Engineering News 7330

Newton, MA --The U.S. economy should see another year of solid if not spectacular growth in 1996, forecasters say, although the electronics industry is likely to enjoy continued hot growth. "I think '96 will be not too unlike 1995 in the sense that economic growth will be about 2.6%--with no recession in the forecast," says John J. McDevitt, 3M corporate economist.

A consensus projection of 50 economists and analysts calls for a 2.5% rise in real (inflation-adjusted) Gross Domestic Product (GDP) this year, with predictions ranging from a low of 1.8% to a high of 4%. Virtually all major sectors of the economy should grow more slowly this year than last--but none are expected to contract outside the defense and space industries. And, inflation is expected to remain in check.

The manufacturing sector will experience a 2.4% rise in production, according to the consensus forecast published in the Blue Chip Economic Indicators, Sedona, AZ. Capital investment should remain strong, growing at 6.5%--good news for companies that design and build equipment.

"In our estimation, capital-equipment spending will continue to be the major driving force for U.S. economic expansion in 1996," Cahners Economics predicts in its annual Economic Outlook. Cahners, parent company of Design News, forecasts a 5.3% gain in this sector.

Red-hot chips. The electronics industry continued stunning growth last year as demand for semiconductors remained surprisingly strong. Last fall, for example, a report of a 1.18 "book-to-bill ratio"--meaning that chip makers garnered $1.18 worth of new orders for every $1 in product they shipped--helped push up the entire stock market. Cahners Economics expects a 25.9% rise in sales this year, on the heels of a 39% jump in '95.

One reason for the high demand: Engineers are replacing less-advanced passive components with semiconductors in many designs, taking advantage of digital technology and high-level IC integration, Cahners notes. This helps create faster, more powerful, yet lower cost OEM products.

Cashing in on the demand: semiconductor-equipment sales, which are expected to soar more than 25%, following a 46% jump in '95.

Office and computing equipment should post a healthy 17% rise this year, the U.S. Federal Reserve Board projects, far outpacing any other category of industrial machinery. The next-highest rise is expected in special-industry machinery, at 5.7%, followed by general industrial machinery, 3.4%. Engines and turbines are likely to post only a slender gain of 0.2%, the Fed expects, while construction and farm-ma-chine output may slip 1.2% and 0.7% respectively.

The auto and light-truck industry (vehicles and parts) should see a 1.8% rise in '96, more than double the 0.08% increase in 1995. "There is a mix of positive and negative factors that should contribute to an 'okay'--but by the standards of 1992-94, disappointing--1996 for the auto and light-truck market," Cahners Economics concludes.

Growth abroad. Overseas economies should pick up steam next year, Cahners predicts. Strongest growth rates will come from Latin America and still-developing Asian economies, but America's biggest trading partners--Canada, Japan, and Mexico--should also see modest growth. "A major positive for U.S. manufacturers is the expected trend in business investment spending abroad," Cahners notes.

"With few exceptions, capital spending in the rest of the world lagged that in the U.S. from 1992-1995. The manufacturing sector in many other countries has some catching up to do now to be more competitive with their American counterparts--a stunning reversal of roles from earlier in the decade." This should boost demand for such things as industrial machinery, computers, and communications equipment.

However, while economic growth has been solid the past few years, many Americans nevertheless re-main fearful about their jobs. In fact, the fast-growing computer and office-equipment market saw a job decrease be-tween 1994 and 1995 despite tremendous growth.

"The economy has done well, but this hasn't translated into better labor-market conditions," notes Daryl Delano at Cahners Economics. "The engineering occupations are not exempt from this." This has caused a major rise in productivity figures--smaller number of workers doing more work. But, some analysts say, it may also turn out to be a politically explosive issue in the 1996 presidential campaign, as workers feel they are not sharing in corporate America's windfall.

CalComp updates wide-format plotters

Anaheim--CalComp has replaced its popular TechJET Color series of wide-format inkjet plotters with the TechJET Color GT, offering more performance for the same price.

