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issue: June 2006 APPLIANCE Magazine

Connectors and Wire Harnesses
Finding a Reliable Connection


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by Lisa Bonnema, Senior Editor

As appliances get more complex, manufacturers are leaning on their connector and wire harness suppliers to ensure safe, reliable products.

The use of RAST connectors has become more common as appliance manufacturers strive to standardize their components. The system-based approach has been a standard in Europe, but is just now gaining momentum in the U.S. and Asia. According to Molex Incorporated, a supplier of RAST products and other connectors to the appliance industry, the technology offers overall applied lower costs and virtually eliminates field failures.

Reliability has always been an important aspect of engineering appliances: When the average consumer expects their washer and dryer to last more than 10 years, there is little room for error. But as manufacturers continue to beef up their appliances with sophisticated electronics, ensuring a strong, safe connection has gotten more complicated.
“The industry is moving toward electronic and touch-screen applications, affecting the number of connections needed,” notes Brian Dorich, market development manager at Panduit Corp., a wiring component supplier based in Tinley Park, Illinois, U.S. “These additional connections drive the need for consistent and reliable tooling.”
Add safety and environmental considerations to the mix, and connectors and wire harnesses become more than design afterthoughts: they are key ingredients to a functional, successful appliance.
Just ask Melissa Cisewski, a design engineer at Wolf Appliance, LLC, who says details as small as harness material choice can affect product reliability. Wolf, a Madison, Wisconsin, U.S.-based cooking appliance manufacturer, was using a fiberglass-enforced silicon rubber insulation in its wiring harnesses, but found the material was causing some design issues. “The insulation was desirable because of the high temperatures that it can withstand,” Cisewski explains. “However, it is also very soft and gets cut or nicked very easily, causing wires to short out on the chassis or other components.”
Looking for a more durable solution, Wolf turned to its harness supplier, EDS Manufacturing, based in Nogales, Arizona, U.S. “They researched our needs and provided us with samples of harnesses made with a Tefzel insulation, which can also withstand our high temperatures, but is a much tougher material and does not tear near as easily,” Cisewski says. “It’s too early to say what the impact of the switch is on our reliability or Service Incident Rate (SIR), but we’re confident that we will see an improvement.”
Joint efforts like these are not only helping appliance companies build products that stand the test of time, but establish consumer relationships that will hopefully last even longer. And in today’s competitive marketplace, there is no stronger connection.

Appliance Best Practices

To achieve the best possible wire harness solution, Wolf Appliance, LLC uses a cross-functional design approach. According to Melissa Cisewski, design engineer, this requires constant communication throughout the design phase. “When I’m designing a harness, I have the assembly engineer giving me feedback on routings, and operators who are experienced in harnesses giving me feed back on potential problems, the typical tendencies of an operator or what could happen when there is an operator assembling many of them in one day,” Cisewski says. “I also include the drafter to ensure that the intent of the design is captured. I get feedback from the service trainers and manufacturing test engineers for their needs. It is truly a team effort.”

FCI, an Etters, Pennsylvania, U.S.-based supplier of connectors and interconnect systems, has developed a connector to support the next-generation interface for consumer electronic products such as digital TVs, DVD players and set-top boxes. The high-definition multimedia interface (HDMI) integrates video and audio into one connector, replacing digital video interface (DVI), which only carries video signaling. The RoHS-compliant receptacle contains metal shields for better EMI protection and is said to provide low impedance mismatch.

