Troubleshooting Flexographic Printing Defects: A Guide to Better Print Quality

Hi there! Welcome to MTED’s guide on flexographic printing defects and troubleshooting. With over 20 years in the printing and packaging industry, we understand the common challenges printers face—whether it’s dot gain, misregistration, or ink transfer issues.

To create this guide, we analyzed real printing problems, tested solutions, and gathered insights from industry experts. Our goal is to provide clear, practical steps to help you identify issues quickly and keep your production running smoothly.

By the end of this article, you’ll know how to fix common flexo printing defects, improve print quality, and reduce waste and downtime. Whether you’re printing packaging, labels, or commercial materials, this guide will help you troubleshoot problems with confidence.

Let’s dive in and get your flexo prints looking perfect!

Table of Contents hide

6 6. Missing Print Areas

7 7. Misregistration

8 8. Mottling (Uneven Ink Coverage)

1. Dot Gain

What It Looks Like:

Dots in the printed image look bigger than they should. This makes details blurry, edges unclear, and colors too dark. It is easiest to see in light and middle shades, making the image look too thick or smudged.

Effects:

✅ Loss of fine details, making prints look low-quality.
✅ Color shifts, especially in multi-color printing.

Causes & Fixes:

Cause	Fix
Excessive pressure	Reduce pressure to a “kiss” level to avoid squeezing ink outward.
Anilox roll volume too high	Use a lower-volume anilox roll to prevent excessive ink transfer.
Low ink viscosity	Maintain proper ink viscosity using a viscometer.
Contamination (dust, ink buildup)	Keep plates and rollers clean to prevent uneven ink transfer.
Ink pH imbalance	Keep pH between 8.5 – 9.5 to stabilize ink flow.

2. Gear Marks

What It Looks Like:

Repeating lines or stripes appear across the print, matching the movement of the gears. These marks usually run side to side instead of following the print direction.

Effects:

✅ Uneven color, especially in large solid areas.
✅ Lower print quality, affecting customer satisfaction.

Causes & Fixes:

Cause	Fix
Worn or misaligned gears	Inspect and replace worn gears, ensure proper alignment.
Uneven pressure	Adjust pressure settings to prevent vibration.
Dirty or poorly lubricated gears	Clean and lubricate gears regularly.
Damaged anilox roll	Replace or clean worn-out anilox rolls to improve ink distribution.

3. Halo Effect

What It Looks Like:

Text and graphics have blurry or fuzzy edges, making them look like they have a glow or halo around them. This is most noticeable in thin lines and small text.

Effects:

✅ Reduced sharpness and readability of text.
✅ Unprofessional print quality, especially in labels and packaging.

Causes & Fixes:

Cause	Fix
Excessive pressure	Reduce pressure between the plate and substrate.
Ink transferring too much	Adjust ink viscosity to prevent over-transfer.
Large anilox roll volume	Switch to a finer anilox roll to control ink flow.
Slow drying speed	Increase drying temperature or airflow to set ink faster.

4. Feathering

What It Looks Like:

Ink spreads outside the edges of lines or text, making them look fuzzy or feathered. This often happens on rough or absorbent materials like corrugated cardboard.

Effects:

✅ Blurry text and images that look unprofessional.
✅ Hard-to-read fine details in labels and packaging.

Causes & Fixes:

Cause	Fix
Too much pressure	Reduce plate pressure to prevent ink from spreading.
Low ink viscosity	Increase viscosity to prevent over-absorption into the material.
Slow drying speed	Speed up drying to prevent excess ink absorption.
Dirty plates or rollers	Clean regularly to prevent ink buildup.

5. Ring Marks

What It Looks Like:

Circular or wave-like marks in the print, often forming concentric rings. These marks usually follow the rotation of the rollers.

Effects:

✅ Uneven ink coverage, ruining the final look.
✅ Especially noticeable in large solid areas and background colors.

Causes & Fixes:

Cause	Fix
Unbalanced rollers	Adjust or replace rollers to ensure smooth rotation.
Ink pooling in anilox cells	Clean anilox rolls to ensure even ink distribution.
Drying too slowly	Increase drying temperature to prevent ink movement.

6. Missing Print Areas

What It Looks Like:

Certain parts of the print are completely blank or missing ink, especially on edges or specific zones of the substrate.

Effects:

✅ Incomplete designs, making labels or barcodes unreadable.
✅ Wasted materials and potential reprints.

Causes & Fixes:

Cause	Fix
Plate swelling	Use solvent-resistant plates to prevent distortion.
Ink transfer issues	Check and clean ink supply lines.
Pressure imbalance	Adjust pressure for even ink transfer.

