Digital Printing Technology and Closure Inspection in High-Performance Segments - IMDvista
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66 IN FOCUS DIGITAL PRINTING DIGITAL PRINTING IN FOCUS 67
3 The Digital Printing Process
Everything has to go hand in hand. Specialists
first analyze the closure application,
Pool Competencies carefully considering the polymerization
kinetics of the ink and the curing times.
The value of the dynamic behavior of an
Innovative: ink in terms of viscosity, surface tension,
flow properties, adhesion and opacity on
the respective print head is calculated
Digital Printing Technology to optimize the printability of each ink
for accurate placement of the ink drops.
(fig. 2).
and Closure Inspection in
High-Performance Segments Fig 3: Difgital printing process
Matthias Hermle, CEO, IMD, Switzerland
3.1.1 Surface Pre-Treatment with 3.1.2 Surface Wettability
The closure is a part of every bottle. Every consumer touches it, uses it and pays attention to it.
Plasma
Mostly it’s the only part that consumers can see when the bottle is on the shelf, the ideal place for The wettability depends on a specific
advertising and messages. As well as closure is suitable as a collector’s item. In order to successfully print a plastic property of the surface: surface energy,
surface, ink should be able to wet the often referred to as surface tension
surface to achieve proper liquid adhesion. (fig. 4).
This requires Corona Treatment and
Fig 2: Colour drops Plasma Treatment technologies. The wettability can be easily detected
Plasma can be described as partially by contact angle measurements. The
1 Introduction ionized gas. Therefore, by selecting a contact angle is the angle between the
3.1 Technology gas mixture, pressure, and power, the tangent line at the contact point and
Mechanical printing machines, either effects of the plasma treatment on any the horizontal line of the solid surface.
based on pad or dry-offset technology, Our technology is utilising inkjet-based surface can be precisely tuned. (fig. 5).
are the established printing options for digital printers. The inkjet printer creates
closures. Digital printing for closures your image by transferring tiny droplets of
is a relatively new and innovative, ink to the closure. The first layer is white, if
even revolutionary technology. The necessary, then cyan, magenta, yellow and
motivation for printing a closure will black. By mixing these colours up to 80%
change completely with digital printing, of the Pantone colours can be printed
because now almost everything can (fig. 3).
be printed, at any time with absolutely
flexible in format and printing. It’s all The digital printing process is well
about flexibility and time-to-market. suited for personalized direct marketing.
With this type of printing process, variable
printing is possible, which allows any
2 Artwork type of direct marketing. In this day and
age, it is common marketing practice to
A RIP service (Raster Image Process) consider each customer as an individual
allows artwork to be transferred directly with different composition and needs -
from digital production to the file to be and personalization is unrivaled thanks to Fig. 4: Wettability of plastic surfaces: Low surface energy material (left); Liquid does
Fig 1: The preprint workflow not „wet“ the surfaces. High surface energy material (right); Liquis „wets“ surface
loaded onto the digital printer (Fig. 1). digital printing.
CONNECTING COMPETENCE | TWO:19 COPYRIGHT PETNOLOGY/TECPET GMBH
68 IN FOCUS DIGITAL PRINTING DIGITAL PRINTING IN FOCUS 69
3.1.3 The UV Ink 3.1.4 UV Curing Process The flexible “REDCUBE Plus” printing Special lighting and a high-resolution Easy operation for the complete system
module from Hapa is the heart of the colour camera ensure that every printed with just one HMI, the IMDvista V5
UV inks are typically highly viscous, Long lifetime UV LEDs are carefully digital printer. It is able to print CMYK closure has perfect print quality before Vision Control Center controls the entire
limiting the flow on the substrate. This, paired with the photo initiators in the and white. Print-head maintenance is shipment to the customer. system including the print parameters.
in combination with the instant or spot ink. Power, ramp and time under UV light fully automatic with automated ink
fixation provided by UV curing lamps, and the entire UV station is precisely conservation and cleaning. For colour-
results in excellent print quality and fast selected for perfect ink cure and good on-colour printing, two pinning stations
overall operating speeds. migration results. are integrated as well.
