Flexo Printing Defects Troubleshooting | 12 Common Problems & Fixes
The High Cost of Print Defects
Flexographic printing is a high-speed, efficient process, but it is not immune to errors. Whether you are running a narrow web label press or a wide web packaging line, a print defect that goes unnoticed for even a few minutes can result in hundreds of meters of wasted substrate and costly downtime.
Diagnosing the root cause—whether it is mechanical, chemical, or operational—is the first step to a solution. This comprehensive guide categorizes the 12 most frequent flexo defects into actionable diagnostic charts to help your operators fix issues fast.
Category 1: Ink-Related Defects
Issues involving ink viscosity, pH balance, and drying speed are the most common culprits in the pressroom.
| Defect | Possible Causes | Recommended Solutions |
|---|---|---|
| Pinholing |
Tiny unprinted voids in solid areas. - Dirty anilox roller. - Ink viscosity too high. - Low substrate surface tension. |
- Clean the anilox thoroughly. - Reduce ink viscosity. - Increase Corona treatment level. |
| Ink Smearing |
Ink rubs off on the back of the web. - Ink not drying fast enough. - Ink film is too thick. |
- Increase dryer temperature/airflow. - Switch to a lower volume anilox. |
| Foaming |
Bubbles appearing in the print. - Pump cavitation (air in lines). - Excessive agitation. |
- Add a defoamer additive. - Check ink pumps for air leaks. - Reduce circulation speed. |
Category 2: Pressure-Related Defects
Flexography is a "kiss impression" process. Excessive pressure is the enemy of quality.
| Defect | Possible Causes | Recommended Solutions |
|---|---|---|
| Dot Gain |
Images look dark/muddy; dots grow in size. - Too much impression pressure. - Mounting tape too hard. |
- Back off pressure to a "kiss" setting. - Switch to softer cushion tape. |
| Feathering |
Ragged edges around text. - Excessive pressure. - Ink drying too fast on the plate. |
- Reduce impression pressure. - Add a retarder to slow drying. |
| Filling-in |
Small text or reverse lines get clogged. - Excess ink volume. - Dirty plates. |
- Use a finer anilox roller. - Stop and clean printing plates. |
Category 3: Mechanical & Registration Issues
These defects often point to hardware wear or improper setup of the press mechanics.
| Defect | Possible Causes | Recommended Solutions |
|---|---|---|
| Misregistration |
Colors do not align (halo effect). - Unstable web tension. - Plates mounted incorrectly. |
- Check tension control settings. - Re-mount plates using video mounting. |
| Gear Marks (Banding) |
Horizontal stripes across the print. - Worn gears. - Machine vibration. |
- Inspect and replace drive gears. - Ensure the machine is leveled properly. |
| Wrinkling |
Creases in the substrate. - Tension too high. - Rollers not parallel. |
- Reduce web tension. - Calibrate roller alignment. |
Category 4: Complex & Advanced Defects
Some problems require a deeper dive into fluid dynamics and press configuration.
Ghosting
Ghosting appears as a faint, repeated image in solid color areas. It is notoriously difficult to solve because it can be caused by "ink starvation" or mechanical bounce. If you are struggling with this specific issue, we have a dedicated guide to help you Fix Ghosting in Flexo Printing which covers root causes like ink viscosity and anilox cell volume in detail.
Ink Spitting
This occurs when the doctor blade vibrates, allowing extra ink to pass through and "spit" onto the web. It is often solved by changing the blade angle or using a stiffer doctor blade material.
Summary: The Manufacturer's Advantage
While troubleshooting is a necessary skill, the best solution is prevention. Modern flexo presses, like those manufactured by Newtop Machinery, are designed with advanced digital tension controls and servo-driven motors that eliminate many mechanical causes of defects like gear marks and misregistration.
Investing in a stable, high-precision machine reduces the burden on your operators and ensures consistent quality from the first meter to the last.
