Stretch wrapping is considered the most common and efficient method for securing pallets. The goal of stretch wrapping is for products to arrive at their destination in perfect condition. Unfortunately, there’s no universal way to stretch film a shipping pallet. The process involves many variables, including different load configurations, contents, and more. That doesn’t mean the process of stretch wrapping is a complete mystery, though. There are certain principles that apply to stretch wrapping a pallet, all of which can help you quickly and effectively secure your loads for shipping. If you’re interested in learning more about stretch wrapping your pallets, let’s go over some of the most important pallet wrapping guidelines to follow.
The Basics of Stretch Wrapping
Before we delve into the specifics of proper stretch wrapping techniques, it’s important to familiarize yourself with the basics of stretch film material. The most common stretch film plastic is made from low-density polyethylene (LLDPE). LLDPE is a complex chemical film. Depending on its gauge and thickness, it can expand up to five times its inert length. You can divide LLPDE products into two categories: cast film and blown film. Cast film is suitable for light-to-medium-duty pallet wraps. It’s clear, glossy, and easy to unwind. It also has a consistent cling quality and a uniform thickness. Blown film is tougher and suited to medium-to-heavy-duty loads. Blown film is more expensive to manufacturers than cast film. For this reason, packaging facilities rely on cast film for most of their pallet shipments. Knowing the difference between these two types of stretch film is a crucial part of understanding proper stretch film techniques. Let’s look at the main differences between cast and blown stretch film. These qualities can have a major impact on the proper stretch wrapping techniques:
If you’re looking for strength, blown stretch film is your best bet. Even when the thickness or gauge is equal, blown stretch film is stronger than cast film. It’s also less likely to tear when snagged on a sharp edge.
Blown stretch film has a higher yield point, or breaking point, than cast film. It can stretch well beyond its design capacity before snapping.
This refers to the film’s elastic qualities, or how well the film reverts to its original, inert state. Blown stretch film has a better memory capacity than cast film, which makes it ideal for tough applications.
Blown stretch film won’t continue stretching after it’s applied. Cast stretch film, on the other hand, will continue to expand.
Compared to cast film, blown stretch film is more resistant to punctures and cuts.
If you want your pallet to be visible, cast film is more transparent than blown stretch film, which is naturally opaque.
Blown stretch film is tougher and more durable than cast film, but it’s also noisier when it’s unwound from its spool. When you’re applying cast stretch film, it’s virtually silent.
Blown stretch film has one-sided cling, while cast film will cling on both faces. Pallets wrapped with blown film won’t ever stick to each other, but pallets wrapped with cast film might.
Proper Pallet Wrapping Techniques
There’s a long list of proven and practical techniques for stretch wrapping pallets. These techniques apply regardless of the type of film or equipment you’re using. Insecure or improper pallet wraps can result in damaged, destroyed, or lost goods, but by training your employees in effective pallet wrapping techniques, you can cut down on loss. To effectively stretch film a pallet, you’ll need to:
Pick the Right Pallet
Picking the right pallets is important. They should be made of the proper material, in good condition, and capable of supporting the full weight of the load.
Choose Your Stretch Wrapping Equipment
For light pallet wraps, some handlers might prefer to hand wrap their loads. If your warehouse is continually shipping out larger loads, mechanical stretch wrapping machines are better. You can use a semi-automatic turntable model, overhead rotary arm, horizontal machines, or—for complete automation—an automatic stretch wrapper.
Secure the Film
Start wrapping at the bottom and spiral up toward the top. Make sure to fix the leading end of the film to the pallet base before you wrap it. For semi-automatic models, your operator will need to tie the film to the base or the pallet or into the film cup on the turntable. Many automatic stretch wrappers are available with a film tucking system where the device clamps, cuts, and threads the film.
Wrap the Product
Start with full coverage of the product laps to the pallet base. You can make two or more revolutions around the base to ensure there’s a sufficient grip anchoring the load to the pallet frame. You’ll want to make sure 50 percent of the material overlaps as the film move upwards. You can set certain machinery, like automatic pallet wrappers, for specific overlap coverage.
Control Wrap Tension
Tension controls how tightly the load is compressed. Sensitive products need light tension in relation to the wrap’s stretch factor, while heavy and solid loads can withstand greater tension.
Decide Whether To Double Wrap
When you reach the top of the upward spiral, you need to decide whether to tie-off the film on top of the load or spiral downhill. When in doubt, you’re better off double wrapping. Double wrapping uses more stretch film but can protect your product against damage.
Adhere Film Tail
Finally, you’ll want to adhere the film tail at the end of the wrap cycle. Many automatic stretch wrappers come with various film clamps for cutting film and adhering to load at the end of the wrap cycle. This avoids loose film tails that get caught by the truck forks or other items during shipment, compromising containment force at the bottom of the load. This can lead to failure during shipment and damaged products. A pneumatically driven film clamp unit with hot wire film cutting incorporates the device for final sealing of the film tail. A nip and tuck device clamps, cuts, and threads the film without a sealer. The last tail of the wrapping film is inserted into the winding itself.
Tips for Safely Wrapping Pallets
Protecting your parts from damage is important. To help your pallet get to its destination safely, here are some pallet wrapping guidelines to follow:
Use the Right Amount of Containment Force
Containment force is what holds loads together. Depending on the products you’re shipping, you’ll need different amounts of containment on different areas of the load. Thankfully, containment force is easy to calculate. To calculate containment force, multiply the amount of wrap force by the number of film layers. Wrap force refers to how tightly each layer of film is wrapped around the load. Containment force is the total pressure of all layers of the film. The wrap force multiplies as you continue to add layers. When you’re measuring containment force, you’ll need to check the top, the middle, and the bottom of your stretch wrapped pallet. Having the correct amount of force in all three areas is crucial to ensure your products arrive at their final destination without primary packaging or product damage.
Use Film Cable
To prevent them from sliding off their pallet, you’ll need to lock your loads to the pallet with a film cable. Applying film to the bottom of the pallet might make it look secure, but it doesn’t properly lock the load to the pallet. When it’s picked up by a forklift or pallet jack, the forks will tear the film. This can spread up the load, which reduces containment force and increases the risk of load failure. Full web film roping is the best way to lock the load to the pallet.
Check for Long or Dragging Film Tails
Always check your pallet for long or dragging film tails. These tails can get tangled in conveyors, forklift wheels, automatic storage and retrieval systems, and other downstream equipment, which can cause the film to unravel or pull products off their pallets.
At Robopac USA, we pride ourselves on our shrink and stretch wrapping machinery’s superior technology and quality. If you’re in need of fast, reliable, and consistent machines for your packaging facility, come and shop our full line of equipment today!