After curing UV inks are typically 100% For final inspection, an IMDvista print
solid, meaning that everything that 4 System and Engineering control system is part of the system to
is printed remains on the substrate. ensure that your customers receive only
By using UV ink, there are no longer Since the system must be flexible 100% compliant prints. The V5 Vision
polluting VOCs that escape from ink to handle multiple print and closure Control Center is the single controlling
solvents. Reducing air pollution is an formats, many challenging mechanical HMI that makes operation easy as found
advantage for those who want to pursue engineering aspects regarding alignment with all IMDvista vision systems.
a greener approach to production. rails, guides, jet streams, UV light holders
This is also of particular importance as had to be taken into account. The complete system with the plasma
most countries have strict laws that are pre-treatment, printing, UV curing agent
constantly updating in terms of VOCs. The system is also designed to easily and the visual inspection, has production
Fig 5: The difference between good
The use of UV inks is one way to avoid print samples for customers. This capacities of up to 1500 closures per
and poor wettability.
production traps that may occur due to shows one of the biggest advantages of minute (28 mm).
legal regulations. digital printing: you can print samples
with a very large format variation in The system can be operated practically
The higher the surface energy of the The photo initiator is the key to the curing minutes. independently for days with only filling
solid substrate in relation to the surface process as it starts the polymerization the ink tanks once per shift (fig. 7).
tension of the liquid, the better its and cross-linking reaction. Under UV In addition, an intelligent sampling
wettability and the smaller the contact irradiation, the photo initiator fragments function enables quality control to
angle. into free radicals, which are the reactive remove any number of samples from 4.1 Caps and Closure Positioning
species for the polymerization of the production run at any time without
For proper bonding between a liquid and unsaturated species (moieties). stopping the process. In general, it can be said that print shifts
a substrate surface, the surface energy of more than 0.1 mm can be seen by
of the substrate should exceed the liquid the human eye. Requiring this level of
tension by about 2-10 mN/m. precision means that the closure must
Surface energy Needed surface energy
not move more than 0.05 mm during the
of base material for adhesion with:
Fig. 6 shows the absolute surface energy 5 print stations!
values for solid materials, and the surface PTFE < 20 mN/m UV ink 48-56 mN/m
tension of many plastics, including Silicone < 20 mN/m Waterbased 50-56 mN/m In order to achieve this level of accuracy,
polyethylene and polypropylene, is often the closures are precisely transported on
PP 30 mN/m Coatings 46-52 mN/m
insufficient for bonding or printing. an innovative stainless-steel vacuum belt
PE 32 mN/m UV glue 44-50 mN/m that resists the heat and energy of pre-
A surface treatment can improve the PS 34 mN/m Waterbased glue 48-56 mN/m treatment and UV curing. Plastic belts
wettability of the material by increasing PC 34 mN/m are unsuitable due to the extreme loads.
the surface energy of the material and ABS 34 mN/m
positively affect the adhesive properties
XLPE 32 mN/m
by producing bonding sites. The most 4.2 Inspection and HMI
advanced and successful surface PUR 34 mN/m
treatment methods are based on the Finally, the well-known IMDvista Vision
principle of high voltage discharge in air. Fig 6: Values of surface energy for solid materials and the surface tension System inspects the printed closure.
