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Under the Hood

IST Hot Swap drying system

Brian Sims goes under the hood of the IST Hot Swap drying system, which straddles two technologies offering more choice to printers

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The IST Hot Swap drying system

Drying is hot stuff...

The use of ultra violet (UV) light for curing printed material has been used for many years. The industry is now focusing on hybrid/high efficiency or low energy (H-UV/LE UV) as a refinement of the previous UV drying process. On top of this change in tack, the added variation of light emitting diode (LED) drying systems has been thrown into the mix.

Quite often we can be overwhelmed with the acronyms and technologies, so hopefully we can lift any clouds of confusion on this topic, and in the process review a solution from IST that gives the printer, for the first-time, real choice.

Chris Schofield is the managing director of IST

The original use of UV inks and varnishes was then centred on the food and packaging industry, as this form of printing is safest for the packaging and provides some form of protection from water with regard to refrigerated products.

In an ever-competitive consumer market, the more attractive the food can look in the freezer of any supermarket, the more likely we are to pick up that pizza or ready meal rather than cook for ourselves. UV printing has always brought that punch or lift to the packaging and offers special effects and varnishes to pharmaceutical products to name just one group that greatly benefits from its use.

What of the downsides; UV printing has always brought the user specific challenges. Whilst the product cures immediately, there are issues of power consumption, special inks and solvents and other technical issues such as waste and mercury lamps that require factoring in before the use of this process can be seen as advantageous.

It was mainly these issues that did not lead to the take up of the UV process industry wide, despite the notable advantages of the process. If drying was needed, infra-red drying was generally used which oxidises inks and evaporates the water used in the process without the use of specialist products.

The process of H-UV (LE UV) has been known for many years; the matching of specific wave length UV light to specifically manufactured photo reactive inks was first suggested in the 1980’s. Typically, the wave length for the H-UV inks is between 315-400 nanometres (nm) in the UV-A spectrum.

The process H-UV (LE UV) has been known for many years; the matching of specific wave length UV light to specifically manufactured photo reactive inks was first suggested in the 1980’s

Around ten years ago, the use of the H-UV process came to the fore and companies pressed forward with the use of UV drying outside of the main markets of packaging and specialised finish products.

This focused wave length of H-UV systems means the amount of light emitted is reduced significantly whilst intensity is maintained. This, in turn, means the power required by an H-UV unit is far less, with focused light there is less heat and less heat means the system starts to become far simpler. Needing fewer cooling systems, for instance, makes it more adaptable to the main stream market as the equipment can be greatly simplified.

Clearly there is still the need to match the inks directly to the H-UV system you are using but these inks are now widely available. It took until recently for the harmonisation of benefits against investment to make the process both available and commercially viable and start the ‘buzz’.

As for the change in light source, the use of an LED is now also viable due to technological advancement. An LED is a small electrical device of the semiconductor family. At the root of an LED is a process called electroluminescence. This is the effect of a material emitting light when current is passed through it.

(Above & below) Around ten years ago, the use of the H-UV process came to the fore and companies pressed forward with the use of UV drying outside the main markets

Texas Instruments made the first commercially used LEDs in the 1970's and they have been developed from initially only red coloured diodes into practical RGB devices such as monitors and televisions and replacement white diodes for commercial, house-hold and automotive lighting systems. They are now truly replacing energy inefficient filament bulbs and lighting systems used extensively. So why is this new lighting source meant to give so many advantages?

LED lamps do exactly the same as H-UV technology in this respect; provide a focused UV light source at a very specific wave length. You need to use the inks or varnishes supplied for the specific lamp as the bandwidth is narrow – typically between 385/395nm, but you do get all of the advantages of H-UV, reduced heat and power consumption for instance. There are some other significant differences with LED technology over the mercury lamp UV technology that H-UV is based on.

One of the first and most obvious differences is that it has the ability to turn the light on and off in an instant. With traditional UV lamps systems, whether they are H-UV or conventional UV, there is a period of time where the lamp needs to come up to the specific light intensity, typically around a minute or so. With the LED technology, this is not the case. As soon as you turn the lamp on, it is at full luminosity.

With regard to the issue of lamp design, the LED system can be used as banks of lamps within the lamp head. This means that, unlike UV lamp technology, you can switch down the number of lamps to the desired sheet width which can reduce power usage and improve life. The LED-UV lamps themselves use less power so energy savings are projected on usage alone.

Whilst the variations of H-UV lamps consume significantly less power (hence heat) than traditional UV lamps, it is claimed that the LED versions produce significantly less heat again due to their design. They are all still in need of cooling but as the initial heat output is reduced, the amount of cooling capacity is equally reduced.

A further claim of the suppliers of LED UV lamps is longer life cycles for their product. H-UV lamps need to have Iron additives that degrade, which can reduce the Mercury lamp to around a 1000 hour service life for transformer powered systems. With the use of new power supplies such as IST’s ELC®-X series controller, they will now provide a guarantee of 2,500 hours. However, LED UV lamps have a life cycle of typically 20,000 hours which is obviously significantly higher.

Hopefully you are now clearer on the systems available and the reasons H-UV and LED is now becoming mainstream. However, there is still one overriding question only you as a printer can ask. Which system do I use or need, H-UV or low energy UV (LE-UV) as IST refers to it as or LED UV, LUV from IST?

Well IST have taken this decision away from you by providing the use of both systems in one clever housing, swapping in quick time between either when needed.

The market is clearly keen to pursue the advantages of H-UV and LED UV and as the technology becomes mainstream, it will become cheaper and more available. In the meantime, the printer needs to take a competitive advantage of either system and the Hot Swap concept from IST allows the easy swapping between H-UV and LED UV or LE-UV and LUV in IST speak.

Both drying heads are designed to fit into one common carrier and can switched in minutes to accommodate which ever process you need to use. It is slim, compact and can be placed as an end of press or interdeck position.

Whether you are using the IST mercury based lamp, LAMPcure or the new LEDcure version the drying heads are both driven and powered via the ELC®-X series of controller. This is a well proven technology which IST has used for the LAMPcure UV system on both web or sheetfed presses. Regardless of which process you have on press, the lamp heads are managed by IST's Smart Control interface.

Adding further flexibility to the printer, IST are able to retrofit this technology onto most types of printing press regardless of manufacturer or process, web or sheet fed. IST have cleverly been able to hedge the bets as to which way the market will follow. Not often do you find equipment that can straddle two technologies whilst people decide which will be favoured, but IST have completed this giving genuine choice to a printer.

Brian Sims Principal Consultant, Metis Print Consultancy, www.metis-uk.eu

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