Stretch film, also known as stretch wrap or pallet wrap, is one of the most popular unitization materials on the market. By “unitization”, we simply mean the process of bundling and securing several individual packages together, often on a pallet. Other unitization techniques commonly used include shrink wrapping, bagging and strapping. The following outlines the benefits of stretch film over other unitization techniques as well as identifies its weaknesses.
Benefits of Stretch Film
Weaknesses of Stretch Film
There are three main causes of compression-loss when palletizing boxes:
Pallet Overhang, Wooden Pallets, and Interlocked Stacking Patterns.
We know, boxes are not rocket science. But, did you know that merely changing the way you stack and palletize your boxes could significantly affect their performance? Incredibly, it has been found that improper palletization can result in boxes losing up to 50% of their compression strength!
The most common culprit of compression-loss is boxes hanging over the edge of the pallet. When this occurs, the two vertical edges of the box not hanging over the pallet edge are primarily supporting the load. In fact, when boxes are stacked on a pallet with as little as ½ inch hanging-over, as much as 30% of their strength is lost! The solution here is to make sure you are using the proper pallet size or the proper palletizing pattern to avoid overhang. You may also want to look at reconfiguring the box dimensions to fit the pallet.
With the space between deckboards on a wooden pallet averaging 1-4 inches, it is common that the bottom of the box is not being entirely supported. This too can cause significant compression losses in the unit load. In fact, up to 15% of compression strength may be destroyed. This may be avoided by choosing pallets with deckboards that are strategically positioned so all of the vertical edges of the box (corners) are being supported. Another option would be to use corrugated pallet liners to cover the bottom of the pallet (pallet deck) to make it a solid surface.
Interlocked Stacking Patterns
This situation can be much like a double-edged sword. Using an interlocked pattern, which rotates each layer on the load, can destroy up to 50% of the compression strength. Palletizing boxes so that they are columnar, or vertically stacked (stacking one box directly on top of the other) is the preferred method. This method, however, makes it difficult to keep the load intact during handling. One solution to this problem is to stabilize the load by using stretch wrap. This can be done by using a stretch wrap machine, or by simply spiral wrapping the load by hand.
Box users make major investments in the development, production and promotion of their products. The boxes they need for shipping represent, on average, less than 1% of the value of their contents. Consequently, if a few boxes are unusable, the loss involved is relatively insignificant, right? Wrong! Remember, without the lowly corrugated box, the product cannot be shipped! Simply stated, unusable boxes can result in unsold products. Therefore, it is worth protecting your inventory of empty corrugated boxes to ensure that:
Guidelines for proper handling and storage of empty boxes, developed by the Fibre Box Association and the Packaging Machinery Manufacturers Institute, have been summarized and presented below. Following these simple guidelines will maximize the performance and prolong the useful life of your corrugated boxes:
The preceding information and illustrations on how to store and handle corrugated boxes are from the Fibre Box Handbook (Fibre Box Association, Rolling Meadows, IL, 1992)