Cushioning


Cushioning

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. Shock and vibration are controlled by cushioning so that the chance of product damage is greatly reduced.

Cushioning is usually inside a shipping container such as a corrugated box. It is designed to deform or crush to help keep levels of shock and vibration below levels that 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.

Molded expanded polystyrene (Styrofoam) cushioning

Contents

Design factors

When designing packaging, the choice of cushioning may depend on many factors:

  • effective protection of product from shock and vibration
  • whether cushioning is resilient (performs for multiple impacts)
  • resistance to creep – cushion deformation under static load
  • material costs
  • labor costs, productivity
  • effects of temperature,[1] humidity, and air pressure on cushioning
  • cleanliness of cushioning (dust, insects, etc.)
  • effect on size of external shipping container
  • environmental and recycling issues
  • sensitivity of product to static electricity.
  • 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 polystyrene foam pieces (Foam peanuts), similar pieces made of starch-based foams, and common popcorn. The amount of loose fill material required and the transmitted shock levels vary with the specific type of material.[2]

Paper - 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. (Movers often wrap objects with several layers of Kraft paper or embossed pulp before putting them into boxes.)

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. Paperboard composite honeycomb structures are also used for cushioning.[3]

Foam structures - Several types of polymeric foams are used for cushioning. The most common are: Expanded Polystyrene (also Styrofoam), polypropylene, polyethylene, and polyurethane. These can be molded engineered shapes or sheets which are cut and glued into cushion structures.

Blocks and Caps.jpg

Foam-in-place is another method of using polyurethane foams. These fill the box, fully encapsulating the product to immobilize it. It is also used to form engineered structures.

Molded pulp -

Molded pulp cushioning

Pulp can be molded into shapes suitable for cushioning and for immobilizing products in a package. Molded pulp is made from recycled newspapers and is recyclable.

Inflated Products - Bubble Wrap consists of sheets of plastic film with enclosed “bubbles” of air. These sheets can be layered or wrapped around items to be shipped. A variety of engineered inflatable air cushions are also available. Note that inflated air pillows used for void-fill are not suited for cushioning.

Other - Several other types of cushioning are available including suspension cushions, thermoformed end caps, and shock mounts.

Design for shock protection

Drop test of cushioned package to measure the transmitted shock

Proper performance of cushioning is dependent on its proper design and use. It is often best to use a trained packaging engineer, 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 standards 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 [4] 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 resonance, or 3) isolate the product from the vibration. Proper design is critical for cushion performance.

Evaluation of finished package

Verification and validation 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 package testing protocols are available to evaluate the performance of a proposed package. Field performance should be monitored for feedback into the design process.

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

See also

Notes

  1. ^ Marcondes, Jorge; Hatton, Graham, Schueueman (July 2003). "Effect of temperature on the cushioning properties of some foamed plastic materials". Packaging Technology and Science 16 (2): 69–76. doi:10.1002/pts.614. 
  2. ^ Singh, S. P.; Chonhenchob and Burges (1994). "Compariison of Various Loose Fill Cushioning Materials Based on Protective and Environmental Performance". Packaging Technology and Science (Wiley) 7: 229 - -241. doi:10.1002/pts.2770070504. 
  3. ^ Wang, Dong-Mei; Wang, Zhi-Wei (October 2008). "Experimental investigation into the cushioning properties of honeycomb paperboard". Packaging Technology and Science 21 (6): 309–373. doi:10.1002/pts.808. 
  4. ^ Burgess, G (March 2000). "Extensnion and Evaluation of fatigue Model for Product Shock Fragility Used in Package Design". J. Testing and Evaluation 28 (2). 

Further reading

  • MIL-HDBK 304C, “Package Cushioning Design”, 1997
  • Root, D, “Six-Step Method for Cushioned Package Development”, Lansmont, 1997, http://www.lansmont.com/
  • Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6

External links


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Look at other dictionaries:

  • cushioning — n. soft or resilient material used to fill or give shape or protect or add comfort. Syn: padding. [WordNet 1.5] …   The Collaborative International Dictionary of English

  • cushioning — [[t]k ʊʃənɪŋ[/t]] N UNCOUNT Cushioning is something soft that protects an object when it hits something. Walkers need cushioning under the ball of the foot …   English dictionary

  • Cushioning — Cushion Cush ion (k[oo^]sh [u^]n), v. t. [imp. & p. p. {Cushioned} ( [u^]nd); p. pr. & vb. n. {Cushioning}.] 1. To seat or place on, or as on a cushion. [1913 Webster] Many who are cushioned on thrones would have remained in obscurity.… …   The Collaborative International Dictionary of English

  • cushioning — cush|ion|ing [ˈkuʃənıŋ] n [U] something soft that protects someone or something when they hit a surface ▪ A special pad in the heel offers good cushioning as you walk …   Dictionary of contemporary English

  • cushioning — Synonyms and related words: abating, allaying, alleviating, assuaging, blunting, chastening, dampening, damping, deadening, diminishing, dulling, easing, laxation, lessening, mellowing, mitigating, mollification, mollifying, padding, reducing,… …   Moby Thesaurus

  • cushioning — cush·ion || kʊʃn n. pillow, soft padded object v. upholster; reduce; protect; soften …   English contemporary dictionary

  • cushioning — cush·ion·ing …   English syllables

  • cushioning — noun artifact consisting of soft or resilient material used to fill or give shape or protect or add comfort (Freq. 1) • Syn: ↑padding • Derivationally related forms: ↑cushion, ↑pad (for: ↑padding) …   Useful english dictionary

  • cushioning effect — A temporary gain in lift and decrease in drag during flight near the ground or water caused by the compression of air between the wings of the aircraft and the surface below. Also called ground effect. Cushioning effect (in ground effect) …   Aviation dictionary

  • dunnage — Cushioning material placed among cargo to prevent their motion …   Dictionary of automotive terms