Connectors & Wire Harnesses
Standardizing Connectors and Wire Harnesses

by David Simpson, contributing editor

In a growing global appliance industry, companies and industry associations are working toward the standardization of connectors, materials, and even wire harness requirements.

A DIN rail adapter for MATE-N-LOK cap housings allows wire and harness installers to bring two ends of a cable assembly or wire harness together at a DIN rail mounted location. The DIN rail adapters, from Tyco Electronics Corporation (Harrisburg, PA, U.S.), allow designers to enjoy the benefits of using a proven pin and socket connector and the convenience of DIN rail mounting.

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Today's appliance industry is increasingly designing globally. For instance, Whirlpool Corporation (Benton Harbor, MI, U.S.) recently developed a low-cost washing machine in Brazil for use there as well as in China and India. Not surprisingly, appliances designed and produced across borders are likely to share components. This may be especially true with appliance companies that have preferred suppliers that support them around the world. With global markets and manufacturing, it is hardly surprising that component standardization is a hot topic.

In the area of wire harnesses, cables, and connectors, some of the recent momentum is coming from Europe. RAST connectors, standardized in Europe in the 1980s, are beginning to make their presence felt elsewhere, such as in the U.S. Europe also seems to be taking the lead in lead; that is, many European companies are removing lead stabilizer from wire insulation.

Another recent initiative, meanwhile, comes from the U.S. January 2002 saw the release of wire harness standards under the auspices of the Wiring Harness Manufacturer's Association (WHMA) in Eden Prairie, MN, U.S. The standard followed several years of involvement by technical personnel from harness makers, suppliers, and users. Among the 18 areas covered by the standard are inspection, strand damage, solder terminations, preparing for soldering, solder requirements, cleanliness, insulation, connection requirements, and crimp terminations.

"Until recently, there was no group that addressed the needs of wire harness makers," reports Larry Oden, senior engineer at Unicable Inc. (Bowling Green, KY, U.S.). "The WHMA standards try to be comprehensive as far as the theory of harness assembly methods without getting into the details of the materials or the specifics of how to design for every environment. This is still under the purview of the manufacturer, and the standards will not inhibit innovation.

"We've been incorporating elements of the standards at critical points in our operation, and [are] using them to judge the quality of our own work," he continues. "To date, the standards are not widely known, and most of the OEM drawings we've gotten have not made reference to them. But we feel the standards are valuable as a way of assuring and judging harnesses workmanship."

In-Sure push-in wire connectors safely terminate any combination of 12-18 AWG solid or tin-bonded copper conductors without twisting to eliminate repetitive motion fatigue and provide increased productivity. An installer glides the wire in place using a minimal amount of insertion force. Clear polycarbonate housings permit visual connector verification. The connectors, from Ideal Industries (Sycamore, IL, U.S.), come in seven multi-port models, ranging from two to eight ports, each color-coded.Â

Mitch Samuels, president of Electri-Cord Manufacturing (Westfield, PA, U.S.), also finds the WHMA standard useful. "WHMA Standard 620 has proven to be a great tool in accurately producing new products," Mr. Samuel notes. "Because there is a fairly low barrier of entry into wire harness production, the WHMA standard helps maintain standards and consistency on each aspect of production from proper crimping through the soldering of joints. Appliance producers would be prudent to check that their suppliers are producing all wire harnesses to the strict specifications set by 620."

Out of Europe

About 15 years ago, the European appliance industry put together a committee to standardize connectors and harnesses for the appliance industry. "This was modeled after an approach implemented by the Japanese auto industry," recalls John Risch, sales and marketing manager, Electronic Products for Lumberg, Inc. (Midlothian, VA, U.S.). "Standards were established for 2.5-mm connectors used for lower current and control systems, and 5-mm connectors used for power. Today, suppliers are providing motors, switches, and other components with built-in RAST headers. Components such as turbidity sensors, which may be available only from European suppliers, have found their way to North American appliance producers. These companies need to use RAST connectors to plug into the headers," Mr. Risch adds.

"With RAST, appliance companies can use an IDC or crimp/snap," points out Ronald Weber, new business development manager at Tyco Electronics Corporation (Harrisburg, PA U.S.). "The IDC version is typically more automated, with the cable being made and checked automatically. The equipment may even be able to terminate and test anywhere along a wire. RAST connectors have productivity, and sometimes ergonomic, advantages as well."