The Color GT uses ink cartridges that hold about three times more ink than the previous models. It also handles more types of media and boasts 360 x 360 dpi resolution. A white-space sensing system detects areas where no imaging is required, immediately moving to the next data-point and speeding throughput.

Prices are $5,295 for the D-size TechJET Color GT, and $5,995 for E-size. A PostScript version, TechJET Color GT/PS, comes standard with internal PostScript interpreter and 16M of RAM for $6,995.

Hytrel helps allergy sufferers sleep better

Granville, Australia--Allergy sufferers in Australia are sleeping better these days thanks to new bedding covers made with breathable Hytrel(R) engineering thermoplastic elastomer from DuPont. The covers, made by Allersearch Pty. Ltd., provide an effective barrier to dust mites and allergens present in bedding while keeping the sleeper dry.

Medical research shows that dust mites and their allergens are one of the most common causes of allergies, and can also be a trigger factor for an asthma attack. Invisible to the naked eye, dust mites thrive in warm, dark, and humid conditions and live deep inside mattresses, bedding, and carpets.

The Allersearch covers are made of a cotton-blend fabric laminated to a thin film of DuPont Hytrel that is specially formulated for high permeability to moisture vapor. The film allows the evaporation and evacuation of sweat moisture faster than a person's skin can exude it. While allowing moisture to escape, the Hytrel film also blocks the passage of microscopic dust mites and allergenic particles.

According to Murray Horn, DuPont development manager, Hytrel is an effective barrier to liquids as well. "It is often used in waterproof apparel because it can keep the wearer dry and comfortable, yet it costs much less than most breathable microporous structures," he says.

For optimum protection, the Allersearch covers have seams with micro stitches, bias binding, and zippers with a special filter material.

MacNeal-Schwendler donates to education foundation

Los Angeles, CA--A $10,000 contribution to the non-profit Design News Engineering Education Foundation adds The MacNeal- Schwendler Corp. to the growing list of companies supporting grants to engineering schools, as chosen by winners in the annual Design News Engineering Awards program.

"Mechanical and structural analysis has three components: basic theory, applications, and mechanics of running the software," says Ken Blakely, vice president, MacNeal-Schwendler. "Engineering education--which occurs both in school and on the job--applies to all three."

Headquartered in Los Angeles, MSC product de-velopment offices are also located in Costa Mesa, CA; Lowell, MA; Milwaukee, WI; and Gouda, The Netherlands. The company has 43 worldwide sales and support offices, along with numerous representatives and agents.

As the largest Mechanical Computer-Aided Engineering (MCAE) vendor, MSC supplies a comprehensive set of software and services. The company notes that its finite element programs--MSC/NASTRAN for analysis and MSC/PATRAN for modeling--are used in the design of virtually every automobile, airplane, and satellite in the world. These programs, along with others offered by MSC, perform structural, thermal, impact, and electromagnetic analysis. The results simulate and optimize performance prior to manufacture of the structure or component.

Beyond the many applications in the automobile and aerospace industries, MSC products are now being increasingly adopted in fields ranging from music to recreation. For example, Fender Musical In-struments Corp. uses MSC products to fine tune the design of its bass guitars.

The grant to the Design News Engineering Education Foundation awards is part of MSC's ongoing commitment to engineering education. MSC provides more than 250 leading engineering schools with its software. In addition, MSC's Institute of Technology offers more than 400 courses yearly from 48 dif-ferent curricula, thereby bridging the gap between bachelor's degree theory and practical application experience. "Combined with the major donations announced earlier this year from Omron and BASF, this generous donation from MSC pushes the total dollars supporting our foundation to record levels," says Design News Editorial Director Larry Maloney. "The magazine is very grateful to these companies."

When push comes to PCs

Cambridge, MA--A leading start-up in the fledgling field of VR "force feedback" has developed a commercial version of its Phantom device. "With this technology, we can now sit down at a computer terminal and touch objects that exist only in the 'mind' of the computer," says co-inventor J. Kenneth Salisbury.

