DN Staff

December 15, 1997

28 Min Read
Engineering News

From aircraft to ship design:
Get ready for a 'bumpy' ride

Providence, RI--More than a century ago, golfers noticed a curious phenomenon: Used golf balls flew better than new, smooth ones. Random patterns of dents on the used balls actually stabilized their flight and, in some cases, made them go farther. Eventually, the golf world incorporated that knowledge into the design of new balls, providing them with dimples.

Now, engineers may benefit from a similar phenomenon that offers potential improvements in disciplines ranging from aircraft design to pump operation. A recently published study in the journal Nature describes a technique for reducing skin friction drag by up to 13% on aerodynamic surfaces. Aircraft engineers say that if such reductions could be achieved on production aircraft, it would be a significant step forward. "When we try to reduce drag, we normally work in second decimal places," notes William W. Greer, vice president of engineering and quality assurance for Learjet (Wichita, KS). "So 13% represents a revolution to us."

Drag reduction has long been an area of concentration among aircraft designers, for good reason. Some estimate that a typical commercial aircraft can save between $100,000 and $120,000 a year in fuel costs by cutting overall drag just 1%. Worldwide, a 1% drag reduction could translate to fuel savings of more than $1 billion a year. What's more, the new technique could apply to a wide variety of other applications, including designs of ships, submarines, torpedoes, pumps, HVAC ducting, mixing machinery, and pipe flow systems.

Random pattern is key. The new reductions in skin friction drag involve the use of a simple aerodynamic surface geometry. Researchers Sture Karlsson, an emeritus professor of engineering at Brown University, and Lawrence Sirovich, director of the applied mathematics laboratory at CUNY/Mt. Sinai in New York, found that a random pattern of small bumps could lower skin friction drag. The size of the bumps, or so-called "chevrons," is determined by the thickness of the viscous wall layer on the aerodynamic surface, they say. Though the precise size of the chevrons is proprietary, they do describe them as being on the order of a "fraction of a millimeter."

The real key to the extraordinarily high reductions, however, is not the size of the bumps, but their overall pattern. Sirovich and Karlsson found that the chevron pattern must be random. When using a random pattern, they achieved skin friction drag reductions between 12% and 13%. In contrast, aligned bumps not only failed to lower the drag, they raised it by as much as 20%.

The theory behind their findings is complex, but it basically says that the random chevrons reduce "bursting" near an aerodynamic surface. Bursting, which is caused by low speed air streaks near the wall, is generally believed to be responsible for intense turbulence and, therefore, greater drag.

Sirovich and Karlsson aren't the first to employ surface geometry changes as a means of lowering drag. Researchers have been trying to find ways to "energize the boundary layer" for almost two decades. They've tried putting microscopic holes on aerodynamic surfaces to suck the boundary layer off, and they've applied grooves to wing surfaces to decrease turbulence. 3M Aerospace is currently testing Drag Reduction Film, which employs small riblets in the air flow direction. Used on an Airbus A-340, the film has been successful in reducing drag. Cathay Pacific Airlines applied it on one commercial aircraft that flies long routes, and it has achieved drag reductions of approximately 0.8%. "It has allowed Cathay to fly from Hong Kong to Toronto without a refueling stop," notes Tom Ihbe, 3M Aerospace market development supervisor. "Sometimes in the past, they had to refuel in Anchorage." Ihbe adds that the riblet film offered drag reductions ranging from 2-4% in wind tunnel tests.

Up to now, however, no one has achieved skin friction drag reductions as great as 12-13%. Because the figures are so high, some experts believe that airframe manufacturers might be inclined to invest substantial capital in it if the concept proves out.

Still, they warn, much remains to be learned about it. "Its success will depend on how it affects an aircraft's handling and sound characteristics," Greer says. "It will also depend on how maintainable it is and what it costs." One way to implement the concept, Greer says, is to program CNC systems to ma-chine the random chevrons into the wing skins during regular machining operations.

