Engineering News

CAMPUS schools engineers in plastics

Newton, MA--In their quest for weight reduction, improved energy efficiency, and consumer appeal and styling, engineers have increasingly turned to plastics in place of traditional materials like steel and die-cast metals. Such metal-replacement opportunities exploit various features of plastics, such as part consolidation, design flexibility, molded-in color, and net shape form.

In order to specify plastics in their applications, engineers and material specifiers need access to reliable data on which to base their decisions. However, comparable data among similar resins obtained from different material suppliers has been scarce. The problem stems from lack of standardization in the acquisition and reporting format for materials properties data in the plastics industry.

Over time, a multiplicity of national test standards has become widely used to procure data on materials. This, in turn, allowed a broad flexibility in the choice of test specimen shapes and geometry, conditions for preparing the test specimens, test variables, and test conditions and units, rendering any comparison between materials extremely difficult.

Now, however, product designers and processors looking for computer-based materials selection have at their command a software program designed to overcome this confusion--Computer Aided Material Preselection by Uniform Standards, or CAMPUS for short. The database addresses single-point (mechanical, thermal, electrical, etc.) and multi-point (rheological and isochronous stress-strain) data in both international (SI) and U.S. units.

"Multi-point data capability, in particular, makes CAMPUS software a valuable design tool," says Kishor S. Mehta, manager-design engineering services, polymers division, Bayer Corp., Pittsburgh. Mehta and Dr. Ranganath Shastri of Dow Plastics spearheaded the drive to get CAMPUS introduced in the U.S. "And because it's tailored to the American plastic industry," Mehta adds, "it's substantially different in look and feel than earlier versions that originated in Europe. We also had significant input in improving the user friendliness of the program using the Windows environment format."

Actually, the same situation existed in Europe as in the U.S. until the late 1980s. To address this plight, British Standard BS 7008, which lists preferred test methods and test conditions, was developed by a joint committee composed of members of the British Plastics Federation (BPF), National Physical Laboratory (NPL), and British Standards Institute (BSI). At the same time in Germany, subcommittee 102.1 and 303 of Deutsches Institut für Normung, Fachnormenausschu{beta} Kunststoffe (DIN-FNK) developed a similar list of preferred test methods, as well as a directive for developing material designation standards.

Using both the BS 7008 and the DIN-FNK directives as the basis, three international standards (ISO/DIS 10350, ISO/DIS 11403-1, and ISO/DIS 11403-2) for single- and multi-point data were developed by the "tripartite forum" of British, German, and French delegations. Adoption of a single, uniform standard paved the way for a true "apples-to-apples" comparison.

To accomplish this feat, four plastic industry leaders in Europe (Bayer, BASF, Hoechst, and Hüls) jointly initiated the development of the CAMPUS database, and were recently joined by Dow Chemical and DuPont. The effort involved a commitment of considerable financial and technical resources on the part of the founding members. Development cost of the standard mold alone exceeded $1 million, for example, not to mention the hundreds of hours invested in round-robin tests for validation.

In the U.S., Hoechst Technical Polymers became the first resin supplier to formally declare its commitment to complete conversion to the ISO test methods in January 1995. Other leading suppliers and members of the Society of the Plastics Industry (SPI) Polymeric Material Producers Division (PMPD) soon followed suit. They included Dow Chemical, DuPont, Bayer, BASF, and Monsanto. In truth, some of these companies made the program available to their customers on-disk before its official introduction in the U.S.

Major automotive OEMs like Ford and GM also got behind the program and gave it a big boost. Appliance and electronics industry customers have indicated their interest in the program, as have several key U.S. government agencies.

With this widespread backing, leading CAMPUS participants announced the global launch of CAMPUS version 3.0 at the 1994 National Plastics Exposition in Chicago. Today, more than 45 internationally known plastics producers provide technical data on their products using CAMPUS. More than 125,000 copies have been distributed in Europe alone, with some 6,000 already disseminated in the U.S.

Keep in mind that the CAMPUS database does not encompass an exhaustive list of properties for each product. But it does include typical single-point values that are traditionally reported in product literature acceptable for preselection of resins. It also incorporates such comprehensive engineering data as:

• Isothermal stress-strain over a wide range of temperatures.

• Secant modulus vs. strain curves.

• Temperature dependence of shear modulus.

• Isochronous creep curves at ambient and elevated temperatures and several stress levels.

