Why Stretch Wrapping is the Solution for Unitizing Loads for Shipment

To understand how stretch wrapping works you first have to understand why we stretch wrap loads in the first place.

WHY DO WE STRETCH WRAP?

There are many reasons why we stretch wrap. One main reason is unitizing a load for shipment. Building one large package from many small packages makes it easier to transport, ship and protect individual products from damage. Preventing damage is key to getting loads from their point of origin to their destination in “as made” condition. Stretch wrapping allows us to achieve both goals (unitization for easy transportation and delivering goods without damage) in the most cost-effective way.

Stretch wrapping loads keeps them from moving and shifting during transportation, which is a major source of damage. There are certainly other ways for loads to be damaged during shipment, but stretch wrapping provides a measure of protection that increases the odds of “as made” condition arrival. In turn, that means lower returns, administration duties, credit due to receiver and rework costs – not to mention happier customers and colleagues.

In the 1970’s, stretch wrapping machines established themselves as the preferred packaging method for unitizing goods for shipment. Meaning that any company that deals with production, reselling, or warehousing of products probably has some familiarity with stretch wrapping.

To make the best decisions about stretch wrapping machines and film, however, it is useful to understand how the mechanics of stretch wrapping work.

STRETCH WRAPPING BEGINS WITH PALLET LOADING

Before the stretch wrapping process can begin a load must first be assembled on a pallet. Once the load is on the pallet, the whole ensemble (pallet and load) is stretch wrapped together.

Assembling the load on the pallet is an important step. Load placement on the pallet is key. The load should not overhang the sides of the pallet or be more than four inches inboard. The pallet itself also plays a role and should be in good condition.

It is important when stretch wrapping not to skip steps that secure the load the pallet. One option is to wrap all the way down to the bottom of the pallet. However, this runs the risk of film punctures from forklifts or pallet jacks when picking up the load. Such large punctures to the film can propagate up the load, causing a loss of containment force and increasing the risk for load failure.

Pallet Grip® is a great solution to lock the load to the pallet and avoid film punctures. The bottom few inches of the film web are automatically rolled into a tight cable at the end of the wrap cycle. The cable is driven down just below the top deck boards of the pallet. This strong cable locks the load to the pallet and leaves enough room to clear forks and avoid the puncture problem.

3 WAYS TO APPLY STRETCH WRAP

There are three ways to apply stretch wrap to a pallet of products: manual, semi-automatic stretch wrapper, or high-speed automatic stretch wrapper.

MANUAL STRETCH WRAPPING

Hand wrapping, as the name implies, relies on people to manually stretch wrap a load. A worker secures the film to the pallet and then walks the film around the load.

Pulling a heavy roll of film around a pallet is wrapping is physically demanding – especially if done right. Imagine the awful dizzy feeling in a hot warehouse. Hand wrapping generally has the highest material cost because there is no consistency of film usage and no substantial pre-stretch. It is also very difficult to wrap a safe-to-ship load consistently.

SEMI-AUTOMATIC STRETCH WRAPPER

Semi-automatic and automatic stretch wrappers come in two different machine styles – turntable and straddle. The load is placed on or in the stretch wrapper’s wrap zone and stretch film is applied. Turntable models will rotate the load on a turntable while straddle style models have a wrap arm that will move around the load and apply film. Straddle models do not require the load to rotate. Instead a wrap arm moves around the load, applying the stretch film while the load remains stationary. This type of stretch wrapper is best used for extremely heavy, extremely light, or unstable loads.

HIGH SPEED AUTOMATIC STRETCH WRAPPERS

These are similar to semi-automatic styles in that a machine performs the actual stretch wrapping of a load. However, automatic stretch wrappers typically include infeed and exit conveyors to automatically cycle loads through the machine.

There are a number of features that can be added to semi-automatic machines that offer some increased automation. For instance, automatically cutting and clamping the film and a remote start lanyard allow fork truck operators to remain safely buckled in their seats on the trucks even while wrapping loads on a semi-automatic machine.

