by Catherine Green, All Printing Resources
In flexography, print defects can stem from a multitude of moving parts, making troubleshooting feel like a constant game of chase. Much like the human body, with proper care and maintenance, all parts of this highly complex system can work together in harmony.
While the anilox roll is the heart of the printing press, the doctor blades are the workhorses that let the anilox do its job properly. Without even, consistent ink metering, the anilox is unable to deliver a uniform, measured ink film to the printing plate surface– its primary (and only) function. Ensuring your doctor blades are set properly in the press can make or break your printed result.
By inspecting the contact patch surface, information can be gathered to determine if the blade pressure across the chamber is set evenly. Uneven blade pressure can be due to misaligned chambers or incorrect installation of the doctor blade into the blade holder. Also, contaminants in the ink can leave behind score lines in the blade, or worse, the anilox roll. Looking for these clues and correcting the issue with proper ink filtration can prevent anilox refinishing and costly press downtime.
Installation of the doctor blade into the holder is easily one of the most commonly overlooked factors in the process. If the blade is installed incorrectly, it is nearly impossible to achieve proper ink metering. Doctor blades should always be installed into a clean holder, completely free of ink residue or other debris. When placing the new blade into the holder, ensure the blade is fully seated, then secure the blade from the center, working your way out to the ends. Following this simple procedure will ensure you’re starting a straight and true blade with each changeover.
If the press uses a chambered system, you’ll need to ensure the end seals fit properly and the blades are in the proper position in relation to the end seal. Check the fit of the seal in the chamber by looking for any gaps or excess compression around the seal. Also be sure that the anilox radius is an exact match to the anilox used on press. The fit should always be snug and accurate. To further prevent leaks, ensure the doctor blade overlaps the end seal halfway.
Once the blades are properly installed, the correct blade pressure is set, and the press is up and running, how can we know everything is performing as expected? This is where doctor blade analysis comes in. By carefully analyzing the used blades (both metering and containment, where applicable), APR’s Technical Solutions Group can pinpoint issues such as improper blade angles, poor blade mounting, or uneven chambers. This can be quite helpful when troubleshooting an existing problem, setting up a new press, or testing doctor blades.
To schedule a doctor blade trial or find out more about our analysis services, contact Catherine Green at firstname.lastname@example.org.
About the Author:
Catherine Green – Catherine has over 12 years experience in graphic arts. An honors graduate of Clemson University’s Graphic Communications program, she has held positions in prepress, platemaking, and technical support. Before joining APR’s Technical Solutions Group, Catherine worked for Asahi Photoproducts as their Technical Specialist for North America. She brings expertise in digital platemaking, prepress, and process improvement to the TSG. She is an active member of the FTA, serving on both the Excellence in Flexography judging panel and FQC groups.
All Printing Resources, Inc. (APR) is a proven resource for solutions, trusted service, and support to the flexographic printing industry. APR delivers measurable performance enhancements and total cost reductions, including the after sale attention needed to see optimal results. APR represents some of the most innovative product lines worldwide and takes a “team” approach to deliver process improvement and innovative solutions
Source: FlexoGlobal Blog