Sunday, 17 December 2017

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Distribution Packaging and Protective Cushioning

In the world of packaging, cushioning is the material that protects a product from shock or vibration hazards in distribution. More specifically, according to Frankovich, the fundamental role of cushioning material is to “reduce the forces created when one surface comes abruptly into contact with another – by compressing or deforming in such a way as to produce a gradual, rather than instantaneous, change in velocity, thereby minimizing damaging impact forces.”

In order to develop protective cushioning for a product, ExpandOS identified four steps required of cushion designers. The steps are as follows:

Determining the product fragility – (i.e., the estimated shock or frequency at which the product will become damaged)

Determining the handling and distribution environment – (i.e., both the drop height and band of frequencies the product is likely to encounter)

Determining the type and amount of material needed for cushioning, given the weight and surface area of the product, which produces the static stress or static load (i.e., pounds per square inch or psi loads) placed on the cushioning

Evaluating the cushioning materials via either a shock cushion curve or a vibration cushion curve.

Frankovich proffers that the use of cushioning efficiency curves, or J-curves. Plot cushioning efficiency (J) as a function of impact energy density (U) may be the most direct method for selecting impact-cushioning material. He states that because the curves are generated using standard impact tests, the curves indicate the energy density, or impact severity, over which cushioning material is effective. Thus, cushioning materials can be selected based on an actual shock event. In contrast, Zhang et al proposes that traditional methods for selecting cushioning packaging are insufficient. Specifically,they state that traditional methods, while adequate for evaluating shock hazards, are insufficient for considering vibration hazards. They propose a new process called “Hybrid Damping Package Design,” where testing of cushioning and anti-vibration package designs are conducted together; thus reducing the costly redesign problems associated with separately assessing shock and vibration hazards.

While there may be some disagreement about how better to evaluate the effectiveness of cushioning materials, all seem to agree that evaluation is necessary. Moreover, the research contributes to innovation. Frankovich focuses on the performance of the cushioning material – paying specific attention to whether the material exhibits quick or slow recovery properties and how that relates to minimizing impact forces. He states that materials with quick recovery properties exhibit an immediate return to their original height, as well as a return of a high percentage of compressional energy when relieved of a compression load. In contrast, cushioning materials with slow recovery properties do not instantaneously recover, and as a result, do not return stored energy. Recognizing the beneficial properties of each, Frankovich concludes that cushioning materials exhibit a combination of slow and quick recovery characteristics that might be the optimal choice for energy absorption and impact cushioning. Since these materials have slow recovery properties, but good on dampening, shock absorption, and rebound, they may not produce the minimum value of deceleration needed for adequate protection.

Taking into consideration each of these cushioning design methods, it should be noted that multiple cushioning options already exist on the market and can generally be categorized by the method they employ for product protection – blocking and bracing, wrapping, or mold enclosing. Identifying the method and material best suited for protecting a product is both the challenge and goal, and entails balancing costs and protection. In regards to protection, an optimal design strikes a balance between cushion effectiveness and the costs listed above. Consequently, both cost and cushion effectiveness are dependent upon design. Expandos offers a four-step guide for evaluating cushioning capabilities. The guide provides estimates for drop heights and product fragility, and offers instruction on calculating static stress or load, and ordering the data for use with cushion curves. Expandos recommends, however, that the information provided should simply be used as a general guideline, and that packaging configurations be tested before adopting new standards.

References

ExpandOS Brandable Protective Packaging. (2012, January). Understanding Internal Packaging Materials. Retrieved October 12, 2016, from [https://expandos.com/media/wysiwyg/Guide_to_Internal_Packaging_Material_2012_.pdf]

Frankovich, D. (n.d.) Proper Performance Data Ease the Task of Specifying Cushioning Materials. Retrieved October 12, 2016, from [http://www.trelleborg.com/Documents/Trelleborg%20Applied%20Technology/CONFOR-Foam-Specifying-Cushioning-Materials.pdf]

Zhang, Q., Saito, K., & Nagaoka, K. Proposal of Hybrid Damping Package Design. Journal of Applied Packaging Research. 2016. 8 (3) 61-72.

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