Sponsored By

Engineering News 7479

DN Staff

September 23, 1996

29 Min Read
Engineering News

SERCOS fieldbus standard comes of age

Interface simplifies communications between digital drives and their controllers

Frankfurt--It's been almost ten years since German machine-tool builders joined forces with the country's electrical and electronic manufacturers' association, as well as motor, drive, and CNC makers, to develop an open communication bus for digital drives. Today, SERCOS (SErial Real-time COmmunication System) is firmly rooted in the U.S. and Europe, and is published as the international standard, IEC 1491.

Using a serial-bus configuration, SERCOS is based on a fiber-optic ring. A master, typically the controller, communicates at up to 4 Mbits/sec with several drives which form the slaves. One ring can accommodate as many as 254 slaves.

Maximum segment length between the devices is 60m for plastic fiber or 250m when using glass. "Telegrams" carry messages between master and slaves with the minimum message cycle time being 0.062 msec. Message telegrams are tightly synchronized, and drives signaling the controller insert their portion of the telegram at the relevant slot in the telegram chain.

To reduce the cost of implementing the SERCOS interface, the technology is available on an ASIC developed by the Institute of Applied Microelectronics in Braunschweig, Germany, and made by SGS-Thomson. This chip, SERCON 410, interacts with the CPU, enabling connection to al-most any processor, digital signal processor, or controller, and relieving the CPU of all time-critical communication tasks. Additionally, there are cards containing the chip for use with the VME, PC, and microprocessor buses.

Expanding use. Benefits for drive manufacturers and users are plentiful, which is why Indramat, a division of Mannesmann Rexroth, complements its servodrives with a full range of SERCOS-based controls. Scott Hibbard, vice president of Indramat's Ma-chine Tool Industry Group, says SERCOS provides more features per unit cost. As an example, many drives supply probing and soft oscilloscope features through the SERCOS interface.

Other fieldbus protocols
There are several fieldbus protocols for industrial and machine automation. Here are others besides SERCOS:
- Seriplex(R)
- Interbus-S
- Smart Distributed System
- CompactPCI
- DeviceNet

"The interface also helps you re-use valuable development, and allows concentration on the control without becoming entangled with the servo design," Hibbard adds. On the question of speed compared to analog controls, he has yet to make concessions: "Throughput is no problem. In all our applications to date, the interface is not the weak link--processors and mechanics are."

The German company Krause of Bremen is also using the SERCOS interface. The company supplies gantries and other assembly equipment, particularly for the automotive industry. In many applications, Krause is moving from PLC to PC-based solutions. Its KA-DESS 2000 control concept follows this strategy, incorporating Indramat's CLC-P PC card, the "world's smallest multi-axis CNC controller," linked to the drives via the SERCOS interface.

Tom McDunn, chief engineer at Ingersoll Milling Machine Company, likes the flexibility SERCOS offers. His company is now using linear motors in some machines instead of more conventional rotary motors for feed drives.

"We don't have to worry about communication between the drive and the control," McDunn explains. "SERCOS handles that, irrespective of whether the drive is based on linear or rotary motors. This cuts down redevelopment effort, and we're quicker to market with our products."

East vs. West. In contrast to U.S. and European companies, Japanese drive manufacturers have been slower in embracing the SERCOS standard. Reasons for Japanese reluctance run from the lack of a certifying agency for SERCOS conformity testing, to the difficulty in using currently supplied chips for velocity and torque commands, to the general lack of support in Japan.

This picture may be changing, however. On its new GC21C CNC grinding ma-chine, Toyoda Machine Works uses a PC for the man-ma-chine interface, with SERCOS providing communications between the control and the servo drive.

What this means to you
- The SERCOS standard is moving toward universal acceptance.
- SERCOS-based controls can offer increased productivity, superior processing precision, re-duced machining costs.

What of the future? Consider the General Motors Powertrain Group (GMPTG). Over the last ten years, GMPTG has been involved in implementing open, modular architecture controller (OMAC) technologies in its manufacturing applications. Recently, GMPTG and General Motors Europe announced their cooperation in developing standards for powertrain equipment. They recognize SERCOS as the only defined standard for an interface between an open digital CNC and the drive system, and are requiring suppliers to provide products to meet their specification.