The idea behind Phantom and other force-feedback devices: Create a more realistic experience in a virtual world.

Phantom uses a finger thimble at the end of a robotic arm, along with three motors that track finger movement and control forces exerted on the user's fingertips. The basic technology was developed by Massachusetts Institute of Technology student Thomas Massie and Salisbury, his senior-thesis adviser.

The $19,500 commercial version developed by SensAble Devices Inc., Phantom A, offers high-fidelity force feedback, 900-dpi resolution, and compatibility with standard PCs and Silicon Graphics workstations. Among the early expected users: medical researchers.

Already, a doctor at Penn State Medical College used the device to do a "virtual biopsy" of a brain tumor, "holding" a "needle"--actually just pressure from the Phantom--to interact with a computer image of a brain tumor. Now, researchers in Nova Scotia are developing a virtual prostate exam using the device.

Who needs such virtual medical procedures? "How do you teach medical students to do prostate exams?" responds Wayne Bell at Digital Image FX, Dartmouth, Nova Scotia. "What does an unhealthy prostate feel like? That's how you have to teach the physician, because it's done by feel." In the case of virtual surgery, physicians would have a chance to practice a planned procedure before opening up the patient. Someday, such devices may even enable telesurgery--allowing a specialist to operate on injured patients in remote rural areas, on a battlefield, or perhaps in outer space.

Cray assists pacemaker design

Minneapolis--Keep going. That's the job of a pacemaker, no matter what happens.

Engineers at Medtronic, Inc., have a similar job description. In order to continually improve pacemaker capabilities and make the devices more robust, they must identify and meet a host of design challenges.

Medtronic's Center for Biomaterial Research recently added a new member to the design team: a J916 supercomputer from Cray Research, Inc., Eagan, MN. Now, Medtronic engineers are using the supercomputer to speed the development and optimization of pacemaker leads and implantable lithium batteries.

Using packages such as MARC K6.2 FEA software from MARC Analysis Research Corp., Palo Alto, CA, engineers are optimizing the leads' ability to withstand the environment inside the human body.

Simulations allow engineers to evaluate the mechanical and structural performance of the lead design based on tension, compression, bending, and torsion loads. Because the lead assembly consists of many components and the loads experienced in the human body often exceed normal limits for the materials, the analysis is complex; engineers must use nonlinear material properties.

"Simulation studies of leads performed on workstations often required days, weeks, or months to complete," explains Medtronic Senior Research Scientist Svenn Borgersen. "These same complex simulations are now solved on the Cray in a matter of hours."

Engineers also use HEXAR software from Cray to save time by automatically creating 3-D models from raw CAD data in minutes. The software generates a "hexahedral mesh" composed of six-sided bricks. Such meshes are particularly useful for medical applications, where modeling complex organic shapes is traditionally difficult and time-consuming, say Cray engineers.

Batteries, too. Likewise, Medtronic enlisted the supercomputer for work on the pacemaker's lithium battery. Lithium is highly moisture-sensitive and very reactive with other materials, making it difficult to handle in high-volume production. To address this, Medtronic's Metals and Structural Mechanics Research Group ran MARC K6.2 FEA software on the Cray to determine the compression behavior of lithium preforms.

"The Cray solution is exactly what we needed to solve our complex computational problems associated with new product designs," says Paul Citron, Medtronic vice president of science and technology. The air-cooled J916 supercomputer lists at under $1 million.

Wrangler designers preserve 'essential Jeepness'

By Walter Wingo, Washington Editor

Washington, DC--Design engineers at Chrysler Corp. have completed a big assignment: totally modernize the legendary Jeep, but retain its 55-year-old look and feel.

The result is the 1997 Jeep Wrangler, unveiled in Washington, DC. It is scheduled to begin rolling off an assembly line in Toledo, OH, this month.

Jeep engineers received the redesign order nearly three years ago. They were to make the Wrangler safer and more comfortable than earlier versions of the mini sports-utility vehicle. Also, they were to enhance both on-road and off-road handling and performance.