Jim Connors, account and industry manager at Tyco, notes: "The global appliance companies all have or are considering going to RAST, sometimes out of necessity because of the available components. While maximum RAST advantages come from IDC, this is a big change and requires new equipment. Because of this, North American appliance companies are considering both IDC and crimp RAST connectors."

Mr. Risch of Lumberg believes that all the major U.S. appliance companies are now looking into RAST connectors. "In a global appliance industry, it makes sense to have standardized components that will be widely accepted," he explains. "Beyond that, RAST lends itself to automation and improved reliability, and can incorporate automated test stations."

Home appliance maker BSH Bosch und Siemens Hausgeräte GmbH uses RAST connectors worldwide, including at its recently expanded major appliance production operation in New Bern, NC, U.S. "To automate the production of cable harnesses, insulation displacement is necessary," says Dr. Clemens Schaller, executive vice president of Manufacturing and Engineering. "Other advantages are that these harnesses are easy to check so that the quality increases and the costs go down. The insulation displacement is realized by using RAST technology. An additional advantage affects the assembly of the appliances. Due to the opportunity to integrate keys in the connectors, we can reduce assembly failures."

Standard Pitches?

"Modularization and standardization are the key words today," observes Faraz Hasan, national appliance industry manager, JST Corporation (Jamestown, NC, U.S.). "Instead of using single connections, now appliance OEMs are using more ganged-up connections, thus leading to modularization. This reduces assembly time and also chances of mis-wiring when you are assembling the wiring harness in an appliance," he says.

Mr. Hasan believes that most of the appliance producers are moving toward using standard pitch connectors. "RAST (both crimp and IDC) is a step in this direction," he notes. "Just like what D-Subs and USB did for the computer industry in the last decade, RAST will do for the appliance industry in the coming years. RAST 5 and 2.5 connectors are standardized on the pitch and most other dimensions. Using them, you can standardize connections in an appliance. It does not matter which connector manufacturer you use, since connectors are the same dimensionally in most cases.

According to JST Corporation (Waukegan, IL, U.S.), the RSF RAST 5 PS Series provides easy and fast positive locking to 0.250- x 0.032-in tabs found on numerous devices such as controls, switches, and printed circuit boards. At the heart of the system is the low insertion force PS contact. In addition to the RSF housings, the contact will work with all existing 0.250 PS housings.

"What IDC RAST connectors bring to the table is speed and automation in harness manufacturing," Mr. Hasan continues. "One can achieve up to 15 parts per million (ppm) or less harness defects using fully automatic machines and IDC RAST connectors. These kinds of ppm levels are unheard of using 'crimp and poke' technology, which is inherently less automated and has a fairly high manual content," Mr. Hasan concludes.

Currently, the U.S. appliance industry is primarily using this "crimp and poke" technology, according to Mr. Hasan. "Where the appliance industry would want to be in 3 to 5 years is completely into IDC RAST 5 and 2.5 technology," he says. "In the interim, there would be a stage where one would see a mixture of both crimp and IDC technology. Also in this interim, we will see a considerable use of the crimp RAST 5 technology."

RAST Alternatives

"In general, RAST is of interest in North America due to the increase in quality and efficiency it offers," observes Dean Norton, marketing manager at Wago Corporation (Germantown, WI, U.S.). "However, both of these benefits can be realized in non-RAST standard connectors. In fact, there are other connector systems available that offer greater product quality, reduced size, greater efficiencies, and broader vendor selection," he explains.

One option appliance producers may want to explore are the connector systems used for industrial control applications, according to Mr. Norton. "These are the connectors they themselves rely on in the manufacturing of their appliances. These connectors are highly reliable and offer greater flexibility than RAST connectors," he notes.

Mr. Norton adds that with much of today's manufacturing moving to low-labor-rate countries, appliance producers are realizing that screw and/or crimp style connectors require a certain degree of skilled labor to properly terminate the wires. "With spring pressure connection technology, highly reliable wiring is accomplished easily - simply insert the screwdriver, insert the stripped wire, and remove the screwdriver," he explains. "The contact pressure is pre-programmed via the spring so there is no need for torque screwdrivers or precise crimping tools. In addition, spring pressure connectors are vibration-proof. With this feature, you don't have to worry about the effects of a loose screw due to the vibration of an appliance, such as a washing machine, or due to shipping/handling the appliance to its final destination. Another advantage of this spring technology is that there are a number of vendors to choose from."

