When a die used by Innovia Shrinkfilms for making shrink sleeve film yielded product that was often out of tolerance, the company switched to a die from Nordson, and saw tolerances improve by 30 per cent, and experienced reduced startup times.
Innovia is a speciality film manufacturer and a division of CCL Industries, the world’s largest producer of labels. To supply the fast-growing shrink sleeve segment of the label market, Innovia produces transparent film that is printed on the inside surface, slipped over a container, and made to conform to the container surface by means of heat shrinking. On the cast film line in which the Nordson die has been installed, Innovia processes a polystyrene blend into monoaxially-oriented film.
The new die, replacing one from another supplier, is an EDI Autoflex VI-RE H40 unit. Like the previous die, the Autoflex die is an automatic one, using data from a computerised downstream gauging system to adjust the transverse thickness profile, by making changes to the flexible upper lip of the die.
“In comparison with our previous die, the EDI Autoflex die from Nordson produces more uniform film with better tolerances,” said Giuseppe Ronzoni, Innovia plant manager. “The automatic control of the flexible lip is faster and more accurate, and startups are faster than before.”
The flexible lip of an Autoflex die is made up of thermally-actuated adjuster blocks that expand or contract to adjust the lip gap in areas of the film that are thicker or thinner than the target dimension. “The upper lip of the Autoflex die is more flexible in that the adjustments to the lip gap take place more rapidly,” said Patrick Meinen, polymer dies product manager for Nordson.
Another critical factor for ensuring product quality is the length of the lip land - the lip surface just before the die exit. “The lip land can be made longer or shorter to optimise product thickness, flatness, and surface finish,” said Meinen. “Besides having a stiff upper lip, the older die had a lip land that was too short. In our Autoflex die, we optimised the lip land to control the product profile and manage die pressure.”
At startups, the rapid gauge profile adjustment provided by the Autoflex system reduces the time before saleable product is produced. Also helping to shorten startups is the design of the flow channel, or manifold, inside the die.
“The greater uniformity of the film produced with the EDI die reduces the potential for gauge bands on the product roll,” said Ronzoni. “This leads to less stretching of the final product and better printing results.”