Before the adaptation of flexographic printing for commercial packaging use, printing on corrugated substrates was highly troublesome.
The delicate material would either be crushed during the printing process or printing had to be done so lightly that graphics were limited to simple, unappealing designs and text that made use of only one or two colors.
Flexographic printing has made it possible to achieve much higher resolution, multi-color, intricate images and text on corrugated substrates without harming the integrity of the materials. In spite of its seemingly limitless possibilities, flexo printing on corrugated still has its own set of challenges.
If you're experiencing issues with flexo printing on corrugated materials and not achieving the printing results you desire, consider the following troubleshooting tips.
Top 4 Culprits: Troubleshooting Problems with Flexo Printing on Corrugated Substrates
If your print has a streaky appearance, washboard-like look, or spotty, uneven inking, you likely have an issue with the ink's compatibility with the project. Using inks that are incompatible with your image carrier and/ or substrate can leave smears across your print.
In addition, using contaminated ink can result in foreign particles or hickeys on your finished products.
2. Printing Plates
It's important to check plates before every print run and to maintain them properly. Dirty, damaged, soft, uneven, worn, or loose plates can lead to dirty prints, spotty printing, washboard effects, uneven ink transfer, streaking, and image bleeding.
Switching to more durable, elastomer printing sleeves may also be a solution to consider.
3. Ink pH
If you're finding uneven color deposits, smeared images, streaking, or image bleeding, and your printing plates are in good shape, then your ink's pH could be to blame. The pH level of ink affects how quickly or slowly ink dries and how well the color will absorb and stick to your substrate.
Ink that dries too quickly or too slowly could be at the heart of your corrugated print run troubles.
Ink viscosity affects how well ink deposits on and clings to your substrate, and different substrate materials with different surface tensions call for various levels of viscosity. If your viscosity is too low, your print runs might have trouble with foaming, abrasion, spotty ink deposits, or uneven appearance.
If ink viscosity is too high, you could face similar issues plus smeared ink, uneven color, color that's darker than expected, halos, fisheyes, and contaminants in the ink.
How to Improve Common Corrugated Printing Problems
- Improve press maintenance: Working equipment has parts that can wear down and become inefficient. Maintain your presses properly, monitor printing pressure, and reduce wobbling.
- Increase pressure monitoring: Take a “kiss” impression and adjust the pressure accordingly. Carefully check the working parts, and consistently monitor surface tension.
- Watch worn gears: Check the condition, lubrication and cleaning of gears regularly to keep them from damaging the print.
- Reduce contamination: Control airborne contaminants, keep image carriers in top condition, look for dried ink on the cartridge and check for plate swelling to keep an even ink distribution.
- Rethink inks: Ink choices may be too abrasive or non-absorbent. Look at ink viscosity and pH level.
- Take care of the image carrier: Beware of using harsh solvents or cleaning agents that could lead to swollen sleeves or damaged plates.
- Improve distribution: Reduce cylinder or plate swelling by switching to sturdier elastomer sleeves.
- Aim for the right anilox: Choose an anilox with cells that hold and support ink transfer at the appropriate rate.
- Don't hurry drying: Don’t get so caught up in productivity that you perform all print processes properly, and then fail to allow proper drying time.
Flexo Problem Still Not Solved?
Flexo printing — especially on corrugated substrates — requires a delicate balance of several components all working in harmony. For a print run to turn out exactly as expected, all components have to be exactly right.
That means pairing the proper ink viscosity with the right surface tension, storing inks as instructed, always using compatible inks, proper maintenance and cleaning of printing plates, and more.
For more information about troubleshooting your corrugated substrate print run problems or other concerns, contact a flexographic printing expert at Luminite.