For more help choosing the right level of automation and machine style check out our Stretch Wrapping Fundamentals pages. For instance, how many loads/day may not capture the surges which often occur late in the day as shipments are picked up. So, loads/hour is an important factor to consider.

IT’S ALL ABOUT CONTAINMENT FORCE

No matter which type of stretch wrapper you use, containment force is the most important thing to get right. Containment force can mean the difference between a load arriving at its destination intact and arriving damaged and unsaleable. So, what is containment force?

Containment force is what holds the load together. Officially, it’s the wrap force times the number of film layers. Wrap force is simply a measure of how tightly each layer of film is wrapped around the load. Film layers are the number of wraps applied to a load at a specific point.

There is no magic formula to determine the right amount of containment force. It is done through trial and error. Wrap, test, change and repeat until you can safely say loads are arriving without damage. Using our over 45 years of experience we developed some Containment Force Guidelines. These are not hard and fast rules, but this chart will give you a good place to start.

Once you’ve found the right amount of containment force works and the stretch wrapper’s settings have been set, it is always a good idea to check periodically to ensure every load is being wrapped correctly. We recommend measuring the containment force once a shift for most operations to ensure the machine settings were not tampered with accidentally or to resolve other issues the machine may have been experiencing, like repetitive film breaks after a film roll change.

Let’s face it. Machines are better than humans at doing rote tasks, but they’re not better at doing work that requires intellectual decisions. In the world of stretch wrapping, machines wrap loads better than people do. A lot better, actually.

But companies around the world wrap a staggering amount of loads every day by hand. Most of these loads arrive at their destinations just fine, without damage. But many fail during shipping because the loads aren’t wrapped tight enough. This happens, most likely, because during their journey the vibration from the truck causes layers of the load to shift and eventually fall apart. Many recipients will reject damaged loads, return them to the manufacturers, or worse, dump them in a landfill.

HAND WRAPPING PALLETS LEADS TO INCONSISTENCY

The biggest problem with hand wrapping is that operators aren’t as consistent at wrapping loads as machines. Don’t get us wrong, an operator has the potential to wrap several, good loads in a row, but it’s hard to do it well each and every time.

Another challenge that faces hand wrapping is the process of securing loads to pallets. When loads aren’t secured they may slide off their pallets and hit another load damaging the secondary and primary packaging and, sometimes, even the product inside. It’s difficult for people to bend over and wrap film all the way down to the bottom of the pallet over and over again.

Hand wrapped loads that have film applied all the way down to the bottom are at risk for failure. Bad things happen to these loads when forklifts pick them up. Forks puncture the film. Sometimes, the punctured area has a tendency to spread, leaving the load vulnerable.

Lantech stretch wrappers, though, are able to lock the load to the pallet with a tight film cable applied just below the top board of the pallet. The cable placement allows plenty of room for the forks to pick up the load without puncturing the film.

CUT DOWN FILM USAGE WITH MACHINES

Finally, when it comes to saving costs, hand wrapping doesn’t cut it. Machines can significantly cut down on film usage. Stretch wrappers with powered film delivery systems stretch film up to 300 percent, which decreases film consumption by at least half. It’s almost impossible for a person hand wrapping a load to stretch the film at the same levels as powered film delivery systems.

So why do so many people still wrap loads by hand when a machine can do it safer, cheaper and more efficiently? That’s one of the many mysteries of life – or at least of the secondary packaging industry.

Since its introduction, stretch wrapping has become the dominant method of unitizing products for safe shipment to their destinations. But, it has become so routine that sometimes we lose sight of the fundamentals.

The following five fundamentals of stretch wrapping underlie the process of load unitization and containment.

1. UNITIZATION

Before the 1970’s, companies would floor load trucks with individual boxes, a method that was labor intensive and time consuming.

In 1972 Lantech invented the stretch wrapper. Because of its ergonomic and economic benefits, unitizing products on a pallet with stretch film became the most widely used material handling method for shipping products. Instead of taking many workers hours to floor load a truck, now a forklift driver could load an entire truck in less than 30 minutes.

