Package cushioning is used to help protect fragile items during shipment. It is common for a transport package to be dropped, kicked, and impacted: These events may produce potentially damaging shocks. Transportation vibration from conveyors, trucks, railroads, or aircraft can also damage some items.
ShockA mechanical or physical shock is a sudden acceleration or deceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation....
and
vibrationVibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...
are controlled by cushioning so that the chance of product damage is greatly reduced.
Cushioning is usually inside a
shipping containerA shipping container is a container with strength sutiable to withstand shipment, storage, and handling. Shipping containers range from large reusable steel boxes used for intermodal shipments to ubiquitous corrugated boxes.-Intermodal freight containers:...
such as a corrugated
boxBox describes a variety of containers and receptacles for permanent use as storage, or for temporary use often for transporting contents....
.
Package cushioning is used to help protect fragile items during shipment. It is common for a transport package to be dropped, kicked, and impacted: These events may produce potentially damaging shocks. Transportation vibration from conveyors, trucks, railroads, or aircraft can also damage some items.
ShockA mechanical or physical shock is a sudden acceleration or deceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation....
and
vibrationVibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...
are controlled by cushioning so that the chance of product damage is greatly reduced.
Cushioning is usually inside a
shipping containerA shipping container is a container with strength sutiable to withstand shipment, storage, and handling. Shipping containers range from large reusable steel boxes used for intermodal shipments to ubiquitous corrugated boxes.-Intermodal freight containers:...
such as a corrugated
boxBox describes a variety of containers and receptacles for permanent use as storage, or for temporary use often for transporting contents....
. It is designed to deform or crush to help keep levels of shock and vibration below levels that which may damage the product inside the box. Depending on the specific situation, package cushioning can often be between two and three inches thick.
Internal packaging materials (sometimes the same ones used for cushioning) are also used for functions other than cushioning. Some are used just to immobilize the products in the box and to block them in place. Others are just used to fill a void and do not have a cushioning function.
Design factors
When designing packaging, the choice of cushioning may depend on many factors:
- effective protection of product from shock
A mechanical or physical shock is a sudden acceleration or deceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation....
and vibrationVibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...
- whether cushioning is resilient (performs for multiple impacts)
- resistance to creep – cushion deformation under static load
- material costs
- labor costs, productivity
- effects of temperature , humidity, and air pressure on cushioning
- cleanliness of cushioning (dust, insects, etc)
- effect on size of external shipping container
- environmental and recycling
Recycling involves processing used materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution and water pollution by reducing the need for "conventional" waste disposal, and lower...
issues
- sensitivity of product to static electricity
Static electricity refers to the buildup of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge...
.
- etc
Common Types of Cushioning
Loose Fill -
Some cushion products are flowable and are packed loosely around the items in the box. The box is closed to tighten the pack. This includes expanded
polystyrenePolystyrene , sometimes abbreviated PS, is an aromatic polymer made from the aromatic monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry...
foam pieces (
Foam peanutFoam peanuts, also known as packing peanuts, are a common loose-fill packaging and cushioning material used to prevent damage to fragile objects during shipping. They are shaped to interlock when compressed and free flow when not compressed...
s), similar pieces made of starch based foams, and common
PopcornPopcorn or popping corn is a type of corn which explodes from the kernel and puffs up when heated. Corn popping was originally discovered by Native Americans, but became popular as a snack food during the United States Great Depression, especially in movie theaters.Corn is able to pop because,...
.
PaperPaper is thin material mainly used for writing upon, printing upon or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
-
Paper can be manually or mechanically wadded up and used as a cushioning material. Heavier grades of paper provide more weight bearing ability than old newspapers. Creped cellulose wadding is also available.
Corrugated fiberboard pads -
Multi-layer or cut-and-folded shapes of corrugated board can be used as cushions. These structures are designed to crush and deform under shock stress and provide some degree of cushioning. Honeycomb paper structures are also used for cushioning.
FoamThe most general definition of foam is a substance that is formed by trapping many gas bubbles in a liquid or solid. It can also refer to anything that is analogous to such a phenomenon, such as quantum foam. Often the term is used in reference to polyurethane foam , XPS foam, Polystyrene, or many...
structures -
Several types of polymeric foams are used for cushioning. The most common are: Expanded
PolystyrenePolystyrene , sometimes abbreviated PS, is an aromatic polymer made from the aromatic monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry...
(also
StyrofoamStyrofoam is a trademark of Dow Chemical Company for presently made for thermal insulation and craft applications..In 1941, researchers in Dow's Chemical Physics Lab found a way to make foamed polystyrene...
),
polypropylenePolypropylene or polypropene is a thermoplastic polymer, made by the chemical industry and used in a wide variety of applications, including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and...
,
polyethylenePolyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons. Its primary use is within packaging .- Description :Polyethylene is a thermoplastic polymer consisting of long chains of the monomer ethylene...
, and
polyurethaneA polyurethane, IUPAC abbreviation PUR, but commonly abbreviated PU, is any polymer consisting of a chain of organic units joined by urethane links...
. These can be molded engineered shapes or sheets which are cut and glued into cushion structures.