Business jet manufacturers might be willing to make such accommodations, not because of fuel savings, but because of the additional range the concept could provide. Greer says that the newest Learjet could extend its 2,000-mile range by as much as 120 miles by employing the concept. "For business jet operators, that's where the real advantage is," Greer says.

More than aerospace. Even if the concept ultimately loses its appeal to the aircraft industry, Sirovich and Karlsson believe that it offers advantages elsewhere. Like 3M's riblet film, which was used on Stars and Stripes in the America's Cup competition in 1988, the random chevrons could find application in the design of large ships and racing boats.

Bursting, which is caused by low speed air streaks near the wall, is generally believed to be responsible for skin friction drag. (Reprinted with permission from Nature; Copyright 1997; Macmillan Magazines, Ltd.)

Sirovich also believes that the concept could play a role on submarines. By reducing drag on a submarine's hull, the concept could enable submarine powerplant designers to employ less powerful pumps. As a result, submarines employing the concept would be more difficult to pick up on enemy sonar.

The concept could also play a key role in water pumping equipment. If used on the inside of a pipe, for example, it could reduce the horse-power required to pumpwater. As a result, it could be valuable for fire fighting equipment and water hydraulics systems.

Ironically, Sirovich believes that the aligned chevron concept, which raises drag by 20%, could eventually be as important as the random chevron idea. Because the aligned concept causes greater turbulence, it could serve in applications that require fluid mixing and heat transfer. In HVAC, for example, designers might employ it on the insides of air ducts. There, greater turbulence could cause more effective heat transfer. As a result, furnaces could use less powerful blower motors. The same technique could also serve in electronic package design, where more efficient heat transfer enables chips to run cooler, as well as in chemical mixing equipment.

Ultimately, the concept's success will depend on how well it can be replicated in further wind tunnel tests, and how effectively it translates to real-world engineering. If Sirovich and Karlsson's results are correct, a 13% skin friction drag reduction could lead to overall aircraft drag reductions of as much as 6.5%. (Skin friction drag typically comprises about half of an aircraft's overall drag.) But even if the concept only achieves one-third of that in actual application, aircraft manufacturers would be elated. "It's not yet clear how much real-world drag reduction we can achieve with this concept," Sirovich says. "But in our experiments it's been a factor of two better than any technique out there now."

What this means to you

Reduced skin friction drag could:

Extend aircraft range and cut fuel consumption.

  • Cut pumping power requirements.

Increased skin friction drag could:

Enhance heat transfer in HVAC and electronic cooling applications.

Design News readers who wish to learn more about this research may contact Lawrence Sirovich at [email protected] or Sture Karlsson at [email protected]

Valve with integral electronics simplifies machine set-up

Leicester, England--The introduction of proportional valve technology has produced a level of performance in motion control beyond that obtainable with simple switching or manual devices. Now, flow or pressure control can be modulated with a low-power electronic signal to give true proportional control. Achieving the full potential of modern proportional valves with spool-position feedback usually requires an electronic amplifier to control solenoid current. Traditionally, this has been a separate rack-mounted card, but modern valves now have integral electronics.

In 1991, in response to market research, Vickers Systems introduced a range of proportional directional controls with a pre-set integral amplifier. At that time, Swiss manufacturer Heinrich Schmid Maschinen Werkzeugbau AG was quick to seize the opportunity to rationalize the power hydraulics on its automatic fine-blanking presses. Today, the integrated-electronics concept has progressed, with the latest Vickers KB series featuring a new amplifier design, together with full EMC and IP67 environmental ratings.

One successful user of Schmid machinery is Leicester Engineering Services, whose activities focus on automotive components. Its Schmid HSR 400 hydraulic presses develop a blanking pressure of 4,000 kN to produce, from coils of mild steel, up to 2,000 disk-pad backing plates an hour.

