Question from Sherry:
Would a lighter gauge full web film provide more savings, or would we not be able to apply as much pre-stretch resulting in the same weight of film per pallet wrapped?
Hi Sherry, I really appreciate your question. Many purchasing professionals, like yourself, look for every opportunity to minimize their stretch film spend. This question shows you are really thinking outside the box!
We have tested various combinations of downgauged films, in the range of 35-gauge and less, at our lab in Phoenix. While the filaments created by the rolled edges of our bands do prevent web breaks, it’s important to consider that we are stretching the film well over two times more than conventional film. As the film is stretched, it becomes thinner and thinner. We offer a 42-gauge film after finding that it provides a comfortable performance margin and excellent value when stretched to 300% or more. Film thinner than 42 gauge, and stretched to the same level, is not only extremely thin but it becomes far less puncture or tear resistant. This has to do with the modulus of elasticity of the film as a function of thickness. (So much for the technical terms…) There is a real-world limit that we also need to recognize, and it comes down to pure economics.
The yield in pounds per hour of an extruder (that transforms pelletized resin into film) is one of the factors that drives the price of the film. That means the thinner the film, the fewer pounds per hour are generated from the extruder (and it typically runs at a slower speed than thicker gauge films) resulting in a much higher price per pound. Another factor affecting film price is the difficulty to produce. The thinner the film, the less forgiving it is. For example, a small imperfection such as a gel (a spot of resin not fully melted and incorporated into the resin flow) in a 35-gauge film now becomes a point of failure, where it may not affect the performance of a thicker gauge film. Small variations in the thickness (within process limits), known as gauge bands, also become problematic, not only when the film is produced, reflected in the price per pound, but also when it is being applied at your facility. Last, but not least, it is far more difficult to control the web (without wrinkles) as it is being wound. Understanding why, it makes sense that the higher price per pound will offset a large percentage of the gain by downgauging.
So, the bottom line is that your analysis is right on target, we would not be able to stretch the film as far meaning an increase in film weight per pallet. Also, since the elasticity has not been removed through stretch (necessary for optimal load containment), you will need to apply additional wraps to meet your load containment standard, meaning even more film weight added. The potential for web breaks increases as well, which, along with the additional time to apply more wraps, will impact your plant’s output.
On paper, and without considering all the factors, it may look like you can save money, however, it doesn’t really reduce your cost per wrapped pallet, in addition it can adversely impact plant output, and/or lead to costly load failures.
It is important that you know we are continuing to develop different resin blends and manufacturing methods so that we always remain the class of the field when it comes to the thinnest stretch film with the highest level of performance. What doesn’t make sense today may make “cents” tomorrow.
Thanks for asking,