Screen June 09 P10-11:Screen Feb09 P12-14 15/05/2009 08:14 Page 10
SCREEN: INDUSTRIAL
Precision cures print
problems
Stencil quality and drying and curing equipment both have a major impact on
the accuracy of industrial screen printing. As ever, precision and consistency are
key to achieving the desired result by Peter Kiddell
WHAT MAKES screen printing so attractive to production process engineers is the Screen printing in industrial applications is no different, and it can be taken for
ability to apply a controlled film thickness over large areas relatively quickly and granted that precision machinery is essential. Variations in speed, pressure and
yet with precise positioning. In the graphics industry the material printed is an alignment can all alter the lay-down of the ink, but interestingly it is often the
ink with a coloured pigment or dye that that can be adhered to a range of drying and curing process which requires the most attention as this can
substrates for visual effect. Being able to control the ink film thickness and the determine the overall production rate and even the choice of printing equipment.
precise position and shape of the image is crucial to the final appearance. Common drying and curing methods include radiation curing, such as ultra
violet (UV) light and infra-red.
As an example of stencil
Ultra violet energy does not have
technology, Dek’s new VectorGuard
to have a heating effect,
Platinum was developed for ultra
although most emitters produce
fine-pitch printing
heat energy as a by-product of
producing UV. Efforts are often
made to filter out the heat with
water cooling, quartz filters and
air movement to eliminate
substrate distortion. Light
emitting diodes (LEDs) produce
cold UV but they are restricted in
the wavelength that they
produce and this needs to be
matched to the chemistry of the
printing medium to effect a full
cure.
Infra red energy, on the other
hand, does emit heat. Short,
medium and long wave curing
are all possibilities. Short wave is
closest to the visible spectrum
and is combined with a lot of
white light, while medium wave
is further away so the emitter
glows red. Long wave is the
furthest away and the emitter
does not give off any light. Short
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