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issue: August 2007 APPLIANCE Magazine

Plastic Materials & Equipment
Pliable Advantages


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by Lisa Bonnema, Senior Editor

As appliance OEMs demand both flexibility and strength in their product designs, plastics suppliers are responding with materials and technology that can meet a variety of demands.

BMC thermoset plastics from Bulk Molding Compounds Inc. (BMCI) are being used in the sole plate covers of Rowenta’s line of laundry care products. Attached directly to the back of the polished metallic ironing surface, the sole plate cover must provide structural support and impact resistance while simultaneously contending with internal temperatures nearing 160°C. In addition to maintaining physical properties while heated, this plastic component must also have exceptionally low water absorption characteristics to be useful in steam conditions. The component must be resistant to starch and other laundry care reagents, while maintaining its color in spite of the aforementioned use factors.

BMCI says its plastic solution to the sole plate cover provides 160°C continuous-use temperatures and can be accurately manufactured to tight color specifications. The material is processed with contemporary injection molding equipment and reportedly generates part yields that are equivalent to, or in excess of, those of high-speed thermoplastic processes. It is also said to provide greater impact values than standard polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) materials.

Most manufacturers will agree that one of the main benefits plastic materials can offer is versatility. That advantage is perhaps more relevant now than ever. New technologies are enabling materials that are durable enough to replace metal, but can also provide design flexibility and a variety of aesthetic options. And let’s not forget about the cost advantages.

Sybill Kraemer, global market segment manager for Santoprene-brand TPVs at ExxonMobil Chemical, confirms that highly functional plastic parts are moving from “function only” to “function and aesthetics.” Case in point: a new kettle introduced by Kenwood, a kitchen appliance manufacturer based in Kenwood, UK. The company wanted to develop a kettle that was both reliable and stylish by creating a smooth, white, soft-touch handle that incorporated an integrally molded button operating a novel “seesaw” lid.

After researching several materials, Kenwood chose a thermoplastic vulcanizate (TPV) from ExxonMobil for the soft-touch grip and “sealed-in” membrane covering the lid release button on the handle. Darren Prosser, Kenwood project manager, explains: “Santoprene TPV was selected for the grip because it could provide a tactile surface, and for the membrane covering the lid release button because of its functional performance, which is particularly important when the kettle gets hot.”

According to Kraemer of Houston, TX, U.S.-based ExxonMobil, the material can deliver equal or better performance at a significantly lower cost than thermoset rubbers. “[It provides] improved chemical, heat, and sealing performance and can be processed on existing thermoplastics extrusion and co-extrusion, injection and co-injection molding, blow molding, or overmolding equipment,” she tells APPLIANCE.

The material is also designed to offer designers creative flexibility. “A number of Santoprene-brand TPV grades bond to multiple substrates, especially engineering thermoplastics, eliminating the need for adhesives, bonding agents, and physical or mechanical interlocks,” Kraemer says. “As well as enhancing design opportunities, combining different materials in this way can provide improved functionality, part consolidation for easier assembly, and reduced costs. These grades can also be easily colored for additional creative design opportunities.”

Tough as Metal

China Array Plastics LLC, a Pittsfield, MA, U.S.–headquartered manufacturer of high-performance thermoplastic components, has introduced a replacement lid for the Model R8 Food Processor from Robot Coupe (Jackson, MS, U.S.). Molded from clear Lexan polycarbonate (PC) resin from GE Plastics of Pittsfield, MA, U.S., the lid is said to feature excellent cleanability, chemical resistance, impact strength, and dimensional stability. This particular grade of thermoplastic is suited for filling out large structural parts, such as the 14-in. diameter lid, while keeping stress low, resulting in greater strength and durability. It is also said to cater to aesthetic demands by molding to a smooth finish with brilliant clarity for superior cleaning, sanitation, and visibility.

Although not as creatively flexible as plastic, the durability of metal is undisputable, especially in demanding applications such as washing machine and dishwasher interiors. However, that fact has only motivated plastic suppliers to work harder at developing high-performance materials that are also more cost-effective than plastics’ robust competitor.

That is certainly the strategy behind recent product development at Bulk Molding Compounds Inc. (BMCI). The company, based in West Chicago, IL, U.S., is working on material solutions to replace the metal sole plate used in steam irons. “The most expensive part of the iron is the polished metal sole plate and heater assembly,” explains Nunnery. “By injection molding a heat-conductive BMC product in high gloss, the secondary polishing operations required of die-cast metallic materials will be eliminated. Further, by encapsulating the OEM heating technology during the injection molding process, another step in the iron assembly chain will be consolidated.”

With strong OEM partnerships, Nunnery feels the industry could take the technology to the next level, potentially saving iron manufacturers millions of dollars in production costs as the price of metal continues to climb.

One material that is replacing metal is vinyl, according to Roger Steller, senior applications development engineer, Vinyl Compounds at PolyOne Corp. “Washer doors on front-loading washers and pedestal storage units are now being made with vinyl instead of steel, allowing for greater design flexibility,” he says. “Work surface boards made with vinyl result in a chemical-resistant workspace across the top of the washer and dryer.”

Steller adds that the time and cost involved to tool a vinyl part compared to stamped metal is significantly less. “In addition, vinyl can be molded to create complex angles and curved surfaces—design features that are extremely difficult to achieve with stamped metal,” he says.

Avon Lake, OH, U.S.–based PolyOne is also seeing appliance companies use vinyl in modular consoles and internal parts such as circuit board housings. “As more appliances incorporate digital electronics, vinyl can be used in many parts where ultrahigh heat-performance plastics were once required,” Steller tells APPLIANCE. “Vinyl can also be used to manufacture snap-in-place components, which allow for faster and more economical assembly.”