In a closed-loop control system, Vickers KBFDG4V-5 feedback-type directional valves, located on the side of the machine, control the position of two single-acting cylinders used for the approach and return of the main blanking ram. The direct-acting solenoid configuration of the units obviates the requirement for a hydraulic pilot reducer valve, increasing reliability. So much so, in fact, that the company has noticed a marked reduction in machine downtime with the new valves.

Vickers supplies its valves as factory-wired units fully tuned for gain and deadband. The control amplifier itself is integrated into a die-cast zinc housing mounted directly on top of the valve body, giving a low-profile, compact arrangement. Calibration of the valves at the factory also means that the plug 'n' play facility can be put to full use, allowing the valves to be quickly replaced for maintenance.

According to John Watts, maintenance manager at Leicester Engineering Services, the main benefit of the pre-set integral amplifiers is the enhanced motion control. As Watts puts it: "Whereas before, it was always trial and error with a screwdriver in the control cabinet; now I never even need to touch the factory settings." Also, he says that serviceability is improved now that the valve can be directly set up from the main PLC controlling the machine, rather than from a separate control cabinet containing the control card.

A generation change pays off

Munich, Germany--A "genuine" industrial PC is no cheaper than a programmable controller. At least that's the contention of BMW Planning Engineer Heinz Schwenk. That's why, despite all the industrial-PC hype in the manufacturing sector, BMW's Series-3 plant recently upgraded its Siemens S5 controllers to next generation S7s. In fact, Schwenk estimates that the upgrade actually cost 20% less than if BMW continued to use the S5s.

During the recent assembly line redesign, major goals included ergonomic and logistical improvements, and better use of floor space. Plant programming also had to meet IEC 1131 compliance, according to Schwenk. Because further development of the existing Siemens S5 controllers had largely been completed, BMW decided to use the S7 controllers to automate all transfer points on the new line.

BMW Plant Configuration

BMW's Series-3 plant recently upgraded its Siemens S5 controllers to next generation S7s.

Because of limited floor space, two existing lines were combined into one new line. The result: a complex assembly line, more than two kilometers long, that incorporates six different conveyor systems. Twenty S7-400s with 414-2DP CPUs control the conveyors and transfer points. Profibus-DP and distributed I/O systems link approximately 160 frequency controlled drives that are housed in more than 50 cubicles. Thanks to their double-bus structure, the distributed field devices and operator interfaces (OI) can operate independently of one another.

A total of 60 operator panels allows communication with controller and programming devices via a multi-point interface (MPI). This permits simultaneous programming at start up, as long as the same function blocks are not used. Linked via industrial Ethernet to the host computer, and to the existing ID system through serial I/O, the S7-400 proved adept at handling the entire communications spectrum on the plant floor during the pilot phase. And since reaching full capacity in September, no control problems have been reported.

Schwenk explains that the factory is ready for the future because the Profibus/S7 concept supports central control with an industrial PC, while electricians--with little knowledge of high-level languages--can easily maintain control on the factory floor.

Resin improves EGR-valve performance

Troy, MI--An electrically operated exhaust gas recirculation (EGR) valve promises to outperform vacuum-controlled systems in reducing auto emissions of smog-causing nitrogen oxides. The electrical heart of the EGR valve is a linear solenoid with a coil bobbin molded from DuPont ZeniteTM LCP liquid crystal polymer resin.

"Even though the solenoid's operating temperature reaches as high as 240C, the LCP material meets required mechanical strength, dimensional stability, and creep resistance," explains Siemens Automotive's Product Leader Gary Everingham.

Zenite LCP also cuts assembly costs, according to Everingham. The coil is mounted on the valve's metal stator by heat staking, an economical technique that was incompatible with previous thermoset bobbins. The bobbin's dimensional accuracy is crucial during automated coil winding, and its low creep ensures that press-fit terminals stay in the bobbin's integrally molded wells.

