Troubleshooting of water-based ink flexographic printing

Date: Nov 07 2024 From: Star Color

We know that most flexographic printing uses water-based inks, especially in places with stringent environmental and safety regulations. Water-based inks can be printed on absorbent materials such as paper and also on non-absorbent materials like plastic films. For factories that have just started using water-based inks, they may encounter various issues during the printing process. Here are some common faults and their troubleshooting methods:

Poor Drying

Cause: High viscosity of the water-based ink, ink edge expansion, poor drying of the ink, and low absorbency of the paper.
Troubleshooting: Adjust the printing viscosity of the ink, adjust the plate pressure, use quick-drying water-based inks, and choose paper with good absorbency.
White Gaps in Printing

Cause: Poor flatness of corrugated paper, especially A-flute with low-weight facing paper, prone to showing corrugations.
Troubleshooting: Appropriately reduce the gap between the printing plate cylinders. For large-area printing, use facial glue to appropriately pad up the middle part of the printing area to eliminate white gaps.
Incomplete Overlay of Colors

Cause: Significant difference in surface tension between the pigments of water-based inks, preventing the second-color ink from evenly covering the first-color ink.
Troubleshooting: Increase the drying speed of the first color, add fast-evaporating alcohol or other alcoholic solvents in moderation to reduce the surface tension of the second-color ink, and incorporate surfactants.
Blurred Edges or Fine Text in Prints

Cause: Insufficient precision of the printing plate, excessive pressure between the printing plate and the anilox roller, and high viscosity of the ink.
Troubleshooting: Re-make the plate or adjust the plate thickness, adjust the pressure, and adjust the viscosity, preferably using low-viscosity inks.
Poor Dot Registration

Cause: Excessive printing pressure for the previous color, high viscosity of the previous color ink, and slow drying of the previous color ink.
Troubleshooting: Adjust the relative printing pressures of each color, reduce the viscosity of the previous color ink, and adjust the drying differences between the various ink colors.
Poor Transfer

Cause: Insufficient printing pressure, mismatched plate hardness, excessive water repellency of the paper, wear and aging of rollers.
Troubleshooting: Increase the printing pressure, verify the plate hardness, use water-repellent matched water-based inks, and inspect and replace rubber rolls and anilox rolls.
Ink Foaming

Cause: Insufficient foam suppression ability of the ink, insufficient ink circulation, and air leakage in the circulation pump.
Troubleshooting: Add a defoamer, increase the circulation rate, and prevent pump leakage.
Pinholes in Prints

Cause: Excessive use of defoamers, overly thin ink, uneven paper fibers, and insufficient impression.
Troubleshooting: Limit the use of defoamers, add penetrants for adjustment, and adjust the pressure of the ink transfer rollers.
Increased Viscosity and Darkened Colors

Cause: Volatilization of ammonia in the ink leads to a decrease in pH value and an increase in viscosity.
Troubleshooting: Control the ink viscosity during printing and adjust the pH value of the ink to ensure consistent color before and after printing.
Poor Water Resistance of Prints

Cause: Poor water and abrasion resistance of the ink or unsuitable paper used.
Troubleshooting: Choose suitable inks and appropriate paper.

The above are troubleshooting methods for faults in flexographic printing with water-based inks. In actual printing, corresponding troubleshooting methods need to be taken according to the specific causes. Identify and solve problems promptly to ensure the quality and efficiency of printed products.