Fix flexo ink picking when dots lift from plate or film during printing. YAOSHG covers anilox, impression, dyne level, and ink checks for stable laydown.
What Ink Picking Looks Like on Press
Ink picking occurs when part of the wet or partially dried ink film separates from the plate or the substrate instead of transferring cleanly—leaving pinholes, mottled solids, or ragged halftone edges. It is often confused with low dyne level or contaminated anilox, so split the diagnosis by whether missing ink appears in the plate image area or randomly across the web. Picking worsens as speed rises because split time at the nip shortens. On entry stack presses like the Nova 4-color stack press, picking on the last deck sometimes reflects dried ink debris from upstream rather than local setup.
Anilox Condition and Doctor Blade Setup
Plugged cells reduce ink release and starve highlights, which operators compensate with higher impression—inviting picking from the plate shoulders. Deep clean or exchange anilox before chasing ink formulas. Blade angle and pressure must meter ink without scoring the ceramic surface; a scored roll picks intermittently. Confirm line count matches job screen ruling; excessive volume floods the plate and prevents clean release. CI paper platforms such as the Apex 4-color CI paper press use chamber doctor systems—inspect seals for leaks that dilute ink locally.
Impression, Plate Hardness, and Tape Stack
Too much impression drives ink into plate shoulders and causes partial pick on subsequent revolutions. Too little impression leaves ink in cells that picks away in chunks. Match plate hardness to substrate: soft plates on film need lighter kiss impression than paper jobs. Mounting tape softness affects micro-impression—change tape type before rewriting ink. Sleeve systems on the King 4-color sleeve CI film press require verified sleeve roundness; oval sleeves modulate pressure and mimic picking bands. Measure sleeve OD at mount when picking appears only on one side of the web.
Ink Formulation and Substrate Readiness
Ink tack must align with press speed and downstream die cutting—over-tack pulls film fibers or coating from the surface. Check viscosity and temperature every hour; cold ink picks differently than warm. Verify dyne level on film per corona treatment guidance before blaming ink. Static on dry winter runs can pull ink off the web; ionizers at critical nips help. For PE work, cross-read PE film printing tips when picking appears only on low-slip rolls. Retain picked samples for ink lab review when supplier tack adjustments are requested.
Corrective Sequence Without Overreaction
Clean anilox, reset blade, confirm impression, then adjust ink with supplier guidance—never all three simultaneously or cause becomes untraceable. Run a solid at reduced speed; if picking clears, suspect speed-related tack or drying. Archive a retained sample of picked web for lab analysis when field returns occur. Link chronic picking with ghosting per ghosting troubleshooting when both appear on heavy solids. Update job recipes only after a verified fix survives a full shift. Note ambient temperature on the traveler when seasonal picking spikes appear on the Nova 4-color stack press.
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