Technology Links

Most manufacturers know that creating a reliable end product begins with choosing reliable components. While selecting the right connector and wire harness solution varies according to application, the industry is seeing some general trends that are literally changing the face of appliance connections.
Bernie Finneganm, industry marketing manager at Molex Incorporated, says the increased use of sensors and controls in today’s feature-rich appliances is causing a shift in connection technologies. “For example, a refrigerator with a built-in door monitor for Internet access or TV, or a user interface keypad that regulates a variety of water dispensing options such as a measured-fill alternative—designs such as these often require connectors that traditionally have not been used in appliances, such as modular jacks and high-speed data connectors,” Finneganm says.
Connectors are also getting smaller, notes Roy Jahangard, president of Z-Tronix, Inc. (Paramount, California, U.S.) “As the industry moves toward smaller and more efficient units, it creates demands for smaller connectors and harnesses,” he says. “This leads to board-level design, with LED displays versus the old light bulb and large-sized connectors.”
Perhaps the greatest industry change, however, has been the move to RAST, an acronym for the German words “raster anschluss steck technik,” which translate to “pitch connection plug technology.” Widely used in Europe for almost two decades, some North American and Asian manufacturers have started to integrate the standardized connection technology in the last few years. Finneganm says appliance companies are considering both insulation displacement technology (IDT) and crimp RAST connectors, but says more and more manufacturers are migrating to IDT. “The major benefits include the reduction of miswiring and backouts, the two most common manufacturing problems facing harness suppliers today,” he says. “Other benefits include the ability for complete automation, cost reduction and speed. Results like these cannot be achieved with the present crimp-and-poke technology.”
Cisewski says that Wolf recently made the switch to RAST-style connectors because they are easy to use. “Individual connections add up quickly and are difficult and tedious to remove for serviceability,” she says. “[RAST] connectors allow you to group many spaces in a plastic housing to provide less connections for an operator to perform.”
Beyond the benefits of the technology, Stefan Jörgens, director of Development at Lumberg Connect GmbH & Co. KG in Schalksmühle, Germany, believes RAST acceptance has grown because the logistics and production infrastructure is in place, making the switch easier for manufacturers. To start, various components such as main switches, motors and sensors are starting to use pin and tab headers based on the RAST standard. According to Jörgens, this has been very influential in the past 2 years.
Another influence has been advancements in processing technology. “Each plug-in connector manufacturer uses processing machines that are individually adapted to the respective plugs, and are able to manufacture all of the wire harnesses ordered by the OEM,” Jörgens notes. “In this process, combined wire harnesses—IDT plug-in connectors and plug-in connectors based on crimping technology—no longer pose a challenge. Modern design concepts for assembly machines adopt the well-known ideas of modular structures from many industry branches. This means that a basic machine with basic functions can be expanded using modules that can, for example, process various plug-in connectors.”
Jörgens adds that different kinds of quality-checking stations can be integrated into these machines, so that in the end, the assembler has the ability to individually design how assembling machines are put together according to OEM requests. “This type of machine concept can also be used to meet the need of OEMs for flexible reactions to constantly changing wiring requests,” he says.
While no one argues that RAST is gaining popularity, many U.S. and Asian manufacturers are only slowly easing themselves into the technology, which often requires some capital investment and changes in engineering approach. “The changeover to RAST harnesses can be dramatic, depending on the level of integration the manufacturer implements,” explains Ronald Weber, business development manager at Tyco Electronics Corporation. “More RAST content equals more change.” (See the sidebar, “Implementing RAST Interconnects.”)
According to Weber, most companies find that the switch is worth it. “Generally, integration of RAST harnesses has improved the appliance assembly process in terms of speed, quality and installed (or applied) cost,” he says.

Two new power cord connectors from Schurter Inc. are angled for closer placement of the equipment to the wall, reportedly consuming less space and minimizing the potential for tangling or tripping. According to the Santa Rosa, California, U.S.-based company, the stronger connection assures a safer and more reliable supply of power to the equipment. Two types, 4789 and 4790 (plug or connector), are rated for use with cordage up to 16/21 A and are ideal for high-end household appliances, as well as IT, power electronics and industrial applications.