Thermotech, Division of Menasha Corp. (Hopkins, MN) molds the bobbin from Zenite 7130. Tom McNamara, Thermotech's director of research and engineering, says: "We know how to mold quality parts with many materials, but Zenite LCP is among the easiest to handle. It has excellent flow characteristics for filling complex molds."

Like all EGR valves, the Siemens unit controls the flow of exhaust gas back into the engine's combustion chambers in order to hold combustion temperatures low enough to reduce nitrogen oxide production. Precise metering of exhaust gas at different engine speeds and loads is crucial, according to Everingham. Too little exhaust gas fed back into the engine increases emissions; too much would reduce engine performance.

In contrast to vacuum-operated EGR valves, the car's on-board computer directly controls Siemens' electrically operated unit. "This speeds response to computer commands," says Everingham. Another plus for the Siemens valve is its built-in diagnostic capability, which transmits signals to the car's computer confirming proper operation. If malfunction occurs, the computer sends a control signal to alert the driver.

Snowboarding goes to extremes

Sun Valley, CA--Original snowboards were quite simple, looking similar to a water ski with a rope attached to the nose to aid steering. This design met riders' expectations in the 1960s. But current snowboard enthusiasts expect their equipment to do much more. Nowadays, they want to accelerate quickly, land hard, and be able to easily tote their boards up hills or wherever they want to go.

To make matters worse, some of those expectations seem to conflict. Snowboarding equipment must be strong, yet light. Firm, yet flexible. And what about price? Quality is important, but most sports-equipment consumers are price sensitive. Even high-quality equipment must be priced at a level the market considers appropriate.

To respond to what often appears to be irreconcilable demands, designers of snowboard equipment are eagerly exploring and experimenting with new materials--and some are having very good results. Aastro Molds, Inc., a maker of snowboard bindings, is one such company.

During its first year of binding production, Aastro experimented with a wide variety of materials, eventually approving a super-tough nylon. "For several years, the plastic material provided satisfactory performance for snowboarders," says Aastro Molds Plant Manager Randy Smith. "Recently, however, extreme riders told us our binding baseplate was a little soft and caused heel and toe lift when performing trick maneuvers. This was unacceptable."

In response, Aastro once again tested many glass-filled products which proved workable but made the bindings too heavy. Then the designer tried a polycarbonate, which seemed like a good solution. It provided the appropriate combination of flexibility and stiffness riders needed. However, after selling 3,000 pairs, the company was getting a high number of returns. It turned out that the salt used on roads at ski resorts attacked the material. In addition, many of the polycarbonate bindings showed stress cracks. Aastro continued its search for a superior material.

"We talked with Amoco Polymers (Alpharetta, GA) about our need for a lightweight material that was stiffer than the nylon we'd been using, had good chemical resistance, and would injection mold without any warpage or stress," Smith recalls. As if that order wasn't tall enough, Aastro needed a material that "wouldn't cost an arm and a leg," Smith adds.

Amoco suggested AMODEL(R) polyphthalamide (PPA) resin for the new binding material. The supplier thought the resin would be a good candidate due to its proven strength, stiffness, fatigue and creep resistance, and low moisture absorption qualities. Also, other manufacturers had found the resin worked well with conventional molding equipment, and did not corrode tooling or require intricate drying procedures.

"Not only did the material seem to have the product performance properties we desired, it also scored high on appearance qualities," Smith notes. "We'd been very disappointed with the surface appearance of the glass-filled materials we'd tested."

Using the new resin, Aastro Molds developed its Price BreakTM binding. The binding has the high-performance characteristics of expensive snowboard bindings, but at a price comparable with products at the lower end of the price scale.

After several months of heavy use, Aastro has experienced no breakage, no warpage, and no complaints about too much flex. In short, Aastro faced the challenge as an extreme snowboarder might: "Just because something looks impossible doesn't mean it can't be done." The Price Break bindings provide the proof.

