Appliance Design - August 2007 - (Page 44)

JOINING Loctite 5600 Silicone Sealant is applied using Baron’s robotic/ automated assembly equipment onto a glass stovetop just prior to assembly of the frame. New Two-Part Silicones Strength RTV Min utes Hour s Time Fig. 1. Cure time vs. strength for one-part RTV and new two-part silicones. materials is 140 DegC with a maximum cure depth of 3/8-in., factors that limit their usefulness in a variety of appliance assembly applications. Two-part silicones Recently, new, highly engineered two-part silicones have been developed specifically for the appliance market to overcome the problems associated with RTV silicones. Fig. 1 illustrates a typical strength-vs.-cure-time curve for an RTV silicone and the two-part technology. The graph highlights the superior strength/cure time performance of two-part silicones. The two-part silicones offer a number of benefits over RTV silicones. These products skin over in 5 minutes or less, develop sufficient bond strength to allow burner assembly in 3 to 5 minutes, and are ready for packaging in 5 to 10 minutes. Racking is not required, and parts can be continuously processed without costly WIP. As the initial curing process does not require moisture, the expense and floor space requirements related to humidity chambers are eliminat- ed. In addition, no offensive or corrosive odors are emitted. New two-part silicones provide high adhesion and excellent bond strength on glass, metals, and other materials, and can be used for bonding, gasketing, potting and sealing. These adhesives carry a UL temperature rating of 180 DegC, an improvement of 40 DegC over the temperature ratings of RTV silicones. The higher temperature rating allows two-part silicones to be used in range/oven applications that historically required welding or mechanical fasteners. The shelf life of the twopart silicones exceeds one year, and bond strength is greatly improved as a result of added adhesion promoters. Table 1 highlights the major benefits of a two-part silicone vs. an RTV silicone. Cost savings Although every appliance manufacturer is unique, and costs vary from plant to plant and region to region, significant cost savings can be achieved by switching from RTV silicone to the fast-curing two-part silicones. Table 2 illustrates typical cost savings achieved with the two-part silicone technology. The savings can be attributed to a number of areas: 4Labor: An RTV silicone line typically requires two workers to transport assembled stovetops onto racks, while two-part silicones require no labor as parts are processed on a slow conveyor for 5 to 10 minutes before proceeding directly to burner assembly. Based on typical, fully burdened labor rates of $30,000 per year, immediate cost savings of $60,000 can be realized using the two-part silicones. 4Production time/work-in-process: Costper-minute of finished goods varies with the number and type of units manufactured, the average cost of all units produced, and overhead. In a high-volume facility that produces 750,000 smoothtop ranges annually, the WIP value is estimated at $22,500. A facility producing 250,000 units annually has an estimated WIP value of $9,000. High Volume Operations 3000 Stove Tops per Day $60, 000 $22, 500 $20, 000 $102,500 $35, 000 Less than 5 months Medium Volume Operations 1000 Stove Tops per Day La b o r S a v in gs W o rk-I n -P ro ce s s F lo o r S p a c e $60, 000 $9, 000 $20, 000 $89,000 $35, 000 Less than 5 months Table 2. Cost savings with new two-part silicone in high-volume and medium-volume stovetop production. 44 applianceDESIGN August 2007 Annual Process Savings C a p ita l C o s ts Payback Period 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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