"The first design they came up with was a lot zoomier than we wanted--much too much a departure from the objective," Robert J. Eaton, Chrysler chairman, recalls. It did not convey what he terms "essential Jeepness."

The final Wrangler design looked more like a direct descendent of the original general-purpose vehicle of World War II. But no GI ever enjoyed such a plush-riding Jeep.

Engineers strengthened the Jeep's ladder frame to increase overall chassis stiffness and allow for more precise suspension tuning. A new Quadra-Coil suspension provides an additional seven inches of articulation over the previous leaf-spring setup.

To contain--for the first time--dual air bags and an integrated HVAC system, the cowl is one inch higher.

The base of the windshield has moved forward four inches, making it easier to fold--even though 99% of Wrangler owners never flip down their windshield. Designers further obliged Jeep aficionados by returning to round headlights.

Redesigning the softtop for the convertible version of the Wrangler was especially tricky, Executive Engineer Donald F. Buser of Chrysler told Design News. Supported by three hinged bows that fold rearward, the manually operated top can come down in three minutes. It took nine to 12 minutes on prior Jeeps.

Motorists get a choice of a four- or six-cylinder engine for the four-wheel-drive Wrangler. A new camshaft profile and valve springs increase low-speed torque. New pistons of lightweight cast aluminum with contour-machined skirts and new rings further reduce noise and vibration.

"Jeep owners place as much importance on engineering as we do," states Chrysler's Eaton. They don't just look under the hood, he adds; they crawl under the vehicle.

Plasma display replaces TV tubes

Wilmington, DE --Future TVs that use a plasma display panel (PDP) in place of a traditional picture could be reduced in size to a slim two inches. In addition, the displays would contain significantly more pixels than traditional TVs.

Consumers will get a chance to view the PDPs in mid-1996, when Matsushita Electronics Corp. introduces a 26-inch-diagonal, 1.56-inch-thick model to the market. The company also plans to debut a 40-inch-diagonal, 1.95-inch-thick, wall-mounted, high-definition version in time for the 1998 Winter Olympics.

Serving as the building blocks for the PDPs are high-density hybrid circuits and ceramic multichip modules based on DuPont's Microcircuit Materials' thick-film materials and patterning technologies. "This new development is a good example of extending the benefits of ceramic, thick-film technology into new areas," says Sam Horowitz, marketing manager at DuPont Microcircuit Materials.

The Matsushita PDPs use three high-precision, thick-film composition and tape technologies from DuPont. DuPont's first contribution to the project involved the development of a high-precision resistor material placed in every one of the PDPs' discharge cells. The resistor technology provides excellent resistance control and consistency, Horowitz says.

For ceramic circuit applications, the resistor technology, the basis for DuPont Birox(R) Series 2000, provides improved temperature coefficient of resistance, has a low sensitivity to refiring, and works with silver and silver/palladium terminations.

DuPont's second materials invention, a ceramic-film material and high-precision patterning technique, is used to fabricate each discharge cell to a high level of accuracy and precision. The uniform thickness of the ceramic films proved critical to the function of each cell in the display.

The film-coating technology employed in creating the PDP ceramic film produces DuPont's Low-Temperature Cofired Ceramic (LTCC) product, Green Tape(TM).

Finally, DuPont provided photolithographic techniques to form features in special photosensitive thick-film materials (Fodel(R)) to allow for high accuracy and precision lay down of conductor and dielectric materials over large areas.

Combining these technologies helped give the PDPs a brightness of 150 can-delas/sq. meter. The panels display 16,770,000 colors, in 256 color gradations, and they have a 150:1 contrast ratio.

Plastic peaks asthma peak- flow-meter performance

Cedar Grove, NJ--Asthma patients can breathe easier, thanks to a redesigned peak-flow meter from HealthScan Products Inc. Making the meter more efficient and less costly: an ABS material from the Monsanto Co., St. Louis.

