This article is part of the FLEXO FLAW FIXING series
What Is The Skip Out Effect In Flexo Printing?
Insufficient or absent ink transfer to the substrate of a portion of the picture is typically caused by inconsistencies in contact pressure between the anilox roll, printing form, and/or substrate, resulting in poor ink transfer to the end output.
Your ink must thoroughly wet out on the substrate (in essence, excellent ink transfer). Press mechanics are crucial in this equation. If there is wobbling, pieces of the printing form will contact the substrate unevenly. However, you may be encountering additional concerns ranging from ink composition to comprehensive maintenance and cleaning.
Causes Of Skip Out Effect
Even minor resonance vibrations and other press mechanical difficulties can influence how well the print cylinder hits the substrate. Unintentional movement of press components might easily result in skipping out. Other possible reasons include:
- High or low image carrier regions, bent shafts, or out-of-round components
- ink surface tension and substrate surface energy
- pH and ink viscosity
- Cleaning and routine maintenance
The Appearance of the Skip-Out Effect
You will see that your prints have parts that are either overly light or completely absent.
What are the Flaws of Skip Out Effect in Flexo Printing?
- Press Mechanics
The necessity of precisely balancing rollers and cylinders holding the image carrier, web, and substrate in today’s flexographic printing business cannot be overstated. Balancing distributes the bulk of the roller, avoiding the following concerns that might distort your imagery:
- Resonant vibrations
- Excessive cylinder or plate wear
Drive systems, which are designed to draw the web equally through the press and its rollers, must be set to provide a consistent speed and even pressure so that the substrate hits the image carrier uniformly. Worn-out bearings and gears can also cause unwanted side-to-side or up-and-down movement across or away from the web. In addition, ink transmission is hampered by inadequate contact.
- Surface Tension And Surface Energy
Wettability is affected by flexo surface tension and surface energy. Therefore, proper substrate wetting is determined by the surface tension of the ink, the surface tension of the image carrier, and the surface energy of the substrate.
- Surface tension, measured in dynes/cm, is the propensity of liquids in the open air to behave as though an elastic barrier surrounds them. Consider it like water droplets developing on a freshly polished automobile. Ink surface tensions that are too high might prohibit the ink from transferring and sticking to the substrate.
- Surface energy, measured in joules per square meter, is a related notion that applies to solids. It is the surplus energy at a material’s surface relative to its bulk.
- For the ink to attach to the image carrier, it must have a lower surface tension than the image carrier. As a result, the substrate’s surface energy must be greater to properly draw the ink off the image carrier.
As your printing plates or sleeves make contact with the substrate, pressure applies ink. A fading or scarcely visible print arises from insufficient pressure or ink. On the other end of the spectrum, applying too much pressure can cause the ink to expand beyond the margins of the print area, a printing problem known as feathering. The best strategy to minimize pressure-related faults is to maintain continuous and consistent pressure across the web.
- Ink Viscosity and PH
Controlling ink viscosity for solvent-based inks and pH level for water-based inks carefully should result in excellent flexo prints.
Temperature and viscosity are closely related. Water-based inks rely on pH management to ensure the solubility and stability of the resins and solvents contained inside. Automated systems may now control these critical factors.
- Maintenance and Cleaning
Show some love to your flexo sleeves, plates, and cylinders. They truly require it. Maintaining and cleaning them will not only lengthen their usable life but will also aid in the production of high-quality prints.
Use non-abrasive cleaning products and materials that are suited for the job. On most elastomer kinds, use mild soap and water or industrial alcohol to remove water-based ink. For the following inks, use a suitable solvent:
You must do the cleaning as soon as the press is removed. To remove stubborn ink and dirt, always use a soft-bristled brush. Allow your flexo items to air dry before properly storing them in temperate circumstances and away from ozone-emitting appliances for at least 4 hours.
- Avoiding Poor Ink Transfer Leave Now
Down press time and squandered substrate due to picture skips can cost you money. It’s most likely an ink transfer problem, which might have a variety of causes.
Calibrate your equipment and inks carefully to ensure:
- Effortless operation
- Image carrier uniform contact throughout the substrate
- Absorption and complete wet out
A Solution To Skip Out Effect In Flexo Printing
- Determine whether there is any change in the thickness of the printing form
- Adjust the press’s pressure setting. Check for proper form preparation
- Change the pressure applied to the printing form and the anilox roller
- Inspect the nuts on the printing group’s lock-up mechanism
- Examine the concentricity of the form cylinders (and gears)
- Examine the shafts, bolts, bearings, and gears for dirt and signs of wear
- Examine the printing unit for lateral parallelism
- Wash the printing forms thoroughly with the appropriate solvent. You should replace printing forms