The capabilities of UV curing have become ever more topical as a dominant and practical aspect of successful printing direct to rigid and flexible materials. Yet, as the demand for greater versatility requires more careful and sympathetic handling of different media, so the need for more sensitive types of lamp behaviour becomes essential. Greener principles are also playing a part in how print is generated, with environmental considerations growing in relevance, with the result that sign-makers and digital print specialists are looking at the wider eco-aware picture when investing in new equipment.
Because of these criteria, there has been an increase of interest in the use of alternative curing technologies, with LED lamps now being incorporated into wide-format inkjet platforms. These lamps are considered a good solution, as they emit UV within a narrow band of wavelengths and do not generate the high levels of infrared heat, which can pose a problem with mercury arc lamp technology.
Initial doubts about the efficacy of LED lamps in high-speed UV-curable flat-bed and roll-fed printers have certainly been removed. Our own VUTEk GS32050LX and GS2000LX incorporate ‘cool cure’ technology, which is being used successfully without any issues or areas of compromise.
A sensitive touch
The EFI GS2000LX uses ‘cool-cure’ technology, enabling the use of heat-sensitive
substrates
Businesses that have invested in this type of curing have proved that working with LEDs instead of mercury arc lamps has resulted in far greater application flexibility, opening up a whole new range of material possibilities, which formerly could not be printed and cured successfully using UV-curable inks. Substrates or surfaces showing an intolerance of heat with conventional UV lamps can now be printed and cured with LED lamps, without suffering detrimental effects, such as badly buckled and warped results. Additionally, the chance of head crashes is negated, so machine uptime is also improved.
At one time, there were rumours that both speed and efficiency tend to be compromised when LED curing is incorporated into a printer, but real-time production assessments have proved these not to be true. Certainly, in EFI’s VUTEK printers, throughput rates match those of equivalent machines that use mercury arc lamps. There is no reduction in quality of output either, with high colour accuracy being maintained with excellent adhesion across different surfaces and thicknesses.
Users are also commenting on lower power consumption with LED lamps when comparing running costs of their machines against former models that incorporated mercury arc technology. There are no lengthy warm-up periods to be factored in, so time as well as energy savings need to be considered when making economic comparisons. It has also been noted that the print-heads stay cleaner; the instant start-up for LED lamps means that they can
be switched off between print runs without incurring delays when the next job is ready.
Initial doubts about the efficacy of LED lamps in high-speed UV-curable flat-bed and roll-fed printers have certainly been removed”
The arrays used in LED lamp technology have a solid-state construction and this is one of the key benefits of transferring to a machine that incorporates this type of curing. Mercury arc lamps have a finite life cycle, typically of 1,000 hours. During this period of time their quality of emission is not consistent and they lose power as they age. Conversely, LED curing lamps should be able to generate many thousands of hours of active service, offering even results through-out their life-time, which simplifies operation by guaranteeing consistency.
Surprisingly few manufacturers thus far have incorporated LED lamp technology into their wide-format printers. In smaller ink-jet devices, this type of curing is proving itself for system integrators who need an efficient and compact option that can fit into a small footprint and not generate high levels of heat that might damage the host machine as well as the material being printed on it. A typical narrow-format example can be seen in the development of new digital label engines where, increasingly, the convenience of LED curing is now appreciated for its ability to work with highly heat sensitive and very thin stocks.
Greener accuracy
This graphic for an anti-crack cocaine campaign in Brazil was printed onto pizza
dough. The image was then slowly eaten by meal worms placed in a specialised
framework behind the graphic. It was the Inca Onset flatbed’s UV LED lamps that
allowed for good ink adhesion, while the low curing heat prevented the dough
from cooking
LED curing also has a valuable role in pin curing, which is used in situations where precision droplet control is critical. This technique, which is incorporated into EFI’s latest high-speed VUTEk HS100 Pro, uses an LED light source to place a partial cure on the inks, which makes it easier to stop them from spreading in their uncured state. Final images are sharper and cleaner, and there is reduced dot gain so that quality is enhanced. Additionally, pin curing can be used to produce different finishes on the material, so that matt, satin and gloss prints can be output effectively via simple operator or software control, without the need for a special clear varnish.
LED curing also has a valuable role in pin curing, which is used in situations where precision droplet control is critical”
The overall advantages to be gained from using LED curing certainly seem to outweigh the doubts about this technology. It is now well enough established across various ink-jet devices to be a strong contender when future wide-format investments are being considered, particularly where businesses are wanting to be able to experiment with more diverse materials and tricky surfaces. From my own experience I know of customers that have worked with a variety of unusual types of media successfully, with one LX user even printing direct to bubble wrap.
Adding application versatility to the benefits of LED curing technology is the icing on the cake. This advantage, added to the overall cost savings gained through far longer lamp life and lower power requirements, makes LEDs an attractive option for sign-makers and display producers. Finally, the benefits of improving environ-mental credentials cannot be ignored, so expect to see this alternative to mercury arc curing grow in demand and popularity in the years to come.