Reusing disposable devices poses design challenges
As medical providers reuse single-use devices, suppliers evaluate their sterilization standards
Newton, MA--In an effort to contain skyrocketing medical costs, medical providers--hospitals, clinics, and group practices--are reusing disposable devices that were once considered single-use products.
Sterile disposable devices--such as catheters and syringes--typically come into contact with blood or body fluids, so reusing these products requires multiple cycles of sterilization to ensure safety. The problem: Most of the devices were originally designed to withstand only one or two sterilization procedures. Multiple sterilizations could weaken plastics and decrease bond strength in adhesives.
To overcome these potential problems, engineers need to incorporate into designs substrates, adhesives, and other materials that will stand up to multiple cycles of sterilization, yet still be non-toxic to patients.
Where do they get them? For the most part, they don't exist, say suppliers. Products for medical disposables aren't currently designed to withstand such rigorous sterilization. Of course, some materials for disposable devices, such as certain plastics, may stand up to several sterilization procedures, but that's a fortunate coincidence.
"We test our products to ensure they meet sterilization requirements for one, two, or three processes typically. And we do look at disposable products occasionally being resterilized before re-use, for example, if the packaging breaks," notes Nancy Hermanson, medical market technical leader for Dow Plastics (Midland, MI). "But we're not saying 'We know this device is being abused so let's do something about it.' That's really the manufacturer's responsibility."
One step further. Some suppliers see this trend as a challenge to improve their products. Loctite Corp. (Rocky Hill, CT), for example, is taking steps to raise the sterilization levels that its medical adhesives can survive. The company's current medical device adhesives are USP Class VI certified and withstand limited exposure to standard sterilization methods, such as three cycles of ethylene oxide (EO), up to 7.5 mega-rads of gamma radiation in a 60 cobalt field, or one cycle of steam autoclave. Yet Loctite recently completed preliminary testing of the effects of repeated sterilization on several substrates and adhesives.
"We wanted to give our customers an even higher level of confidence that our products can withstand whatever rigors they put them through," says Kyle Eales, marketing manager, General Industrial OEM, for Loctite.
Conducted in cooperation with Amoco Polymers Inc. (Alpharetta, GA), GE Plastics (Pittsfield, MA), and Hoechst Celanese Corp. (Summit, NJ), the testing project involved a range of adhesives, including acrylics, cyanoacrylates, UV/silicone compounds, and anaerobic acrylic threadlockers, retaining compounds, and structural adhesives; along with substrates such as stainless steel, polyetherimide, and polycarbonate.
Testing involved three sterilization processes: steam autoclave, hydrogen peroxide, and glutaraldehyde. Technicians tested each adhesive after 10, 50, and 100 sterilization cycles and compared with control samples. They judged results by comparing the tensile or torque strength of the sterilized adhesive to that of the control samples.
"This first phase validated that all our adhesives can withstand 100 cycles of sterilization,"says Christine Salerny, application chemist at Loctite. "Of course, in actual applications, the substrates chosen, the gap, and other factors could affect the results," she notes. "But our preliminary results were impressive enough for us to plan phase two. Now we can move to bring all our adhesives to the 500-cycle level." In the future, Loctite will test each new product it develops for the medical market.
The basics of sterilization
Sterilization of medical devices can take many forms and frequently involves extreme heat or long-term exposure to harsh chemicals. Loctite offers this primer on current sterilization techniques.
Autoclaving--which sterilizes using steam under pressure at temperatures between 115 and 134C (239 and 273F)--is the most aggressive sterilization method for adhesives, plastics, and metals. Yet the process is used for about 80% of all medical re-sterilization because of its low cost, rapid results (10 minute cycle times), and reliability.
Ethylene oxide (EO) and liquid sterilants such as glutaraldehyde are alternative sterilization methods for devices that cannot survive the autoclave's steam environment. Each has its own disadvantages, however. EO is costly, and sterilized devices must be aerated for up to 24 hours before reuse to allow toxic gases to dissipate. Because these toxic gasses are regulated by the Environmental Protection Agency, compliance issues are a serious concern when sterilizing with this method.
Glutaraldehyde is another time consuming process, requiring a minimum of 10 hours to fully sterilize a device (though disinfection takes only 20 minutes). Since most medical facilities rarely have hours or days between procedures, or a sufficient number of devices to replace those being sterilized, neither EO nor glutaraldehyde is practical for day-to-day sterilization.