CAPE leads to a competitive edge

Houston-Halliburton Energy Services is creating a CAPE (concurrent art-to-part environment) architecture that will bolster the firm's competitiveness well into the future. To attain this goal, the company standardized on Electronic Product Definition (EPD) products from Computervision Corporation (Bedford, MA).

Halliburton first recognized the need for new solid modeling products to replace old mainframe CAD software. Management then realized it needed a design automation strategy that would include an enterprise data management system as well. Halliburton standardized on Computervision's CADDS 5 software, and selected the company's Optegra products for its product data management (PDM) system.

At the heart of Halliburton's CAPE implementation, Optegra data management software features a distributed vaulting capability that enables users in different locations to share data as if they were in the same office.

Jim Landmark, Halliburton's Engineering Systems manager, expects Optegra's distributed vaulting feature to promote concurrent design and manufacturing, and to help the company reuse existing components within new-product designs.

"Eventually we may have distributed Optegra vaults in eight or more locations in the U.S. and overseas," he says. "Our intent is to store all product data in the vaults, in addition to CAD models. That would include engineering specifications, concept deliverables, engineering analysis results, and even NC programs.

"Also, we'll be able to standardize component libraries available to our engineers, so it will be easy for them to determine how they can reuse existing parts in new designs. This will help tremendously in saving costs and in cutting time-to-market for some new products."

According to Halliburton's CAPE timeline, the Optegra data management capabilities will be rolled out during the next two years. Eventually, as many as 11 groups, from design engineering to shop floor cells and suppliers, may be tied into the Optegra data management system.

"Even though we're now in the early stages, we're able to see how concurrent design and manufacturing will benefit from the ability to access up-to-date product information from different locations," says Landmark.

Moreover, the information sharing permitted by the Optegra vaults will help geographically dispersed teams design, assemble, and manufacture the increasingly complex system packages that will help Halliburton gain a competitive advantage. The company's Early Evaluation System product is one example.

"We'll have design engineers at one site and manufacturing engineers at another," says Landmark. "There will be about 15 or 20 people spread over two sites, and they'll be able to collaborate as if they're in the same building." "The key benefit will still come down to helping us get our products to market faster than competitors," says Landmark. "Our goal at this point is to see a general reduction in time-to-market of 50%. We think that is a realistic goal thanks to our CAPE strategy and Computervision's EPD product families."

Sensor checks tire pressure while you drive

Hannover, Germany--Be honest, how often do you check the tire pressure on your car? Once per week or per month? Or do you just give them a good kick? Soon a Tire Pressure Monitoring System (TPMS) will handle this chore for you and even monitor the tire pressure when the car is being driven on the road.

The manufacturer of the system, Continental Automotive Systems, estimates that approximately 80% of tire failures occur due to a gradual loss of inflation pressure. In response to this, the company has developed the TPMS, which continuously monitors the tire pressure and gives a warning well before a blowout can occur.

Weighing only 35 grams, the TPMS sensor, which is based on the piezo-resistive principle, is fitted to each tire valve between the wheel rim and the tire. From there it transmits the temperature-compensated inflation pressure to the control unit inside the vehicle using radio-frequency telemetry. The transmission frequency can be varied to suit national regulations; for example, 433 MHz in Germany and 315 MHz in the U.S. Each wheel transmits its own identification number. The control unit uses a sophisticated warning algorithm and checks all the data for plausibility before displaying the tire pressure to the driver.

The TPMS compares the pressure to a value set by the driver, and gives a warning if a trend is detected against the background of normal tire-pressure variations. The driver can therefore avoid the potentially dangerous situation of driving for too long on under-inflated tires. However, the system reacts immediately for a fast drop in pressure. Centrifugal forces should not present a problem, as the sensor module is designed to withstand speeds of over 300 km/hour.

Continental is currently subjecting prototypes of the system to long-term tests under arduous conditions. It expects to have the system to market in 1999.

