Most Common Flexo Print Defects
1. Excessive Dot Gain
Symptoms: Highlight dots appear larger than intended, images look dark and muddy. Causes: Excessive impression pressure, wrong anilox volume (too high), ink viscosity too low. Solutions: Reduce impression pressure to lightest touch, select lower-volume anilox, increase ink viscosity, review plate hardness specification.
2. Gear Marks / Banding
Symptoms: Periodic light/dark bands in solid areas at regular intervals matching gear frequency. Cause: Mechanical gear mesh vibration transmitted to print. Solution: Upgrade to gearless servo drive (only permanent fix), check gear condition and lubrication for existing geared machines.
3. Registration Errors
Symptoms: Colors misaligned by more than 0.1mm. Causes: Tension fluctuation, register motor wear, plate slip on sleeve. Solutions: Check and recalibrate tension control loops, inspect servo encoder feedback, verify plate tape adhesion and mounting procedure.
4. Ink Smearing
Symptoms: Wet ink transferring to subsequent printing units or slitting/rewind equipment. Causes: Insufficient drying between colors, incorrect drying temperature/airflow for ink type. Solutions: Increase inter-deck drying temperature or airflow, reduce production speed, verify ink formulation matches drying system type.
5. Anilox Scoring
Symptoms: Fine lines in print direction across solid areas. Cause: Hard contaminant (dried ink chunk, substrate particle) caught between doctor blade and anilox. Solution: Stop production immediately, remove anilox for inspection, clean thoroughly, inspect doctor blade for damage, implement ink filtration.
