Home' FLEXO Magazine : November 2014 Contents QUESTIONS & ANSWERS
To prove accuracy, two questions need to be asked:
• How accurate does the measurement system need to be?
• What reference should be used to qualify “accurate”?
How accurate do we need to be? Achieving the correct densities in
process colors is the most costly part of press setup because of the
need to achieve correct color density and is therefore a good starting
point. In various studies it has been shown that process’ aniloxes
engraved to within 0.4 -cm3/m2 or better of each other will typically
achieve a color accuracy of 3 ΔE. So if the inventory is within 0.4-cm3/
m2, the printer will achieve the desired color target faster and mini-
mize waste. Therefore, a suitable target for the measurement instru-
ment would be to have a repeatable accuracy of ±0.1 -cm3/m2 for the
range of process aniloxes and ±0.2-cm3/m2 for coarser screen counts.
Accurate to what? With electronic scanning devices it has been possi-
ble to prove volumetric accuracy, which has simply not been possible
with the historic analog (ink drawdown) systems.
HOW DO WE PROVE ACCURACY?
The ability to prove accuracy has been an evolutionary process and,
this year, became a practical solution.
If the diameter of a (ball bearing) ground sphere is known in the X, Y
and Z dimensions, its volume, surface area and any other parameters
can be calculated through simple math. E xtrapolating that data makes
it possible to calibrate the electronic scanning microscopes very accu-
rately—to within ±1-μm—and subsequently accurately define the vol-
ume of the sphere. Once the three dimensional scanning microscope
(AniCAM) is calibrated to the sphere, the analysis program (Anilox
QC application) will correctly measure the volumes of any anilox.
Proving the theory : In February, working in conjunction with WCPC
at Swansea University under professor Tim Claypole, Troika under-
took a project to test the
depth and volumetric
accuracy of a sphere
against the WCPC very
high end interferometer
on a 12 banded anilox,
engraved from 1,500 lpi
down to 100 lpi. Both
devices used different
to calculate the volumes
on the 12 different
anilox engravings used
for the test.
The correlation of measurement between the two systems was excep-
tionally close and, as Dr. Davide Deganello stated, “As there is a recog-
nized inevitable variability of volume due to surface roughness, minor
variations in measurement were expected. However, there is a very
high degree of consistency between the two systems. The accuracy of
the measurement systems is certainly well within the measurement
requirements of the industry.”
As I noted at the time, “For printers, a standard of volumetric
measurement has now been scientifically proven with a practical
instrument that can be used on the shop floor. Printers and anilox
manufacturers alike can now have the confidence that measurements
are realistic and based on credible data, from which the industry can
work from as a proven point of reference.”
Will this development have any impact on the future of our industry?
Almost certainly : The ability to measure aniloxes accurately will allow
printers to have a reference from which to work from and allow great-
er freedom when choosing between different suppliers and to check
the quality and consistency of aniloxes purchased.
It is also anticipated that it will contribute to future developments in
electronic printing and allow the ongoing development of ink release
characteristics to be calculated from different engraving shapes and
styles, and consequently the optimizing of ink rheology for different
cell structure. ■
About the Author: Phil Hall is the managing
director of Troika Systems Ltd. in the U.K . He has
been involved in the industry for more than 35
years. He has presented papers at FTAs in the U.S.,
Germany, Asia, Poland, Italy and the Netherlands
on anilox measurements and management, and re-
cently presented at the global International Associa-
tion of Research Organizations for the Information,
Media and Graphic Arts Industries (IARIGAI) meeting of the Welsh
Centre for Printing and Coating (WCPC) at Swansea University U.K.
Over the past 10 years, Phil has focused his company’s developments on
quality control tools designed to make time saving and reduce waste at
its more than 600 customer sites globally.
Troika Systems was founded in 1996 and employs 14 people with
distribution in all major countries. Troika Systems is entirely focused
on quality control products for augmenting efficiencies in the flexo and
Troika Systems gratefully acknowledge the contribution of Swansea
University for their part in this study. In particular, professor Tim
Claypole for giving access to the facilities and equipment at the WCPC,
and for the considerable time given by Dr. Davide Deganello Ph.D and
Sakulrat Foulston in taking the measurements, computing the results,
and compiling their repor t.
42 FLEXO | NOVEMBER 2014
An AniCAM operator
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