Hydrogen peroxide has the potential to replace EO, liquid sterilization, and autoclaving in healthcare facilities. Since it is mild and generates no toxic by-products, devices can be used immediately after sterilization is complete. Peroxide plasma sterilization is portable; environmentally safe; and uses low temperature plasma without requiring heat or moisture, or generating toxic residues. The biggest obstacle: The equipment required for this method of sterilization is expensive. Since investments in EO and autoclaves have already been made, it may take some time for healthcare facilities to switch over to peroxide sterilization.
Polyurethane spoilers beat sun's heat
Alexandria, VA--The competition may call a rigid polyurethane structural foam system a spoiler. But after making 35 different models of aftermarket rear spoilers from the material, including one for the 1997 Pontiac Grand Prix, Electrodyne Inc. calls it a success.
Electrodyne has used the Baydur® 730 IBS system from Bayer Corp., Pittsburgh, for six years. In that time, not one spoiler has been returned due to the material having sagged.
Baydur 730 IBS incorporates the IBS blowing system technology that develops a hard skin without using CFC (chlorofluorocarbon) or HCFC (hydrochlorofluorocarbon). The system helped the company save at least 25% in costs and time by eliminating the traditional metal insert for stiffness.
"Sagging due to the radiant heat of the sun is the bane of the spoiler industry," explains Chester Vincentz, Electrodyne president. "We wanted to eliminate the insert, but our first polyurethane didn't work. Bayer then stepped in with the Baydur system, which performed well in our 160F heat test. We wound up with a much better product and far superior engineering back-up at a competitive price."
The rear spoilers range from 50 to 60 inches long, 3 to 4 inches high, and 4 to 8 inches wide. Weighing in at 4 to 7 lbs, the spoilers measure 1/2 to 11/4 inches thick. Electrodyne molds the spoilers in-house. Cycle times average 8 to 15 minutes.
Cellular phone gets lighter, tougher
Stockholm, Sweden--How small and light can a cellular telephone get? GE Plastics helped answer this question when Ericsson asked the engineering thermoplastics producer to participate in the design of one of its smallest and lightest ultra-compact cellular phones--the Ericsson AF 738 Advanced Mobile Phone Service (AMPS) unit.
"By tapping our expertise in reducing the wall thickness of portable electronics, Ericsson developed the AF 738, which is not only lightweight but impact resistant," says Tom Barone, industry manger, GE Plastics. "Ericsson used our CYCOLOY® C1200HF, a plastic resin blend that allows innovative molding techniques, to design a housing with a wall thickness of just 0.040 inches--without sacrificing impact resistance."
Designers of thermoplastic parts used in the consumer electronics market are constantly looking for ways to increase productivity, lower costs, and decrease weight and size without sacrificing part performance, Barone adds. To meet this need, GE Plastics developed advanced plastic thinwall applications and technology that can create smaller and lighter enclosures for high-performance computers, phones, and other electronic devices.
Thinwall molding requires the right resin with the right property balance and high flow characteristics. With thinner walls, processing requirements change with respect to fill time, cooling time, part ejection, and gating scenarios. Acceptable processing parameters become narrower and more precise.
Injection pressures of 16,000 to 20,000 psi are typical for applications, such as a notebook computer housing, using a single-gate melt-delivery system--that is, parts from 1.5 to 2.0 mm thick. For walls thinner than 1.5 mm, pressures up to 35,000 psi are required. In general, a thinwall material will have good flow length, high impact strength, aesthetics, stiffness, heat resistance, and mechanical integrity.
"Conventional applications typically have cycle times of 40 to 60 seconds," notes Mike Farese, vice president of Ericsson's American Standards Business Group. "GE Plastics' leading-edge thinwall technology and resin enabled us to greatly reduce our production cycle time, which allowed us to benefit from de-creased costs, reduced weight and size, and increased productivity."
Pneumatic system cradles heart
Benton Harbor, MI--A non-invasive cardiac support system developed by Gast Manufacturing Corp. uses pneumatics to stimulate an ailing heart for as long as six months. The company's Cardiac Assist Unit (CAU) can be tuned to the beat and rhythm of the heart to keep it beating steadily. Smart AirTM technology, which integrates electronic sensing and control with pneumatics, powers the unit.
Gast's system cradles a diseased heart in a cardiac support cup. Made from flexible elastomer, the cup has a double outer wall. Smart Air electronics, air storage plenums, and valves connect the cavity between the cup's inner and outer walls to an air compressor and vacuum pump (both also made by Gast).