HealthScan switched to Lustran(R) ABS 248 from a competitive ABS material it had been using because of the service and cost-savings associated with the Monsanto material. "Medical device manufacturers are looking at more than just price and performance when specifying materials," explains Victoria M. Holt, commercial manager for Monsanto's Medical and Personal Products Team. "They are looking for such services as mold-flow analysis and help in product certification. Monsanto provides these and other value-added services to assist customers in selecting the optimum materials for their needs."

The Personal Best(R) peak flow meter is a portable device that enables asthma sufferers to test their peak expiratory flow rate--a means of determining the current status of their asthmatic condition--without having to visit a doctor. Monitoring patients' peak flow rate can identify the severity of their condition, as well as provide needed information for treatment decisions. The device can signal an impending asthma attack.

HealthScan injection molds the Lustran material to form components that make up the device. Because the housing is welded, it was essential that the ABS be strong and durable. "Lustran's high-impact resistance makes it an excellent choice for such portable medical devices," Holt adds.

The company also needed a material that could withstand sterilization and the high-heat conditions of a dishwasher. Lustran fulfilled both requirements, while also meeting all FDA USP class VI and Tripartite standards. A final reason for HealthScan choosing Lustran, Holt concludes: "The material offers a very pure, consistent white color."

Technology enables 'interactive architecture'

Miami, FL--Christopher Janney hasn't forgotten that the word "technology" derives from the Greek "tekhne," meaning art or craft. His works over the last 19 years have combined computer and sensing technology with music, color, and choreography.

His latest creation, "Harmonic Runway," recently debuted at Miami International Airport. The piece uses the motion of passengers along Concourse A to trigger a cascade of colors, tones, and snippets of natural sounds recorded in Florida's Everglades. With all the elements working together, says Janney, "it makes a movie in your mind."

The technology behind the piece begins with three Allen-Bradley Photoswitch 5000-series photosensors embedded in each of six columns spaced along the concourse's 180-ft length. Vertical spacing of the retroreflecting sensors ensures a random sequence of signals as passengers of various heights and postures pass by.

An Apple Macintosh computer with a standard musical instrument digital interface (MIDI), sound synthesizer, and sampler receives the photosensor signals and commands a random tone or chord from overhead speakers in response. As passengers continue down the concourse, they enter six zones denoted by panes of differently colored glass and different natural sounds. Orchestrated by custom software, each trip through the runway is unique.

At night, stationary colored lights as well as moving spotlights with anemone-like figures suggest the region's ties to the sea. The control program turns down the lights when the concourse is empty, then brings up the lights in sequence as people enter the walkway. "They get the impression of an animal awakening," explains Janney.

Harmonic Runway invites interaction and experimentation. At its inauguration, "People who were passing through for the first time seemed incredulous," says Jim Jerschefske of Allen-Bradley's Industrial Control Group. "But once they experienced it, they began waving their arms like orchestra conductors."

Boat delivers maintenance-free sailing

Noank, CT--One of the best two-person sailing boats just got better. The JY(R) 15, introduced in 1990 by JY Sailboats, now features a hull and deck protected by a weather-resistant, easy-to-maintain surface of acrylonitrile/styrene/acrylate (ASA).

The multi-layered hull and deck consist of an outer layer of unpainted, white, Luran(R) S ASA from BASF Corp. Plastic Materials, Mt. Olive, NJ. The ASA is backed by a layer of ABS, a flotation layer of rigid urethane foam, and a rigid inner layer of urethane-impregnated glass-fiber cloth. Spartech Plastics, Inc., Paulding, OH, makes the coextruded, 10-foot-wide ASA/ABS sheets used to form the components. The result: a hull that JY Sailboats says is "the strongest high-performance sailing dingy ever built."

The switch from fiberglass to the outer skin of ASA means that the JY 15s "will never require painting," enthuses Timothy P. O'Neil, vice president of Advance USA, East Haddam, CT, who helped set up the proprietary thermoforming process. "They are also more resistant to impacts," he adds.

