Shrink wrap sizing also known as package sizing is the act of determining the appropriate size film for overwrapping of a specific package with shrink wrap. Many factors must be considered when sizing the shrink wrap requirements. The actual product dimensions, the orientation of the package as it will introduce into the film and the type of equipment to be used are all required information. Failure to obtain this information or incorrect specifications may result in inappropriate film size being calculated.
Each package has three dimensions which must be known. These measurements should be made with the orientation (positioning) of the package as it enters the film identified.
- Product Width: The dimension of the product in the Transverse (parallel to the cut-off or cross seal) direction.
- Product Length: The dimension of the product in the Machine (parallel to the fold of the film, in cases of centerfold film) direction.
- Product Height: The actual height of the product. In cases of products with uneven surfaces, the height should be considered from the bottom to the highest point of the package.
- Product Orientation: When measuring a product for film sizing, remember to use the longer dimension as the product width (bearing in mind, it must not surpass the seal dimensions of the equipment being used).
- Less shrink waste: By orienting the package using the shortest possible dimension as the product length results in the smallest amount of waste, in cases of centerfold use or side seal applications.
- Increased packaging speed: A shorter product length results in faster cycling of product’s into and out of the sealing area. Over the course of a production shift this incremental time savings can produce large dividends.
- Increased film roll bag yield: Although a product requires the same square inches of film regardless of orientation, the amount of scrap produced is decreased.
Another consideration when recommending film size is production speed. In many cases, the formula to calculate required film size turns out not to be a whole number. Although 1/2″ increments are available, most users opt for a standard inch size, usually rounding down in an attempt to save money. Many times this practice actually costs more than the cost had they rounded up and increased the film size. By trying to use the narrowest shrink wrap size possible, users may actually make an operator’s job more difficult, reducing production speed and increasing the overall package cost.
Once package orientation and dimensions are established, the next consideration is the type of equipment upon which the package is to be wrapped. Specific types of equipment dictate the use of either centerfolded or singlewound film. Furthermore, some types of machinery demand the use of wider shrink wrap sizes than others due to the mechanics of their operation.
When using the shrink wrap sizing formulas to calculate film sizes, be sure to use the formula for the type of equipment it is to be used on.