(Wh) Writing Head Banding; (Lut) Screening And Machine Lut Artifact Banding - HP Indigo press 3050 Troubleshooting Manual

(WH) Writing head banding

Press component
(WH1)
Focus adjustment
(WH3)
(WH2)
Dynamic mirror
(WH3) Writing head
press interfaces
General solutions for banding caused by the writing head
1. Adjust the writing head focus and leveling.
2. Verify that the writing head parameter files correspond to the writing head serial number.
Reinstall the writing head parameters.
3. Physically unlock the dynamic mirror according to the instruction sticker on the writing head.
4. Adjust image scaling.
5. Check the de-skew calibration.
6. Check the writing head mechanical installation.
7. Check the press installation - press wheels should not touch the floor.

(LUT) Screening and machine LUT artifact banding

•
Screening banding is caused by intrinsic screening artifacts, for example:
•
3.8 mm period banding on Sequin screening.
•
Machine LUT banding is caused by faulty machine LUT generation.
Images most affected are screen tints that change from say 5% to 100% in a gradual way:
•
Vignettes are light to dark or dark to light areas of a single color.
•
Blends are composed of process colors (C, M, Y, and K) that change from one specific color to
another.
•
Vignettes and blends may also exhibit some banding if they contain too many steps or if the
machine LUT is not correct.
•
For example if the machine LUT was set to the following numbers:
•
Step 20 is 20, step 30 is 32, step 40 is 38 and step 50 is 50. (Note that these numbers
are within normal tolerance.)
•
If a vignette falls within this range, a band will be created between 30% and 40%.
•
The LUT in this example, actually compresses the vignette and generates banding.
General solutions for screening and machine LUT artifact banding
1. Run the Machine LUT generation wizard.
2. Try to print with a different job screen definition for a diagnostic.
3. Replace - blanket. (Run the Machine LUT generation wizard, print again).
4. Replace - PIP (Run the Machine LUT generation wizard, print again).
5. Check the Ink density and conductivity calibration.
Run the Machine LUT generation wizard again.
EN
Possible Causes
Faulty focus adjustment
•
Focus adjustment.
•
Image scaling adjustment.
•
De-skew calibration.
Dynamic mirror malfunction (or
dynamic prism in the HP Indigo
press 3050).
Faulty Writing head installation
on press interfaces.
Appearance / Banding type
Usually produces 2.25 mm period banding.
0.375 mm period banding.
This can cause any type of banding.
Usually accompanied by random misregistration
issues.
Usually vibration banding 0.7—2.5 mm - constant
groups or periodic groups. (Especially on the HP
Indigo press 3050.)
Causes of Banding 13