• Creep modulus vs. time curves.

• Viscosity vs. shear rate data within the range of processing temperatures, all in graphical as well as tabular form.

Most important, engineers can obtain all this information at no cost: It comes on a 3.5-inch diskette directly from the resin suppliers (see box). The disk includes the operating system, graphic drivers, data, and auxiliary information.

The initial program proved simple to use due to its user-friendly format (MS-DOS based) for PCs. Today, it is not only available as a Windows program compatible with Windows 95, but has English, German, French, Spanish, Italian, and most recently Japanese versions.

Another useful feature of the database is its unit-conversion capability. This feature was incorporated for U.S.-based users not yet familiar or comfortable with SI units. Even though the program generates data using international standards and reports them primarily in SI units, a simple option lets users switch between SI and U.S. units.

What does the CAMPUS database hold in store for the future? Based on user feedback, plans call for the database to include pvT data, meaningful shrinkage data, and data on resistance to environmental influences such as chemicals/solvents, UV exposure/weathering, and thermal aging. Work is also in progress to develop uniform test methods for pvT and shrinkage data.

Already available in Europe through a few CAMPUS participants, the new 4.0 Windows version will be officially announced at NPE '97 (June 16 to 20 at Chicago's McCor-mick Place). In addition, there will be a CAMPUS exhibit at NPE to demonstrate the program, and several program participants such as Bayer and Dow will also demonstrate the software at their booths.

There's one more CAMPUS activity currently underway that engineers should be aware of--development of an interface between CAMPUS and CAE systems. And it won't be long before you can find a CAMPUS home page on the Internet. Under a special agreement with some participants, engineers will be able to download the database directly off a "hot link" from the CAMPUS home page onto their own computer systems.

--Gary Chamberlain, Senior Editor

What this means to you

• Cost and time savings from eliminating the need to retest or invest time in comparing test methods.

• Easier procurement of materials worldwide for the growing global manufacturing environment through global uniformity.

• I ncreased opportunities for access to international markets.

• I mproved communication with suppliers and customers.

• Enhanced resin quality and reliability of products through greater consistency of data based on more stringent and uniform methodology.

CAMPUS CONTACTS

COMPANY	FOR MORE INFORMATION	FOR DISKS
ALLIED SIGNAL PLASTICS	MS. CATHY RUIZ	NOT AVAILABLE YET
	FAX: (201) 455-4892
BASF CORP.	DR. WOLFGANG MULLER
	FAX: (313) 246-5254	PHONE: (800)-BC-RESIN
BAYER CORP.	KISHOR MEHTA
	FAX: (412) 777-7849	PHONE: (412) 777-2000
CYRO INDUSTRIES	PETER COLBURN
	FAX: (203) 795-5800	NOT AVAILABLE YET
DOW PLASTICS	DR. RANGANATH SHASTRI
	FAX: (517) 636-8813	FAX: (517) 832-1465
DUPONT ENGINEERING	DR. ROGER LATHAM
POLYMERS	FAX: (302) 999-5659	PHONE: (302) 999-4592
EASTMAN CHEMICAL CO.	BRIAN L. DOWLER
	FAX: (423) 229-1262	FAX: (423) 224-0413
EMS AMERICAN	JOSEPH GEIGER
GRILON INC.	FAX: (803) 481-6121	FAX: (803) 481-6121
ENCHEM AMERICA	GEORGIO GIANI
	FAX: (713) 940-0724	FAX: (713) 940-0724
HOECHST TECHNICAL	DR. JACK GRATES
POLYMERS	PHONE: (908) 552-7638	PHONE: (800) 833-4882

Bearings resist saw loads

Central City, KY--A horizontal bandsaw converts 12 × 12, 20-ft-long beams into ten accurately sized boards after a two-axis planer processes them.

Nine arbors support the saw wheels. To handle severe loads and abrasive sawdust, designers at saw manufacturer Brewer Inc. fitted each arbor with two Rex® 9000 Series spherical roller bearings from Rexnord Corp. Tapered adapter sleeves mount the bearings to the shafts, while flange housings rigidly support the loads.