In addition, Luran S will not chalk when exposed to outdoor conditions and resists fading. Using a detergent solution, owners can clean the ASA easily. It also resists aqueous salt solutions, gasoline, oil, and stress cracks.

The combination of Luran S ASA and the patented thermoforming process, in comparison to glass-fiber-re-inforced plastic molding, produces hulls "that are ex-actly the same in material consistency (no soft spots) and weight," says O'Neil. Moreover, the process cre-ates no fumes from resin curing, enabling the JY Sailboat facility to meet clean- air requirements.

Including sails and all mounting hardware, the 15-foot sailboats have a price tag of $5,000.

PVC resists hardening during tracheal procedures

Pawtucket, RI --During an endotracheal-tube insertion, patients in need of respiratory assistance have a clear vinyl tube inserted through the mouth or throat and into the tracheal region. A four-mil-thick, two-inch-long, balloon-like cuff is attached to the tube by a solvent cementing process. The one-half-inch-diameter cuff is inflated to one inch to seal off any esophageal reflux. It is also exposed to the rigorous conditions of the digestive system for the potentially lengthy time it is in the body.

As a result, tempera- ture and conditions inside the body can cause the monomeric plasticizer in some poly-vinyl chloride (PVC) medi-cal tubing to migrate. Ul- timately, this leads to hardening of the PVC. In endotracheal tube cuffs, for example, the hardened plastic membrane can result in a difficult removal when surgery is finished--possibly even injuring the patient.

To eliminate this problem, Teknor Apex has developed a clear, flexible, lipid-resistant PVC compound. The Apex 91-G1386A-60-NT material, rated at 60 Shore A, will remain soft for extended time periods at the elevated temperature inherent when inside a patient. Other physical properties of the PVC include: specific gravity of 1.22 n0.02, elongation of 340%, and a tensile strength of 1,720 psi.

"The success of this PVC compound in the tracheal-tube application has opened the door for a multitude of tissue-contact medical applications," says Peter Galland, Teknor Apex industry manager of specialty compounds. "We are also beginning to look at a variety of other medical uses, including delivery of lipid-based drugs."

Vending machine eliminates bottle breakage

Orlando, FL--Vending machine designers faced a tough question: How do you keep a glass bottle from breaking when it free falls for 42 inches? The answer: Use a shock-absorbing elastomeric polyurethane for the delivery system.

That's what ECC International Corp. did in designing its new bottle vending machine. The design walked off with first place in the appliance market category of the New Product Design Competition at the Structural Plastics '95 Conference. Consumers will soon see the award-winning design when purchasing Snapple products from Quaker Oats Beverage Div. machines.

Originally, ECC Vending Products used vacuum-formed ABS for its vending-machine delivery system. However, after only five months, the firm switched to Bayflex(R) 110-50 reaction injection molding (RIM) from Bayer Corp.'s Polymers Div., Pittsburgh. The changeover to a solid polyurethane elastomer reduced the system's part count from 16 to just three RIM parts and two vacuum-formed parts. It also increased the production rate 500%.

"We got much more uniformity in the RIM parts, and much better performance, since RIM absorbs more of the shock than ABS," says Phillip South, an electromechanical engineer at ECC. "The RIM system also is quieter, and wears better."

Unlike traditional soda vending machines, which feature eight to ten different products, the Snapple machine offers customers a choice of up to 54 varieties. The machine resembles a candy-dispensing counterpart, with a glass front and buttons with letters and numbers.

"We went with this design because we wanted our customer to see the different flavors, and also have a surprising, quirky, and fun experience in using the machine," reports Quaker Oats Beverages' Patti Jo Snopoli. "The customers can't believe that a bottle can drop from so far and emerge intact."

Software helps keep Waterworld afloat

Sunnyvale, CA--A central element in the movie Waterworld is a full-scale floating city called the "atoll." Measuring one quarter mile in circumference, with a 365-foot diameter, the atoll posed numerous design challenges to the production company, King Kona Productions.