If more major drives users adopt GMPTG's policy, the future for SERCOS looks bright indeed.

--Roy O'Connor, European Editor, Germany

French prototyping process makes big parts fast

Saint Die, France--Low-cost rapid-prototyping technology developed by a group of re-searchers in France eliminates the step-effect common with many other rapid prototyping techniques, its inventors claim. StratoconceptionTM uses a three-axis, portal-type milling machine to cut out profiled layers that are assembled manually to create the prototype.

The cutting tool mounts on a vertical 700W spindle which rotates at 42,000 rpm. It makes several cutting passes for each layer of the prototype to achieve the exact form of surface required. It also cuts out insert holes in each layer. Their location not only facilitates assembly of the layers, but also ensures that the insert acts as a reinforcement forthe final model.

Running on PC hardware, the new process accepts CAD solid models in STL or ISO formats. Stratoconception automatically decomposes the model into appropriate layers, determines best insert positions, and calculates optimum tool paths. Prototypes can be made from any material capable of being milled, including plastics, wood, and non-ferrous metals.

Stratoconception complements other rapid-prototyping technologies, says Claude Barlier, manager of the research team. "We cannot compete on components measuring less than 20mm, nor on parts which have fine, delicate features," he says. "Where Stratoconception consistently beats the other methods is on large components and rapid tooling."

One Belgium research center employing the technology has produced a set of plastic injection-molding tooling for making a batch of 500 engine housings measuring 450 x 200 x 80mm. Shoe company Bata uses it as an aid in developing new product designs. Another recent customer: Peugeot Automobiles for concept models.

--Anna Kochan, European Editor, France

Plastics fashion eyeglass frames

Campinas, Brazil--When it comes to fashion eyewear, shape, size, color, and decoration of the frames vary according to international fashion. That's why Montmartre selected a propionate plastic for its hand-painted eyeglass frames.

"Frames created by using the propionate have a smooth finish," explains Cesar Luiz De Barros Rangel, Montmartre president. And because the material (Tenite(R) from Eastman Chemical Co., Kingport, TN) includes less plasticizer during production, it is more dimensionally stable than cellulose acetate.

This stability proves to be a major benefit for optical frames. The frames must retain their precise shapes over time to minimize the possibility for the lenses to loosen or pop out.

"The plastic is created from cellulose esters derived from wood pulp," explains Deborah Baum, business unit manager for Personal Care at Eastman's Performance Plastics Business Organization. "Cellulosics are the only plastic made from a renewable resource: softwood forests, harvested under a program of sustainable yield."

The material has another advantage when it comes to eyeglasses: The propionate resists attack by common household chemicals such as bleach, detergents, and vegetable and mineral oils.

French recycling machine to process half a billion bottles

Puteaux, France--France's RecyPVC specializes in recovering and recycling polyvinyl chloride bottles, which according to health regulations in France cannot be reused to contain foodstuffs. This year, the company plans to regenerate 20,000 metric tons of PVC from 500 million bottles.

Although most plastic bottles in France consist of PVC, polyethylene terephthalate (PET) and high-density polyethylene (HDPE) are also commonly used. With backing from Valorplast/Eco-emballages, an organization of plastic-packaging producers in France, French-based Sydel (Lorient) has developed the Dibop machine used in the RecyPVC process. It decompacts the incoming waste material; sifts out small objects, such as bottle caps; identifies and sorts the bottles by material category; and spits out the results as bales of pro-cessable plastic.

The machine's identification sensor includes a near-infrared spectrometer that can take 50 to 250 readings per object with high identi-fication accuracy. The sensor can handle 500 kg (1,100 lbs) per hour. Optional equipment in-cludes: a color sen-sor, metal detector, baling press, and suction transfer system to load the sorted material into the press.