The horizontal and vertical planing heads that shape the beams are each powered via belt drive by a 75-hp electric motor operating at 3,500 rpm. To support each head, Brewer selected two 11/16-inch ID Link-Belt® FE-U343 heavy-duty ball-bearing flanged units. The grease-purgable seals on the bearings don't quite touch their races, so they avoid overheating problems. Also, they withstand fine, abrasive sawdust generated by the saw. Brewer designers used Rexnord's CadCat® software to integrate both the roller bearings and ball bearings into the saw and planer.

With a footprint of 11 × 65 feet, the bandsaw assembly includes two pressure rolls-driven by two six-inch-bore cylinders-that apply 1,000 lbs of force to the workpiece. The rolls remove bowing from the workpiece, and by doing so ensure production of boards of uniform thickness. As the beams move through the saw, cuts are made progressively from the top down. Blades are spaced at intervals of 72 inches and begin their cuts before succeeding ones finish. Wheel and blade speed is 3,000 surface ft/minute and boards travel at 50 to 200 ft/minute.

Thin-wall polymer helps redesign needle-free syringe

Minneapolis, MN--People with diabetes appreciate needle-free syringes that can administer daily doses of life-saving pharmaceuticals without pain. Medi-Ject is making needleless injection not only possible, but increasingly less costly.

Medi-Ject first introduced the syringes in 1979. Since then, the devices have gained increasing clinical and commercial acceptance. Triggered by a push-button, the syringes use a plunger to force liquid out through an orifice one-third smaller than the diameter of a 30-gauge needle. A high-velocity microjet penetrates the skin with minimal discomfort and scarring.

However, since that introduction, Medi-Ject has found a way to make its Medi-Jector® needleless syringes lighter, easier to use, and less expensive. Making the advances possible: thin-wall, impact-resistant Vectra® liquid-crystal polymer (LCP) supplied by Hoechst Celanese Technical Polymers, Summit, NJ. Using the molded LCP, key internal parts are now 75% lighter and 50% less costly than their metal counterparts.

In addition, the switch from metal to self-lubricating plastic made the precision, spring-loaded devices easier for the user to wind up before each injection. It also opened new application opportunities for the syringe maker in partnership with pharmaceutical manufacturers.

"We are going from small-volume production to much larger volumes," says Peter Sadowski, vice president of product development for Medi-Ject. "As you go up in scale, you don't gain a lotof manufacturing econ-omies with machined metal. Plastic parts bring you lots of cost advantages."

Different drug manufacturers may request that Medi-Ject modify the devices, either to accommodate different fluids or to provide a competitive advantage. "To retool the injector in steel would be difficult. Making these modifications in plastics is not as problematic," explains Medi-Ject Vice President of Sales and Marketing Todd Leonard.

The Medi-Jector syringe should last long enough to deliver 3,000 doses. "Over that service life, materials have to take the impact of thousands of doses," Sadowski says.

Medi-Ject engineers not only achieved their cost and weight savings, but made the syringe easier to use in the process. "We find the new device to be significantly easier to wind," Sadowski notes. "Patients notice it. The less difficult actions do not deteriorate with age. In fact, the device is a little easier to wind with time."

NMB Technologies again supports Design News Foundation

Chatsworth, CA--NMB Technologies Inc. has announced that it will once again support the annual Design News Engineering Awards program with a $10,000 gift to the Engineering Education Foundation. The gift marks NMB's fifth year of participation in the program benefiting engineering students at the university level. Other Engineering Education Foundation supporters include Intergraph Computer Systems, Omron Electronics Inc., and ANSYS Inc.

"Innovation is the key to the survival of any company. At NMB, we place a great deal of emphasis on the driving force of the engineering team to meet customer product solutions," explains Myron D. Jones, president of NMB Technologies Inc. "Without the knowledge and skill sets of our engineers, NMB could not uphold the high quality and technical excellence of new products."

NMB ranks as one of the world's leading suppliers of electronic components, including keyboards, axial cooling fans, step motors, power supplies, measuring components, and audio speakers. As an example of NMBTechnologies' commitment to quality, they recently received ISO 9002 certification of the keyboard manufacturing facility in Bang Pa-In, Thailand, as well as the power-supply manufacturing facility in Lop Buri, Thailand.

"The [high-quality of our product line] can only be achieved through a knowledgeable and talented staff," says Jones. "Engineers within NMB are encouraged to continue their formal education as an investment by the company."

In addition to encouraging growth within the organization, NMB donates time and effort to various engineering schools at colleges and universities. For instance, this past year at Brigham Young University's engineering school, a senior engineering student team was provided with funding on a project from NMB. The project involved the development of a state-of-the-art keyboard tester, the Keyboard Automatic Tester System (KATS).