New rules aim to slow down Formula One

Paris--Technical regulations introduced by FIA, the motor sports governing body, will result in new shapes but old speeds on the world's Formula One tracks in 1998. The main motivation has been safety but with a nod toward spectator appeal. Although some drivers have made derogatory comments about the changes, engineers have been unfazed.

Shaded areas show changes that will have to be made to the Tyrell '97 racecar to comply with the FIA's Formula One '98 regulations.

"Under the revised 1998 rules, the driver will have more room, more crash resistance, more rollover security, better fuel-tank security, indeed greater security all round," explains Max Mosley, president of FIA.

The most striking change will be the narrower appearance of cars, because the overall width has been reduced from 2 to 1.8m. At the same time the bodywork is a little wider to allow for a larger cockpit opening.

"I felt as though I had no grip at all," said Mika Salo of Tyrrell Racing after driving a prototype narrow car. "The speed through the corners was much slower, and I found myself having to use the whole of the track."

The use of grooved tires, mandated by the 1998 regulations, will add to the novelty. The trend in F1 for some years has been smooth tires with lower rolling resistance. The name for these tires, slicks, says it all.

The normal racing line on a course has better adhesion as the traffic has laid down rubber on the road surface from the passage of the tires. Stray off that line with slicks, and grip is poor. Yet overtaking requires drivers to accelerate off the normal racing line. With grooved tires, drivers should get as much grip off-line as on the normal racing line.

With narrower, slower cars and more equal grip on all areas of the track, there will be more opportunities for overtaking by enterprising drivers.

"The cars will be very different and I am sure we will get used to them," says Salo. The FIA has promised that with adoption of the latest safety improvements, there would be no other design changes affecting the chassis for a few years. The FIA plans to use tire regulations to keep lap speeds under control by deepening the grooves or increasing their number. With no chassis changes to worry about, it is expected that the smaller teams will be able to catch up technically with the bigger ones. In theory, this should narrow the technology gap and make for more open competitions.

The 20 or so firms involved in F1 production are now busily working on adaptations to their current designs. The 1998 season will show which companies have come up with the right answers.

For FIA Technical Regulations see www.fia.com

Parametric buys Computervision

by Paul E. Teague

Waltham, MA--Two major players in the CAD wars, Parametric Technology Corporation and Computervision Corporation, have announced a merger agreement. Under the terms of the deal, the Waltham, MA-based PTC will acquire Computervision in a stock-for-stock transaction expected to be completed in early 1998.

Computervision, also a Massachusetts-based company, will become a wholly owned subsidiary of PTC, which will continue to develop, maintain, and support Computervision products independent of its own Pro/ENGINEER product line.

PTC is the world's tenth-largest independent software company and a leading supplier of CAD/CAM/CAE software tools used to automate mechanical design. Computervision produced CADDS5 and supplies electronic pro-duct definition (EPD) solutions that allow users to create, manage, share, and reuse product information in a collaborative setting.

"Computervision was looking for a safe harbor for its customers," explains Wayne George, director of communications for the company. "Unfortunately, the financial challenges of competition got in the way of people buying our product."

For PTC, the acquisition provides access to industries such as automotive and aerospace, which the company has had difficulty penetrating, as well as to Computervision's large customer base. Perhaps more importantly, it gives PTC access to Computervision's Optegra product data management software.

This recent acquisition is the third in a string of mergers within the CAD industry. Several months ago Dassault Systemes bought SolidWorks. Even more recently, EDS Unigraphics and Intergraph agreed to form a new company for mechanical computer-aided design.

Solids reduce modeling time, speed conveyors to market

Arlington, TX--Many users of 2-D CAD believe solid modeling is difficult to use and slower than 2-D for creating initial models. But at Martin Sprocket & Gear Inc., Solid Edge software (Intergraph Corp., Huntsville, AL) enabled designer Dylan Malek to create hundreds of sprockets from scratch in four months. He estimates that creating the same number of sprockets in 2-D would have taken an entire year.