Once sorted, two recycling lines made by Micronyl-Wedco, Montereau, France, each with a capacity of 6,000 metric tons per year, fine-sorts the coarsely sorted Dibop-processed material. First, the coarse material is chopped, screened, dried, and taken through an initial sorting process by pneumatic separations, followed by a second sort through a water bath. The PVC is then dried and granulated to produce two grades of regenerated compound: one with a particle size below 600 mum; the other with a particle size below 1,000 mum. To perform this operation, the plant consumes only 450 kW/h to regenerate one metric ton of material.

The regenerated PVC takes the form of a compound that contains 90% pure PVC resin, plus heat stabilizers and lubricants to facilitate transformation.

"Potentially, the market for recycled PVC represents over two-thirds of the market for virgin PVC," says RecyPVC Sales Manager Michel Tribut. "The critical issue is the break-even point between purification costs and the price that end users are prepared to pay."

In France, recycled PVC with a purity above 99.98% costs 20 to 30% less than virgin PVC.

Piping will account for an estimated 55 to 65% of recycled PVC use, Tribut says.

Windows swing--and slide--with acetal

Weston, Ontario--Hardware developed by Preferred Engineering Products, called "Tilt'n Slide," allows windows to open by both sliding and swinging. The hardware design swings inwards, permitting easy cleaning and full opening for ventilation or emergency exit. The sliding action provides the kind of window movement many people prefer.

Helping to make both actions easier: components made from Delrin(R) acetal resin supplied by DuPont Engineering Polymers, Wilmington, DE. The parts are incorporated into a truck assembly that permits sliding, swinging, and locking of the window sash at various opening angles. Locking prevents the windows from swinging in the wind, according to Bob Davies, vice president of engineering at Preferred Engineering Products.

The truck assembly consists of a chassis, operating lever, and brake shoe injection molded from the acetal, plus a pair of brass rollers and a pivoting metal drum. An integral hoop surrounds the drum, which mates with the window sash. The operating lever has an integral cam at its bases. Raising the lever clamps the drum between the brake shoe and hoop, preventing window rotation.

"The springiness and creep resistance of Delrin are important for our design," says Davies. "The hoop in the chassis stretches slightly to provide locking force. When the window is unlocked, the hoop returns the drum precisely to its original position. Accurate positioning is important for window operation in the sliding mode."

Dialysis machine beats the heat

Lund, Sweden--Dialysis machines come in contact with heat and aggressive fluids. This makes selecting the right material for these units critical. Gambro Lundia, a Swedish manufacturer of specialized medical equipment, found such a material in polyetheretherketone, or PEEK.

For dialysis-machine components, Gambro Lundia specified Victrex 450G PEEK from Victrex USA Inc., West Chester, PA. The unreinforced grade, suitable for injection molding, combines heat and chemical resistance with high strength and dimensional and hydrolytic stability. It is used in the machine's heater housings, pressure transducer housing, and seats for electro-valves.

"Because the heater brings the fluid temperature up to 208F to provide dis-infection, the housing needs to with-stand a continuous-use temperature ofup to 284F," says Erik Linderup, Gam-bro Lundia project leader. "Victrex does this easily.

"Even though heat is used for disinfection, the equipment still has to be cleaned with chemicals periodically," Linderup adds. "Therefore, all components in the fluid path must resist heat and aggressive chemicals."

Moreover, since PEEK withstands corrosion and wear, it continues to replace metals for applications in difficult environments. "PEEK performs even better than stainless steel in many applications," Linderup notes. "This has resulted in a longer and improved working life for our equipment, which is between six and ten years, depending upon machine use."

Acquisition to push USB

Santa Clara, CA--Phoenix Technologies Ltd., a leading supplier of BIOS and other compatibility software for the PC industry, is acquiring Virtual Chips, a major supplier of synthesizable cores--key chip building blocks for computer and communications interconnect standards. The move should help accelerate availability of USB peripherals that will work with USB-enabled motherboards using Phoenix BIOS.

