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What causes a series of wrinkles (fish-tail patterns) on the surface of shrink film in heat shrink packaging, and how can it be resolved?
Heat shrink packaging “fish-tail wrinkles” typically appear as a series of fine wrinkles along the corners and edges of the shrink film—often radiating outward from the package corners. They frequently occur alongside “dog ears” (triangular protrusions at package corners, a common shrink-wrapping issue caused by insufficient corner shrinkage). These wrinkles result from excess film accumulating around the product’s corners. There are two primary ways to reduce or eliminate fish-tail wrinkles: first, use a smaller shrink bag or sleeve that better fits the product; second, ensure the heat tunnel delivers sufficient and uniform heat to fully contract the film.
Solutions for fish-tail wrinkles in heat shrink packaging:
• Too many vent holes in the shrink film cause air to escape too quickly, preventing the film from fully shrinking—reduce the number of vent holes.
• The conveyor speed of the shrink wrapping machine is too high—slow down the belt to allow adequate time for complete shrinking.
• The temperature of the automatic shrink packaging machine is too low—increase the tunnel temperature to ensure proper film contraction.
• The recirculating airflow in the automatic shrink tunnel is insufficient—increase the fan speed or adjust air nozzles to enhance hot air circulation around the package.