"As a contribution to the engineering community, NMB is proud to donate $10,000 to the 1996 Design News Engineering Education Foundation," says Jones.

"NMBTechnologies has been a long-time supporter of both the Design News Engineering Awards program, as well as the Education Foundation," notes Design News Publisher Larry Maloney. "They truly appreciate the value of engineering towards the development of new products."

On a wing and a shoestring: Hams design their next-generation communications satellite

Newton, MA--Just four years after the Soviet Union launched Sputnik--an achievement that rattledthe U.S. scientific community and touched off a decades-long Cold War space race--a private group of Americans sent up a satellite of their own. West Coast hobbyists, they designed and built a communications satellite in their basements and garages.

Hobbyists? Designing satellites? Since the 1960s?

Those early tinkerers were amateur radio operators, and their efforts with colleagues around the world launched AMSAT, a group of hams that has been designing com-munications satellites for a quarter century. AMSAT claims credit for a numberof firsts in space: first CMOS semiconductor technologyin space, first "clear demon-stration" that multiple stations can simultaneously use a single satellite, and first "store-and-forward" digital satellite communications.

AMSAT's latest endeavor, "Phase 3D," is slated to launch from the next European Space Agency Ariane 5 mission in late spring. Volunteer engineers from 14 countries on five continents are contributing to 3D, which will use higher power transmitters and higher gain antennas than any of its ham predecessors in orbit. Amateur radio operators on the ground will use the satellite to make long-range contacts by voice, Morse code, and "packet"--computer-to-computer communication via radio wave.

"This is probably a $50 million to $100 million project," says Dick Jansson, AMSAT's volunteer vice president of engineering. "We're doing it for around $4 million." Keyto project affordability: donations of material and expertise, streamlined designs, and using materials at hand.

AMSAT members barter their engineering know-how for affordable launches. AMSAT engineers are working with the European Space Agency to help design a platform for Ariane 5 to launch mid-sized (300 to 600 kg) satellites--a capability the rocket doesn't now have. Such a platform would make fu-ture Ariane 5 launches more economically viable, since currently the rocketis configured to launch large payloads and "mi-crosats." Adding some mid-sized paying customers would boost po-tential revenue, using space that otherwise would go unoccupied. AMSAT first worked with ESA in 1989-90 to develop the mi-crosat launching capability on Ariane 4.

The mid-size design plan will raise by 1 meter an Ariane upper stage that holds bolt rings for mounting large payloads, and add a 2.6-meter-diameter Specific Bearing Structure (SBS) cylindrical adapter for a secondary payload.

The satellite's 20-foot solar array will be de-ployed and stabilizedin orbit using a device "no more complex than an ordinary 'bar-door' hinge," according to Jansson. "The spacecraft's structure will be made from ordinarysheet aluminum which will be subsequently painted for thermal balance considerations.

AMSAT satellites, while designed with unconventional procedures, must still meet the same vigorous space-qualification standards as any government or commercial customer before riding aboard an Ariane rocket. "We are working very closely together to reach a good product," says Bernard Lacoste at the European Space Agency, who heads the integration of AMSAT designs on the Ariane for ESA.

It can be difficult to getnecessary paperwork out of AMSAT, which is a much more informal organization than the typical aerospace outfit, Lacoste admits. But that can also be an advantage.  "They react very quicklyif any problems occur," he says. "They work with their heart."

--Sharon Machlis, Contributing Editor

For more information about AMSAT, visit http://www.am sat.org

Phase 3D Facts

Height: 1 meter (3 feet)

Weight: 400 kg (80 lbs)

Diameter: 2.3 meters (7.5 feet)

Wingspan: More than 6 meters (20 feet)

Orbit: Elliptical, from 4,000 km (2,400 miles) to 47,000 km (29,000) miles above the Earth

Switches help joystick fight back

Vista, CA--A joystick that fights back demands components worthy of the battle. So gaming-control-maker CH Products turned to switch-supplier Omron Electronics Inc., Schaumburg, IL, for unusually durable and reliable components for its Force FX feedback joystick.

The new Force FX joystick adds physical experience to the traditional visual and audio thrills of playing computer games. Force-feedback technology offers jolt, vector force, x and y vibration, spring, button reflex, and buffeting effects.

