The bundle shrink wrap packaging method using printed shrink wrap film is most commonly used for the collation of multiple items like bottled or canned products, usually in three or six pack configuration. The main purpose of this method is for the sale of multiple items as one at retail point of sale.

When designing the artwork for the print on the shrink wrap film, the following points has to be taken into consideration to avoid costly mistakes and lengthy delays. This procedure includes approving of the artwork, manufacturing of the printing plates, printing of the shrink film and delivery to the contract packing company. Getting the artwork wrong can cause weeks of delay and reject printed shrink wrap film.

This procedure suits Jetpak bundle shrink wrap packaging machines that use printed film at the top and plain film at the bottom:

Calculating the correct repeat length of the print

The repeat length refers to the distance between registration mark centers on the shrink wrap film. A correct distance will ensure that the pack will fit within the print and the shrink wrap machine will be able to correct the print to pack synchronization successfully. To correctly calculate the repeat length, form a bundle of product, hold a piece of shrink wrap film over it and add the distance from the base of one side, over the top to the base on the other side plus 40mm. The additional 40mm will allow the pack to clear the seal bar during the sealing cycle and there will be sufficient length left over for correction of print to pack synchronization.

If the repeat length is too short, the registration mark will be positioned at the wrong side of the sensor after the sealing cycle and film synchronization will not be achieved. If this happens the shrink wrap film will not be able to be used.

Background density of the bar code

Some cans and bottles that are bundled together already have labels with artwork. Once the shrink wrap film has shrinked tightly onto the pack the bar code on the film needs to be dense enough so that the underlying images are not transferred through it. If this happens it may effect the bar code scanning. 

Position of the bar code

The sides of the shrink wrap film will shrink to a rounded hole on the sides of the pack. The size of the hole is determined by the width of the film in relation to the width of the pack. The wider the film the smaller these holes and also the more wrinkled the sides of the film. If the bar code is printed too close to the side it will cause it to be wrinkled and bar code scanners will not be able to read it. It is best to position the bar code near the middle of the film to prevent distortion as the middle area of the film will be kept tight and wrinkle free.

Color and size of the registration mark

The best color for the registration mark is a color that is in contrast to the background. This makes it easier for sensors to detect without the need for expensive color detecting sensors. The size of the square should be at least 10mm x 10mm.

Positioning of the print

When the shrink wrap film is applied to the package, the back seal is visible on the back side of the pack. If the print on the film is too low on this side the seal will cut it off. We advise that the artwork is higher up on the pack to avoid this.

Conclusion

The above tips and advice is a guide only and is intended to assist you in understanding the process. We advise that you speak with our packaging specialists first before deciding to purchase printed film for bundle shrink wrapping applications.

Call us now on (03 9544 9777) and ask to speak with Digby or Gary

Or email us info[at]ittjetpak.com.au

By: Marius Liebenberg
Technical Support and Service