USB stands for Universal Serial Bus--a 4-wire bus designed to connect up to 128 serial peripherals to a PC in a star topology. USB connectors are surprisingly small and almost impossible to plug in wrong. A consortium that includes Intel and Compaq helped define the standard, and products should be available by year's end.

Virtual's cores are reusable semiconductor process-independent circuit descriptions that engineers use as building blocks for such interconnect standards as USB and PCI (Peripheral Component Interconnect) in complex IC designs.

Phoenix executives estimate that more than 25% of new chip designs will include reusable building blocks for major interconnect standards by 1999 and that by the same year the number of systems and peripherals that incorporate the USB standard will exceed 500 million units per year.

The acquisition lets Phoenix assure interconnect software and silicon interoperability for these evolving interconnect standards. Potential customers include manufacturers of PCs and peripherals, workstations, application-specific PCs, adapter cards, and chips.

NASA administrator dedicates Robotics Engineering Consortium

Pittsburgh, PA--Robots and space exploration--sounds like the vintage TV show "Lost in Space." But this summer, NASA Administrator Daniel S. Goldin presided over the grand opening of the Robotics Engineering Consortium--a collaborative government/academia/industry effort to rapidly move robotics technology out of federal labs and into the private sector.

The building, a newly renovated 19th-century foundry, houses a consortium established in 1994 with a $2.5 million grant from NASA's Office of Advanced Concepts and Technology. Its purpose: to commercialize the mobile robotic technologies NASA developed over the years. The center aims to work directly with industry and send viable technologies back to NASA for use in space projects.

"The future of the space program is a partnership between robots and astronauts," says Goldin. "Robots that can see, hear, speak, smell, have tactile sensation, and have the intelligence to say, 'I need more information.'" He predicts that the mobile robotic industry could affect American productivity by hundreds of millions of dollars annually.

Initial REC projects include an autonomous harvester being developed with New Holland North America Inc.; an autonomous excavator under development with Caterpillar Corp.; and Nomad, aprototype lunar rover being developed at Carnegie Mellon's Robotics Institute for LunaCorp of Arlington, VA. LunaCorp plans to send one of these rovers to the Moonso it can be teleoperated from Earth at sites in amusement parks--and used for scientific exploration.

The REC requires equal participation by government and industry, and NASA ultimately expects it to be self-sustaining. In addition, the REC has attracted $10 million in matching funds from the city of Pittsburgh and the state of Pennsylvania, and more than $10 million in corporate sponsorship from Caterpillar, New Holland, Silicon Graphics, LunaCorp, Deneb, Joy Manufacturing, and Heister Corp. Ford, the Children's Hospital at Pittsburgh, and Boeing Helicopters are ex-pected to soon be on boardas well.

Electronic modeling helps Airbus cut design time

Filton-in-Bristol, UK--At Airbus Industrie, a simple modeling benchmark led toa three-month evaluation pilot program to demonstrate the benefits of Computervision's (Bedford, MA) Electronic Product Definition (EPD)--both for derivative designs and totally new, ground-up projects.

For the ground-up program, Computervision software helped a Design-Build team create an EPD of a small aircraft wing. To model a multi-site design process, the evaluation took place at sites in Filton-in-Bristol and Chester, England.

Optegra lifecycle data-management software was the primary EPD infrastructure in the pilot. The software groups product-structure components in a tree-like hierarchy that lets users select a component and view all related components or relevant in-formation about that component. Also, Optegra's TCP/IP-based Network Services feature enabled engineers at both test sites to access design information stored in the Filton-based Op-tegra "vault."

The CAMU (Concurrent Assembly and Mock-Up) digitalpre-assembly engine allowed a cross-functional team to perform in-terference checking and similar tests via a digital prototype rather than a physical prototype.

Hybrid modeling was also an important part of the project. CADDS 5 parametric modeling was used for the complex design of a 100-ft spar that required hundreds of "pockets" cut at strategic points in the material to reduce weight. Explicit modeling was used for wing skin and routed systems, en-abling engineers to more easily regenerate components to fit wing-skin modifications.