"It's the stick that fights back," says Rick Salvador, director of technical services for CH Products. "If you've been shot by your opponent, for example, you can actually feel, through the joystick handle, the shock of being shot."

To stand up to this shock, CH Products design engineers chose Omron's B3F mechanical keyswitches. "Our requirements for switches include high reliability and durability because these things are getting hammered on pretty hard," notes Salvador. Switches for this application also had to be small and have a consistent, snappy feel when they are depressed.

Engineers designed a 4-way switch configuration because they couldn't find an inexpensive product to drop into the joysticks. This mechanism incorporates four B3F switches positioned around a center shaft that actuates the four components. This set-up provides flexibility and ease of use at one-tenth the price of a switch configuration from an outside source, say CH Products officials.

Advanced ball screw positions V-22 engines

Ft. Worth, TX--A custom-designed ball screw, designed and manufactured by Thomson Saginaw Ball Screw Co., controls rotor positioning on Bell Boeing's V-22 Osprey. Innovations such as the hollow screw's wall thickness, the raceway's metallurgy, and the ball-return system in the ball make this design truly unique.

Designed to perform a variety of missions ranging from transporting troops to rescuing downed pilots behind enemy lines, the V-22's tiltrotor technology achieves vertical takeoff, hover, and landing capabilities, while maintaining the speed and range of conventional turboprop aircraft.

Nacelles, located on the ends of both wings, house engines and associated gearboxes that allow smooth transition from one flight mode to another. For vertical takeoff, 38-foot-diameter rotor blades are positioned horizontally, then during cruise mode, they are repositioned vertically.

Each ball-screw as-sembly includes a 23-inch-long, 2.5-inch-di-ameter hollow ball screw nestled inside a 22.5-inch-long, 4-inch-diameter hollow screw. They operate together and extend fully to 45.5 inches when rotating the engines from horizontal up to 5 degrees past vertical. According to Thomson's manager of product engineering, David Lange, strict military structural and ballistic requirements called for redundant load paths on several levels, while aggressive weight and envelope parameters further complicated the design.

The shaft walls and ball nuts of both inner and outer ball screws are extremely thin, says Lange, enabling accommodation of a titanium load cylinder that maintains structural integrity in the unlikely event of screw separation. "We never made a ball screw this light-weight before," Lange explains. Each ball screw weighs less than 60 lb.

Thin-wall design required heat-treatment process development at Saginaw. After experiments on a number of prototypes, engineers used a specific heating coil geometry, and some stress-relieving and metallurgical operations. Result: selective induction hardening on the ball-screw shafts that give uniform, hardened ball raceways, while maintaining tough, ductile thread roots and core material to better survive ground-fire attacks.

To maintain mass-balance and a symmetrical cross-section, Saginaw engineers employed an internal-crossover ball return within the ball nut, instead of the typical end-return. In addition, redundant load path requirements between both the inner and outer ball nut and ball screw resulted in patented integral extensions on the recirculation system. In the highly unlikely event that all balls are lost, the extensions (normally in clearance) engage the screw shaft enabling acme-type screw operation.

--John Lewis, Northeast Technical Editor

Materials save onV-22 production costs

The V-22 Osprey typifies design innovation and creativity common to the aerospace industry. For example, using the latest materials and technologies, engineers cut production costs by 22%. An RTP 2200 series polyetheretherketone (PEEK) carbon-fiber-reinforced compound was specified for the engine-air particle-separator doors and door housings. The material's high strength, rigidity, and heat resistance reduce heat-induced warpage, so the part retains its airfoil shape.

Produced by "lost core" molding, the V-22's fuel tank vents employ an RTP 2200 series (PEEK) carbon-fiber reinforced formulation. Low-melt-temperature core metals are liquefied then drained out of the molded part. Nacelle-blower impellers, designed by Able Corp., Yorba Linda, CA, are fabricated from an RTP series 2200 (PEEK) compound with high carbon-fiber loading.

Currently in research and development, the V-22's drive-assembly spline-adapter is injection molded from an RTP 4200 series thermoplastic polyamide (TPI) compound. The reinforced TPI is formulated to achieve excellent dimensional stability, strength, and rigidity.

