Flexo Printing Press Quality Control FAQ

Why is my flexo print register drifting during the run?

Register drift usually traces to web tension changes, plate cylinder or gear wear, or thermal growth after warm-up. Confirm the tension is stable left to right, check cylinders and gears for wear or backlash, and let the press reach running temperature before you set final register — drift that appears late in a run is almost always thermal or tension, not the initial setup.

How do you control ink viscosity on a flexo press?

Measure viscosity with a flow cup at fixed intervals — typically every 30 to 60 minutes on solvent inks and more often in hot weather — and add solvent in small, logged steps. Viscosity drift changes dot gain and color density before the eye notices, so a viscosity log is the cheapest color control on the press.

What is a first-article check in flexo printing?

A first-article check is an approved sample taken at the start of the run — register, color against the approved proof, dot gain, and print defects — signed off before production speed is set. The approved sample becomes the reference for the whole run, and any drift is compared against it rather than against memory.

Why does color fade during a long flexo run?

Color fade through a run almost always means the anilox roll is plugging or ink viscosity is climbing as solvent evaporates. Clean the anilox on a calendar rather than when color fades, and keep the viscosity log running — a plugged cell delivers less ink volume at the same setting, which no amount of press-side adjustment fully corrects.

How often should anilox rolls be cleaned?

Clean anilox rolls on a fixed calendar — typically every one to two weeks of running for water-based inks and more often for heavy pigment loads — plus after every job that leaves visible residue. Cleaning by calendar prevents the gradual cell plugging that shows up first as fading color and later as banding that takes a full roll service to fix.

Why is there a color difference between the proof and the production run?

Proof-to-production color differences usually come from three gaps: substrate difference between proof stock and run stock, anilox cell volume or plate dot gain not matched to the proof condition, and ink batch variation. Verify the stock and the proof substrate match first, then confirm the ink batch and anilox volume against the job spec before touching the color settings.