Anilox Roll Wear Indicators
As print customers push for lower costs to go along with finer print demands, printers are forced by necessity to find ways to keep margins profitable through continuous improvement efforts to save on waste while meeting objectives. Customer expectations for flexo-printed products in the past simply consisted of looking at a Pantone book and visually comparing color, shingling to monitor for color consistency and visual inspection of random sampling throughout the production run.
Today’s customer expectations are moving deeply into continuous electronic measurement using tools, such as inline spectrophotometers. Instead of a single measurement to satisfy, they look for trends and documentation of color consistency via SPC charts, as well as further monitoring quality through video/digital defect identification tools. This puts a greater emphasis on anilox condition and the proper recertification of the volume and deposit efficiency. Anilox rolls wear naturally. Recertifying your anilox inventory is paramount to understanding your rate of wear, which includes volume and deposit efficiency loss.
Audits of your anilox inventory involve taking impressions of the anilox rolls and having them measured and documented. Results from such an audit show the current cell wall and opening size in comparison to the original specification. The audit will also record score lines, dings, blistering and other damage to the roll that is not always reported from the pressroom.
Optimize & Prioritize
Although not all printers are using these practices, a lot of customers are looking for this confidence that products are being produced with a level of repeatability, as well as color management, across multiple SKUs and printing processes for primary and secondary packaging. The way for printers to manage this is to optimize and standardize their printing process. Doing the following helps:
- Reduce makeready times by trying to eliminate color matching at this stage
- Reduce downtime during the run by optimizing press conditions between the anilox, ink, plates and substrates
- Ultimately reducing ink inventories
Continuous improvement with the anilox can also mean what has been done in regard to press and print optimization of the printing press. This starts with determining what inputs you are putting into your process. Discovering the proper combination of ink, tape, plate and anilox specification involves using a banded anilox roll. A banded roll is an anilox with several bands, each with different engravings that include the recommended cells per inch and volume from the ink supplier and plate manufacturer. Test to failure.
Don’t undershoot your capability as a printer; you may well surprise yourself with what you can accomplish on press. Testing to failure means testing specifications above and below the recommendation. Include elements that serve as tools. Tone scales, slur marks and other print indicators must be aligned with each band and printed at expected press speeds without adjusting the ink, outside of recommended specs. Once measured, it is simple to find the anilox CPI and volume, in conjunction with plate and ink, that together give the best dot reproduction while holding proper solid ink density.
Banded roll testing and optimization should always be done with both process and line work anilox sets, but banded rolls are also used for many coatings and special effects, since some of those elements are subjective and cannot really be satisfactorily measured. Once this is achieved, the printer can standardize the inputs to the process for all ink and substrate types and then proceed to fingerprinting, characterization and, ultimately, standardization.
The press will need to be set up to the established standards for all jobs that require each press configuration. Following these steps will help standardize your anilox sets and thereby reduce your anilox variation in the pressroom.
Proofing Correlation
Now it is time to turn to anilox rollers and the proofing of the ink in the inkroom for color control. The goal is to have the ink ready to pour in and run at press with the benefit of reducing makeready times and ink inventories. Wet proofing of the ink in the lab to achieve a color on target prior to the press is called proofer correlation. This step is most important when matching spot colors, but is useful in testing any and all inks heading to press for accuracy.
The process begins by achieving color at press and at run speed. Once the color is achieved, a wet sample is taken to be proofed on the same substrate being printed. Drawdowns are done using multiple proofing rolls at different volumes until the color matches what was approved press side. This may or may not be the same CPI or volume as what is being run on press, due to speed, transfer, and process differences between press and proofing.
Once the CPI and volume of the proofer are correlated to the standardized anilox rolls at press, that proofer roll should be used to match color as a standard. The reciprocal occurs: You match in the inkroom and that ink will then match when delivered to press. If done right, ink inventories should stabilize because of less anilox variation on the pressroom floor.
Ink matching time at press will reduce, as you have made it an external process. Downtime during the run for ink issues should reduce, if the ink is kept in the same stable state during production as it was when brought to press. You create the control from the inkroom and the ability to cut costs at press.
Standardizing Anilox Inventory
Auditing your anilox inventory on a regular basis is key to understanding when you are losing volume on your rolls, which negatively impacts color matching and color control. Volume loss without knowing will creep up ink inventories and ink matching time. Therefore, anilox standardization is important. If you are standardized with your anilox inventory, another roll should be available while the worn roll can be taken out of service and/or remanufactured.
The anilox roll has come a long way in a short time, continually improving and evolving as technology and growth continues to challenge the flexo process. The ongoing challenge to the pressroom is to keep anilox rolls in serviceable condition for as long as possible through training and understanding of them and their role in continuous improvement efforts.
Customers are constantly shopping for competitive pricing while increasing the need for high quality and pushing the boundaries of flexography’s capabilities. The burden falls on the printer to find ways to keep margins up while still offering competitive pricing in a very challenging market. This burden also falls on the anilox manufacturer to offer printers the highest-quality product along with offering value added services to help the printers achieve the best margins possible using their rolls. Printers should take advantage of knowledge and guidance from their vendors for processes and best practices on how to achieve the best results of the critical inputs to their process.
Continuous improvement is just that—It’s continuous. It takes a lot of effort to keep pushing and looking for new ways to positively impact your business. The one thing we can always count on is that necessity is the mother of invention, so as long as customer needs continue to grow, so too will the improvement of the flexographic process.
About the Author
Greg is a Lean Six Sigma Black Belt and is also FIRST Implementation Specialist certified. He has served both as chair and co-chair of sessions at FTA events, most recently chairing the Pressroom Pressures session at FORUM 2017 and speaking on a panel at Fall Conference 2016. Greg has participated as a judge in the Excellence in Flexography Awards on three occasions and has published articles in FLEXO Magazine. Greg is now applying his years of industry experience to helping Harper Corporation of America and the Harper Graphic Solution Group’s customers as a technical service representative in the Central Plains and Southwest regions.