Print Technologies and Design Concepts for Hybrid Printing Systems

DPP2001: International Conference on Digital Production Printing and Industrial Applications
Print Technologies and Design Concepts for
Hybrid Printing Systems
Walter d’Heureuse and Helmut Kipphan
Heidelberger Druckmaschinen AG,
Heidelberg, Germany
Abstract
strength of the individual print technologies. Especially
for digital production printing the combination of
computer to press with offset direct imaging technology
and an ink jet imprinting unit (page wide) is also
described.
The several printing technologies, conventional (e.g.
offset, flexo) and non-impact printing (NIP) (e.g. electrophotography, ink jet) have their special applications,
strengths and weaknesses. This is especially visible when
considering the economical run-length, the print quality,
the cost structure in general and the ability to vary the
image during the print run. The combination of different
printing technologies can create efficient and powerful
production possibilities and systems such as in-line
imprinting, personalization and coating (print finishing).
This paper mainly discusses hybrid-systems,
combining conventional and Non-Impact Printing
technologies (e.g. offset with ink jet), but also discusses
hybrid-systems of NIP with NIP (e.g. electrophotography and ink jet) and conventional with conventional
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(e.g. offset with flexo) as shown in figure 1.
The hybrid-systems of conventional with NIP (e.g.
offset with ink jet or electrophotography) can achieve the
superior image quality associated with conventional
technologies while adding customized information on a
page by page or job by job basis.
The attributes associated with the various
technologies in hybrid printing technologies such as the
necessary paper specifications, speed and architecture as
well as examples of existing and possible hybrid-systems
are described. These systems take advantage of the
Introduction
In today’s market, there is an ever growing demand for
print products that fit the special, individual needs of the
customer, or a whole customer group. Personalized print
products (i.e. names and/or addresses that vary from
print to print in an otherwise fixed print image) and
segmented print orders (i.e. parts of the print run that are
modified) try to meet this demand.
At the same time, the market requires high print
quality, short times for completing the whole process
from order to delivery, and the usual cost structure for
medium run lengths. In order to meet these demands,
companies have to make use of the special advantages of
the various printing technologies and integrate these in a
complete workflow for the production of a print
1-5
product.
Hybrid systems, combining the strengths of different
printing technologies in one printing system, are capable
of producing special print products while maintaining a
4
high level of economic efficiency and productivity.
Figure 1. Combination of various printing technologies to set up hybrid printing systems.
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DPP2001: International Conference on Digital Production Printing and Industrial Applications
Printing Technologies for Hybrid Printing
technologies. From an economic efficiency point of
view, a very fast system should not be combined with a
slow one. The requirement to print with variable speed,
for instance in case of feeding difficult paper, might
reduce the variety of combinations. In table 1 the most
relevant properties of print technologies are shown for
building up hybrid systems.
It is evident that every technology has its own special
applications which can be characterized by the run
length, the quality of the print, further processing
options, cost structure and economic efficiency.
The diagram (fig.1) gives an overview of the most
important conventional printing technologies requiring a
master as well as non-impact technologies which operate
without a master and shows how so-called hybrid
printing systems can be set up from a combination of
1
these technologies. Production on sheet or web material
using the relevant inks is possible. Sheet-fed printing
systems are generally characterized by a higher degree of
format flexibility, web-fed systems by a higher
productivity. Printing is done on different substrates such
as uncoated and coated paper, cardboard and also plastic
film material. The different substrates require special
inks tailored to the printing process itself and to the use
of the end product (in- or outdoor, food packaging, etc.).
The highest print quality is achievable with offset
(with the exception of gravure printing), in particular for
multicolor images. High printing speed is possible
(sheet-fed up to around 4 m/s and web-fed up to 15 m/s)
and the printing plates are produced quickly and
economically compared to other technologies.
Flexographic printing technology is especially
suitable for printing with varying inks and ink/varnishing
systems particularly in high film thickness.
High ink film thickness is also applied with gravure
and screen printing. Gravure printing is however only of
low importance in connection with hybrid printing
systems due to the expensive production of the printing
plate/cylinder. Rotary screen printing is preferred for
very high ink layers with high color density.
NIP- printing technologies, such as ink jet and
electrophotography, make it possible to print a variable
image page per page but in general at a lower print
quality and higher cost per page than with offset or
1,6,7
gravure printing.
The combination of various printing technologies
can bring about very interesting production options with
both a high degree of economy for the printing company
and benefit to the customer. Figure 1 also shows how
technologies can be combined with hybrid systems,
merging conventional technologies, NIP-technologies or
conventional with NIP.
