TL;DR
Low image density on an HP Indigo press usually points to low ink (ElectroInk) concentration or a degraded photo imaging plate (PIP). Check ink concentration first, then PIP condition.
What you might see
- low color density across all colors
- image fading or washing out on output
- density dropping progressively during a print run
- ink consumption higher than baseline for same output
Likely causes
ElectroInk concentration below the target level in the ink reservoir
Photo imaging plate (PIP) worn or contaminated reducing toner transfer efficiency
Imaging unit charge voltage drifted from calibration
Ink delivery system partially blocked reducing ink feed to the imaging station
Required tools
- Densitometer
- Press management software access
- ElectroInk refill cartridges (if needed)
Safety first
- ElectroInk contains organic solvents. Use nitrile gloves when handling ink cartridges or cleaning spills. Work in a ventilated area.
- The imaging drum and fuser unit operate at elevated temperature. Allow the press to go through its cool-down sequence before opening panels for inspection.
Procedure
- 1
Run a diagnostic print test from the press management software and measure density with a densitometer on the output sheet.[1]
- 2
Check the ink concentration readout for each color on the press control screen. Low concentration indicates ink dispenser consumption has exceeded the refill trigger.
- 3
Confirm the ink reservoir levels. Add ElectroInk per the press operating procedure if the level is at or below the low-level indicator.
- 4
Run a system calibration sequence from the press management menu. Calibration adjusts charge voltage and transfer parameters.[1]
- 5
If density is low after calibration and ink level is adequate, check the PIP drum surface for visible scoring, contamination, or wear marks.
- 6
If PIP wear is visible, schedule a PIP replacement. The PIP is a consumable with a rated image count service life.
- 7
After all corrections, run a test print and confirm density with a densitometer before releasing to production.
Sources
HP HP Indigo 7K / 100K Digital Press general technical documentation, HP
Digital press ink density diagnosis and imaging unit calibration, general digital printing practice (general)
More guides for HP HP Indigo 7K / 100K
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How to clear a paper jam in the fuser of an HP Indigo 100K Digital Press
Fuser jams on digital presses require a careful manual clear following the press jam-clearing procedure. Forcing the sheet out risks fuser damage. Follow the step-by-step jam-release sequence.
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