In a flexographic printing workshop, the most frustrating issue

is often not a machine breakdown, but rather print results that fail to

meet expectations. Problems include solid areas that are too thick,

slow drying, or halftone dots merging together (due to excessive ink

transfer); or conversely, prints that appear patchy, show the substrate

through the ink, or lack sufficient ink coverage (due to inadequate

ink transfer).

When sales representatives receive complaints from

clients—such as, “ The print quality isn’t what we expected; could

the anilox roller be the problem? ”—they don’t simply jump to

providing a quote for a new roller. Instead, they ask three key

questions: “ What substrate are you printing on? What is the

machine speed? And what are the current line count and BCM

(ink-carrying capacity) specifications? ” Experienced sales staff

know that while the anilox roller is often called the “heart” of the

flexographic printing process, it is rarely the sole culprit when ink

transfer issues arise. Today, we will walk you through a standard

troubleshooting process to help you identify the root cause.Before adjusting your press, examine the defects in your rejected

prints:

• Excessive ink transfer: Solid areas appear overly thick—sometimes

even reflective—halftone dots expand (causing “ plugging ” or

filling in), and the ink fails to dry thoroughly, leading to smudging.

• Insufficient ink transfer: The printed surface appears patchy or

streaky; solid areas lack density, revealing the substrate; and fine

highlight dots disappear entirely

When a client complains that “ the color isn’t strong enough, no

matter how much ink I add ”,the issue is often clogged anilox cells.

Conversely, complaints about “ ink smearing on the back of the

sheet or slow drying ” are typically caused by an excessive volume

of ink being transferred.

If there is too much ink transfer, what should you check first?

• Doctor blade system: The blade edge may be worn, or the angle

may be too shallow (for a reverse-angle doctor blade, this is

typically around 30°), failing to effectively scrape excess ink off the

roller surface.

• Ink viscosity: If the viscosity is too low, the ink becomes too thin

and spreads uncontrollably across the entire surface.

• Excessive pressure: Too much pressure between the anilox roller

and the printing plate cylinder can “ squeeze ” the ink out of the

anilox cells.

If there is too little ink transfer, what should you check first?

• Clogged cells: Dried ink or impurities fill the cells—this is the

most common culprit.

• Anilox roller wear: Long-term friction from the doctor blade wears

down the cell walls, causing an irreversible reduction in cell volume

(BCM).

• Excessive ink viscosity: The ink is too thick, becoming trapped inthe cells and failing to release.
• Excessive doctor blade pressure: This effectively scrapes the ink

right out of the cells.

Q: How can you identify a clogged anilox roller? What is the

difference between wear and clogging?

A: Use a high-magnification loupe. Clogging appears as shiny,

dried-on foreign matter inside the cells; this can often be resolved

through deep cleaning (e.g., using an ultrasonic cleaner). Wear, by

contrast, involves the wearing down of the cell walls (the partitions

between cells), resulting in a permanent loss of volume—this cannot

be repaired and requires either re-engraving or replacing the roller.

Q: What is the ideal doctor blade angle? How does ink viscosity

affect ink transfer?

A: A reverse-angle doctor blade is typically set at around 30°. If the

angle is too shallow, ink may leak (resulting in excessive ink

transfer); if it is too steep, it can “ scoop ” the ink out of the cells

(resulting in insufficient ink transfer). If ink viscosity is too low, the

ink becomes too fluid, leading to excessive transfer; if it is too high,

the ink fails to release from the cells, leading to insufficient transfer.

Q: How often should rollers be cleaned or replaced?

A: Perform surface cleaning daily; schedule deep cleaning (such as

ultrasonic cleaning) periodically, based on production volume. If,following deep cleaning, the print density still fails to meet

requirements—and testing confirms a significant reduction in BCM

(cell volume)—it is time to consider replacing the roller.