When using hybrid printing systems the
characteristics of the printing substrates, ink acceptance,
print quality expectations and paper transport are of
particular importance. The combined printing
technologies have to fulfill requirements and must be
well suited to each other. The type of drying and fixing
process used to attach the ink to the substrate largely
determines the sequence of printing. Chemical and
physical reactions of the inks with each other (e.g.
decomposing or non-wetting) must also be taken into
consideration. Furthermore the design of high economic
print systems are determined by the maximum and
reasonable printing speeds of the respective print
Table 1. Selected Important Features of Print
Technologies (see also fig. 1)
Offset
- transfer of one ink film/color separation
(around 1 micron ink film thickness) with
high pressure onto the paper
- almost independent of paper substrates,
but limited to plastic material
- high print quality
- high speed (up to around 4m/s in sheetfed) and variable speed is common
- ink is not dry (exception UV-ink)
- ink cost is a very low percentage of the
TCO (total cost of ownership)
Flexo
- ink film (around 1 micron) with
“kissprinting” onto the substrate, but also
high ink/varnish film thickness possible
(around 2.5 microns)
- printing on various substrates
- print quality not as good as offset
- high speed and variable speed
- UV-curing inks are preferred (fast drying,
good quality and high density
- ink cost is a very low percentage of the
TCO
Screen
- transfer of ink film with low pressure
- technology is preferred if very high
densities (ink film thickness up to around
12 microns) or special effects are
requested
- printing on various substrates
Ink jet
- no contact with print substrate
- very low viscous ink (nearly like water)
- print quality dependent on substrate;
penetration into the substrate (spreading)
or non-wetting the "glossy" substrate
surface (UV-curing inks and hot-melt inks
are less “critical“)
- speed up to around 2 m/s (400 ft/min),
variable speed is possible
- drying, depending on ink type
- ink cost is a high percentage of theTCO
Electro- - transfer of toner by contact with print
photosubstrate and electrostatic field (toner layer
graphy
thickness around 5-10 microns)
- overall print quality worse than offset
- limited printing substrates
- speed up to around 1 m/s, no variable
speed (control of process) in general
- toner fixing usually by heat and pressure
- ink cost is a very high percentage of the
TCO
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DPP2001: International Conference on Digital Production Printing and Industrial Applications
Concepts and Examples of Production
Systems Combining Different Printing
Technologies
with an ink jet printer for imprinting additional
1,6
information in spot colors. The electrophoto-graphic
printer is the main system and can print a page-wide
image. The ink jet unit (piezo drop-on-demand, using
hot-melt ink) for imprinting spot colors can only print a
width of around one inch per head. Several print heads
(e.g. eight) can be positioned across the width of the web
and each head can print with a different color.
Highlighting of names and results in bills or lists is done
with this printer. It is fast, up to around 1 m/s (200 fpm,
240 dpi), and the quality of the printed image/text is
acceptable. A multicolor electrophotographic system
capable of this high speed and also suitable for this type
of work (black and one or two spot colors) is not yet
available for cost reasons.
Combination of Conventional Technologies
Within conventional printing technologies, hybrid
systems that combine offset and flexographic printing,
such as sheet-fed offset presses (see fig. 2), are already
well-known. The latter have an attached coating unit for
printing on the whole surface or partial (spot coating)
application of a coating onto a high-quality multicolor
1
print produced in the same press. With these systems it
is also possible to produce colored imprints using a
flexographic plate, for instance, with special effect
coatings or special colors (spot color). The coating or
varnishing unit consists of a plate cylinder, a chambered
doctor blade inking unit and an impression cylinder. The
varnish is laid on top of the offset ink, which is not yet
dry. In this example, drying of ink and varnish (or
special effect inks) is done by an IR-dryer.