CONNECTING COMPETENCE | TWO:19 COPYRIGHT PETNOLOGY/TECPET GMBH
70 IN FOCUS DIGITAL PRINTING DIGITAL PRINTING IN FOCUS
increasingly stringent regulations. Almost analytical proof that migration values 7.2 Curved surfaces
all countries now have detailed standards are complied with each order. Reliable
for food safety. proof of conformity is therefore only Concave or curved head-plates of
possible through cooperation along the closures are always a big challenge for
The umbrella regulation for the production entire value added chain. the mechanical printers. These hurdles do
and marketing of food products is the not affect Inkjet technology. The print is
food safety regulation (EC) 178/2002. Manufacturers of branded goods and as perfect on smooth surfaces as it is on
There are also a number of subordinate
regulations regarding food contact
retail chains fear above all, in addition to
the legal consequences, a loss of image.
curved forms. Not even the injection gate
presents an obstacle to this technology.
THE PET
materials and their production. The
European Food Safety Authority (EFSA)
Many of the major food manufacturers
and retail chains have therefore already 7.3 Recycling
COMMUNITY
designates all items that are intended developed house standards derived
to come into contact with food as food from EU regulations and that are applied This is a very interesting aspect of this
contact materials. accordingly throughout the value new technology. Undyed, transparent
chain (e.g. Nestlé, Danone, REWE and closures are best for recycling. Therefore
The main regulations are as follows: McDonalds). HDPE in its “pure” form would be ideal
for recycling, also for circular use and
¡ Food Contact Materials (EC) Low-migration ink systems promise a way re-producing closures. Individualization
1935/2004 out of this situation, but do not expect and differentiation can be achieved very
¡ Plastics (Plastic Implementation any standard or EU regulations for low- efficiently by digital printing. At this
Measures) (EU) 10/2011 migration inks. The term “low migration” point, the investigations and tests are still
¡ GMP (Good Manufacturing Practice) is rather used by ink manufacturers to ongoing. The question is how to separate
(EC) 2023/2006 identify UV inks that can comply with the ink from the HDPE material.
regulations when used properly on the
5.1 Who is Responsible? particular type of packaging. 7.4 Marketing Options
Basically, the person or company In addition to the high print quality, the
that markets a product is legally 6 Abrasion with test results security and stability of the process, it is
responsible for ensuring that the the marketing options that enable the
manufacturing process for both food Ink adhesion is often confused with system to make a breakthrough. And
(content) and packaging complies with inadequate drying, which is not here I come back to the introduction: A
the regulations. Partial responsibility always the case. It is advisable to use closure is suitable as a collector’s item.
for the various packaging components appropriate test methods to reliably Imagine that you can print 20 different
is, however, usually delegated to the determine the actual cause. images in a repeating sequence in the CONNECTING
suppliers through a declaration of same printing process. This opens up an comPETence
conformity. IMD has introduced their own test unimaginable field of marketing options.
powered by PETnology
procedures because tape and cross-cut
This sounds relatively simple in theory tape tests are controlled by the operator
however is far more difficult in practice. and/or depend on the test material
The main problem is that the proof of (tape). Therefore, the tests are not
conformity cannot be provided directly repeatable. AUTHOR
Fig 7: Machine panel during the manufacturing process of Matthias Hermle
the closures, but only after a time- CEO
consuming process carried out by an 7 Future and outlook
COMPANY
accredited institute. In addition, the
The system is secured though a biometric 5 Food Contact Materials and relevant migration properties depend 7.1 Current status IMD Ltd.
CH-2555 Brügg BE, Switzerland
authentication system to ensure system Migration on the content, the barrier properties of www.imdvista.ch
validation. the packaging, the storage conditions, The first system has been running in real Surface treatment, text and pictures
Tantec A/S
More and more food products are being the shelf life of the products and production since February 2017. Over www.tantec.com
In other words, printing on a digital printer manufactured on an industrial scale their further processing. In practice, 200 million closures have already been Ink and Redcube, text and pictures
always gives the same results in terms of and sold through retail chains. Their closure printers hardly know all these printed, from standard logos to special from Hapa Ltd.
www.hapa.ch
both print quality and ink quantity. production and distribution are subject to parameters and can rarely provide ads.
CONNECTING COMPETENCE | TWO:19 COPYRIGHT PETNOLOGY/TECPET GMBH
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