How to resolve “fish-eye” wrinkles or uneven surface wrinkles on shrink film after heat shrinking?

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  During heat shrink packaging, the shrink film may occasionally develop "fish-eyes"—circular or oval-shaped patterns that cause an uneven, blotchy appearance. Fish-eyes are often caused by insufficient heat exposure. If this issue occurs frequently, verify that all heating elements in your shrink tunnel are functioning properly.

  Fish-eyes are also common when airflow inside the tunnel is too low. Therefore, carefully check whether the air velocity in the heating chamber is adequate. Another contributing factor can be micro-perforations or inconsistencies in the film itself. Reducing the conveyor speed can help minimize this effect by allowing more uniform heat distribution.
  
  

  Solutions for fish-eye defects in heat shrink packaging:

  • The temperature of the automatic heat shrink packaging machine may be too low—gradually increase the tunnel temperature to ensure complete and even shrinking.

  • The conveyor speed may be too high—slow down the belt to allow sufficient dwell time in the heating zone.

  • The internal recirculating airflow may be insufficient—increase the fan speed or adjust the air nozzles to enhance hot air circulation around the package.