This article explores various packaging materials and techniques for the inside of the distribution packaging. Both cushioning and non-cushioning approaches are reviewed.
ISOLATION AND DEFLECTION
The function of interior protective packaging for distribution can be categorized as isolation or deflection.
Compliant materials, such as expanded foam plastics, wadded paper, and molded pulp, will deflect under the loads that result from distribution activities such as drops and vehicle vibration. This deflection allows the mitigation of these forces. A material deflects when the package is dropped and hits the floor; and the resulting shock is spread over a greater time duration, which reduces the peak acceleration that the product receives.
This deflection and the trading of time for acceleration is the foundation of cushioning. Deflecting materials may be specifically designed for a required performance level, or may function generally in shock mitigation and vibration protection. Isolation is also an important function of interior packaging. These materials include corrugated and solid fiberboard, foamed plastic, wood, and other relatively rigid materials. Products are isolated from the outside environment, preventing contact damage with the package’s surroundings. While deflecting interior packaging works by reducing applied load, isolation interior packaging works by preventing direct contact.
Products take many shapes. Packages usually perform best when they are rectilinear in shape. The differences are accommodated by void fill. The goal is to make a tight fit inside and avoid excess movement in response to distribution forces. A void fill package material should be robust enough to stay in position, inexpensive and easy to use, and light in weight to minimize transportation expenses. A wide variety of materials have been used for void fill, for example, wadded paper, loose-fill materials, air-inflated and foam-in-place expanded plastic. Void fill systems can support hand packing or semi-automated operations. When considering a void fill system, consider the weight of the product, the size of the void to fill and the density of the void fill material when in place. Determine if the material will allow flow and settling inside the exterior container, which may in turn allow the product to migrate to the wall of the container where it is more susceptible to damage. Consider whether the size of the individual units or particles of the void fill material are compatible with the characteristics of the product. Having packaging material stuck into the structure of the product can be damaging. Also consider the needs of the receiving and unpacking operation, and look for compatibility with that end of distribution. Figure
14.1. shows an inflatable packaging system in use (SAC, 2008).
Interior blocking isolates the product or a component of the product inside of the package to minimize contact
damage and product or component movement when subjected to distribution hazards. Relatively rigid materials such as wood, built-up corrugated, molded pulp and rigid foamed plastic are effective.
PARTITIONS, PADS AND LINERS
Using paperboard, corrugated, plastic corrugated and other materials, partitions, pads and liners are used to create individual protective cells within the interior space of a distribution package. Designs can be simple
scored and slotted sheets, or more complex designs. See Figure 14.2 for a simple corrugated partition design. Partitions, pads and liners are also used in combination with void fill, blocking, and cushioning as needed.
Corrugated pads are also used to fill in the space between the short flaps on slotted containers, providing a flat, two-layer surface for the contents of the package.
Cushions are designed for specific performance, to meet a required maximum acceleration level at a target design drop height. In order to accomplish these goals, the cushion size is specified to control the static Cushion Configurations 159 FIGURE 14.2 stress (weight/area) on the cushion. The cushion size and configuration are therefore critical to cushion performance. A total required contact area may be accomplished in many design alternatives. Face pads, end caps, corner and edge cushions are all effective. Figure 14.3 shows examples.
Interior packaging is typically in close contact with the surface of the product. Many products have finished surfaces that can be damaged by abrasion or scratching initiated by distribution forces. Special packaging
materials are used to help protect these surfaces. A simple solution is to place the product in a plastic bag. More demanding surfaces can benefit from wrapping with soft paper-based materials, thin sheets of foamed plastic such as polyurethane, plastic film, foamed polypropylene sheet material, or bubble materials. These materials are available with cohesive coatings so they that will adhere to themselves but not to surrounding items. This characteristic is useful to intimately wrap structures such as furniture legs.
MULTIPLE PRODUCTS AND KITS
When multiple products are packaged in one outer container, the interior packaging aids in product protection by separating products from each other. Whether the combination is a standardized kits of parts to perform a product function or a one-time assortment to fill a specific customer order, the package needs to provide individual protection and a tight fit to avoid movement in response to distribution forces.
Techniques such as plastic skin packaging are used for kitting. Heated plastic film is adhered to a corrugated substrate that has heat-seal coating and a vacuum system pulls the air out from between the plastic and corrugated. This captures the kit of items between the two, with the products serving as molds for the plastic shape (Selke, 2004). Medical device manufacturers and specialized re-packagers put together kits of medical tools to perform a certain procedure. Virtually all forms of sterile medical device packaging is used, including thermometer lidded trays, bags and pouches, and sterile wraps. Direct-to-consumer distribution puts a premium on interior packaging. With hundreds or thousands of products available, the specific mix for a given order is hugely variable. Items for an order are picked from inventory and given to a packer for packaging. The proper size shipper and appropriate interior packaging are key to a successful and damage-free delivery to the customer. Free-flow, air-filled and similar systems provide very flexible solutions and can be used to separate and protect a variety of products.