7. Misregistration

What It Looks Like:

Color layers or design elements don’t align properly, causing a blurry, shadowed, or offset look.

Effects:

✅ Poor color accuracy, making images look off.
✅ Reduces print quality, especially in multi-color jobs.

Causes & Fixes:

Cause	Fix
Press components not synchronized	Adjust rollers and tension settings.
Plate swelling	Replace plates if they expand due to chemicals.
Tension issues	Use a tension control system for stable feeding.

8. Mottling (Uneven Ink Coverage)

What It Looks Like:

Irregular dark and light patches in the ink, making the surface look like an “orange peel.”

Effects:

✅ Rough or inconsistent finish, reducing product appeal.
✅ Unprofessional look, especially in luxury packaging.

Causes & Fixes:

Cause	Fix
Uneven ink transfer	Adjust anilox roll and ink supply.
Surface contamination	Keep plates and substrate clean.
Drying too fast or slow	Balance drying temperature and airflow.

9. Bridging/Filling

What It Looks Like:

Fine lines, dots, or small text merge together due to excess ink.
Bridging happens when nearby details connect unexpectedly.
Filling occurs when too much ink pools in small areas, making text or images thicker than intended.

Why It Happens:

Anilox Roller: Ink cells are too large, transferring too much ink.
Printing Pressure: High pressure pushes ink into fine details.
Plate Swelling: Printing plates expand, reducing detail sharpness.

How to Fix It:
✔ Use a lower-volume anilox roller to reduce ink transfer.
✔ Reduce printing pressure to prevent ink spread.
✔ Adjust ink viscosity so it flows properly without pooling.

10. Pinholes

What It Looks Like:

Small, randomly distributed holes appear in solid printed areas.
Affects image coverage and makes prints look incomplete.
Can cause problems in protective coatings and barrier layers in packaging.

Why It Happens:

High Ink Viscosity: Thick ink doesn’t spread evenly.
Contaminants in Ink or Substrate: Dirt, dust, or fibers block ink adhesion.
Fast Drying Speed: Ink dries before fully spreading, leaving gaps.

How to Fix It:
✔ Lower ink viscosity so it flows smoothly.
✔ Clean the substrate and ink system to remove dust and debris.
✔ Adjust drying settings to give ink enough time to spread evenly.

11. Dirty Print

What It Looks Like:

Smudges, spots, or ink stains appear on the print.
Colors look muddy or unclear.
In high-quality printing (like food or pharma labels), this can cause compliance issues.

Why It Happens:

Contamination: Dust, fibers, or static attract particles to the ink or substrate.
Ink Viscosity Issues: Ink mixes with debris, causing uneven printing.
Dirty Anilox Roller: Leftover ink causes random spots.

How to Fix It:
✔ Use anti-static devices and keep the print area clean.
✔ Adjust ink viscosity so it transfers evenly.
✔ Regularly clean anilox rollers to prevent ink buildup.

Flexo Printing Defects & Causes Summary

Defect Type	Pressure	Machine Mechanics	Anilox Roller	Ink Transfer	Ink Viscosity	Contamination	Plate Swelling	Drying Speed	Paper Absorption
Dot Gain	✔		✔	✔	✔	✔		✔	✔
Gear Marks	✔	✔	✔			✔
Halo Effect	✔		✔	✔		✔		✔
Feathering	✔		✔	✔	✔	✔		✔	✔
Ring Marks	✔	✔	✔	✔		✔
Missing Print	✔	✔	✔			✔	✔
Misregistration	✔	✔	✔	✔		✔	✔		✔
Mottle	✔		✔	✔		✔		✔	✔
Bridging/Filling	✔	✔	✔	✔		✔	✔
Pinholes	✔				✔	✔	✔	✔
Dirty Print	✔		✔		✔	✔		✔

Explanation:

✔ Each checkmark indicates a possible cause for that specific printing defect.
✔ This table helps identify root causes and related factors for different flexo printing issues.
✔ By understanding these connections, operators can troubleshoot problems faster and optimize print quality.

Wrapping Up: How to Get Better Flexo Prints

Every flexo printer runs into defects sometimes, but knowing what causes them and how to fix them can help you reduce waste, work faster, and get high-quality prints every time.

At MTED, we know the struggles of flexo printing. That’s why our machines are built for accuracy, smooth operation, and fewer defects. Whether you need better ink flow, tension control, or reliable anilox rolls, we’ve got solutions to help you print with confidence.

Want to improve your flexo printing? Let’s talk! We’re ready to help you find the best setup for your business.