Just keeping something this massive afloat was one challenge. The atoll would reach 55 feet at its tallest point and was expected to weigh more than 1,000 tons. Another concern was how to move the atoll to various locations for filming.

Dennis Gassner, production designer for the Waterworld sets, approached the Marine Systems Group of Lockheed Martin Missiles & Space (Sunnyvale, CA) to design the foundation of the atoll. The company agreed to handle the design and engineering of the floating barges on which the atoll set would be built.

Production designers had decided that the atoll would consist of nine separate modules linked together. They gave Lockheed a description of the modules, the estimated weight of the set elements for each, and a 2-D AutoCAD drawing showing the top view of the entire atoll.

Lockheed started preliminary design, analysis, and detail design concurrently. The first step was converting the AutoCAD file to SDRC's (Milford, OH) I-DEAS Master Series, for preliminary design and structural analysis.

Using the I-DEAS drafting package, Bob Gardner, senior staff engineer at Lockheed, did an initial layout of the basic steel framework of the modules and the joints that connected them. He converted that plan view to CADAM format so the detail designers could position welded joints and gussets and determine I-beam cuts. Meanwhile Gardner performed structural analyses of the joints, individual modules, and moorings.

The joints connecting the modules were critical to link the sections securely, but also to allow some flexibility so that the atoll could move with wavelike motion. Another concern was the stresses on the joints when the atoll was towed out to sea.

Gardner made a 2-D finite-element model of the entire atoll. Since he was not sure what the complete atoll set would weigh, or what the drag would be, he took the maximum tow load of the tug and applied it to the I-DEAS finite-element model. Analysis results indicated the loads at each of the joints. Gardner used that information to revise his original design until the joints could withstand the load.

Individual modules were analyzed next. Gardner built 3-D finite-element models for each module and performed structural analyses of the steel framework to ensure it would support the weight of the set.

Gardner's next step was to determine mooring loads for the entire atoll. He used I-DEAS Finite Element Modeling to see what forces would be placed on the mooring lines to make sure they had sufficient anchoring. While Gardner was doing all this, others within Lockheed's Marine Systems Group were performing buoyancy and hydrodynamics analysis of the modules. In just under five months, design and engineering were finished and construction of the modules began.

Prototyping aids successful Siamese-twin separation

Lackland Air Force Base, TX--Engineers typically use stereolithography to better understand projects they are trying to put together. But recently, a surgical team at Wilford Hall Medical Center turned to rapid prototyping for an operation to take something apart: the fused bones of six-month-old Siamese twins joined at the chest, pelvis, and leg.

Surgeons planning the operation hoped to split the one shared leg by cutting the upper leg bone lengthwise, explains David Chance, director of dental laboratory services at Wilford Hall Medical Center. However, when viewing CT-scan data alone, doctors were unsure whether this would be possible. The alternative? "One girl would have the leg, while the other girl would have nothing, just her one leg," Chance says. "One girl would be able to walk with the assistance of a prosthesis, but the other one would probably never be able to walk. You can't wear a prosthesis on nothing."

The surgical team sent the girls' CT-scan to Cyberform International, which generated a full-scale model of the girls' bone structure using a stereolithography system from 3D Systems, Valencia, CA.

Doctors were surprised to see the bone was bigger than expected, and there was a possibility of dividing it between the girls. "With the aid of the preoperative model, the surgical team designed a procedure to split the one leg bone lengthwise," Chance says.

During the 23-hour operation, an orthopedic surgeon actually removed the bone as planned, split it, and replaced the two parts. "Each will be able to walk," according to Chance. The other bone and organ separations also succeeded as planned, and both girls are now doing well.

The operation highlights what Chance sees as the increasing role prototyping technology will play in the operating room of the future. "This is very exciting technology," he says. Other researchers are using Selective Laser Sintering technology--creating models from powders--on some in-organic calcium models. The ultimate goal: De-sign SLS calcium im-plants that could be fused to actual bone, and in-duce damaged bone to grow into the structure. Says David Crook at Cyberform: "We bridge the medical and engineering worlds."