CIR emitters offer high-speed print drying

Edited by the Engineeringtalk editorial team Mar 8, 2007

The Lettershop Group, of Leeds has used carbon infra-red (CIR) emitters from Heraeus Noblelight to achieve the rapid print drying demanded by its high-speed Kodak print heads.

By using carbon infra-red (CIR) emitters from Heraeus Noblelight to achieve the rapid print drying demanded by its high-speed Kodak print heads, The Lettershop Group, of Leeds has achieved significant savings in energy and running costs compared with their previous NIR infra-red system.

As it is air-cooled rather than water-cooled, the new drying system has also allowed further operational benefits in terms of reduced maintenance, easier cleaning and less downtime.

The Lettershop Group (TLG) is an independent company, which has invested millions of pounds to ensure that it maintains its position as one of the most advanced integrated direct communications groups in Europe.

It uses the latest web and sheet-fed technology to produce the highest quality direct mail print.

An important part of this work is the generation of personalised mailings, where the basic sales material is produced on large machines such as Heidelberg web presses.

Part-finished reels are then transferred to a personalisation area, where a range of options, both laser and ink-jet, is available to complete the mailing printing with personalised details.

For large runs, TLG offers Kodak technology, where printing heads can print at up to 300m/min, delivering up to 280 million ink droplets per second.

It is essential that this ink is completely dried before the mailings are passed on to the finishing department, where the reel is cut, folded and glued as required.

Conventionally, this important drying process has been carried out by fitting very high power, NIR short wave infra-red emitters immediately after the Kodak heads.

These transfer a large amount of energy into the ink to effect the drying at high speeds.

However, their high power also necessitates water cooling of the emitters, involving chiller units and pipework.

Moreover, the NIR lamps are difficult to clean and traditionally have a short working life, which means that maintenance costs can be high because of frequent downtime.

Recognising all these problems, TLG contacted a specialist in lithographic printing equipment, who in turn contacted Heraeus.

Having established that the Kodak inks were water-based, Heraeus proposed that the drying could be carried out more efficiently if medium wave emitters were applied, as water absorbs infra-red most strongly in the medium wave section of the infra-red spectrum.

It was also proposed that carbon infra-red (CIR) emitters would be ideally suited for the application, as they combine the energy efficiency of medium wave in drying with the fast response times of short wave emitters.

Following extensive tests to prove the technology, two complete lines have now been equipped with CIR emitters installed at TLG's Leeds site.

Each line is equipped with 2 CIR systems, which consists of a heater module, an exhaust module and a control panel.

The heater module contains twenty one 8.3kW twin-tube carbon emitters, with a total power output of 174.3kW, providing a total power density of 140kW/m.

This compares with the installed power of between 300 and 400kW of the NIR systems.

Moreover, the control panel allows switching of emitters in banks of three depending on the web area which needs drying whilst PID control ensures that the correct amount of power is applied irrespective of line speed.

Since installation, all four systems have proved extremely efficient, providing annual energy savings of around GBP 30,000 on each line.

They have also required very little maintenance, as cleaning now takes around two to three hours compared with the two days of the NIR system and their original lamps are still functioning perfectly after nearly two years.

In addition to saving considerable space, as there is no need for the equipment required for water cooling, the new systems are also proving more tolerant of sensitive papers, as the paper temperature for the CIR system is just 30-35C, as opposed to the 60-70C of NIR.

Removing the requirements for water cooling also has a health and safety benefit as it eliminates the potential of personnel being burnt by the hot water pipes.