The pneumatic system controls the volume of air in the support cup's cavity. When the heart pumps blood (the systolic period), a valve opens to fill the cup with air. This action squeezes the heart to help it pump. When the heart relaxes (diastolic period), the vacuum valve opens to remove air from the cup, relieving pressure on the heart. In the CAU's auto sync mode, operation of the valving to the support cup is automatically synchronized via electronics to the heart's natural rhythm.
If the physician prefers he or she can select the control mode, in which operation of the valving depends on several adjustable parameters. This second approach allows the doctor to determine exactly how the heart will be stimulated. Control mode variables include duration of the systolic and diastolic periods, pulse rate, and diastolic pressure.
Under a research grant from the National Institutes of Health, Dr. James E. Lowe of Duke University Hospital, Durham, NC, is testing and perfecting the CAU. Lowe is using a prototype built by Gast for testing mock heart circulation outside the body. It will be used at a later date for tests on beating and fibrillating hearts in anesthetized adult sheep.
Bearings help surgical instrument do more for less
by Mark A. Gottschalk Western Technical Editor
Seal Beach, CA--Design changes to an innovative surgical instrument known as the Rotablator should result in reduced expense and time for certain heart surgeries. The savings are part of an effort that added operational capability to the device while also making it easier to manufacture. Critical enhancements include a completely revised assembly process that replaced most adhesive joints with snap fits, redesigned bearings, and a new detachable catheter that allows a single Rotablator power unit to do a job formerly performed by several.
An alternative to traditional balloon angioplasty, the Rotablator is a pneumatically powered angioplasty system that uses tiny burrs turning at 150,000 to 190,000 rpm to grind away arterial plaque buildup. Developed by Boston Scientific, Redmond, WA, the instrument was approved by the FDA in 1993. And while this first-generation design has been successful, engineers felt there was room to improve what was "pretty much a prototype design that carried forward into production," says Gary Swinford, Boston Scientific's manufacturing engineering manager.
The original Rotablator design consisted of a tube that technicians loaded from one end with the turbine, bearings, and other guts. Then, to preload the bearings, they placed weights on the assembly while waiting for the adhesive holding the bearings to dry. "It was a real hassle," says Swinford.
With the new design they split the Rotablator's shell into two injection-molded halves that snap together. The bearings now fit into the assembly with a snug friction fit and no glue. The result: 75% fewer adhesive joints overall, a 7% reduction in the number of required assembly operators, and 35% less manufacturing space.
The custom bearings, supplied by New Hampshire Ball Bearing's Precision Division (NHBB) in Chatsworth, CA, were also redesigned to improve the assembly. Part of NHBB's High-Speed Specialty Bearing line, the 1/4-inch-bore bearings have double-honed raceways, grade 3 balls, and cages machined from polyimide.
For the new Rotablator, NHBB added a flange to give the bearings a seat, extended the inner rings for the tooling to key off, and increased control over the dimension between the inboard flange face and inner-ring outboard face--ensuring a bearing preload of 0.75 lbs.
Engineers added the catheter disconnect to help shorten the time spent performing the operation. Surgeons often start a plaque-removal procedure with a small burr and then apply increasingly larger-size burrs to remove the lesion. With the original design, every burr change required a completely new power unit, and each unit had to be disposed of following the operation. But with the catheter disconnect, surgeons can step up the burr size while using just a single Rotablator, potentially saving on the cost of the operation.
Swinford is justifiably proud of the changes. "To be able to go to this press-together assembly and to do it without affecting the quality of the end product was a big boost for us," he says.
Stereolithography speeds lancet design
Seal Beach, CA--By leveraging the power of stereolithography, engineers designing a new family of needle-withdrawal devices reduced product-development cycle time by 50%. Result: Before committing to a final design, marketing representatives were able to present the product to potential customers at an early stage for testing and feedback.
Produced by Specialized Health Products (SHP), Bountiful, UT, the ExtreSafeTM SafetyStrip LancetTM was developed to reduce or eliminate accidental needle sticks that can transmit to healthcare workers diseases such as hepatitis and AIDS. It consists of a carrier that holds disposable, hermetically sealed strips of six self-contained lancets. Each lancet can be used only once and is separated from the other lancets by a sterile barrier, which breaks off immediately prior to use. Made from two injection-molded parts and requiring only two moving components, the ExtreSafe Lancet Strip is designed to provide a low cost solution for medical blood sampling.