One of the more innovative materials replacing metal is the conductive polymer, notes John Madden, director of sales, Healthcare Products at Applied Tech Products (ATP) in Wayne, PA, U.S. “Instead of molding a plastic part and adding a contact to it later, we’ll mold the plastic part, and we’ll overmold the conductive materials, so it’s really just one part. So one side of the part is conductive, the other is not.”

This procedure, Madden remarks, is part of the push to integrate components. “One of the other applications we’re working on is creating one part in a thermoplastic and overmolding it with a platable-grade thermoplastic,” he says. “So when it goes through the plater, the end result is a part that looks like two parts—one half is silver, the other half is plastic, but what’s underneath the silver part is actually plastic.”

While these types of materials are currently being used in cell phone and bar code antennas, Madden adds: “That’s not to say that the technology can’t be used elsewhere.”

From Concept to Reality

No matter what material is being used, there is one truth that spans all of appliance production—speed to market. “Product development is happening at an ever-increasing pace,” confirms Kevin Crystal, senior quality engineer at Protomold. “OEMs require prototypes faster, and require real molded parts earlier in the cycle.”

In response to customer demand, the Maple Plain, MN, U.S.–based supplier says it has developed ways to make real molded parts in as fast as one day, and in standard delivery of three weeks. The company also claims that it can quickly incorporate more functionality into plastic components. Complex parts can be molded in three weeks or less, with as many as four side actions per part.

Much of the increase in speed is due to advancements in online quoting, which helps automate the process of supplying plastic parts. Customers can upload a 3-D CAD model of a specific plastic part, and a ProtoQuote is automatically generated. “From our perspective, it is all about speed,” notes Brad Cleveland, Protomold CEO. “We concentrate on being fast, and our customers figure out how to take  advantage of it.”

In addition to getting products to market faster, Cleveland says some OEMs are using the time savings to perfect product designs. “It might take them just as long to get to market, but they have iterated 10 times instead of twice, so their risk is dramatically lower,” he explains.

Another option for appliance OEMs is to use the time savings to manufacture several different versions of a product in the same amount of time it used to take to develop one design. “It’s almost like mass-customization,” Cleveland says. “They can use our very-low-cost tool and very quick response time, and go to market with 10 products in parallel rather than one. And each one of their products can be slightly different.”

Michael Rhoads, national sales manager, Foams Business Unit of Saint-Gobain High-Performance Materials (Granville, NY, U.S.), adds that time to market can often be decreased by simply doing things right the first time. “We are focused on helping OEMs pick the correct part in the beginning of the design phase,” he says. “There are many products that will work in an application. However, it is important not to overengineer solutions.”

Rhoads says that because of the rapid design phase, he often encounters situations in which the OEM engineers are using materials because those materials have worked in the past. “This is a very safe approach, but you often end up with a material that is overengineered for applications,” he explains.

Just as important as speed to market is design flexibility, notes Randy Beavers, business development manager, Specialty Plastics, at Eastman Chemical Company (Kingsport, TN, U.S.). “Appliance OEMs are also increasingly looking for ways to obtain greater design freedom and ease of processing when fabricating plastic appliance parts,” he says. “One way to address this need is to find methods that reduce the residual stress introduced to an appliance part during the molding process. Achieving this goal would provide OEMs with the freedom to create more-innovative and differentiated products, since they would no longer need to design around these stresses.”

Krauss-Maffei has addressed production flexibility with its new In-Line RotoCore System. The Florence, KY, U.S.–based company’s latest refrigerator cabinet-forming fixture is engineered to accommodate manufacturers whose multiple model changes dictate the necessity for a quick-core-change option.

The equipment uses “top-down” technology, where the foam core is indexed down into the refrigerator cabinet while it is lying on the back-support table. The rotary quick-core-change system is a stand-alone unit, located in front of the cabinet-forming fixture rather than on top of it, as is the case with more-traditional core-change designs. The foam core transfers from the fixture to the core-change unit via an in-line linear rail system and a motorized load/unload arm. After a foam core is placed into the core-change rotary unit, the rotary unit indexes the next selected model’s core into the load (or “down”) position. The linear rail system then guides the selected core into the fixture as the motorized load/unload arm moves the newly selected core into place.

According to the supplier, the system’s core-change table can be designed to accommodate up to four different models during production, depending on customer needs. The end result is a reduction in the production downtime associated with typical tooling change-out procedures on standard fixture designs.

As an alternative to steel, PolyOne Corp. says manufacturers are using vinyl compounds to produce doors on front-loading washing machines. The material is also being used to create chemical-resistant work-surface boards across the tops of washers and dryers.

Passing the Buck

Across the board, it seems the main trend among plastic suppliers is making life easier for their appliance customers, whether it is providing adaptable materials and equipment or value-added services such as in-house design and production. In most cases, these closer partnerships provide a more functional appliance that gets to market faster—and saves costs.

In order to satisfy the demands of its medical customers, Madden says ATP went as far as to purchase a minority share in a design company that has full product development capabilities. As a result, Madden says the supplier is seeing projects much further upstream, sometimes 24 months earlier than would normally be the case.

“We’re also in the process of taking on one of our customers’ production in-house, where we had previously just supplied components to them,” he continues. “They were looking at a major expansion, and we showed them that it would be more cost-effective to have us do the entire operation.”

Suppliers mentioned in this article:
Bulk Molding Compounds Inc.
PolyOne Corp.
 

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