RTP Company worked with Bell engineers and molder RAM Inc., Cisco, TX, to achieve critical material performance standards in several areas including weight reduction. "Projects like the Osprey require a team effort," says Bob Morris, RAM general manager. "RTP Co. formulates compounds meeting difficult requirements. Its ability to deliver consistent and quality compounds is a real advantage, especially on projects like this."

Copolymer cuts knife's cost and weight

Bronx, NY--Allway Tools Inc. recently introduced a safer utility knife that automatically retracts its blade when cutting is complete. The knife is expected to reduce the frequency of accidental cuts and puncture wounds associated with the use of conventional utility cutters.

Allway engineers developed a one-piece spring-slider to carry a metal blade. The material for the spring had to provide long-term toughness for day-to-day use, as well as have high lubricity and resilience. It was also important for the material to be easy to mold.

Engineers initially molded a prototype sliding mechanism in Celcon® M270 acetal copolymer from Hoechst Technical Polymers (Summit, NJ) and tested it for durability. "We tested for more than 100,000 life cycles," explains Don Gringer, CEO of Allway. "When we reached that point and the plastic still held up, we stopped the testing because we knew it would work."

The slider is molded with a zigzag spring which, when extended, uncovers the blade. When the thumb button on the side of the housing is pushed forward, the zigzag spring unfolds, uncovering the blade. The blade stays out as long as it is engaged in the cutting material. When the blade is clear of the work, the spring, under tension, returns to its original shape and the blade slides back within the housing.

Unlike a metal slider, the plastic guide does not dull the blade as it extends and retracts. Allway engineers also found that the Celcon M270 spring exhibited greater resiliency, offering better pull than a spring coiled in wire.

Designing the self-retracting knife in plastic eliminated virtually all secondary operations and delivered easy-to-assemble snap-fit parts. "The finished knife costs approximately one third less to manufacture than conventional metal utility knives," says Gringer. "The plastic knife also has fewer parts, and with a lower specific gravity, is about one-third lighter in weight."

The knife is 6 inches long and 11/2 inches wide. With a metal blade, plastic housing, and a slider made from Celcon acetal, the knife weighs approximately 11/2 ounces.

Software helps company solve problems sooner

Jasper, IN--Kimball International's Office Furniture Group (OFG) wanted to cut its product design time, while the Kimball Electronics Group (KEG) sought to get involved earlier in product life cycles. Both groups needed new software capabilities to achieve their objectives.

Most of Kimball's business segments had been using an outdated CAD/-CAM/CAE software package for product development. "We found there were definite technology gaps with our existing system," says Chris Waltz, OFG's project leader for engineering technology. "It could only handle about 20%of our specified 79 software requirements. We were looking for a system that could accommodate at least 80% of our requirements."

Kimball selected I-DEAS Master Series^TM software from Structural Dynamics Research Corp. (SDRC), Milford, OH. Using I-DEAS, OFG reduced its design time by 40%. "Our goal is to eventually cut our design cycle by 50% the first time," says Waltz.

At KEG, engineers use I-DEAS for modeling, surfacing, drafting, tolerance analysis, and some generative machining. "We've made some headway with I-DEAS in reducing the number of mechanical parts in the assemblies we produce by approximately 10 to 15% in general," comments Greg Lengacher, mechanical design engineer at KEG.

The most positive consequence of having I-DEAS, KEG says: less reliance on the prototyping stage to find problems with assemblies. "We're able to detect more and more cases of component interference and misalignments during the design process than at the prototype level," says Lengacher. "We now have prototypes that are closer to production than ever before. That means fewer prototypes before production, which is a definite cost savings for the customer."

"Before I-DEAS, we weren't able to be involved before the product design had reached the point where further change was expensive," adds Bob Weil, CAD/CAM engineering manager for KEG. "This limited us to offering fixes instead of real options.

"Having I-DEAS helps considerably in giving us the time to experiment with more design options, evaluate them, and select the optimum solution," Weil explains. "It's pretty safe to say that without I-DEAS, we wouldn't have been able to tackle the magnitude of jobs we've been handling."

The most challenging part KEG designed with I-DEAS was the first one, an automotive housing for an antilock braking system. "What made this more difficult was that we were trying to learn the software while using it and still be productive," says Lengacher. "When you've had experience with one CAD package, it's always difficult to unlearn that package and learn a new one. Now, I-DEAS itself is no longer the challenge, but the tool for overcoming our engineering challenges."