Engineers at SHP enlisted the expertise of Solid Design & Analysis (SD&A), Salt Lake City, UT, for the rapid prototyping work. SD&A is a service bureau that provides stereolithography services using 3D Systems', Valencia, CA, SLA technology. It also offers turnkey design engineering services to the aerospace, automotive, medical device, and consumer products industries. "While Specialized Health Products has utilized several rapid-prototyping techniques in the past, stereolithography has become our preferred method for product development," says SHP's Dave Thorne. "The ability to hold tight tolerances, simulate a variety of materials, and gain initial market feedback allowed us to move forward rapidly with confidence."
SHP produces two to three new prototypes a week. 3D Systems' services have proven to be an invaluable resource for evaluating new product concepts and ideas, while saving time to market.
The proof is in the final product. Says David A. Robinson, SHP president and CEO, "We believe our needle-withdrawal patent technology is revolutionary in terms of design, safety, and manufacturing cost advantages."
Microsoft offers engineers their own site
Redmond, WA--Microsoft has unveiled a newly redesigned engineering web site, found at www.microsoft.com/industry/cadcam/m_publication.htm. The "new" site not only looks sharper, but now provides more up-to-date information on the latest products, trends, and events in the engineering community.
In a typical "issue" a viewer will find items contributed by Microsoft employees, reprinted magazine articles, a calendar of events, white papers, and benchmarks. A link to Engineers Notebook provides technical data on new products. Example: A case study may reveal why an engineer preferred one workstation over another, or how he or she was able to increase productivity with a new software package.
The Solutions Providers Page has a listing of Microsoft-certified/authorized solutions providers, developers, and trainers. It discusses what these products or services are and what area of engineering they cover. Also new is a solution search database engine, which allows someone interested in a CAD program that works in electronic engineering, for example, to enter search criteria and come up with a list of Microsoft platform-based products.
Other items to look for include a calendar of trade shows and events; an analysts roundtable--a spot where industry analysts will discuss their viewpoints and relevant issues; and guest editorials. Another bonus for the user: Rather than search the entire site to find out about NT, Visual Basic, Excel in engineering, or other engineering-type Microsoft products, the material is readily available on the engineering homepage.
According to Brian Seitz, worldwide industry marketing manager for Microsoft, the focus of the website is "to provide a focal point for people to find content." The site is up and running, and the new content will be put on-line in stages. Present articles on the site include: "Superior 3-D Hardware Foundation for Visual Simulation," "Solution Provider Profiles," and "New Alpha-Based Personal Workstations Boost Digital's Windows NT Lead."
New CAD technology promises unsurpassed ease of use
Milford, OH--"VGXTM may be the most notable innovation to parametric feature-based solids modeling since its introduction a decade ago," says Marc Halpern, director of research: engineering, manufacturing, and design; D.H. Brown Associates (Port Chester, NY). High praise from any engineer.
Debuting in Structural Dynamics Research Corp.'s (SDRC) latest release--I-DEAS Master Series 5TM--VGX, explains Halpern, offers dramatic improvements in the ease of editing parametric feature based solids because it eliminates the need to understand and employ object history to make model changes.
VGX (extended variational technology) combines direct geometry manipulation with history-based modeling, enabling users to dynamically capture and seamlessly integrate design, manufacturing, and simulation intent within a single master model.
"This extension to the variational product architecture allows real-time direct manipulation of a 3-D digital product, including geometry, history, features, and constraints," says William A. Carrelli, SDRC's VP of field marketing. "VGX enables customers to work directly on the electronic product as if they were shaping a real part held in their hands."
"Version 5 is more intuitive and more reliable, so you can create geometry exactly the way you want it," says Bob Embrador, product engineer at American Racing, Rancho Domingues, CA.
Embrador, who's used Master Series since Version 1, predicts Version 5 will help him get products to market even faster. "The ease of use and friendly interface will give us an edge as far as creating geometry faster. Also, there are fewer icon picks, which automatically increases speed. Everything you need most often is right there in front of you."
Greg Miller, applications engineer at Lexmark International (Lexington, KY) says he was anxious to get Master Series 5. "The new functionality is significant for us. The pruning capability, for example, is something we've been longing for."
With more than 90 integrated software modules, Master Series 5 offers gains in several areas. CAD users will benefit from enhanced capabilities in complex part design, advanced surfacing, associative tool design, and collaborative design in the context of large assemblies. For CAE applications, the software boasts new capabilities for FE modeling, sound quality engineering, and durability analysis.