Foam-in-place is another method of using
polyurethaneA polyurethane, IUPAC abbreviation PUR, but commonly abbreviated PU, is any polymer consisting of a chain of organic units joined by urethane links...
foams. These fill the box, fully encapsulating the product to immobilize it. It is also used to form engineered structures.
Inflated Products -
Bubble WrapBubble Wrap is a pliable transparent plastic material commonly used for packing fragile items. Regularly spaced, protruding air-filled hemispheres provide cushioning for precious or breakable items....
consists of sheets of plastic film with enclosed “bubbles” of air. These sheets can be layered or wrapped around items to be shipped. Engineered inflated structures are also available. Note that inflated air pillows used for void-fill are not suited for cushioning.
Molded pulp -
Pulp can be molded into shapes suitable for cushioning and for immobilizing products in a package.
Molded pulpMolded pulp, also named Moulded pulp or Molded Fibre, is a packaging material, typically made from 100% recycled corrugated fiberboard and newspaper. It is used for protective packaging or for food service trays and beverage carriers...
is made from recycled newspapers and is recyclable.
Other -
Several other types of cushioning are available including suspension cushions, thermoformed end caps, and shock mounts.
Design for Shock Protection
Proper performance of cushioning is dependent on its proper design and use. It is often best to use a trained
packaging engineerPackaging engineering, also Package engineering is a broad topic ranging from design conceptualization to product placement. All steps along the manufacturing process, and more, must be taken into account in the design of the package for any given product...
, reputable vendor, consultant, or independent laboratory.
An engineer needs to know the severity of shock (drop height, etc) to protect against. This can be based on an existing specification, published industry
standardA technical standard is an established norm or requirement. It is usually a formal document that establishes uniform engineering or technical criteria, methods, processes and practices....
s and publications, field studies, etc.
Knowledge of the product to be packaged is critical. Field experience may indicate the types of damage previously experienced. Laboratory analysis can help quantify the fragility of the item, often reported in g-s. Engineering judgment can also be an excellent starting point. Sometimes a product can be made more rugged or can be supported to make it less susceptible to breakage.
The amount of shock transmitted by a particular cushioning material is largely dependent on the thickness of the cushion, the drop height, and the load bearing area of the cushion (static loading). A cushion must deform under shock for it to function. If a product is on a large load bearing area, the cushion may not deform and will not cushion the shock. If the load bearing area is too small, the product may “bottom out” during a shock; the shock is not cushioned. Engineers use “cushion curves” to choose the best thickness and load bearing area for a cushioning material. Often two to three inches (50 - 75 mm) of cushioning are needed to protect fragile items.
Design for Vibration Protection
The process for vibration protection (or isolation) involves similar considerations as that for shock. Cushions can be thought of as performing like springs. Depending on cushion thickness and load bearing area and on the vibration frequency, the cushion May 1) not have any influence on input vibration, 2) amplify the input vibration at
resonanceIn physics, resonance is the tendency of a system to oscillate at larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies . At these frequencies, even small periodic driving forces can produce large amplitude vibrations, because the system...
, or 3) isolate the product from the vibration. Proper design is critical for cushion performance.
Evaluation of Finished Package
Verification and validationIn software project management, software testing, and software engineering, Verification and Validation is the process of checking that a software system meets specifications and that it fulfils its intended purpose...
of prototype designs are required. The design of a package and its cushioning is often an iterative process involving several designs, evaluations, redesigns, etc. Several (ASTM, ISTA, and others) published laboratory test protocols are available to evaluate the performance of a proposed package. Field performance should be monitored for feedback into the design process.
See also
- Impact force
In mechanics, an impact is a high force or shock applied over a short time period. Such a force or acceleration can sometimes have a greater effect than a lower force applied over a proportionally longer time period.- Theory :...
- Packaging and labelling
Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of design, evaluation, and production of packages. Packaging can be described as a coordinated system of preparing goods for transport,...
- Shock
A mechanical or physical shock is a sudden acceleration or deceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation....
- Vibration
Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...
- Vibration isolation
Vibration-isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations.-Passive isolation:Passive vibration isolation systems consist essentially of a mass, spring and damper ....
ASTM Standards
- D1596 Standard Test Method for Dynamic Shock Cushioning Characteristics of Packaging Material
- D2221 Standard Test Method for Creep Properties of Package Cushioning Materials
- D3332 Standard Test Methods for Mechanical-Shock Fragility of Products, Using Shock Machines
- D3580 Standard Test Methods for Vibration (Vertical Linear Motion) Test of Products
- D4168 Standard Test Methods for Transmitted Shock Characteristics of Foam-in-Place Cushioning Materials
- D4169 Standard Practice for Performance Testing of Shipping Containers and Systems
- D6198 Standard Guide for Transport Packaging Design
- D6537 Standard Practice for Instrumented Package Shock Testing For Determination of Package Performance
- and others
Further reading
- MIL-HDBK 304C, “Package Cushioning Design”, 1997
- Brody, A. L., and Marsh, K, S., "Encyclopedia of Packaging Technology", John Wiley & Sons, 1997, ISBN 0-471-06397-5
- Root, D, “Six-Step Method for Cushioned Package Development”, Lansmont, 1997, http://www.lansmont.com/
External links