Home' FLEXO iQ : December 2015 Contents ISSUE 4 | FLEXO iQ 2015 15
Whether you need an inexpensive, short run die for a simple paper la-
bel on your 7-in., 3-color vintage press, or a 26-in. wide tight tolerance
die with 1,500-in. of cutting blade and 250 cavities to convert synthet-
ic labels on a thin film liner at 750 fpm—a flexible die can deliver.
The face material is driving the blade angle of the die. The rule of
thumb is: A wider angle for paper and a narrower angle for synthetic
face materials. But it’s not just about face materials and liners. There’s
also the adhesive. Several coatings are available to either avoid adhe-
sive build up on the blade or deal with exposed adhesives.
Flexible dies are suitable not just for pressure sensitive (kiss cutting)
applications as top or under cutter but also for metal to metal appli-
cations, like IML. Dedicated blade geometry (blade angle and flat) is
combined with laser hardening of the tip of the blade and finished
off with the material matching (chrome) treatment. The result: a die
formula that meets a wide range of converting needs.
With brand owners and retailers continuously developing new
packaging strategies, the pace of change has never been faster. New
packaging formulations are targeting the reduction of resource
consumption, packaging weight and waste; not only face materials but
also liners (and adhesives) are getting thinner and lighter. While this
benefits the environment, it poses challenges for many parties in the
value chain, from press manufacturers and die makers, to converters
and label applicators.
Printing and converting
equipment, as well as label ap-
plicators, require sensitive web
handling. Cutting dies have to
deliver an extremely uniform
liner strike to avoid excessive
penetration and subsequently
the risk of it breaking. But the
real challenge lies with label
converters. They not only have
to get the right components
in place but also the perfect
balance and process control.
It’s not just the die, it’s the total
control of the stack that mat-
ters. It’s the flawless magnetic
cylinder and an anvil with smooth surface and concentricity—at the
correct size. Undersized rolls will flex or bend, resulting in uneven liner
strike or lifting labels. It’s recommended to inspect and audit all compo-
nents on a regular basis—your die supplier will help you with that.
A well maintained die station with cutting pressure monitoring and
lubrication system is critical. And more importantly—and often
ignored—a heat management system throughout the press helps to
ensure consistent cutting results across the entire run length. Cutting
accuracy changes with every degree! A real game changer to convert-
ing is an adjustable clearance anvil (ACA). It not only helps to offset a
changing gap between magnetic cylinder body and anvil but to some
extent the wear of the cutting blade or changing liner thicknesses.
If you want to stay ahead of the game, investing in an ACA is a no
brainer and pays for itself in no time.
Flexible dies are also penetrating markets and applications previously
owned by either flatbed or solid rotary tooling. One example is the fold-
ing carton market. Flexible crush cut tools have been around for years
but don’t currently account for much market share. Why? Although the
cost for the flexible die itself is relatively low, it requires an investment
in at least a set of magnetic cylinders matching the print repeat. But the
limited die life is the major reason for its limited market share. You can
find flexible crush tools mainly in short run, digital applications, while
solid tools are the web fed converters’ choice for the long run. This is
beginning to change since the introduction of flexible rotary pressure
cutting (RPC) dies. With cutting (and creasing) blades not touching
each other, the die wear rate goes down while performance and life go
up. A set of flexible RPC tooling can reach up to more than 5 million
revolutions, which makes it a very attractive alternative to both solid
rotary as well as flatbed converting of folding cartons.
Where there is a need to convert, there is a flexible die that is ready to
tackle the job. n
About the Author: Ulrich Kretzschmar is product and business devel-
opment manager at RotoMetrics’ headquarters in St. Louis, MO. He re-
ceived his master’s degree in engineering, soon after entering the printing
industry. After several years of designing and selling label and packaging
printing equipment, he was offered the position of product manager for
major European and American based OEMs.
Born in Germany, he had the opportunity to live and work for several
years in Switzerland and eventually relocated to the United States to join
RotoMetrics in 2009.Transitioning from capital equipment to tooling,
he’s now responsible to further grow RotoMetrics’ flexible die and mag-
netic cylinder product lines, manufactured on four continents.
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