Finished Shrink Wrap Problems: Fish Eyes
Effect: If you notice round or oval shaped patterns across any part of the shrink wrap, this has been caused by the shrink film not shrinking completely.
There's a reason you chose shrink wrap for packaging and that's because it's a transparent wrapper that allows you to view the products held within. Which is why you didn't choose bubble wrap for the same reasons. Fish Eyes are akin to a bubble wrap but there are shrinkwrap machine solutions to eek out this problem.
- Much like Dog ears, one of the sources of these Fish Eyes is an inadequate regular of heat control. Make sure the tunnel temperature is correct at all times and if it isn't go through the machine guide and find out why. Is the tunnel closed off properly, is your product that is to be wrapped in shrink film too large. Is a part which regulates temperature faulty?
- Fish eyes are also caused by the same problems as those of Crow's Feet. As stated in our other helpful answers, if you can resolve one issue you'll probably solve most of your problems with shrink film aesthetics. If you're using a conveyor to move products through a chamber, trial different speeds. It's probable that the tunnel conveyor speed is too fast and the shrink film is not receiving enough heat within the duration.
- Whole movement and longevity of circulating air is often the cause, the sources are various. For instance, your shrink wrap machine works much like an oven. Heat needs to circulate in a vacuum at a constant temperature. If the air velocity is not high enough and adequate controlled ventilation, heat rises too quickly. Check the tunnel air velocity is high enough.
- Fish eyes, Dog Ears, Crows Feet and Hot Spots are all predominately caused by issues of heat regulation within the chamber or tunnel. The product you are shrink wrapping needs to be in the tunnel for the correct amount of time and for the correct for the heat to be high enough across the entire product.
Fish eyes are some of most unsightly problems with shrink wrap that can occur, resolve this issue and you may will resolve others. Keep your machine clean, well serviced and do regular preventive maintenance. Also consider test sampling across a range daily if you have a high tempo production line.