Appliance Design - August 2007 - (Page 26)

NOISE & VIBRATION MSC composites must be tuned to the case. To date, the company has developed more than 100 cores that target noise while meeting specific criteria for required damping, temperature, frequency (hertz), stiffness and operating environment. In addition to the wide range of core developments, Quiet Steel can be manufactured using a diverse combination of metal types, including different stainless grades and finishes used in a variety of appliance and consumer applications today. Not all solutions require Quiet Steel, however. The company also offers a host of other products such as Sound Trap® and Magna Damp®. With Sound Trap, instead of two layers of metal surrounding a core, it features a single layer of metal, a viscoelastic layer, and an adhesive covered by a backing film. Its uses are varied. For example, if a corner of a dryer top was vibrating, the material could be used as a localized sound barrier by peeling off the film backing and applying it to a specific area. By contrast, Magna Damp has no adhesives. Instead it uses a magnetic layer to magnetically bond to a steel part during assembly. Later, during a finishing cure cycle, the MagnaDamp is baked onto the part. The MagnaDamp material damps noise and also adds stiffness. A number of companies offer damping materials in sheet and pad form so that manufacturers can fabricate the material to their own desired configurations. Soundcoat offers a GPDS/foam damping sheets that is a flexible extensional viscoelastic damping product that works over a wide temperature range and can be applied to irregular surfaces. The Polydamp extensional damping pad from Polymer Technology is a lightweight, extensional damping composite with a viscoelastic surface and aggressive pressure-sensitive adhesive that the company says provides effective damping over a broad temperature and frequency range. It is water resistant and odorless. 3M also offers a variety of constrained layer products including the 3M Vibration Control Tape (CL1151) that is designed to reduce resonant noise, vibration, and fatigue in metal, plastic panels and support structures. According to Joan Detloff, marketing manager for 3M Acoustic Solutions, it decreases wear and tear on parts, lowers risk of part loosening and displacement and attenuates noise at its source. The damping foils feature a constrained layer construction consisting of a pressure sensitive viscoelastic polymer and a dead-soft aluminum foil (constraining layer). 26 applianceDESIGN August 2007 Sorbothane’s isolation products can be used in a variety of applications. Airborne noises Reducing airborne noises can be a challenging, but absorption materials and sound barriers are two ways to handle the problem. A number of materials can be used for this purpose, with some of the more common ones being polymer foams and non-woven fiber mats. Foams can be formulated with either open cell or closed cell construction, and they can be made from materials such as polyurethane, polyimide, melamine, and other materials having the capability to reduce reverberant airborne noise. Fiber based absorbers can also be made from different base materials. Ceramic glass fiber was popular for a long time, though polyester fiber materials are now surpassing them in many applications. Absorption materials convert acoustic energy into thermal energy by frictional dissipation through the material’s structure. In addition to being made from different materials, absorption products can also be made with different densities and other specific desired properties such as heat resistance, water resistance, or flame retardance. 3M Acoustic Solutions offers a compressible, formable and easy-to-install product called Thinsulate Acoustic Insulation. This is a nonwoven acoustic insulation material that is naturally hydrophobic. Because it is conformable, it can be engineered into, and around, areas that were previously hard to incorporate absorber materials, says Detloff. She says that the material is made with ultrafine synthetic fibers that can be packed into the same space to create great surface area in a given location. Non-woven acoustic insualtion such as Thinsulate allows the sound waves to enter into the insulation, and then force the sound waves to flow over the large fiber surface areas created by the ultrafine fibers. “We say that the sound waves have to take a tortuous path through the material,” Detloff says. Taking that tortuous path is what causes the sound waves to diminish in intensity. Polymer Technologies offers the Polydamp Acoustical Foam that comes in ether, ester, melamine and polyimide types. Densities range from 0.6 lbs./cu. ft. to 2.0 lbs./cu. ft. and the range of products are temperature rated all the way down to -300 degF and up to 500 degF. Soundcoat offers its Soundfoam products that are polyester-based urethane that provides uniform cell structure, and high physical properties that are meant to provide maximum sound absorption in a minimum thickness. Other products on the market include Isoloss NV damping material from E-A-R Specialty Composites. The materials are faced with a 1mil aluminized polyester film that deflects heat rays and helps to keep the underlay material or components cooler. Whatever material is chosen, Shane says that designers must make sure that it meets flammability requirements. Applicable materials should be UL fire rated. Another technique to reduce noise is to throw up a barrier. A barrier can be made from a variety of materials such as glass, sheet rock, wooden doors, metal enclosures, plastic enclosures, or anything that will keep sound in or keep it out. Barrier products can be flat or molded, three-dimensional shapes. They can offer thermal protection in addition to acoustic blocking, and they come in a variety of combinations, coverings, and wear surfaces. When using a barrier, it is important to surround the noise source as much as possible, www.applianceDESIGN.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - August 2007

Contents Editorial Shipments/Forecasts News Watch A Reed Switch is Simople, yet Versatile, and Designers are Finding New Uses for this Time-Tested Technology A Novel Actuation and Sensing Technology can Register a Light Touch, but Resist Blows from a Hammer Tracing the Source of Noise is Made Easier with Noise Source Identification Methods Appliance Noise can be Annoying, but Designers have Many Material Choices to Help Rein in the Racket Nanocomposites are No Longer a Technology for the Future. These Plastic Materials are Already on the Job A New High-Strength, Low-Density Glass-Microsphere Additive can Improve Plastic Part and Molding Performance A New Electromagnetic Weld/Bonding Process Helps Ensure Long-Term Integrity of Joints in Plastic Parts Snap-Based Technology Eases Installation and Makes Products More Serviceable Two-Part Silicone Adhesives Provide a Rapid-Cure Alternative to Traditional One-Part Silicones Classified DesignMart Advertiser’s Index Association Report: GAMA

Appliance Design - August 2007

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