I already have a Stretch wrap machine, I can't save more money.....CAN I?

You know what I think.....

I recently had an appointment that had taken an all to familiar turn.  If I had a dollar for each of the calls that I made where the customer had the false impression that he had saved every penny that he could have already.  They have already invested in a machine and it featured a powered pre-stretch system, and secured great film pricing.  Only to find out that they purchased from an uneducated sales knucklehead, who left money on the table....the customer's profit.

One of the greatest mis-conceptions in stretch wrapping is that just because you use a machine, you are saving money in film.  Many machines poorly stretch film in spite of the fact that they have pre-stretch systems.  Let's examine the reasons.

1. Own/inherited an old machine : Old machines fall into many potential problem categories.  Most will be covered below.
2. Roll carriage:
1. Rollers damaged or worn: Many times when you look into the carriage you will find that the pre-stretch rollers are cut up or worn out.  This means that there may be either slippage and/or scar-ation of the film.  Slippage occurs when the rollers do not have enough grip on the film to pull effectively.  More will be covered regarding design that impacts slippage.  With regards to damage, look at the rollers.  Operators tend to take knives to the roller coatings and slice them leaving them to over time dry rot.  This will create large gaps in the roller which will keep the film from properly adhering to the roller and create a bad mark on the film which may lead to pre-mature breaking at lower forces.
2. Door not secure: Multiple machines that I walk up to have a roll carriage that is poorly mounted to the front of the machine.  As a result, there is movement when running and the door will not hold the film against the pre-stretch rollers.  Therefore, with inconsistent pressure, the film will tend to slip across the roller.  maintenance may or may not be enough to fix this problem.  It depends upon what additional damage may have occurred as a result of the poorly mounted door.  ONE MORE security issue for the door is the latching mechanism.  Many times, it is not the hinge side but the latch side that is not holding.  This leads to the same item above, film slipping across. Make sure that the latching mechanism is both secure and sound in its construction.
3. Design:  This is a slippery slope because everyone like to think that they use the best method.  I'll tell you what I think but first lets look at the below graphic.
   
4. As you can see there are three prevalent designs in the threading of film through a roll carriage.  Here is MY OPINION after working for over fifteen years with thread patterns.  New all systems will work but in a short period of time you will start to see large differences between them.  I believe that I have the sketches ranked in their long term effectiveness with the best being the top of the chart and the quality decreases as you go down the chart.  S-Style provides excellent film/roller surface contact.  This system does not allow for the fastest threading but typically these style of rollers are larger diameter (in some cases twice the diameter) which significantly increases the surface contact area between the film and the roller.  This will mean less slippage.  W-Style is my second favorite because although rollers are a smaller diameter (typically) than the S style, it maximizes the contact surface area over a smaller  roller versus the U-Style which frankly is a very poor design (This BLOG is called YOU KNOW WHAT I THINK...NOT....You know what you think :)   ).  It only goes without saying that the slippage will be exponentially increased with the U-Style because there is only about 90 degree contact surface area over the pre-stretch roller versus the 180 degrees on the W-Style.
3. Temperature:  Did you guess this one?  Stretch film in a cold room will perform much differently than if you are running it in a warm room.  WHY?  Well without getting scientific (because I am a packaging guy, not a scientist), the film in a cold room will become brittle.  The tackiness (not how I dress, but what makes film stick to itself) does not have the ability to grip on the roller so the colder it gets, the more the film slides through the roll carriage.  There are some methods to address this issue so if you have this as a problem please let me know and I will help you overcome it and get back on the savings road.

So what it all boils down to is.......HOW DO YOU KNOW IF YOU ARE LOSING MONEY?  Allow me to provide you with the simple test to see how much money you may be leaving in un-stretched film.  No special tools required here, just a simple business card.  Once a pallet is wrapped, take the pallet, and this is the hard part, find a single layer of film.  I start with the tail and without unwrapping the load walk back with my hands to the single layer only but at least half way around the pallet from the film tail (that is the hard way to say opposite side of the film tail).  Do this in the middle of the pallet length (not too close to either corner).  Now at the top of the film grab it  between your thumb and index finger and have your hands about 3.5" apart (the width of the business card).  Now slowly and evenly pull your hands apart.  You will get to a point where the film will stiffen then break.  At the point that the film becomes stiff (just before breaking) press the film on the pallet and measure how far apart your fingers were (what did you stretch your 3.5" to).  If you are more than 8", you most likely would benefit from a new machine, or potentially additional service on yours.  If you are less than 8" you are probably pretty good.  

WHY PROBABLY?  It depends on how your stretch occurred.  Pre or Post stretch.  Those will be covered in another BLOG but rest assured that either way, for now, your machine is providing enough control over your film to wrap without breaking.

That's what I think!  

Re-Thinking Non-Powered Pre-stretch Stretch Wrappers

You know what I think........

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, or what some people would call a 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.

1. Powered Pre-Stretch: 
1. Our Legs are replaced by an electric motor
2. So every time the motor turns sprocket A one time, sprocket B turns twice
3. 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%
4. HERE IS THE PART YOU DO NOT WANT TO MISS #1 - 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.
2. NON-Powered Pre-Stretch
1. The film is pulled through the rollers and attached to the pallet to be wrapped.
2. So every time the motor turns sprocket A one time, sprocket B turns twice
3. In the above sprocket example, you will still get 100% stretch but not the pallet will rotate pulling the film out f the machine.
4. HERE IS THE PART YOU DO NOT WANT TO MISS #2 - 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.
5. 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 LETS TIE IT ALL TOGETHER AND LET ME TELL YOU WHAT I THINK:

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:

1. What is the value of the load being wrapped?
2. How far is it travelling?
3. How is it being shipped?
4. 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

THAT IS WHAT I THINK!