In CAM, Master Series 5 offers the first level of integration of the Camand® and I-DEAS Generative MachiningTM technologies. Customer-driven performance improvements include a graphics display two to seven times faster than in previous versions. Also included in Version 5: a VRML translator and a direct interface with SDRC's Metaphase SeriesTM 2 PDM product.
The product's new technology can help companies developing electronic prototypes of complete vehicles, as well as highly complex products from the aerospace, electromechanical, and industrial equipment industries.
"We can now use Master Series in all aspects of digital prototype development for complete vehicles," says Richard Riff, manager of Ford Motor Company's C3P Project Office. Ford liked Master Series 5 so much, in fact, that it plans to put the software into production on a world-wide basis this year.
Trowels 'get a grip' with elastomer
Marshalltown, IA--After a century of all-wood handles on its trowels, Marshalltown Trowel Co. switched to a thermoplastic rubber for an ergonomic handle that is more durable, comfortable, and resilient. The patented Durasoft® handle is designed for extended use in extreme conditions. It features an unbreakable, molded bond between the no-slip elastomeric grip and the tough polypropylene core.
"This helps eliminate the potential for tearing, wrapping, cracking, and splintering," says the inventor, Curt Kelsay, vice president of engineering at Marshalltown.
The trowels have flat blades and handles used to deposit and work mortar, plaster, and similar materials. Most trowels have wooden handles that can expand and contract under different working and environment conditions.
Professionals who use trowels on a daily basis typically have the tool in their hands for several hours at a time, and often work under adverse and extreme weather conditions. Marshalltown wanted to provide these workers with a comfortable handle that would allow their hands to feel better at the end of the day, yet remain resilient enough to survive tough treatment.
Kelsay explains that a typical wood handle has certain properties that just can't be controlled, especially when used in adverse conditions such mud, water, and extreme temperatures. In contrast, Durasoft trowel handles feature two components: a tough polypropylene core and a non-slip, soft-touch rubber grip made with Santoprene®.
The thermoplastic rubber, supplied by Advanced Elastomer Systems, Akron, OH, was chosen in part because it can form an unbreakable, molded bond with the polypropylene core. An insert-molding process fuses the two materials, ensuring that the comfortable rubber handle cannot be peeled off or torn.
"Santoprene rubber had the best all-around characteristics of any elastomer out there," says Kelsay. "It offered the chance to provide a solution to a 100-year-old problem. We know what it will do in the field with the extremes, and it offers consistency from morning to night."
Made-to-order ceramic bones and joints
Argonne, IL--Lower costs and faster production of joint and bone segment replacements could result from a collaborative research product involving Zimmer Inc., Midwest Orthopedics, and the U.S. Department of Energy's Argonne National Laboratory. The research aims at developing new ways to produce ceramic prostheses using rapid prototyping technology and 3-D X-ray imaging.
Currently, when surgeons need to replace bone segments, they create a replacement by manually shaping a cadaver bone or one of the patient's less critical bones. When replacing joints, prosthetic devices are usually ordered from manufacturers. However, these devices are not typically manufactured to fit a specific individual.
The researchers are designing orthopedic implants using information from 3D X-ray imaging, a scanning technology developed by Argonne. By coupling data from these images with rapid prototyping, a process that directly makes the ceramic part, custom made ceramic replacements could be produced quickly and inexpensively, the researchers say.
The technology could allow surgeons to create a replacement bone segment for a patient's left foot, for example, by X-raying the right foot and entering the digitized image into a computer. Using special software, the computer could flip the right foot's image to produce a mirror image for the left foot.
A computer can use the image to create a file that can be read directly by the rapid prototyping machine, or even modified to incorporate holes for suturing a bone segment in place. The rapid-prototyping machine then builds the ceramic part with the hole in the right spot.
At Argonne, a rapid prototyping machine makes the ceramic prosthesis using a process called "fused deposition." Similar to a computer controlled hot-glue gun, the machine oozes ceramic material out a nozzle and builds the part layer by layer.
Researchers are working with wrist bones and parts of the forearm bone that vary widely from person to person. Using a model of a hand, scientists have already obtained 3D X-ray image data sets, generated a file for rapid prototyping, and produced plastic bone segments. They have also made ceramic parts, but not bone segments, using aluminum oxide.
