The movement of goods across the supply chain subjects cargo to constant motion, vibration, and impact. Protecting products from this dynamic environment is a major challenge for businesses shipping merchandise worldwide. While external boxes and pallets are visible components of freight handling, an interior material works behind the scenes to maintain the structural integrity of the shipment. This material stabilizes the load and prevents movement during transit, ensuring safe and secure transportation.
Defining Dunnage in Logistics
Dunnage is the material used to secure, support, and protect cargo within a larger transportation unit, such as a shipping container, truck trailer, or rail car. It is placed between items, around them, or beneath them to fill empty spaces and prevent the freight from shifting. The material’s purpose is to ensure the entire load remains stable and intact throughout the journey, not to package the individual item itself. Dunnage can be made from a wide range of materials, including wood, plastic, paper, and foam, depending on the specific demands of the cargo.
The Primary Functions of Dunnage
The main role of dunnage is to prevent cargo movement, which is the largest cause of freight damage during transport. This material acts as a brace, filling voids between packages or between the cargo and the container walls to ensure load stabilization. When a truck brakes suddenly or a vessel encounters rough seas, the dunnage absorbs the momentum and prevents the stacked load from shifting or tipping over.
Dunnage also functions as a shock absorber, cushioning the cargo against the continuous vibration and jarring motions inherent in long-distance travel. Continuous vibration can weaken packaging, loosen seals, and damage sensitive internal components of products. By providing a buffer, the material dampens these forces, ensuring the product’s integrity is maintained. Dunnage also serves to separate layers or individual items of cargo, preventing chafing or abrasion between surfaces.
Common Types of Dunnage Materials
Air Bags and Inflatable Dunnage
Inflatable dunnage bags, often made from woven polypropylene or kraft paper, fill large, irregular voids within a container quickly and efficiently. These bags are placed in empty spaces between cargo and inflated with compressed air until they exert pressure against the load, bracing it securely against the container walls. Their primary benefit is their ability to conform to various shapes and provide significant load restraint without adding substantial weight. Many inflatable options are reusable, offering a cost-effective solution for securing bulkier freight.
Wooden Blocks and Bracing
Wood, in the form of blocks, planks, or custom-built frames, is traditionally used for blocking and bracing heavy or irregularly shaped industrial cargo. Wooden dunnage provides superior strength and rigidity, making it the material of choice for securing heavy machinery or large, non-palletized items directly to the floor of a rail car or shipping container. This method physically restrains the cargo, preventing horizontal and vertical movement that lighter materials could not withstand.
Foam and Custom Inserts
Foam dunnage, including materials like polyethylene and polyurethane, is primarily used for high-level cushioning and shock absorption for fragile or high-value items. These materials can be custom-molded or die-cut to fit precisely around a product, creating a protective enclosure that isolates the item from external forces. Custom inserts are valuable in industries like electronics and medical devices, where the precision-fit design ensures the product is suspended securely, maximizing protection against impact.
Corrugated Cardboard and Paper
Corrugated cardboard sheets and wadded kraft paper are utilized as lightweight, economical dunnage for filling smaller gaps and separating layers of product. Corrugated cardboard is often converted into inserts, dividers, or edge protectors to prevent adjacent packages from rubbing against each other. Kraft paper, shredded or rolled, is commonly used as a general void filler to prevent movement in less dense shipments. These paper-based options are highly recyclable and represent a low-cost solution for securing light to moderately weighted goods.
Selecting the Right Dunnage for Your Shipment
Choosing the appropriate dunnage involves balancing criteria related to the cargo, the journey, and the shipper’s operational goals.
- Fragility: This dictates the required level of shock absorption, which may necessitate specialized foam instead of simple void fill.
- Weight and Density: Heavy loads require the structural support of wood or plastic, while lightweight goods can be secured with paper products.
- Mode of Transport: Rail shipments generally experience greater longitudinal forces than over-the-road trucking, influencing the required restraint.
- Cost Efficiency: Shippers must weigh the expense of a material against the cost of potential damage and returns.
- Environmental Impact: Many businesses prioritize materials that are recyclable, reusable, or made from sustainable sources.
Key Differences Between Dunnage and Other Packaging
Dunnage is frequently confused with other packaging components, but its function is distinct in terms of scale and purpose. Dunnage is defined by its role in securing the entire load within the transport vehicle or container. It is a load-security measure designed to manage the forces exerted on the whole shipment during transit.
In contrast, primary cushioning and void fill materials are used to protect the individual product inside its immediate package or box. For example, bubble wrap or packing peanuts placed around a single item within a retail box are cushioning materials, not dunnage. Dunnage, such as a large wooden brace or an inflatable air bag, operates on a larger scale, preventing the retail box itself from moving relative to the other cargo.