After the pilot project, Airbus determined that it could improve its price/performance by 30 percent, and re-duce average new-aircraft lead time from four years to two-and-a-half years. The project's final result: Airbus standardized its CAD, assembly, data management, and manufacturing tasks on a single architecture that will supply an EPD across all three of its partners.

Intergraph Computer Systems supports Design News Education Foundation

Huntsville, AL--Intergraph Computer Systems announced that, for the first time, it will support the Design News Engineering Awards program with a $10,000 gift to the Engineering Education Foundation. The foundation provides scholarship funds to engineering students at the university level.

"Our support of the awards program is a natural extension of our focus on the mechanical CAD market. We build the finest graphics systems available for engineering and design," says Hans Binnerts, executive director of marketing for ICS. "We like to reward excellence because we ourselves are committed to excellence."

Intergraph Computer Systems, a division of Intergraph Corp., manufactures, sells, and supports desktop com-puter systems for creativeand technical users. Hard-ware products include Pentium Pro/Windows NT-based graphics workstations and servers. A member of the Fortune 1000, Intergraph is one of the largest companies dedicated to supplying interactive computer-graphics systems.

Intergraph has garnered considerable attention over the past year with its TDZTM workstations--Intel-based graphics systems with a powerful 3-D graphics engine.

These systems were de-signed with engineering modeling in mind, says Binnerts. He says the workstations feature uncommonly large frame buf-fers supported by Intergraph-patented acceleration circuitry, providing de-sign engineers with a level of render-ing response thatlets them move models around in real-time.

"Support from companies like In-tergraph will en-sure that the pool of qualified engineers will continue to grow." says Design News Publisher Larry Maloney. "Our magazine is very grateful to them."

Easy-to-use defibrillator may save lives

Seattle,WA--Advanced algorithms and technology adapted from implanted medical electronics enable Heartstream, Inc., to produce a relatively low-cost Automatic External Defibrillator (AED) that weighs 4 lbs and can be used by police officers, lifeguards, and others who respond to medical emergencies.

Ventricular fibrillation (also called sudden cardiac arrest or SCA) kills more than 350,000 people in the United States each year. Defibrillation within 10 minutes can save 70% of victims of SCA. However, less than 1% of police vehicles, 10 to 15% of emergency service fire units, and 25% of basic life-support ambulances carry defibrillators. Fewer than 5% of those struck by SCA receive defibrillation and survive.

Conventional AEDs range in price from $5,000 to $8,000, require daily maintenance, and weigh as much as 20 lbs. Also, they require an operator to remember a treatment protocol and undergo frequent retraining to maintain skills. This prevents more widespread use of conventional AEDs.

"What we have done is piggy-backed on the implant-able defibrillator technology that has really taken off in the last decade" says Carl Morgan, vice president of R&D at Heartstream Inc. "One difference being that with an external defibrillator you have to cope with the whole chest. What we bring to the party is the ability to automatically tune a biphasic waveform and optimize it for each patient on the fly."

A biphasic signal reverses the direction of current flow through the patient's heart during defibrillation. It permits use of less energy to restart the heart, and thus reduces cardiac tissue damage.

Monophasic waveforms must deliver as much as 360 Joules to be effective; because it uses a biphasic waveform, the ForeRunner AED can perform equally effective defibrillation by delivering about 150 Joules, Heartstream officials say. As a result, engineers need to store less energy within the device. Thus engineers can use non-traditional battery technologies in the ForeRunner AED. The device contains a single six-ounce high-energy-density lithium battery, instead of the 2-lb batteries used in larger units. This battery can perform about 100 shocks.

When enough energy re-mains to perform just one more shock, onboard circuitry will alert the user to a low-battery status. In addition, given the smaller battery, all the other energy-related components--for example the capacitor--can be physically smaller and lighter. Consequently the end product, the ForeRunner AED, weighs about 4 lbs.