Current work involves controlling the porosity of the ceramic to imitate real bone, which has variable porosity and allows tissue to grow around it. The project combines Zimmer's expertise in manufacturing prostheses with Midwest Orthopedics' experience in surgical practice, plus Argonne's knowledge of ceramics and X-ray tomography.
Award sponsors support excellence in engineering
Newton, MA--Leading OEM suppliers are stepping forward to show their support as the Design News Engineering Awards program begins its eleventh year.
In its tenth year of support, the Torrington Co., Torrington, CT, is leading the way with a $25,000 award for the Engineer of the Year. The award honors a distinguished engineer chosen by Design News readers. The 1997 honoree was engineer Bernard Dagarin, who led the development team for the Galileo probe at the Hughes Space and Communication Co., El Segundo, CA.
"Looking back at Torrington's decade-long participation in this prestigious awards program, it is easy to be awed by the talent, dedication, and creativity displayed by these outstanding engineers," says Milanne DiElsi, marketing communications manager, The Torrington Co. "Their achievements are especially meaningful to us, since a primary focus of our company is to foster an internal working environment which lends itself to engineering innovation and problem solving."
For the eighth consecutive year, NTN Bearing Corp., Des Plaines, IL, is sponsoring a $15,000 grant to be donated to a college specified by the Design News Special Achievement Award winner. The magazine's editors choose the honoree based on outstanding lifetime achievements in the engineering field. The 1997 recipient, Graham Hawkes, is a pioneer in engineering advanced, one-man submersibles.
"In order to encourage young people to enter the field of engineering, we as an industry must provide the catalyst," says George Hammond, president of NTN Bearing Corp. "These awards do just that, and we are proud to be a part of it."
The Engineering Quality Award is being backed for the ninth year by Schneeberger Inc., a producer of precision bearings based in Bedford, MA. Schneeberger will donate a $15,000 grant to the school of the 1998 winner's choice. This year's winner was Ken Dabrowski, Ford's vice president for quality and process leadership.
"In our fast paced global economy, maintaining a technological edge is often a prerequisite to success. This constant drive towards better technology places increased demands on the engineering profession--demands that can only be met by highly trained people," says George Jaffe, vice president of Schneeberger. "As an award sponsor, it is gratifying to know that Schneeberger is facilitating the education of a future engineer."
Software producer MacNeal-Schwendler will once again provide three $5,000 prizes for the Grand Prize winners of the Excellence in Design contest. Last year's winners: Shimao Ni, designer of the Scroll Air Compressor that features a spiral with variable wall thickness; Richard Varo of Cummins Engine Co., developer of the piston-mounted linear power generator, which gathers engine data over periods of hundreds of hours; and David Sears, quality program manager and designer of the Gigabit Link Module, a low-cost optical port.
"The MacNeal-Schwendler Corporation is proud to continue its support of the Design News Awards," explains Thomas C. Curry, president and CEO. "It is an outstanding program that reinforces the importance of a strong engineering educational system. We thank Design News for the opportunity to participate."
For its second year, the Excellence in Computer-Aided Design Award will once again be provided by Microsoft Corp. The award honors the lead engineer of an outstanding new product whose success can be traced in large part to PC-based computer tools--both hardware and software. David Parish picked up the award this year for his work on robotic designs.
The 1998 award winning engineer will receive a $5,000 prize and will designate an engineering school to receive a $5,000 grant. "The continued professional development and technological education of engineers is critical to the growth of the industry," says Brian Seitz, worldwide marketing manager for the engineering and mapping industries at Microsoft. "We must equip these people with the necessary tools--hardware, software, and intellect--to successfully cultivate innovative ideas now and in the future."
The second place awards in the Excellence in Design competition, now in its eighteenth year, will be supplied by Bose Corp. The firm will donate four of its Acoustic Wave stereo systems to the winners.
Finally, Edmund Scientific Co., New York, NY, has donated four Astroscan telescope packages to the third-place winners in the design contest.
Most of the awards will be presented at the Design News Engineering Awards banquet in Chicago in March of 1998. The event is held in conjunction with the National Design Engineering Show at National Manufacturing Week.
"Our awards program has grown into a highly recognized major industry event," says Design News Publisher Larry Maloney. "Without the generous support of our sponsor companies, none of this would be possible."
Sculpting software provides 3-D relief
New Hyde Park, NY--Some industries with artistic requirements continue to rely on the chisel-in-hand approach. Techno-Isel endeavors to bring the benefits of CAD/CAM to such applications as jewelry-making with its ArtCAM 3-D design and manufacturing package.