Antenna design reflects benefits of engineering automation

Melbourne, FL--By leveraging the power of design automation, Harris Government Aerospace Systems Div. greatly simplified and accelerated the process of developing deployable space- based reflectors. First applied to the creation of an RF antenna prototype of the Asia Cellular Satellite system (ACeS), the design-process automation (DPA) software lets engineers quickly pump out updated analysis and CAD models in response to changes in specifications or requirements. Not simply a one-project solution, the technology can be applied easily to the evaluation and design of similar antennas for other satellite projects.

Harris' DPA weapons are ICAD from Concentra Corp. (Burlington, MA), and Heide Corp. (Medfield, MA), an engineering-automation consultant firm that worked closely with Harris to implement ICAD. Described as a knowledge-based engineering (KBE) program, ICAD captures the expertise and full decision-making process used to develop a product. Engineers cre-ate SmartModels^TM by input-ting rules that not only define a product's geometry, but also the logic behind the geometry, design processes, and manufacturing rules.Possible outputs include complete solid models, di-mensioned drawings, FEA analysis, parts lists, NC tool paths, and cost breakdowns.

"ICAD captures the decisions that you make when doing a design," says Rich White, program manager at Harris. "That way, if the constraints on the design change, [engineers] can put those new parameters in and all the same design rules still apply. They get an updated design out quickly." He likens the process to a sophisticated spreadsheet where, once the equations are established, different inputs can be entered and the results are automatically recalculated.

"It allows a company to deliver a customized product in a period of time that is more associated with a standard off-the-shelf product," says Scott Heide, president of Heide Corp. "You can shorten the development and delivery time dramatically. I've helped clients shorten the design cycle for products from four months to two weeks."

The initial run-through of a new design, however, might take longer because of the time needed to set up the DPA system. Yet Harris found that, due to the relatively lengthy normal development cycle for RF reflectors, they have experienced no time penalty. "We might have to put a bit more work up front, but then the drawings get created more quickly," says White.

Harris uses ICAD to automatically create finite-element models, thermal models, kinematic studies, stress reports, and solid-model geometry. Inputs and interrelated design rules include factors such as:

• The final deployed reflector shape defined in part by the attitude of the antenna relative to the satellite;

• Reflector attitude defined by the umbilical mount to satellite;

• Stowed shape defined by the cargo hold shape of the launch vehicle;

• Design of ribs, hinges, truss chords, and ties determined by the stowed and deployed shape.

Output geometry is passed to Pro/Engineer for final massaging. "We use Pro/E to tweak the design the last little bit and put out drawings, adding fillets and such that you don't want to bother programming into ICAD," says White. This data-exchange process is the one weak link in the system, and he hopes to improve the way ICAD and Pro/Engineer (or other CAD programs) communicate with each other.

The ACeS reflector is a large and unique 50-ft-di-ameter nominally parabolic dish that stores for launch in an 13 × 3-ft space. Starting sometime in 1998, its jobwill be to provide recep-tion for thousands of hand-held mobile communications devices from a geosynchronous orbit 22,300 miles up.

To obtain the stowed shape, engineers developed a mechanism that works much like that of a compact folding umbrella, adding extra hinge points on the reflector's graphite ribs. In place of an umbrella's fabric is a gold-plated RF-reflective wire mesh that, when deployed, attains a smooth, uniform shape to within 0.1 inch over the entire dish.

Harris hopes to apply the basic design to the emerging market for new communications satellites--and thus the motivation to program the development process in ICAD. "The ability to rearrange or move elements of our reflector design to accommodate specific launch-vehicle interfaces is one place we see a lot of benefit to having captured the design in ICAD," White says. The program also lets engineers quickly resize the entire structure and deployment mechanism for different-sized reflectors. Ex-plains White, "[Using ICAD] we can give much more detailed information at a contract award then we ever could in the past."

--Mark A. Gottschalk, Western Technical Editor

Beemer's navigation system really works

Watertown, MA--"You have arrived," said the curiously lifeless male voice. And, indeed, I had. The navigation system of BMW's 540i sports sedan had successfully directed me from Marlborough to my parents' home in Reading, MA, via backroads I wasn't aware of--even though I've lived in the area all my life.

First, the car itself. The strong, silent type with as many high-end conveniences as you could imagine. In fact, the only thing I found annoying was unlocking the doors from inside. You either press a button on the center console or work the door handle twice. The first time unlocks the door; the second actually opens it. After a week with the car, I was still trying to exit after working the handle just once.

