Diagnose flexo ghosting from impression, ink tack, and anilox mismatch. Step-by-step fixes for repeat image shadows on packaging film and paper flexo jobs.
Recognizing Ghosting Versus Other Repeat Defects
Ghosting appears as a faint repeat of solid or heavy tone areas offset circumferentially from the primary image—often described as a shadow or double print. It differs from gear chatter, which shows as regular mechanical banding at gear pitch, and from slur, which smears directionally. Record the repeat distance of the ghost relative to plate repeat to determine whether the source is on the same deck or transferred from another unit. On CI film lines such as the Apex 6-color CI non-stop film press, ghosts from a heavy black deck frequently appear two revolutions later on a vignette deck sharing the same drum.
Impression and Plate Cushion Interactions
Excessive impression on thick plates or soft tape leaves a mechanical set in the plate that prints on the following revolution. Reduce impression until solid density just clears, then adjust ink or anilox instead of squeezing harder. Check for plate lift at edges where mounting tape ends—micro lift ghosts on every repeat. Hard spots on the impression roll or drum covering create localized ghosts visible only in solids. Servo stack units like the Honor 6-color servo stack press allow deck-by-deck impression trim; isolate the offending deck before global changes.
Ink Tack, Speed, and Anilox Pairing
High-tack inks pulled from large solids can pull ink back out of neighboring highlights on the next revolution, producing tonal ghosting. Lower tack resin or reduce anilox volume on the heavy unit. Speed changes alter ghost severity because dwell time on the plate changes. Pair anilox volumes so downstream decks are not starved after upstream heavy laydown. Water-based systems ghost differently than solvent—watch pH and foam stability. Review ink picking diagnostics when ghosting coincides with missing dots in highlights. Log tack and speed together when ghosting appears intermittently across shifts.
Mechanical Drives and Roll Concentricity
Geared presses may show ghosting tied to gear backlash when impression loads spike on heavy type. Inspect gear contact and bearing play on the affected deck. Out-of-round anilox or plate cylinders modulate pressure once per revolution, mimicking ghosting. Gearless CI platforms such as the 6-color gearless full servo press reduce mechanical ghost sources but still suffer from impression-related effects. Verify that vibration dampers and deck locking pins are engaged per manufacturer spec before blaming ink. Schedule backlash checks on geared CI units before long campaigns on solid-heavy artwork.
Systematic Elimination Workflow
Run a solid patch only on the suspect deck at reduced speed; if ghosting vanishes on vignette jobs, focus on impression and tack. Swap anilox to a lower volume test roll temporarily. Document fixes in the job recipe to avoid rediscovery. If ghosting follows a plate change, remount with fresh tape per mounting tolerance procedures. Escalate persistent drum-related patterns to mechanical service with photos showing repeat length measurement. Compare ghost repeat distance to plate and gear pitch before authorizing major repairs on the Apex CI non-stop film press.
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