According to William Frey, application engineer at Techno-Isel, the intricate patterns involved in jewelry-making usually require artisans to hand-carve the wire electron-discharge-machining (EDM) electrodes by which the stamping dies for producing the finished products are made. Craftsmanship is hard to come by, and even when found, it does not come cheap. Plus, hand tooling is a time consuming activity and prone to human error.
"Producing electrodes using a computer-controlled machine is much faster," Frey says. "It eliminates the need for skilled labor, is more accurate, and allows precise duplicates to be produced."
The process begins with line artwork. This can be scanned into the system, imported from other Windows applications, or created directly with ArtCAM's paint functions. Designers fill the line art with color, assigning a 3-D shape profile. These basic profiles can be edited using various add, subtract, and merge tools, which can be combined to produce a nearly unlimited number of operations. The software then calculates a 3-D relief for each color.
Toolpaths are laid directly over the relief profiles; ArtCAM provides full gouge-free machining, and output supports most standard CNC formats. The software also features an inversion command that converts a male model into a female cavity.
Flat fans cool 'cans'
Norcross, GA--Ah, the joys of summer. After a day of fun in the sun--or a hard day at work--how many times have you climbed into your oven-like auto to stick to the seat? Even with an efficient air-conditioning system pumping down the temperature, trapped heat and the lack of air circulation keep a driver's back and bottom hot.
Such a scenario can be a thing of the past next year if you're driving the Saab 9-5 sedan, which makes its U.S. debut in the spring of 1998. (Europeans can buy the car starting this fall.) Front seats in the new car will contain two 1.4-in thick, 6.8-in overall diameter fans, one within the center of the seat cushion and one behind the lower back.
Operating at three speeds up to nearly 13 cfm, the fans supplied by Fergas (Linköping, Sweden) draw warm and humid air trapped between the occupant and the seat through 0.07-in perforations in the leather. The air passes through small channels in the seat padding and out ports under the seat, to be cooled with the rest of the passenger compartment air. The Trollhättan, Sweden subsidiary of Lear Corp. (Detriot, MI) fabricates the seats.
The fans allow for what Saab calls "whole-body airflow," and the company says the 9-5 has the world's first ventilated passenger car front seat. Such seat cooling has been used before in high-end trucks, buses, and construction equipment, where the volume available for installation is less of a concern. But in the new Saab-designed and engineered seat, space is also taken by active head restraints that move forward in a collision, side-impact airbags, and electrical seat heaters--thus the remaining real estate dictated a small fan size.
Peter Virstedt, an engineer who tested the seat under extreme conditions in the Arizona desert, comments: "While the normal air-conditioning system can bring the passenger compartment temperature down from as high as 70C (158F) to a comfortable 20C (68F) in a relatively short time, your back and the underside of your thighs still stay very hot and sweaty. Sitting in the ventilated seats, however, is very comfortable because even the back of your body gets its share of the cooling air flow."
Sleep soundly on plastic springs
Schlosse Holte, Germany--Made from spring elements molded of DuPont Hytrel® polyester elastomer, the Frolexus spring system, developed by Froli Kunststoff-werk Fromme GmbH of Germany, combines back support with sanitary and space-fitting advantages. In this system, individual spring elements interlock to form a mattress underlay.
Molded as one piece, each spring element has three levels: an upper surface intended to support a mattress, a lower surface anchored to the bedstead, and a bellows-like spring between the two. Integral provisions on the lower surface permit snap-locking the spring elements to one another. In its unloaded position, the spring is 60 mm (2.4 inches) high.
Froli manufactures the elements in two sizes. One provides a mattress-bearing surface measuring 105×105 mm (4.1×4.1 inches). A second, handy for configuring springs to fit irregular spaces or make odd sizes, measures 35×105 mm on its bearing surface.
Its modular nature makes the spring system useful when assembling a mattress underlay to fit an irregular space. In addition, the system offers advantages for health care providers. The spring structure is open and nonabsorbent. And because Hytrel exhibits good resistance to chemicals, a mattress underlay made from Froli's spring system can resist disinfectants and antibacterial treatments.
Long-fiber-reinforced extrusions challenge engineered thermoplastics
Hastings, MN--Produced by Intek Plastics Inc. using Celstran® long-fiber-reinforced materials, thermoplastic composite extrusions reportedly offer properties superior to those of PVC and polypropylene--as well as more costly engineered thermoplastics like polycarbonates. Intek refers to this development as Very High Modulus Extrusion (VHME), and has a patent pending on it. (Celstran is supplied to Intek by Polymer Composites Inc., Winona, MN, a subsidiary of Hoechst Technical Polymers.)
