Appliances: Easier (and cheaper) does it

Cost pressures and superior performance are positioning plastics as an alternative to metal-based materials as appliance manufacturers seek greater design flexibility amid increased consumer emphasis on aesthetics.

Household appliance manufacturers are creatures of habit, observers say. They prefer building equipment with tried-and-true materials that provide known performance and value. Nonetheless, plastics industry members say they are leveling the playing field by using materials that offer new and increasing capabilities, heat resistance, and mechanical strength.

"The design and manufacture of next-generation appliances must navigate their way between increasing market demands, costs, and regulatory mandates," says Paola Babka, global market director, commercial and consumer appliances, GE Plastics (Pittsfield, MA). "Fortunately, engineering thermoplastics, in addition to mechanical and chemical performance, provide the aesthetics required to create lifestyle products."

The Assn. of Home Appliance Manufacturers (Washington DC) identifies five major categories in the $20 billion home appliances industry. These are cooking (electric and gas ranges, microwave ovens), home laundry (washers and dryers), kitchen cleanup (disposers, dishwashers, compactors), food preservation (refrigerators, freezers), and home comfort (air conditioners, dehumidifiers). Dow Chemical Co. (Midland, MI) estimates that the North American household appliances market grew 2% to 3% in 2003. ABS, polystyrene, and compounded polypropylene are reportedly the most widely used plastic materials.

"What I see in the appliances industry is [companies] continuing to look for new plastic applications," says Wade Cullen, VP, manufacturing operations, WaDal Plastics (Medford, WI), an injection molder of custom plastic parts for several industries, including appliances. "For example, we just converted a door striker, which used to be metal, to plastics for door assembly for one appliances company."

Attempts to reach officials at Whirlpool Corp. (Benton Harbor, MI), Maytag Appliances (Newton, IA) and Bissell Corp. (Grand Rapids, MI), three leading home appliances manufacturers, for comment were unsuccessful at press time. But according to OEM suppliers contacted by MP, price sensitivity and ever-increasing customer demands for functionality, aesthetics, performance, and ergonomics are among the major trends at work in their business. More OEMs are reportedly realizing that in most instances, a plastic part is not only as good as the conventional metal, but sometimes as strong and very often less expensive.

Price pressures on processors serving the appliance market are said to be high. As a result, processors are reportedly implementing more automation and lean manufacturing techniques, as well as alternative materials in an effort to consolidate material buys and leverage resin suppliers. "We buy electric presses for the majority of our applications because the molding is more energy efficient than with other technologies," Cullen notes. "You also get better shot-to-shot consistency because of the preciseness of the servo motors."

Design flexibility

As OEMs look for ways to differentiate their products from competitors'', more attention is being paid to aesthetics. More designs per product and regular design changes mean OEMs and processors are looking for flexibility.

"Frequent color changes can be an issue due to the lost productivity and the cost of the raw material waste in transitioning," says Denise Kniager, North America market manager, appliances, Dow Engineering Plastics. "Additionally, OEMs and processors face the risk of an inventory of pre-colored resins in obsolete and thus unusable colors."

Design, in fact, is becoming the primary differentiator for applicances in the retail market. "Technical capabilities are becoming less of a differentiating factor between original equipment manufacturers as most appliances offer similar functionality," Kniager says.

The design freedom offered by plastics also allows for a far greater level of molded-in feature integration than is possible in die-cast metals, such as for brackets used to mount electrical motors, pumps, and compressors.

For dynamic structures and moving parts, plastics allow engineers to overcome the relatively low stiffness of plastics vs. metals, while their reduced weight decreases dynamic loads on the structure considerably. In some cases, OEMs are reportedly finding it more desirable to use a hybrid plastic/metal solution in certain sections of the assembly. "Hybrid assemblies can be manufactured using insert molding, where a metal part is inserted in the injection-molding tool, resulting in a fully assembled, fully finished part emerging from the tool," Babka says.

New environmental and regulatory requirements are having an effect on product specification as well. These include, among others, the EC Directive on Waste Electrical and Electronic Equipment, Restriction on the Use of Certain Hazardous Substances in Electrical and Electronic Equipment regulation, and IEC 60335. Experts say these changes could impact future designs and/or selection of appliance materials in North America.

