Category Archives: Elements of Unitization

High Speed Wrapping and Film Breakage

with Luke Venechuk, Sr Packaging Engineer

speed dial pic

What happens when films are run at high wrapping speeds? Why do films breaks increase so much for these applications? Will the same film perform differently at differently at 12, 24, and 40 RPM?

There are some people in our industry that believe film breaks increase at high speeds because the film heats up and lose its integrity. To find out whether this theory is correct Highlight ran films at different speeds and measured its properties to compare.

The graph below shows a single film being ran at speeds equivalent to 12, 24 and 40 RPM:

graph pic


In the graph above we can see that the force to stretch the film (on the left-hand Y-axis) increases slightly as the application speed increases, this is about a 2% increase if we look at the force to stretch at 200% (stretch level is the bottom X-axis, and 200% is within the middle red circle).

We can also see that the stretch at break or ultimate stretch does not change significantly (the right hand red circle).

The increase in force is due to the fact that we’re doing the same work, stretching the film to the same level, in a shorter amount of time, which means we have to pull a little harder to end up with the same result.

There are some small differences that take place for the film at different speeds, but it’s certainly not anything that would cause the film to break.

So what is causing film breaks at high speeds?

Highlight found that the cause of most film breaks at high application speeds is due to poor corner compensation. Corner Compensation is a system within most stretch wrappers that increases the film payout rate for the corners of the load and slows the film speed on the sides of the load while wrapping, usually by changing the speed of the prestretch rollers throughout the wrap cycle

Here’s a top view of a rotating load:

rotating load pic

Corner Compensation is needed as the film demand is constantly changing as the four-sided load rotates. Here’s an example of a changing demand rate through one revolution of wrapping:

graph 2

As we wrap faster and faster, the equipment has less time to change its film speed, so the rate of acceleration for the film delivery gets exponentially higher.

At 12 RPM the film goes from 131 to 200 ft/min in .66 seconds. At 50 RPM the film goes from 550 to 835 ft/min in .16 seconds.

graph 3

This rapid acceleration creates more stress and is the reason why we see more film failures at high wrapping speeds. This is compounded by the fact that many corner compensation systems perform worse as they age, becoming “out of sync” with the wrapping needs of the rotating load.

What’s the solution to all of this?

The correct approach with the film or the equipment can reduce these film breaks.

For the film: high ultimate stretch levels allow films to absorb sudden spikes in stretch levels without breaking. It may be possible that very stiff films will resist stretching when exposed to spikes in stress.

For the equipment: The best solution is to fix the corner compensation system. Highlight responds to corner demand and changing film feed rates without the constant acceleration and deceleration of the prestretch roller, where the most stress on the film occurs. By moving our corner compensation from the high stress area of the prestretch section to the low stress area after that we can almost completely eliminate film breaks due to corner compensation at high speeds.

For more information visit or call us at 800-531-2465


Back to Basics: Critical Concepts for Successful Shipping

with Luke Venechuk, Sr Packaging Engineer

fallen load 02     Unsuccessfully Unitized Loads

Unitized Load: one or more products or packaged-products usually on a skid or pallet, but always secured together or restrained for distribution as a single load.1

For this first post we wanted to start basic, very basic, to build the context of what we’re trying to achieve when we stretch wrap a load. Why do we unitize loads? What are our goals? Why do we do what we do?

We all want to save money, but very often saving money in the short term can create larger hidden costs which continue to take a toll until they’re discovered and corrected.

We unitize to make shipping and handling more efficient, and at the lowest total cost. Total cost not only includes packaging, but labor, damages, and several other factors that need to be considered when unitizing your load.

Before unitization was a concept in packaging, every box or product needed to be handled individually for shipping , and it wasn’t unusual for a truckload or railcar of product to take up to three days to unload, and sometimes longer.2 The introduction of unitization made this handling process much more efficient, saving time and money. Pallets gained widespread use during WWII, where it’s easy to imagine the advantages of saving 20+ man hours per railcar of supplies being shipped, this allowed the military to use their service members for more important tasks and bigger benefits. 2 It’s hard not draw a comparison with today’s competitive marketplace, where each company needs to take full advantage of their personnel’s capabilities and become more adept at increasing efficiency than ever before.

One of the biggest killers of efficiency is damage. A damaged load costs many times the packaging and shipping costs proper handling, and degrades a company’s reputation.

Damage is preventable, but a focus on lowering packaging costs rather than creating a successful system has lead to higher and higher damage rates. Today the average North American company spends 4 to 5 times more in product damages than they spend on stretch film each year.3, 4

The way to prevent damage and create good systems is simple: focus on the basics. When making changes to save on packaging and shipping costs, test the new system and evaluate for success.

In future blog articles we’ll discuss how to test for success, the building blocks of creating a successful system, and tips for making systematic improvements.






[3] 2008 Joint Industry Unsaleable’s Report, authors: GMA, FMI, Deloitte

[4] Strategic challenges facing the stretch and shrink film markets, 

presentation given Fall 2014, John Campin, AMI Consulting