Gray Balance

[pmkprog]

We are using a KM C5501 Biz Hub Pro running the Fiery Command Workstation 5 software.

I can not get a good gray balance even after reading the color strips. I have tried to move any gray printing to a spot color and creating a special spot color mix to color match and I still get streaked printing in the solids and the streaks tend to be red. The drums have been replaced recently.

Any ideas or is this just the nature of the beast?

 

[gordo]

Just a thought...does the hue of the grey shift if you look at it under different lighting conditions?

best. gordo

 

[arossetti]

Sounds like it is the corotron also called a dicor.

 

[pmkprog]

The lighting does not matter for the color.

 

[LoneGoose]

Seems like you have two separate problems there - the streaks and the grey balance. If the streaks are red, it might be a problem with the cyan. Fix this first and achieving a grey balance will come easier.

 

[pmkprog]

Lone Goose,

I can get the grey where I need it on the small swatch, but on the overall sheet, the color shifts and streaks with the magenta. Someone suggested it is the conveyor belt since it is mostly in the middle of the page as it travels through the machine.

 

[dnoone]

Had a similar problem with a Bizhub C360. It took 4 visits from 3 engineers, and after replacing all 'consumables' it was the Laser Unit.
The streakes we only visable on low tints and stuck out like a sore thumb on greys. We don't rely on the C360 for colour accuracy but at least it is now smooth and consistent.

 

[pdan]

The answers to consumables are all valid, but when you calibrate, are you running 34 Random patches?

 

[pmkprog]

Replacing multiple parts for the black has smoothed some things out, but still having some issues getting the happy gray balance. I have not run out the random patches.

 

[pdan]

You're familar with 34 Sorted Patches. One strip each of cmyk in one localized section of the image area. It is possible/probable that the imaging equipment is not in a consistant state across the width of the sheet, hence 34 Random patches randomizes the test patches. Upon scanning the patches, the engine recognizes the variance across the sheet and applies better calibration as needed for each color.