"A major factor in the decision to switch from 2-D AutoCAD to Solid Edge was reducing the time it took to revise existing designs," explains Malek, who works in Martin Sprocket's conveyor design division. "Previously it would have taken an operator using AutoCAD several hours to redo one sprocket. With Solid Edge, it happens in minutes." Once a new sprocket is created, drawings can be generated from the solid model in a fraction of the time it took to create them from scratch.

Although the ability to capture design intent quickly is important to Martin Sprocket & Gear, it is not what originally led the company to solid modeling. After nearly 50 years in business, Martin had accumulated a vast number of engineering drawings on paper.

But engineers often redesign existing parts because the original drawings are not easily accessible. This approach slows the design cycle and wastes valuable resources. In Martin's case, the lack of an electronic parts database hindered the company's ability to achieve fast turnaround on made-to-order systems, a large part of its business.

The conveyor division was particularly aware of this problem, because new systems typically combine off-the-shelf parts with those that are modifications of existing models. Several years ago, engineers decided to switch from 2-D AutoCAD to solid modeling. Explains Malek, "Every day, revisions are done to existing products because most of the things we do are made to order. We hoped that by creating parts as solid models, we could easily revise them and put them into assembly models of the conveyors we're designing."

With a huge amount of legacy data in AutoCAD format, a critical selection criteria for the new system was compatibility with AutoCAD. Beyond that, Martin designers wanted a solid modeler that was easy to use. Solid Edge was the answer.

Since acquiring the software, the division has embarked on the huge task of converting every product in its catalog, now in 2-D AutoCAD format, to solid models. In spite of the modeling efficiencies provided by Solid Edge, the conversion is a long process. But company officials are confident that the effort will pay off in the long run. "Solid Edge allows you to draw something only once," says Malek. "You make changes and you get a new part. It will save a great deal of time." After all existing parts are available as Solid Edge models, Solid Edge will become the division's design tool as well, for both individual parts and assemblies.

Flexible pc-board seal simplifies sensor connection

Weinheim, Germany--Obtaining a signal from a sensor within a closed vessel can be quite a problem, particularly if the vessel contains a medium under pressure. Apart from any seals needed in assembly or mounting, the wires carrying power to the sensor and the signal from it must also be sealed at the interface. The fitting of such seals can be quite labor-intensive, because wires must be connected on both sides of the sealed lead-through connector.

In a joint development project with Bosch, Freudenberg has produced a flexible circuit board with integral molded-on rubber seals. The electrically conductive foil on the circuit board consists of a flexible polyimide-copper compound. An elastomer seal vulcanized to the board provides the sealing function.

Bosch fit the new pc-board/seal combination in radial-piston distributor pumps fitted to the latest injection diesel engines. In the housing, which is filled with diesel fuel, a magneto-resistive sensor samples a coded disk, and passes its signal via the flexible circuit board to the external control unit. The circuit board carries five tracks for sensor excitation and signal transmission.

Freudenberg officials say the technique saves on assembly, component inventory, and quality inspection. With a specified temperature range of -40 to 150C at pressures up to 30 bar, the product is compatible with applications involving a variety of fuels, oils, greases, and brake fluids.

Stickier wicket, what?

Anyone who has tried to remove a bumper sticker may not believe it, but adhesion is a problem for materials researchers. Many materials require special coatings for protection from wear and corrosion. But often there is a problem with getting the coatings to adhere tightly. Los Alamos researchers have developed a method that produces highly adherent layers of common coatings such as metal oxides, plus a diamond-like carbon coating. The method uses a plasma that roots itself in the substrate, creating a graded coating that provides excellent resistance against delamination. The technique is more environmentally friendly than many methods currently in use, and allows creation of coating-substrate combinations that are not currently feasible. The method can be applied in the manufacturing of such things as automobile parts, machine tools, and prosthetics.

For more information contact Kathy DeLucas at (505) 665-9201 or e-mail [email protected]

Sign up for the Design News Daily newsletter.

You May Also Like