The 540i's new 4.4l V-8 engine is larger and torquier than before. The bore has increased by 3 mm and the stroke by 2.7 mm for a displacement of 4,398 cc. The new engine reaches a peak torque of 310 lb-ft at 3,900 rpm, versus 295 lb-ft at 4,500 rpm for its 4.0l predecessor. With the 5-speed automatic transmission in the car I drove, the 0 to 60-mph time was supposed to be 6.6 sec. All I know is that it was truly fast.

Notable engineering improvements over the previous model include a new aluminum suspension and brake system to reduce weight, and increased use of high-strength steels for the body structure. To minimize wind noise, body engineers used 3-segment door seals and foam fillers within 13 body cavities.

Back to the navigation system. I've heard of many such systems that have difficult user interfaces or are pretty much useless due to lack of accurate position calculation. I had neither complaint with the BMW system.

Here's how it works: Drivers program in a destination by turning a dial to move to a letter and pressing the dial to select the letter. At first blush, this process seems tedious. But the system is smart enough to know that if you're in the Northeast and choose a city starting with the letter M, that only five or so letters would be valid choices for the second letter. So, only that alphabet subset is available for choosing. Usually, the system would correctly guess what I was trying to input by the fourth or fifth letter.

The system already knows where you are, thanks to a GPS receiver/transmitter and antenna mounted in the trunk. It calculates a route for you and directs you along that route via maps on the high-resolution active-matrix liquid-crystal monitor and by voice commands. Data from the wheel-speed sensors of the ABS and traction control systems, an electronic compass, and a magnetic field sensor continuously correct the GPS signal to position the car within 33 feet. Map databases are on CD-ROMs; the player sits in the trunk.

Except for occasionally thinking I was on a parallel street when I was in a dense neighborhood, the system had a better handle on where I was than I did. Voice commands weren't annoying because they only issued when a turn was coming up, and, if I was playing the radio, the voice would mute it and give a short instruction. If I missed a turn or exit, the system would recalculate my route. Of course, the first command would be, "If possible, make a U turn." After you resist the urge to make a possibly illegal U turn, the system will start guiding you to your destination again using rights and lefts.

In short, this is the first navigation system I've tried or read about that has truly proved useful. My only quibble is that before it calculates a route, you have to choose between "most" or "least" use of highways. The system appears to interpret "least" as "No." An "average" highway-use option would be a good addition.

--Julie Anne Schofield, Senior Editor

Elastomer breathes new life into analyzer

St. Paul, MN--Faced with a challenging combination of performance requirements for its BreathPath^TM breathing circuit, MedGraphics turned to soft thermoplastic elastomers. The mobile pulmonary PF/Dx® system lab features an advanced design that prevents cross contamination.

"Contamination is an ongoing concern in all health-care operations, and our goal was to develop a device that would make it easer to control and eliminate this concern," says Steve Beren, marketing manager for Medical Graphics. "The design focuses on our breathing circuit, which protects a patient from backflow of breath exhaled into the system. We had to make sure we chose a material that met all our requirements."

Traditionally, a patient breathes into a machine, contacting as many as six diagnostic systems with one breath. The lab or hospital would then have to take the entire machine apart to clean it after each use, an inefficient process that requires a great deal of time. The PF/Dx, however, is designed around the BreathPath. This soft, removable plastic element guides the patient's breath, directing it to analyzers within the system. After use, it can be removed and cleaned or thrown away.

"The BreathPath required a number of material properties," notes John Marshall, market development manager for GLS Corp., Cary, IL, a maker of soft thermo-plastic elastomers that worked with Medical Graphics to help design the breathing circuit. "It had to be both very soft and very durable, crimp easily with little pressure, and return immediately to its molded shape. It also had to be an injection-moldable material medically classified as clean."

After reviewing the performance specifications, GLS recommended Shell KRATON® D-2104, a resilient, injection-moldable, medical-grade thermoplastic elastomer (TPE). "The material offered the best combination of performance and price, with the resiliency and endurance needed in the breathing circuit," he explains.

"The breathing circuit is the heart of the PF/Dx system," Berens adds. "The KRATON material is instrumental to the success of its design, which reduces cross contamination, and, because it is a fairly inexpensive part, it reduces the overall cost of the system."