Materials Migration

Materials, to a large degree, have been standardized. A material such as a wire insulator or plastic connector housing that is acceptable in one country is likely acceptable elsewhere. However, this does not mean there are no changes. Several U.S. appliance companies are now requiring connector housings to withstand a glow wire flammability test, observes Michael O'Connell, director, Product Marketing, Molex Incorporated (Lisle, IL, U.S.). "Each manufacturer has its own procedures and requirements. We have been able to provide housing materials that can pass these tests," he says.

Adds Mr. Hasan of JST, "We are seeing most of the appliance producers mandating that materials used to manufacture plastic parts (PA66) have a flammability rating of UL94V0 as compared to UL94V2 that was used earlier. The UL94V0 rating provides better self-extinguishing properties in the unlikely event that the connector catches on fire. This causes the appliance to be more safe in the unlikely event of a fire."

In metals, Mr. Hasan has seen newer types of steel with better tensile and yield strength. "In fact, we are one of the first companies that is now launching a positive locking terminal in steel, which will be able to withstand temperatures up to 210°C," he explains. "This is ideal for ranges and other high-temperature applications."

Mr. Weber of Tyco points out: "Lead-free has not had much impact in the U.S., but it is a way of life in Europe. For us, as we design for the global market, lead-free figures heavily into our developments across the board. For instance, we are going to lead-free plating baths, and using new processing techniques for soldering lead-free terminals. This even affects the polymer housings, since the lead-free solder baths are higher temperature, and the housings need to withstand this."

Among some of the industry's new products are no-lead-based heat stabilizer formulations from Teknor Apex Vinyl Division that are used in two new vinyl insulation compounds designed to provide a high level of electrical performance in wet-location appliance and industrial wiring. "Of the applications for which the new Apex 80853C and 80853F compounds are appropriate, motor control wire presents the worst case scenario in that its vinyl insulation is thinnest," says Donald G. Ouellette, industry manager, Teknor Apex Vinyl Division (Pawtucket, RI, U.S.). "This makes high levels of insulation resista'ce and dielectric strength of critical importance for good performance in wet locations.

"The electrical properties of our new compounds are equivalent to those of Apex 853, a lead-stabilized compound that has long proven its reliability in the same applications," Mr. Ouellette continues. "A wide range of our wire and cable products are now free of lead stabilizer, yet provide electrical properties as good as or better than the compounds they have replaced."

Reducing Variations

This photo of a Bosch washing machine features RAST connectors from Lumberg, Inc. The connectors, which lend themselves to automation, are widely used in Europe and are starting to be adopted in other areas.

Mr. O'Connell of Molex has seen an increased interest in standardized terminals in the last 2 years. "Many companies are concentrating on using these, even if they are put into a custom housing," he says. "They are looking to get a cost advantage by using standard, off-the-shelf products. Besides this, when developing new models, some appliance companies are continuing to use the same connectors from their earlier models."

Mr. Samuels of Electri-Cord Manufacturing foresees OEMs cutting lead time by 66 percent and precisely planning bare bones inventory levels by implementing the use of cross-platform wire harnesses. "Our customers have found real value in our global manufacturing capabilities," he says. "They have us build the large volume, steady running part numbers and universal subassemblies in Asia and ship them to our closest North American facility, where we warehouse them. As the rapidly changing forecasts come in, we customize the generic subassemblies as well as build the simpler parts in our plants in the U.S. and Mexico. This way they get the low cost of Asian labor and materials blended in with the flexibility and quick service of a North American supplier."

Electri-Cord recently helped one of its clients, a large manufacturer of office equipment, increase production efficiency. "The production manager made it clear that one of his main goals is to always keep a tight line on cost while maximizing the value and quality for his products," Mr. Samuels explains. "By expanding the number of products in which he uses a given wire harness, his company has benefited from both an increased economy of scale and an even higher quality standard.

"By working cooperatively with our engineering department, he is expecting to reduce the number of different wire harnesses required by seven percent in the next 6 months," he continues. "We are gradually integrating the use of the multi-purpose wire harnesses. Within 12 months we should have reduced the number of different harnesses needed by 25 percent. This change is allowing the manufacturer to benefit by more predictable inventory levels and a significantly lower unit cost due to the higher production volume of specific harnesses."

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