Learning to troubleshoot in the pressroom is a valuable skill that helps you maintain quality standards, stay on schedule and identify potential maintenance issues before too much damage is done. Our technical team has put together potential solutions to the twelve most common problems you may encounter when UV Flexo printing. We hope this quick-fix guide serves as useful reference material when you need it most.

Are you familiar with the story of Occam’s Razor? It’s a problem-solving principle that states that the simplest solution is almost always the best and a great axiom to remember when looking to solve issues on press. When you encounter print failures, don’t panic. It’s often as simple as needing to add UV reducer, prime the substrate or change to a different white.

If a simple solution to your problem exists, always try that first!

Problems associated with insufficient ink in solid print areas is typically going to be an issue with ink viscosity being too low. By adjusting viscosity higher, ink will be able to better wet out over the substrate.

When ink density is too low the resulting print can look faded or be absent of color altogether. Using an effective diluent can improve ink flow without affecting adhesion of UV ink.

Ink spitting is a common issue associated with UV inks that does not tend to happen with water or solvent inks. When ink sprays in an uncontrolled manner, turn first to reducing ink viscosity.

As press speeds increase, so does the potential for tiny air bubbles to form when the anilox roll comes into contact with the ink. While UV inks do contain some antifoaming agent, sometimes more must be added to prevent additional foaming or eliminate the bubbles already in the ink.

What it looks like: Ink film is not sticking to the substrate

UV ink adhesion issues can be divided into two separate categories. Pre- and post-cure. Start first by confirming that your ink is curing properly, and if it is, move on to the next step of adjusting the treatment of the substrate for better adhesion.

What it looks like: Ink film is damaged during scratch/rub/abrasion testing

Waxes are an advantageous formulation tool that give printers the ability to improve an ink or coating’s performance and make it more resistant to wear and tear. If additional wax does not provide sufficient protection against scratching, rubbing or abrasion, consider adding an extra coating or protective varnish.

When a more porous substrate is used that absorbs the ink film, a reformulation of the ink or sealing of the substrate is necessary.

Lightfastness is the resistance of colors to fading under the effect of a light source and determined by the pigments used in the formulation of your ink. In the case of printed products that will be exposed to higher degrees of sunlight, a high degree of lightfastness will be required.

Fanal pigments offer exceptional color qualities including high clarity, depth and cleanliness, but due to their poor resistance to solvents, they can also be prone to bleeding. In the event that bleeding becomes a recurring issue during your print run, it is likely that a more resistant pigment will need to be used.

When ink issues are only present during the die-cutting process, the problem is typically due to an overhardening of the ink or complications with the die-cutting machine itself, potentially dull blades.

If adjusting pressure settings on the press do not eliminate the presence of gearwheel stripes, it is likely that the press requires professional maintenance and potentially to have one or more parts repaired or replaced. In some cases, excessive ink tack can lead to striping but this is less common.

Gear chatter is most often caused by a mechanical issue on the press. As gears wear down over time, they no longer fit together the way they used to, causing improper balance, pressure inconsistencies and even bouncing on the press. While it could be that gears simply need cleaning or lubricating, gear marks are typically a sign that teeth are damaged and in need of repair.

Pinholing is one of the more maddening flexographic printing defects as the root cause can be either mechanical or chemical in nature. Along with the following possible causes, a dirty anilox or slow printing speed can also be to blame.

Cleaning the anilox or reducing the gap between the anilox cells on the roll will often solve the ink transfer failure that’s leaving tiny pinholes or causing incomplete printing. Other potential causes include fast-drying ink or high ink viscosity, wrong surface tension or a loss in cell volume on the anilox.
Additionally, check that the substrate surface isn’t responsible. A damaged, dirty or irregular substrate can also lead to pinholes and voids.