2. CONTAINMENT

Containment is the ability to hold unitized loads together. It can be accomplished in many ways depending on the load’s make-up. Today, stretch film has become the most popular way to contain unitized pallet loads because it provides effective and economical containment when properly applied. Other less-popular containment methods include dropping large “hoods” over pallets, using shipping containers or securing pieces with bands made of metal, polyester, polypropylene or nylon.

3. VIBRATION

Trucks, trains, boats and planes are ground zero for vibration and vibration is a palletized load’s worst enemy. Vibration is the term used for the destructive forces exerted on a load as its being transported to its destination.

Things like pot holes, curbs, sharp turns, acceleration, sudden stops and turbulence also puts stress on a load. When pallet loads are ineffectively stretch wrapped these stressors can cause layers or products to shift or to slide off their pallets, leading to damaged goods, customer dissatisfaction, excessive costs and unnecessary waste.

4. DELIVERING CONTAINMENT FORCE

Containment force is the total amount of squeezing pressure the film exerts on the load. It is the key ingredient to effective stretch wrapping. Usually measured in pounds and ounces, it’s what holds the load together.

As a load is being stretch wrapped, every layer of film delivers a certain amount of wrap force. When you multiply the number of layers by the amount of force each layer has applied the result is containment force.

5. DAMAGE PREVENTION

Applying the proper amount of containment force is your best defense against loads being damaged during shipment. Make sure you have enough containment force on each load you ship. If you are unsure how much containment force your loads need start by downloading our containment force recommendation chart here.

Never lose sight of why you are stretch wrapping in the first place. The goal is, and always has been, the safe arrival of product loads at their destinations at the lowest cost effectively shipped.

1 CHANCE IN 200 ISN’T A GOOD BET

Imagine you’re a car dealer. You order hundreds of cars to your dealership, but every once in a while a brand new car just won’t start. You do the math and 1 out of every 200 cars doesn’t start, the car isn’t fixable and is a complete loss. Sure, you get to sell 199 cars but you have to take the loss of the 1 car.

Do you think a dealership would just accept the loss? If you do the math, 99.5 percent of the cars they receive are in perfect working order. A 0.5 percent loss doesn’t seem like that much, but wouldn’t it be fair to say that a better scenario would be the dealer being able to sell all 200 cars?

When we’re accustomed to a load damage rate close to 0 percent – what dealerships actually receive – 0.5 percent is a lot. It means that on average, one car in 200 would be a complete loss. It’s pretty easy to see that this is unacceptable.

SHIPPING DAMAGE STEALS 0.5 PERCENT OF YOUR GROSS SALES!

What’s unacceptable for one transportation mode could be the norm for another. Shipping damage (damage that happens between the factory and the point of sale) for the food, beverage and consumer products industries averages about half a percent of gross sales, according to The Grocery Manufacturers Association (GMA) and the Food Marketing Institute (FMI).

The bad news is this amounts to about a $1 billion a year of damage losses in the U.S. alone. The good news is that much of this damage can be avoided.

STANDARD PRACTICES REDUCE SHIPPING DAMAGE

Shipping pallets of products poses a different set of damage problems. However, they’re problems that can be avoided by using standard processes.

HERE ARE THE MAJOR CAUSES OF SHIPPING DAMAGE TO PALLET LOADS:

1. CREATING PACKAGE INSTABILITY BY REDUCING MATERIALS IN PRIMARY PACKAGES.

2. BUILDING LOADS THAT DON’T FIT THEIR PALLETS.

3. USING PALLETIZERS THAT BUILD LOOSE OR IRREGULAR LOADS.

4. LOADING TRUCKS TOO TIGHTLY OR LEAVING GAPS BETWEEN LOADS.

5. UNIVERSALLY POOR STRETCH WRAPPING.

BETTER STRETCH WRAPPING IS THE BEST WAY TO START REDUCING DAMAGE

Of these causes of damage, stretch wrapping is the easiest, fastest, and least expensive to improve. And if that’s not enough, more effective stretch wrapping is also the “low hanging fruit” or the “band aid” for mitigating or compensating for the other major causes of damage.