Combination of Conventional and NIP-Technology
Combining conventional offset or flexo with a NIPtechnology is shown in figures 5 and 6. Offset and ink jet
printing are shown in figure 5 are similar to the
demonstration by Heidelberg as a technology/concept
study at Drupa 2000 (at Drupa with a single color
Quickmaster). The high quality fixed image is printed on
the QM DI 46-4, a 4-color offset press with direct
1,8-11
imaging technology, and the imprinting,
which adds
variable information to the offset print with one color, is
done over the complete sheet width with ink jet. At full
speed, 10000 A3-sheets/hour are printed. The ink jet
imprinting unit is based on the piezo technology from
Spectra and images with 7680 independently addressable
nozzles (325 mm/12.8” wide) at a resolution of 600 dpi
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and 38 kHz at full speed (1.6 m/s, 320 fpm). At the end
of the imprinting unit a UV-dryer is installed to cure the
UV-offset ink as well as the UV-ink jet ink. Only one
dryer is needed to dry/cure the images of both printing
units simultaneously. After passing through the UVdryer the inks are completely dry and the print is ready
to ship or for additional finishing processes. Since the
ink jet print head has a short distance (about 1 mm) – no
contact - to the paper surface with the wet offset ink, it is
possible to install the imprinting unit after offset
printing. With sheet-fed printing it is preferable to print
the fixed image first and then at the end of the paper
travel the variable image. The workflow for reprinting
sheets in the event of print interruptions (e.g. paper
misfeed) is easier to handle. (In electrophotography the
photoconducting surface or the intermediate carrier has
contact to the substrate; the imprinting unit therefore has
to be installed before offset printing or the offset ink
must be dried in advance.)
Figure 2. Multicolor sheet-fed offset press with coating unit as
a hybrid printing system combining offset and flexographic
printing
Another example of the combination of
conventional printing technologies is demonstrated in
figure 3, a label printing press with flexo and screen
printing units, and an additional unit for hot-foil
1
stamping. UV-dryers are installed between all units to
cure the UV-ink. Wet-on-wet printing, that is without
intermediate drying, is not possible in multicolor
flexo/screen (like in offset). The different printing units
are designed in such a way that they can be changed
according to the special print job requirements.
Combination of NIP-Technologies
Figure 4 shows a system where electrophotography,
for high speed monochrome printing, has been combined
Figure 3. Hybrid printing system for label printing combining flexography, offset and screen, as well as letterpress for hot-foil
1
stamping/embossing (CombiPrint, Goebel/Drent)
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DPP2001: International Conference on Digital Production Printing and Industrial Applications
continuous ink jet technology) are spread over the length
of the last impression cylinder of the offset press. Only
columns can be printed since there is no overlap of the
heads.
Figure 7 shows a possible design of an
electrophotographic printing unit installed in a larger
format sheet-fed offset press. The dryer of the offset ink
(UV-curing ink) is positioned downstream of the offset
units. Instead of an electrophotographic system it is of
course possible to install a magnetographic, ionographic
1
or ink jet system.
Figure 4. Hybrid printing system combining the NIPtechnologies of electrophotography (single-color printing) with
ink jet imprinting system for multicolor (spot color) imprints
(InfoPrint 4000/Info Print Highlight Color, IBM/Accent Color
Sciences)
Figure 6. Hybrid printing system: Multicolor offset printing
press with ink jet imprinting system for numbering,
personalization, addressing and segmentation of the job
(Domino/Heidelberg)
Figure 5. Digital hybrid printing system using the combination
of offset and ink jet technology (Heidelberg)
The hybrid printing system as shown in figure 5 is
modular in design (the imprinting unit is not rigidly
incorporated in the computer to press offset system).
This offers benefits with regard to the flexibility of the
printing system and the modular structure of different
model variants. The complete print job can be processed
with regard to its fixed and variable image content using
digital job definition. Digital in-line imaging of the
master prior to print start is used for the fixed image
portions, and real-time imaging during printing is used
for the variable page content (a detailed description of
the hybrid system and the design of the print head is
given in the presentation of Yong Zhou/Clemens
Rensch; Applications of Page Wide Piezo Ink Jet
12
Printing to Commercial and Industrial Market ).
An early installation of an imprinting system based
on continuous ink jet print heads and used especially for
1
numbering and personalization is shown in figure 6.
Eight separate print heads (with multi-deflection
Figure 7. Hybrid printing system combining offset printing for
multicolor printing with NIP-technology for the imprinting unit
to produce partly variable contents from sheet to sheet
(Heidelberg)
The combination of an electrophotographic system
based on liquid toner with flexographic printing units in
a web-fed label printing system is shown in figure 8. The
electrophotographic printer in front of the flexo units can
print variable multicolor images. The web is fed
intermittently (because the installed electro-photographic
printing system is a multipass system, needing 4 cylinder
1
revolutions for the multicolor print ). The flexo units
have to “wait” (turn without contacting the web) for the
next variable image. The toner image is fixed on the web
before it enters the flexo unit.
