the density is "correct" the dot gain changes will change halftone images. Be sure you include Solid/50%/75% in the color bar. 50% is to monitor dot gain. The 75% for print contrast - ink water balance. Call anytime Dan 412.889.7643