Digital Methods of Anilox Cell Volumetric Measurement
Toward the end of the 1990s, electronic volumetric measurement systems began to evolve. These used interferometric measurements and gave good, reliable readings, but were impractical for printers: They were very sensitive to vibration, expensive and wouldn’t survive long in the print shop environment.
Troika’s entry in the market—its AniCAM with Anilox QC software—made its first appearance in 2005 and, over the years, evolved to meet the demands of the large print groups who recognized the cost benefits that come with knowing the condition and volumes of their anilox inventories.
The demands of label, wide web and corrugated groups can best be summarized by the requirements of one world-leading carton print group, which are:
- Accuracy of ±0.06 bcm for process aniloxes
- Repeatable measurements of ±0.06 bcm when measured in the same place
- The ability of different operators to get the same readings
- Ease of use with data archiving for anilox inventory management
- No time (or minimal time) lost in production due to measurement taking
In achieving these requirements, accuracy of measurement was the biggest obstacle—simply because it had never been proven. This gave all anilox manufacturers the ability to argue their own measurements were correct on historical grounds, and the other anilox manufacturers were wrong—not a very good situation for the industry.
With the significant differences in measurement standards used by all the anilox manufacturers in the aforementioned 2007 research, who was right? Was anyone?
The accurate measurement of anilox cells was proven in 2007 by Dr. Davide Deganello at Swansea University, Welsh Centre for Printing and Coating (WCPC), one of the leading print universities in Europe, under the leadership of Professor Tim Claypole. Dr. Deganello’s thesis and equipment proved the volume of cells through high-end digital analysis using laboratory interferometers.
In comparative tests between the high-end interferometer at WCPC at Swansea University and Troika’s AniCAM, it was found the measurements on all 12 bands were very comparable, and Dr. Deganello stated that the measurements were certainly well within the requirements needed in our industry.
Calibration for Accurate Anilox Volume Measurements
Most important for accurate volumetric measurement is calibration; this is required in all three axes. The x-axis and y-axis are relatively simple and make use of an optical graticule, which is made up of small glass surfaces with a grid etched onto each at 100-μ. spacing, allowing for very accurate calibration in both directions. Depth measurement needs to be particularly accurate, and with the x-axis and y-axis data, the depth is used to calibrate the units to give the exact volume of the cells.
Calibration for depth is achieved by scanning a very small sphere (ball bearing) of a known size, which logically is the same dimension in all three axes. Spheres have been used as a method of calibration by some interferometer manufacturers since 1998 and are known to be mathematically accurate. With this system of measurement and calibration, the industry had—at long last—a mathematically proven, accurate measurement standard from which to work.
In 2013, Troika developed a method of using a sphere of a known size as a valid reference standard for dimensional and volumetric measurement. The AniCAM Calibration Program (ACP) was developed so users could calibrate their AniCAM, usually annually or as frequently as desired.
Anilox Measurements Value Conflicts
Clearly there is a conflict between the accurate, mathematically proven measurement system used by many hundreds of printers globally, and the historic values used by the many anilox manufacturers around the world. It would be very difficult for the manufacturers to change their historic measurement values, so a solution needed to be implemented.
The solution was to export from the Anilox QC both values of measurement, so if an anilox manufacturer’s original measurements are different from the accurate readings, it can export both the accurate value and its individual standard values to the anilox roll information sheet.
Conclusion
The evolution of anilox manufacturing has bought many advantages to all users; they are now produced to a very high standard of consistency and repeatability that was not possible even a decade ago. With the evolution of the anilox, there was a need for accurate and reliable measurement, giving flexo printers the ability to manage their anilox inventories to a point where press setup time is optimized and makeready waste is reduced to a more practical minimum.
This is not the end of the story; there are some very interesting developments on the horizon with different materials being used in the production of aniloxes. Also, now that volumetric measurements can be accurately taken, we can progress to analyzing and optimizing ink release characteristics with different cell structures designed for the individual print or coating processes.
It’s still a very exciting time in flexo.
About the Author: Phil Hall is the owner of Troika Systems Ltd. in the U.K. He has been involved in the print industry for almost 40 years, starting as support technician for Crossfield Electronics on the early color separation scanners in the 1980s, then progressing into sales and marketing over the intervening years. Phil started Troika in 1996, always having an eye for trying to improve production efficiencies, and in the last decade, with environmental considerations, reducing waste, he looked to develop products that could achieve these aims.
For a personal illustration of the productivity and makeready waste benefits, please contact your regional Troika Systems representative or email: [email protected].