If you’re shipping stretch wrapped pallets, unless you have evidence to the contrary, you’re not doing better than a 99.5 percent success rate. And even if you’re hitting 99.5 percent, it’s not good enough. You’re averaging $50 to $500 of damage per truckload and leaving money on the table.

Or put another way, a $100 million company loses $500,000 a year in avoidable shipping damage. How many more widgets does it have to sell to make up that loss?

REDUCE YOUR SHIPPING DAMAGE BY 50 PERCENT

Stop wasting money. There’s low hanging fruit to be picked. One half a percent of damage doesn’t have to be your norm. Lean processes and principles typically reduce damage and waste by 50 percent or more wherever they’re applied.

PLANNING FOR SAFETY

Workplace injuries are incredibly expensive – in a number of ways. Lost days, workers’ comp premium increases, reputation, impact on worker commitment to the company, overtime, and even the basic ethical cost of not doing everything reasonable to protect workers.

So, it’s no surprise that companies work hard to prevent unsafe activities and behaviors that lead to preventable workplace and loading dock injury.

DESIGNING RISK FREE PROCESSES

A typical step is to identify high risk activities (on the loading dock bending, lifting, and similar tasks are easy to identify) and implement process changes to eliminate the requirement for workers to perform actions that lead to injuries.

A great example is using a pallet wrapper to reduce the unpleasant and injury prone task of manually wrapping pallets. Hand wrapping is often thought of as inexpensive and expedient. That’s a misconception. Aside from not requiring a machine, it typically increases operating cost in several ways:

• Requires more film (higher material cost)
• Takes longer (slower throughput)
• Leads to higher rates of product damage in shipping (loads are inconsistently contained and locked to the pallets)

Hand wrapping a pallet means that a worker will have to lift rolls of film and apply steady pressure as they bend and walk backwards around the load. Rolls can be heavy and, like any other heavy object that is manually lifted, carries risks of back injury. But potential injury doesn’t stop there, hand wrapping also creates the risk of repetitive motion injury.

Walking backward in a circle for any length of time can also be dangerous. Not only can workers become dizzy from the circular motion, but they also can’t see where they are going. Working with no line of sight is seriously dangerous in the busy, sometime chaotic, landscape of a loading dock.

With all of the downsides of hand wrapping, it’s obviously an easy place for a plant manager or process engineer to look for opportunities to reduce risks and increase efficiency on the loading dock.

TRADE UP, NOT LATERALLY

But simply replacing hand wrapping with a machine-based process isn’t a universal cure. Things like; throughput, materials consumption and load containment are all subject to a machine’s technical capabilities. And, the machine itself needs to be inherently safe or the ultimate goal of reducing workplace accidents may be missed.

As we mentioned before, a typical loading dock is the scene of lots of activity, with honking horns, opening and closing doors, forklifts zipping to and fro, and loads of products barreling around corners without warning. Amidst all that activity it’s easy to overlook some potential injury risks in a simple machine like a pallet wrapper – but that’s a mistake.

Safety features you should look for in semi-automatic stretch wrappers include:

• An emergency stop button
• Large distance between the mast and the carriage
• Automatic stop if the film breaks
• Anti-crush film delivery system
• All wires and motors enclosed

IMPROVE WAREHOUSE SAFETY

It’s important, when shopping for stretch wrappers, to choose a manufacturer with enough experience to know how to build a machine for safe operation. Find a stretch wrapper manufacturer that’s built enough machines, and seen enough situations, to anticipate potential problems and engineer around them.

For example, the film delivery system on the Lantech Q Semi stretch wrapper is suspended from a belt which loses tension and becomes slack if the film delivery system encounters an obstacle while descending. A switch detects the slack and stops the descent of the film delivery system thus avoiding injuries.