Shrink sleeves with UV flexo – IST shows how

Contour Flexible Packaging Solutions, launched two years ago, has rapidly become an established specialist in UV flexo shrink sleeve printing. The company, based in Stoke-on Trent, in the UK, recently adopted technology that enables it to offer advantages over the traditional gravure approach to shrink sleeve printing. However, with temperature sensitive substrates, high print quality demands and special repro considerations, shrink sleeves are a demanding product sector. To meet these demands Harvey Ball, owner and md, has put together an experienced team and invested in an Edale Sigma flexo press equipped with IST BLK2 water cooled UV modules.

Shrink sleeves have been traditionally printed by gravure and this is still by far the dominant technology used for this sector. However, high origination costs have always been an issue so the gravure process is not well suited to short and medium run work. Contour believes this has prevented many major fillers from experimenting with new designs and many smaller ones from using sleeves.

When UV flexo is compared with gravure the difference is not in the quality but in the price - especially with short runs and new jobs. To capitalize on this fact, the company has invested in the latest UV flexo technology, enabling it to produce short and medium run work and new designs more cost effectively than gravure. The company has also invested in its own shrink line, to make it easier for potential end users to access this technology.

The choice of press and UV lamp system was critical for the success of the project; and the printing system had to be capable of producing this kind of work at high speed and in tight register.

The Sigma is a servo driven nine colour in-line flexo packaging press with a 510mm web width. Its shaftless technology and servo drives provide several benefits when printing and converting difficult substrates. James Boughton, managing director of Edale, adds: ”By independently servo driving each and every driven roller in the press we are able finely to tune the web tension system to ensure that constant torque is applied to the web throughout the press. This ensures accurate and consistent registration stability throughout the speed range, which is critical to achieve the quality of image demanded by Contour on an unsupported film. The use of fully enclosed chambered doctor blades also means that the press can readily handle specialized inks and coatings, even at high speeds.”

When printing UV cured inks on heat sensitive substrates the choice of UV system is of critical importance, as it is necessary to control web temperature while at the same time offering sufficient energy to cure the inks at maximum press speed. IST BLK2 lamps are fitted to all nine units of the press. These are designed to offer high cure speeds and have several built-in temperature control features.

Use of water cooling in the shutters, reflectors and lamp housing is said to ensure that any heat created is removed immediately and efficiently from the UV module. Cold mirror reflectors (CMK) are used to reflect the UV energy onto the web while at the same time absorbing the IR heat energy, which is dissipated by the water cooling system. In addition, to provide for maximum heat management of the substrate, the web is in contact with a water cooled chill drum as it passes under each lamp. The integrated air cooling system removes ozone and is designed to achieve a constant temperature along the length of the lamp. A stepless lamp control (SLC) system automatically adjusts the lamp output from 40-100 per cent, depending on the speed of the press.

Demanding

“The specification of the BLK2 system with chill drums has clearly enabled Contour to print very demanding substrate with an enviable throughput within this market sector,” comments Simon Mitchell, managing director, IST (UK). “This high degree of heat management along with the cooling of the web can only be achieved using this UV technology.”

Harvey Ball comments “It is through the technical competence of the press and the UV that we have been able to produce such high quality print. This combined with the high degree of print and product knowledge at Contour has a produced a winning formula”.

The company plans a total of three presses and two shrink lines in the future. On the strength of its achievement so far, Contour is already negotiating for a second press.