Images Magazine December 2016

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50 IMAGES DECEMBER 2016
COMPUTER-TO-SCREEN & PRE-PRESS KB
exposed in the normal way, using UV light, although the absence of
film means that the exposure process no longer requires a vacuum.
The main difference between these two types of ink jet process is
that water-based inkjet systems will get varying results depending
on the emulsion being used as emulsions naturally absorb water. A
water-based ink could be susceptible to this problem, thereby reduc-
ing the UV-blocking capabilities of the ink.
At its worst this problem will show up as a cross contamination
between the ink and the emulsion, whereby the black ink dot gets
‘trapped’ inside the emulsion prior to exposure. It is important, there-
fore, to make sure that water-based inkjet systems are compatible
with the emulsions you want to use.
With the wax/resin-based inkjet systems, the ink returns to its
natural solid state as soon as it is printed, resulting in a very clean
dot with minimal dot gain and no ‘overspray’. This solid wax ink will
work with all emulsions as it dries immediately on the surface of the
screen and is not absorbed in any way by the emulsion.
Direct emulsion exposure systems
In direct emulsion exposure systems (DMD), such as those from CST
Systems and Signtronic, the emulsion is exposed using laser or LED-
focused lights to directly image the screen without the need of a
UV-blocking mask or stencil.
These systems produce high resolution images (up to 2540 dpi)
and are commonly used in industrial screen print applications. The
advantage of this process is that they use no consumables other than
the screen emulsion, although the process does require a fast expo-
sure emulsion to work properly. These DMD systems are considerably
more expensive than most inkjet CTS technologies and therefore are
less likely to appeal to most garment decorators.
At a screen near you soon...
Mark Evans of Exile Technologies discusses the rise of computer-to-screen and summarises the different
systems on the market
Although some garment decorators may be still somewhat
in the dark about computer-to-screen (CTS, aka direct-to-
screen or DTS), the technology has in fact been around for
many years.
Lüscher’s large format direct inkjet stencil systems were introduced
in the late 1990s, and at the Fespa Expo in Munich in 2005 the num-
ber of CTS systems being shown by manufacturers and suppliers was
nearly into double figures.
What is surprising, then, is how long it has taken for this technology
to actually reach tipping point and become a commercially viable and
well accepted method for screen stencil production.
Part of the problem has been affordability. The early systems were
very expensive and also aimed at the large format graphics market.
The cheapest inkjet based technology shown at Fespa Munich back
in 2005 was in excess of £60,000 – and the direct exposure based
systems were all priced north of £100,000.
In the last 18 months, however, there has been a significant upsurge
in CTS installations within the UK textile screen printing industry.
Since Exile’s Spyder II system was launched early last year there have
been 15 Spyder systems installed in the UK with an additional three
or four systems due for installation by the end of 2016.
So let’s take a look at the CTS technologies that are available...
CTS inkjet imaging systems
Q Water- or liquid-based inkjet, such as the M&R i-Image and
Exile’s FreeStyler
Water-based inkjet systems use a conventional inkjet process to print
a stencil image directly on a normal emulsion coated screen using a
high density, water-based, black ink with UV blocking capabilities.
Q Wax- or resin-based solid inkjet, such as the Exile (and MHM)
Spyder II Direct to Screen
Wax-based inkjet has a specially modified inkjet system that uses
heat to ‘melt’ a solid wax- or resin-based, UV-blocking ink during the
imaging process.
All CTS inkjet systems print onto normal screen emulsions, replac-
ing the film positive with the printed ink stencil. The image is digitally
positioned and printed directly onto the screen. The screen is then
The biggest reason to make the change
to CTS is improved print quality ”