UV system saves energy

UV technology is currently focused on the development of systems that are as energy efficient as possible. For example, label converter Wilkri-Etiketten, in Reutlingen-Betzingen, Germany, has been using a new IST Metz system in a pilot application on a Gidue Combat 370S UV press since May, 2005.

The eight colour Gidue press has two generations of UV systems operating in parallel, so that the difference in energy consumption between standard technology and the new MBS-5 system can be clearly seen in the control cabinet. The first four print units are each fitted with an IST MBS-3 unit with 200W/cm lamps. From the fifth print unit onwards, four of the new MBS-5 units are installed, each with 140W/cm lamps.

Although the new technology operates with only 70 per cent of the previous energy consumption, it produces the same production output. In practice, the same print speeds are achieved and the instruments in the control cabinets show clearly that the MBS-5 lamps are using almost a third less energy. (See the cost comparison calculation below).

The MBS-5 is claimed to produce very good results for applications where it is important to minimize the heat on the substrate, as the UV lamps used are only 140W/cm instead of the usual 200W/cm. In addition to the energy savings, there is a reduction in the exhaust air and less contamination of the individual components of the UV system. A further benefit is longer durability of lamps and reflectors.

As soon as the test phase is completed, Wilkri-Etiketten will regularly measure and record the UV measurements, in line with ISO certification requirements, in order to provide continuous documentation of the output of the UV system. This will also ensure that the UV lamps are only changed when really necessary; the cable-free FLC UV lamp system allows them to be changed quickly and easily, minimizing press downtime.

Wilkri-Etiketten's experiences provide valuable information for IST Metz, confirming the results obtained during extensive test trials for the new system in the manufacturer's Technology Centre in Nürtingen. For example, one essential question was the print speeds that realistically can be achieved with different ink coverages.

For this, a test print sheet was designed which contained specific elements with high ink coverage. The print trials were carried out on the Gidue press equipped with the different types of UV system, with press speeds up to 150m/min. The usual speed for everyday production at Wilkri-Etiketten is around 70-80m/min, but even at the high press speeds there were “no differences at all” in the curing results achieved by the different generations of UV system.

In actual production the MBS-5 system is said to have achieved the same results as in the laboratory trials with 140W/cm lamps and used only 70 per cent of the energy usually used by the conventional units. This efficient use of energy is made possible by different technical developments, such as the new URS reflector technology.

IST Metz has also made comparable tests in co-operation with press manufacturer Gallus. These were carried out on the Gallus EM280 model with integrated UV screen print unit and produced similar results. Regardless of the high ink depths (sometimes over 10 micron) speeds of up to 100m/min were achieved for UV curing screenprint black.

Wilkri-Etiketten has around 55 employees and customers ranging from the food sector to manufacturers of plastics parts. In order to cover as many different applications as possible in the label market, the company has UV flexo and letterpress machines and, for shorter print runs, an HP Indigo ws4050 digital printing system.

Calculation for cost comparison:

Assumptions:

Four print units

Lamp length: 400mm

3,000 production hours per year in two-shift operation

Energy cost: €0.10/Kwh

1. Costs of running a 200W/cm UV system at 100 per cent output:

Four lamps at 40 cm * 200 W/cm * 100 per cent output = 32kW/h

2. Costs of using MBS-5 with 140W/cm at 100 per cent output:

Four lamps at 40 cm * 140 W/cm * 100 per cent output = 22.4kw/h

Potential Cost savings:

9.6 kw/h * 3,000 production hours * €0.10 = €2,880