Parts reinforced by long-fiber materials have been injection molded for 15 years. But Intek Plastics claims that VHME thermoplastic is the first commercial application of long-fiber extrusions. The material consists of a long-fiber-based core for strength and impact resistance, sheathed by inner and outer layers of ABS, polypropylene, or weatherable PVC.
"To date, the fibers we've extruded have been limited to glass and carbon. Right now we're using glass fibers that are about 1/2 inch long," says Greg Mitsch, V.P. and general manager, Diversified Products Division, Intek Plastics. Quite a number of thermoplastics can be used as the matrix in VHME work. "We've used polyurethane, polypropylene, ABS, and polycarbonate. We have not done any of the nylons or polyacetal," says Mitsch, "just because our current equipment is not capable of processing at that high a temperature."
Recent applications for VHME include a commercial refrigeration system and the sub-floor of a refrigerated semi-truck trailer. In the commercial refrigeration application, VHME was used to make a corner support to hold glass in a glass assembly. Engineers chose the material because it offered low thermal conductivity and enough strength to retain the glass. In the trailer application, the material replaced a heavy wood that tended to rot. Aside from its resistance to rot, VHME produced other benefits. "It improved the thermal performance of the unit, and it also reduced the weight about one pound per lineal foot. So on the semi-trailer it saved about 400 lbs."
At the present time, Intek Plastics believes it has a unique capability to provide high modulus extrusions. "As far as we know, nobody else is extruding these materials," states Mitsch.
Milton Bradley 'scales up' for improved plastic productivity
East Longmeadow, MA--What would the game of Life be without the tiny station wagons or plastic spinner? Milton Bradley, the worldwide producer of this and other popular Parker Brother games, relies on its Injection Molding (IM) Division to produce these components. And IM counts on high-precision scales to keep the operation running efficiently.
"We produce one billion plastic components per year for Milton Bradley games," says Jeff Lombard, manager of IM. "With that kind of output, we need to run as smoothly as possible."
To make the plastic parts, Milton Bradley mixes raw plastics with the appropriate colors during the injection molding process. Melted plastic is injected into the mold, the plastic sets, and the desired parts come off the production line.
If IM has to run the molding machine again because of problems with the mold or if too few parts are produced, operation costs rise. "Problems with the equipment are going to happen. However, we can use the scales to control the quality of the pieces and the number produced," Lombard notes.
IM had used balance-beam scales for years, but decided to abandon the outdated technology and upgrade to high-precision counting scales from Setra Systems Inc., Boxborough, MA. For this job, IM selected the Super Count and Quick Count models.
"We chose the Setra scales because of their accuracy, weighing capacity, and ease of use," Lombard explains. "We have 36 scales in our molding operation and one scale on a cart that we take onto the floor for quality checks." Both scale models offer counting resolutions as fine as one part in 500,000 and have weighing capacities up to 110 lbs.
One benefit IM realizes from the scales occurs during the Statistical Process Control (SPC) procedure. SPC checks the shot weight of parts against the target weight. The difference in weight helps determine part quality. For example, if the shot weight is ±1% of the target weight, it passes.
Should the weight differ, however, two scenarios are likely: First, the piece may be faulty and unusable. Second, it may be acceptable but using too much plastic per piece. In both cases, the process becomes more costly.
An added benefit of the new scales occurs during the production of the pieces. If IM has to produce 10,000 plastic spinners, it keeps count with the scales and uses the part-count feature when filling the holding containers. By maintaining an accurate count, IM doesn't have to run the mold again to produce additional parts, increasing efficiency and lowering costs.
The scales also help inventory control. "What we place into inventory may not be requested for weeks. However, when 4,000 plastic spinners are needed, there is no time for inaccuracy," says Lombard. Additionally, molded pieces are "funneled" into a plastic bag and placed in a game box. The scales ensure the proper piece count per bag.
| Polypropylene/VHME properties
||w/m degree K
|Coefficient of Linear
||in/in degree F
|Temperature @ 264 psi**
|Notched Izod @72F**
|Notched Izod @ 32F**
|Notched Izod @ 0F**
|Notched Izod @ -40F**
* Testing for core material only. ** Testing for composite.