The diecutting of extreme label materials such as hotmelt adhesives can often be challenging. Problems can occur not only in the actual diecutting process, but also during the stripping and rewinding of labels, and even when finally applying the labels. While many industries have been using various non-stick coatings to protect their machinery for decades, only in the last few years have repellent coatings become more popular for label diecutting tools, in particular with flexible dies. The main challenges are that converters need extremely tight tolerances of the tools, and the coatings have to resist very high rotating speed without flaking.
Germany-based Wink Stanzwerkzeuge has made inroads in recent years with regard to developing non-stick coatings. In 2006, Wink introduced a non-stick coating for flexible dies, which the company reports has been improved continuously since then. Wink offers four different kinds of non-stick coatings for dies and other equipment. The Black coating is recommended for diecutting standard labels, while the Silver version offers a special anti-color effect and is best for machine parts like guide rollers. The best results against adhesive residues are provided by the new Grey and White coatings, with Grey as a universal solution for difficult materials (e.g. hotmelt), and the White coating also applicable on solid rotary dies.
Rako Etiketten is one of Europe’s largest label converters, with more than 1,400 employees and sites across Europe, Asia and Africa. The company has been using non-stick coatings with success for several years. However, one special multi-layer label caused bigger problems with adhesive residues on the flexible dies. When the top adhesive layer is cut through, the very viscid glue can leak out and literally gum up the cutting edges, which in turn prevents perfect diecutting. Moreover, the leaking adhesive can seriously affect the further processing of the labels.
Wink saw Rako Etiketten’s challenge as an opportunity to systematically test its new non-stick coatings. Compared to a laser-hardened but non-coated flexible die, all non-stick coatings delivered significant improvements, the company reports. While the Black and Grey die needed a first cleaning after 4,200 and 7,300 material meters, Rako could run 40,000 meters without any cleaning or adhesive problems with the White coating.
However, Wink’s technical experts stress the fact that the White non-stick coating is not necessarily the best for all applications, as the performance depends on many factors. For example, for some standard applications even the cost effective black coating is sufficient to reach significantly better performances. To continue to meet the label industry’s challenges, Wink is continuously enhancing its material database in order to give the best possible recommendations.
For more information, visit www.wink.de/nonstick.