For years people have argued that powered pre-stretch stretch wrappers are a must. WHY?
It’s simple really, because that is what we were all trained on years ago to sell a higher priced machine. We also told everyone that 80 gauge film was a down gauged product (of course back then it was).
Now, just because you would run a 70 or 80 gauge stretch film on a powered pre-stretch machine (and in many cases a much lower gauge) does not mean that what is good for the goose (powered pre-stretch machine) is good for the gander (non-powered pre-stretch machine/core brake machine).
Allow me to expand….First we must look at the machine types and determine how they work to get a basic understanding of the fundamentals. To make it easy for me we will use a simple graphic of a bicycle. As you can see below, each time you pedal with your legs, the sprocket labelled A will go one complete turn. Because of the differential in the size of the sprockets between sprocket A and sprocket B, B will turn perhaps 2 times around.
Now lets apply these basics to a stretch wrap machine.
- Our Legs are replaced by an electric motor
- So every time the motor turns sprocket A one time, sprocket B turns twice.
- NOW if each sprocket was attached to a roller that carried film, and they are the same size, for every rotation of sprocket A, B would turn twice which would create a stretch between the rollers of 100%.
- The force it requires to stretch the film is absorbed by the motor. Therefore with a POWERED PRE-STRETCH machine you can lay the film on loose like a dust cover, or so tight it either breaks the film or crushes the product being wrapped.
- The film is pulled through the rollers and attached to the pallet to be wrapped.
- So every time the motor turns sprocket A one time, sprocket B turns twice
- In the above sprocket example, you will still get 100% stretch but not the pallet will rotate pulling the film out f the machine.
- The force it requires to stretch the film is absorbed by the PALLET OF PRODUCT. Therefore with a NON-POWERED PRE-STRETCH machine you can only wrap pallets in film that have the stability to stay in-tact while forces are applied equal to what it takes to stretch the film.
- EXCEPTION TO THE RULE – Core brake technology does not use gears and sprockets to change the stretch, they incorporate a braking method on the roll carriage that will create resistance. Changes to the brake tension will create changes in stretch.
DOES THAT MAKE SENSE?
Stated in a more simple manner, when utilizing a NON-Powered Pre-stretch system, all of the force is absorbed by the pallet of product. Regardless of it is a geared system or a braking system, the force is applied to the load.
NOW LETS TALK THE OTHER PART OF THE EQUATION – FILM!
As you can imagine, if I have an 80 gauge film and a 45 gauge film, they will take different force to stretch them both the same amount. As wise man has taught me over the years “There is no replacement for mass”, so it is most likely the 80 gauge will require more force to stretch 200% than a 45 gauge. So what does that mean to you, the consumer? You will get less containment with a 45 gauge film than an 80 gauge because it takes less force to stretch it to its maximum point of elongation, or it will break with less force than the 80 gauge.
NOW LET’S TIE IT ALL TOGETHER:
Because of what we just discussed regarding film and the types of stretch machines available, what is right for your Non-Powered Pre-Stretch machine? Lets take the following items into consideration:
- What is the value of the load being wrapped?
- How far is it travelling?
- How is it being shipped?
- What is the weight of the pallet load being wrapped?
Now that you answered those questions, consider that if I wrap on a Powered Pre-stretch machine at 250% (which is stretching the film from 10″ to 35″ before the film leaves the machine) I may start with an 80 gauge but it is a 30 gauge possibly as it is applied to the pallet (as the film thins while being stretched).With a Non-Powered Pre-Stretch it may only stretch it using a core brake (which will not allow for more force than the pallet can withstand without the film pulling the pallet load apart) that 80 gauge may only allow for me to stretch 30% (or 10″ to 13″). This film would be applied on the pallet at a 70 gauge (as the film will thin as it stretches).
MY SOLUTION: Apply the 45 gauge so it stretches 125% (again, determined by the force you can apply without pulling your pallet load apart). All of the force is applied to the load giving you excellent containment force and as the film is thinned and applied it is probably in the area of the same thickness of the Powered Pre-Stretch applied film.
WHY DO THIS: It all boils down to ROI (return on investment), if you are wrapping under 30 pallets a day, this is a very viable, justifiable process with tremendous labor savings and typically a great return on film as compared to hand wrapping.
QUESTIONS ABOUT POWERED VERSUS NON POWERED PRE-STRETCH? Ask firstname.lastname@example.org!