A case in point is Underwriters Laboratories Inc.''s (UL; Northbrook, IL) new and revised requirements that impact portable, unattended household equipment. The standards and categories affected are those that directly reference UL 746C in the end-product standard. Effective June 1, UL says the flammability level for the enclosure is required to be a V-rated material (V0, V1, or V2). UL expects the changes will increase the safety of household appliances.

"The biggest change to what is defined as portable unattended equipment are products that switched from metal enclosures to plastic years ago," says Daniel O''Shea, UL''s principal engineer, plastics. "Those products have moved from non-flame-retardant versions to flame-retardant versions."

Processors may need to work closely with both end-product and component manufacturers to choose the appropriate material for their particular application. Says O''Shea, "[OEMs] are looking for assurances that these parts will not have any difficulty meeting UL requirements."

Greg Valero [email protected]

Dishwashers will have more plastics inside

Just as the use of plastics for interior components of clothes washing machines has gradually increased in the last 10 years —most notably polypropylene for the tub on front-loading models—so the same process is now beginning to happen with dishwashers. Borealis (Lyngby, Denmark) is now in the final phase of a project with an undisclosed appliance manufacturer to develop a complete one-piece PP tub. The product will debut later this year.

Last year, Bosch und Siemens Hausgeräte GmbH (BSH; Munich), launched a dishwasher with a tub floor in a PP compound specially developed by Borealis to provide long-term resistance to chemicals used in dishwasher detergents at temperatures around 80C (February 2003 MP, p. 49; MPI, p. 57). Another important feature of the development is that Bosch-Siemens has been able to considerably reduce its production costs for the part.

Werner Posch, a market development engineer in Borealis'' engineering applications business unit in Linz, Austria, says plastic tubs have been developed before, but have not been intended for such high-temperature environments. Especially important for BSH was color stability of the part.

Posch says future dishwashers will contain a lot more polypropylene than they do now, not just for the tubs, but also for interior fittings. He says Borealis is currently working on replacement of steel hinges, as well as various parts of the baskets and their supports that are currently made in PVC-coated steel.

Other dishwasher makers are likely to be working on similar developments, but all those responding to information requests for this article refused to discuss ongoing projects.

Peter Mapleston [email protected]

Fridge door liners transition to ABS materials

There has been a notable transition from HIPS to ABS among processors of refrigerator door liners, according to Kurt Brunner, sales and project engineer at thermoforming machine manufacturer Kiefel (Freilassing, Germany). Using ABS lets these processors downgauge on wall thickness without losing part strength, he says, and often also reduces part cost.

Thermoforming ABS usually requires some sort of pressure assist to get good parts definition, a growing requirement as these liners'' design becomes more detailed. "We''ve developed some special solutions for this [pressure assist of ABS]," Brunner says.

In late 2001, Kiefel acquired the know-how and technology of Italy''s Rigo, until then one of its closest competitors in the market for thermoformers for refrigerator door liners. Rigo (Castelnovetto) no longer makes thermoforming units, only trimming equipment for these door liners, and performs upgrades on machines used to thermoform these parts.

Refrigerator manufacturers are even considering replacing metal external refrigerator doors with ones made of plastic. Turkish OEM Arcelik is working with Austrian sheet extruder Senoplast (Piesendorf) on use of Senoplast''s high-gloss coextruded ABS/PMMA sheet for this application. Senoplast is also developing a grade of sheet using these materials that it says will be suitable for replacing the entire metal housing of a refrigerator. Advantages would include reduced weight, easier recyclability, and increased design options.

Matt Defosse [email protected]

Contact information
GE Plastics www.geplastics.com
Assn. of Home Appliance Manufacturers www.aham.org
Dow Chemical Co. www.dow.com
WaDal Plastics www.wadalplastics.com
Underwriters Laboratories Inc www.ul.com
Borealis www.borealisgroup.com
Senoplast www.senoplast.com
Kiefel www.kiefel.de