When the ForeRunner AED turns on, it uses a voice chip to tell the user how to connect the electrodes. When the electrodes are connected to the patient, the unit senses circuit continuity and autonomously carries out an electrocardiogram (ECG). If multivariable signal-process-ing analysis--which employs fuzzy logic--indicates that the patient should undergo defibrillation, the Motorola 68HC16 microprocessor at the heartof the system activates thedefibrillator's shock circuitry.It then illuminates a large orange switch on the surface of the defibrillator, and tells the user to shock the patient. After the shock, the analy-sis process repeats.

In use, the system charges up a 100-mufarad capacitor to about 1,800V and then discharges it across a pair of electrodes on the patient's chest. "We have a bridge circuit that starts delivering the capacitor discharge across the patient," Morgan explains. "But in the first 100 microseconds we measure some variables related to the patient's impedance, and from that calculate--based on a lookup table--the optimum waveform for the patient." Data collected from the patient determine the width of the pulse delivered in the biphasic discharge, the total pulse duration of the wave, and the amount of energy delivered. The defibrillator then switches to a monitoring mode, and determines whether or not the patient's heart is beating properly.

Self-adhesive electrodes deliver charge to the patient's chest. Emergency personnel don't need to prepare the patient by cleaning the electrode site or applying a gel. Drawings on the pads show the user how to apply them to a patient.

Finally, a microphone permits the defibrillator to store about half an hour of voice data, patient ECG data, and operator actions on a removable PC card. Users leave the site of an emergency with a record of all actions taken.

A custom Silicon Gate Array (SGA) performs many time-intensive tasks, reducing the load on the CPU. It handles display control, communications with the data card, ECG preprocessing, and control of audio subsystems. It controls audio recording by routing signals from the microphone through an adaptive delta pulse code modulation (ADPCM) compression chip before format-ting and storage. Compressed voice prompts remain stored in ROM until routed through an ADPCM by the SGA and sent to the unit's speaker.

Heartstream performed a multi-center clinical study on the ForeRunner AED involving 14 sites and approximately 300 patients. The device is now in-volved in the FDA approval process, and Heartstream ex-pects to receive approval this year. After approval, Heartstream can market it in the United States. Expected cost should be $3,000 to $4,000. The company recently received the European CE mark, which permits it to market the defibrillator in the European Economic Area.

Treadmill measures foot force

Andrezieux Boutheon, France--The Medical Development department of Tecmachine has designed a dynamometric treadmill, the ADAL (Analysis of Data from Locomotive Apparatus), that provides a simple, accurate way to measure the horizontal and vertical ground reaction forces of each foot while a user walks.

Developed in association with physiology and orthopedics teams, the patent-pending, mechanically isolated treadmill measures only the force produced by the feet. Two walking zones about 10 inches wide are located side by side. The treadmill, fixed to the ground by 3-D force measure transducers, transmits signals through crystal force transducers. These signals are sampled and stored on a PC via a 12-bit A/D converter for review. All components, in-cluding the motor, mount on a simple, rigid metal frame.

The treadmill offers a range of possible walking study applications. These include: normal and pathological walking styles, neuromotive disorders, and the aftereffects of hemiplegia, as well as giving assistance in preoperational diagnosis and post-operation follow-up.

In addition, the device can help study the consequences of an injury, proscribe rehabilitation procedures, and determine the effectiveness of prostheses for amputees. Clinical research based on quantitative criteria and the measurement of the influence of shoe soles are other areas of interest.

Matra Datavision leaps in with Euclid Quantum

Andover, MA--Euclid Quantum is a new family of design, analysis, manufacturing, and engineering data-management packages from Matra Datavision. The company is staking its reputation and perhaps its future in the U.S. market on what has become a significant R&D investment.

The product family, written in C++, has a four-pillar architecture: each pillar may be use on its own and all four are designed to provide a full solution.

Euclid Designer provides an object-oriented approach to the creation, storage, and retrieval of STEP-compliant data; feature-based design and updating for automating repetitive tasks; and non-manifold topology for modeling abstract geometries.

Euclid Analyst allows the designer to perform FEA on CAD geometry without translation.

Euclid Machinist provides the ability to manufacture any model a user has created. Designer and Machinist are seamlessly integrated and draw on the same geometry, as maintained in the common database.

