Machine Design

Soft-touch plastic at the heart of a defibrillator

An injection-molded case turned out to be a major challenge in bringing a new portable automated external defibrillator (AED) to market.

The resiliency and flow of EstaGrip TPE make it a good choice for use on many features designed into the case, including the moisture seal between the unit's halves. This eliminated several components, minimizing assembly steps and saving money.

 

EstaGrip TPE was also used to mold several other features inside the defibrillator's case, including: the speaker mounting (the speaker coaches users through machine operation); a snap-fit feature that holds the on/off switch in place; the integral spring that lets the case open easily; wire-routing guides to secure wires during assembly; and nonskid feet that keep the unit from sliding while in use.

Accurate Molded Plastics Inc., Coeur d'Alene, Idaho (www.accurateplastics.com) worked closely with defibrillator maker, Medtronic Physio-Control, Redmond, Wash. (www.physio-control.com) to drop the part count for the case down to five, eliminating 59 parts that previously had to be assembled separately.

The 8 X 3.5 X 9-in. unit uses a plastic shell substrate protected by an overmolded thermoplastic elastomer (TPE). The soft-touch, EstaGrip TPE from Noveon Inc., Cleveland (www.noveoninc.com), was originally selected for its adhesive capabilities and compatibility with difficult-to-bond substrates (PC/ABS as well as styrenics, polyesters, vinyls, polyamides, and TPUs). But it also provides overall shock absorption, resiliency, abrasion resistance, and a nonslip grip. Estagrip bonds securely to rigid substrates without chemical adhesives or mechanical interlocks.

The TPE maintains high resilience and soft feel even in the most frigid climates while resisting scratches, oil, and grease. It readily accepts a broad array of pigments and is also used to create icons and graphics on the case. This eliminated additional processes and components for pad printing and labeling.

AEDs are about the size of a portable laptop computer and provide brief, but powerful, electrical stimulation to a person's chest, interrupting a cardiac arrest and helping restore the heart's natural rhythm. They are designed for stadiums, manufacturing plants, office buildings, and schools, anywhere medical personnel might not be immediately available.

- Jean M. Hoffman

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