Our goal of this five part series is to educate us on the factors that may play a role in the formation of wrinkles throughout the value stream; including film production, adhesive coating and converting and even lamination. Part three of our overlaminate and wrinkles discussion focuses on winding, specifically the effects of uneven winding and winding tension.
This issue includes material of which is tight on one side and loose on the other, has a baggy center with tight edges or inversely has baggy edges and a tight center. Wrinkles due to all of these conditions are due to the web being longer in the machine direction where the roll is loose. If you were to lay flat an extremely long length of material in any of these conditions under no tension, the loose part of the web would actually arc or ripple instead of laying flat. During web handling, this condition creates tensile stress on the tight side and compression on the loose side, causing wrinkles.
Inappropriate winding tension, whether too high or too low will cause wrinkles. High winding tension especially at the outer wraps of the roll can cause inner layers to buckle. This buckling created a starring effect when viewing the end of the roll. This roll characteristic will cause the web to be wrinkled before it enters a converting process.
Low winding tension will allow layers of film to slip on each other, When tension is applied in a subsequent process, this loose wind will allow the film layers to shift making tension control ineffective or intermittent. These compression and decompression forces will allow lateral movement of the web and can cause wrinkles.