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DPP2001: International Conference on Digital Production Printing and Industrial Applications
Figure 8. Digital label printing system with NIP-multicolor printing system (electrophotography with liquid toner; Omnius, Indigo),
flexographic printing, and finishing equipment for coating, laminating, and die-cutting (DO 330, Gallus/Indigo)
1
various printing technologies and hybrid printing
systems is being increasingly taken for granted. It is
also essential for successful economic production of
high quality print media in short throughput times.
Figure 9 shows the components of a hybrid
printing system for the production of print media by
web-fed offset. A direct imaging imprinting unit for
non stop plate change (segmenting the job) is
positioned in front of the multicolor offset printing
system (printing identical images). The imprinting
system with ink jet (non-contact to the web) for
individual text or personalization is integrated after
13
conventional printing. Drying of the ink can take place
after all printing processes.
References
1.
2.
3.
Figure 9. System study: components of a digital hybrid
printing system for web-fed printing for the production of
1
segmented, personalized/individualized print media.
4.
Conclusion
Various print technologies may often be in competition
with each other for the production of print media.
Whether using masters/printing plates or the NIPtechnology, every technology has its advantages for
specific applications, types of production and
production strategies.
As described the combination of various printing
technologies (hybrid printing systems) can create
powerful means of production, making special
production methods and strategies possible. It is to be
expected that an increasing number of combination
systems will be employed for the in-line production of
printed matter, especially with ink jet technology for
variable imprinting and segmentations. With the help of
different digital printing technologies it is possible to
meet the most diverse, job-specific customer
requirements. The use of production systems based on
5.
6.
7.
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Kipphan, H. (editor, author): Handbook of Printmedia Technologies and Production Methods. (Engl. Edition
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Developments in the Graphic Arts Industry for
Producing Multicolor Printed Products. Tenth
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Imaging Science and Technology (IS&T), Springfield
(VA) 1994 pp. 301-306.
Kipphan, H.: Digital Multicolor Printing; State of the Art
and Future Challenges. SPIE Proceedings “Color
Hardcopy and Graphic Arts IV”, Vol. 2413, Bellingham
(WA) 1995, pp. 7-31.
Kipphan, H.: Digital Multicolor Printing and Printmedia
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in Technology, Equipment and Market. 42nd FINAT
World
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Biography
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Einsatzgebiete. Wissenschaftliche Tagung der PrintMedientechnik RAPO 96 (Rationalisierung in der
Polygrafie). Technische Universität Chemnitz-Zwickau,
Institut für Print- und Medientechnik 1996.
Kipphan, H.: Imaging Systems for High-Quality Digital
Production Printing. Focal Paper 4300-01 at
IS&T/SPIE’s 13th International Symposium; Electronic
Imaging 2001, Science & Technology Conference: Color
Imaging: Device-Independent Color Hardcopy and
Graphics Arts VI. San Jose (CA) / Heidelberger
Druckmaschinen AG 2001.
Schmitt-Lewen, M.: Multicolor Production Printing
Using Computer to Plate Technologies (this conference:
IS&T/DPP 2001, Antwerp 2001).
Zhou, Y.; Rensch, C.: Applications of Page Wide Ink Jet
Printing to Commercial and Industrial Market (this
conference: IS&T/DPP 2001, Antwerp 2001).
Hübler, A. C.: Eindruckwerke für Rollendruckmaschinen.
Wissenschaftliche
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Polygrafie). Technische Universität Chemnitz-Zwickau,
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Walter d’Heureuse joined Heidelberger Druckmaschinen AG in 1982. He managed a design department
for 10 years and has worked as a Senior Manager in
“Advanced and Future Technologies” department since
1992. He studied mechanical engineering at the
Technical University of Darmstadt and held the
executive R&D position at a duplicator company in
Germany (former Pelikan Informationstechnik). He is
the holder of several patents.
Dr. Helmut Kipphan did his apprenticeship as a
toolmaker at HEIDELBERG. He studied mechanical
engineering in Mannheim and at the University of
Karlsruhe. Doctoral thesis and professor in
measurement technique. In 1978 he joined Heidelberger
Druckmaschinen AG again as a research engineer. He
has held several management and executive positions in
R&D and technology/product development. Since 1992
he has held the position of Senior Vice President for
Technology and Innovation Research (now: Advanced
and Future Technologies), dealing especially with new
and future technologies for digital printing production
with conventional and NIP-technologies. He holds
leading positions in international committees within the
graphic arts industry and industrial joint research. He is
a member of IS&T and the TAGA board of directors.
He is the holder of many patents, a speaker at various
international technical conferences, author of several
publications as well as author and editor of the newly
published “Handbook of Print Media – Technologies
and Production Methods”.
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