Overcoming Common Web Handling Mistakes in Print Production
- Published: December 19, 2024
Managing Press Variables to Avoid Harmonic Distortion
By Bart Wright, Vice President of Technical Sales/Service, Pacificolor LLC.
Advancements in flexographic press designs and printing plate technologies have provided the means for flexo to compete with offset and gravure printing methods.
As the industry moves toward wider format presses and faster production speeds, taking a proactive approach to managing the variables on the print production floor have become ever more important in today's fast-paced flexographic printing industry.
Managing variables on press can make the difference between success and failure. Many of these variables can come together to create a common issue for flexo printers, called "harmonic distortion."
Having a documented and implemented standard operating procedure (SOP) for maintaining variables on the press floor can help prevent issues such as harmonic distortion, commonly known as press bounce, which negatively impacts print quality.
- Press Maintenance
Regular maintenance and cleanliness of the press are critical in preventing bounce, ensuring smoother operations and consistent print quality.
- Preventive maintenance programs for cleaning impression and anilox rolls.
- Monthly maintenance checks on print stations to ensure proper pitch and parallel of print mandrels. Print stations that are out of sync (un-parallel) will lead to improper print impression and bounce.
- Maintenance or upgrade of web tensioning systems.
- Maintenance checks for worn print mandrel spindles. Worn or damaged spindles will contribute to press chatter.
- Proper gear meshing on older flexo presses. Always replace older or worn gears.
It is worth noting that replacement gears for some older flexo presses are now extremely hard to find. Certain U.S. flexo printers are now producing replacement gears by 3D printing them with carbon fiber substrates.
- Layout Optimization:
Employing strategic layouts to minimize the risk of bounce.
- Staggering stepped designs and/or nesting of print designs will allow for continuous impression to the substrate across the width of the web, therefore reducing press bounce from station to station.
- Impression Adjustments
- Kiss Impression: Maintaining a light impression between the anilox and plate cylinder is essential. Over-impression can exacerbate bounce, leading to scuffing or uneven coating.
- Design Enhancements: Incorporating bearer bars or anti-bounce elements can significantly counteract bounce. Skewing designs slightly may also help by allowing one corner to engage first.
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Press Speed Considerations
Contrary to conventional wisdom, increasing press speed can sometimes reduce bounce. This approach is similar to how a vehicle handles seams on a highway at higher speeds.
- Tooling Upgrades
- Switching to carbon fiber sleeves can reduce chatter. Although costly, these upgrades are particularly effective for addressing problematic print stations.
- Replacing used or damaged print sleeves.
- Conversion from geared system to servo control system. This will help in the control of phasing between anilox and plate cylinders reducing the chatter commonly observed with older geared flexo presses.
- Plate and Tape Adjustments
While printing plates are rarely the primary cause of bounce, having the correct balance of Shore A hardness and cushion tapes can provide additional control and enhance print quality on press.
- Quality Control Integration
Integrating diagnostic marks like slur targets and impression targets into the design can help identify and resolve web handling and press issues early.
Other key variables to consider include ink PH and viscosity, Doctor Blades (metal or composite), ink drying temperatures, substrate (recyclable content or virgin).
Collaborative prepress efforts also play a key role. Early coordination between design, art production and prepress teams is essential to prevent layout-related issues.
Proactive collaboration ensures that potential problems are addressed before they reach the press, resulting in smoother production and higher-quality prints. Aim to solve potential issues which may occur further up-stream by working closely with your pre-press supplier as a partner and not just a flexo plate producer.
To summarize, it's important to always adopt a proactive approach to managing harmonic distortion in order to achieve optimal print quality. It's also important to highlight how innovation and adopting new technologies can enhance graphic quality for brands and increase productivity for converters.
It's crucial to work closely with brands, printers and packaging manufacturers to ensure accurate color reproduction and consistency across all printed materials. This involves advanced color management techniques, the use of sophisticated software, and a deep understanding of the printing process to meet the specific needs of clients to ensure the end product meets both aesthetic and technical specifications.
This relationship between brands and packaging manufacturers helps ensure consistent, accurate color reproduction, aiding companies in maintaining their brand integrity through their packaging.
About the Author
Founded in 1996, Pacificolor LLC is a leading pre-media supplier specializing in wide web flexible packaging, corrugated and offset for consumer goods packaging, with Bart Wright serving as vice president of technical sales/service. With production facilities across the U.S., the company is known for its expertise in ensuring high-quality print results, particularly in managing the challenges of web handling.