Evaluating the Method

The assembly process should also be considered when choosing the perfect connector and harness solution. The easier the components are to work with, the less chance there is for error. Panduit, a supplier of disconnects and other wiring components, helped one appliance harness manufacturer address some installation issues, and in the process, increased the customer’s productivity and reduced costs.
“During installation, operators were getting sore fingers when installing non-insulated disconnects that needed to be post-insulated with heat shrink,” Dorich explains. “Due to this, it was necessary to switch out operators on the production line. Panduit was able to provide a fully insulated disconnect with smooth, rounded edges, which dramatically reduced the installation issues and eliminated the secondary operations of installing the heat shrink. Overall, we provided a part number reduction, reduction in work in process and elimination of worker injuries.”
Of course, even the most reliable, user-friendly solution is useless if manufacturers ignore the quality of the actual connection. Assuming operators got it right is not only risky; it can be costly. “During the past decade, there have been 25 recalls from the U.S. Consumer Product Safety Commission for various appliances. Many of these can be traced to issues related to the assembly or termination of the connectors,” states Brian Stumm, director of engineering at ETCO Incorporated. “Some OEMs have calculated the costs attributed to these failures have reached more than U.S. $100 million a year in repair costs.”
To attack the issue, appliance OEMs like Electrolux are working with suppliers to evaluate the quality of connections. Richard Bing, manager of Commodities at Electrolux Major Appliances North America, says he actively engages his supply base in product teardown analysis to ensure proper connections. “We conduct these sessions on a quarterly basis in different factory locations,” Bing says.
ETCO, a connector supplier based in Warwick, Rhode Island, U.S., has worked internally and externally with various OEMs to leverage the benefits of appliance teardowns. According to Stumm, the process that is selected for a given teardown is typically dictated by the objective of that teardown. “Different types of manufacturers will focus their efforts differently in order to benefit their own business,” he explains. “They will use the teardown process to observe their product in the end-state, as well as to gain information with regard to the impact that their product/process has (both up and down stream) on that product.”
In his 2005 paper, “Major Appliance Teardowns: A Review of Electrical Interconnection Results,” Stumm reports on a series of teardowns that revealed several connection problems related to assembly, design, manufacturing, and termination. In one teardown, Stumm and his team opened the control panel and discovered a disconnect lying against the metal frame. After some investigation, it was determined that the disconnect was supposed to be connected to a tab that was made out of sheet metal. Another teardown showed a motor wire connection that was crushed during assembly.
Stumm also discovered several insulation crimp problems. “Improperly adjusted terminations that are too tight can allow the insulation ear ends to penetrate the insulation and damage the wire strands,” Stumm reports. “In the other extreme…a termination that is adjusted to be loose can allow the wire to move around, which can damage the wire and lead to a failure of the crimp.”
While some of these issues may be one-time occurrences, more than likely, they are a symptom of a larger problem. Crimping problems, for example, could be due to manufacturers using tooling other than that specifically designed by the connector manufacturer for the given terminal and wire combination, Stumm suggests. He also says that these types of problems can be minimized if appliance, harness and electrical connector manufacturers work together to ensure that proper design decisions are made from the beginning. “Working together to eliminate potential failure modes is a key to improving quality,” he says.

With Europe’s RoHS Directive going into effect in July, connector and harness suppliers are offering a slew of RoHS-compliant products. Aries Electronics, Inc. (Frenchtown, New Jersey, U.S.) recently introduced a RoHS-compliant version of its small-outline integrated circuit (SOIC) to dual in-line package (DIP) Correct-A-Chip™ adapter. The device is said to help designers easily upgrade to a SOIC without changing the PCB layout. The top of the adapter accepts SOIC D or SOIC L packages, and the bottom is available in pin counts of eight to 28 pins. It is available on 7.62 mm, 10.16 mm or 15.24 mm pitch centers. Suggested PCB hole diameter is 0.71 mm.

The Bigger Picture

In a perfect world, quality would be the only consideration for an OEM. But in a growing global market, lead times and costs are very real concerns that touch even the smallest component segments. “Current economic conditions have created a very aggressive competitive environment,” notes Finneganm of Molex. “While standardization and safety are important, price will always be a key driver in the decision-making process.”
To stay competitive, some OEMs are outsourcing more high-volume harnesses and cable assemblies to contract manufacturers. According to Finneganm, about 75 percent of today’s connectors are being purchased by contract manufacturers. “Previously, it was common to see OEMs call out a specific part number and supplier,” he says. “Today, the trend is to provide more flexibility in sourcing by calling out specific physical characteristics, allowing for a variety of qualified suppliers to compete on cost.”
The good news for OEMs is that this often turns suppliers into creative problem solvers. Z-Tronix, for instance, found a way to address OEM demands for shorter lead times with a smaller quantity of inventory. “A typical appliance OEM demands for at most 1-week lead time on their harnesses, with 1 month of the finished product commitment, but some of the raw materials have 6 to 8 weeks lead time, plus 1 to 2 weeks of production time for the harnesses,” Jahangard says. “To resolve this issue, we have been looking at improving not only our process to obtain raw material, but also to design new products that can be manufactured in a shorter period of time.”
As one example, the supplier discovered that its braided silicone wire had a long lead time due to the braiding process. Therefore, it designed a new double-layered silicone wire to replace the old braided silicone product. “The new product has a much shorter lead-time since the braiding process has been minimized, and it is more cost-effective,” Jahangard notes. “It has been a complete win-win situation.”
In the end, it seems choosing the right connector and harness supplier is just as important as the choosing the right component. Both decisions could mean the difference between market success and failure.

 

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