Design Manager, is a "work-in-progress" product data-management system. It en-ables designers and managers to work with models that may not have been approved for release.

Matra Datavision says it intends to fully incorporate its current Euclid 3 and Strim families of CAD/CAM systems into Euclid Quantum over time.

Composites cut train/tram weight

Paris--European railway-coach builders are turning to sandwich composite materials to meet tram and railroad demands for faster, lighter trains and lower life-cycle costs.

For example, the French national railroad SNCF, famous for its TGV, or high-speed train, is facing the problem of highly congested lines. Consequently, SNCF wants to increase route capacity--but without adding to the trains' weight, since tracks for the TGV have an axle load limit of 17 tons.

A short-term solution, introduced this year, is the TGV Duplex train with double-deck coaches. These in-crease the capacity of an 8-coach train from 377 to 555 passengers. Built from extruded aluminium instead of the usual steel, the coaches are 20 percent lighter than the equivalent steel structure.

To push TGV route capacities still higher, however, the trains must go faster. SNCF therefore plans a new generation of two-deck trains with cruise speeds of 360 km/h against the current 300 km/h. Because keeping weight down will be one of the biggest design challenges in developing the new TGV, SNCF is considering various techniques for reducing axle loads. One option: fabricating coach bodies from sandwich composites.

Using composites cuts weight by 2.5 tons per coach, reducing dynamic stresses on the track caused by the high running speeds. Faster speed and a lighter body, however, increase interior noise levels, especially for passengers on the lower deck sitting close to the track. So 0.5 tons of the weight saved is sacrificed to add sound-deadening material to bring noise down to the level of today's TGVs.

The French company ACX Industries has developed a preliminary design for a twin-deck coach body built from composites that could be used in the future TGV. Sandwich materials optimize properties of the various parts that make up the body shell, according to desired function. The load-bearing upper- and lower-deck floors, for example, feature a honeycomb core, while the sandwich employed for the walls incorporates a polyurethane foam core to deaden sound.

Skins are built up from laminates of carbon and glass fibers. A prototype, new-generation TGV coach, built from sandwich composites, will be unveiled and tested in 1998.

In addition to high-speed trains, sandwich composites are increasingly being used to build cheaper and lighter trains destined for Europe's rapid-transit and commuter lines. Lighter coaches mean significant energy savings over their typical 40-year life. They also reduce track maintenance costs.

"Weight is a crucial issue for street cars, and a composite body shell weighs 50% less than steel," says Peter Rigg, head of a composites project at Swiss rolling-stock supplier Schindler Waggon. The company has developed a novel filament-winding technique to make large composite structures which, it claims, is faster and less labor-intensive than other composite manufacturing processes, such as hand lamination or resin-transfer molding.

Layers of glass fibers impregnated with resin wind around a tool in the shape of the body section to be manufactured. A foam core is added, and the sandwich is completed by winding its outer skin in similar fashion. The resultant body is stronger than a metal body of similar weight, and complex shapes can be wound as one piece, simplifying design. Maximum part length is 15 meters.

The technology is currently being used to make tram bodies for the German city of Cottbus. "Building the bodies from steel would have required 250 parts; in composite there are just 10," notes Rigg.

Besides parts consolidation, composite coach bodies do not rust in Europe's rainy cities, are easy to repair, and offer good energy absorption. Flame retardants, added during the winding process, minimize fire risk.

Schindler has also discovered a new market for its composite parts: retrofitting old tram and railway coaches that are mechanically sound but aesthetically dated with modern interiors. The coaches are first stripped to their steel shells. Fully equipped interior modules, made from composite material, are then dropped in through the roof. Says Rigg: "You get a new coach for half the price and the coach is idle only a short time."

--Geoff Nairn, European Editor, Spain

Lubricated polymer 'turns on' switch components

Caussade, France--When Apem, a leading French supplier of custom switch gears, was developing a series of automotive door-lock actuator switches, it turned to a U.S. resins supplier for help in meeting the material requirements for switch components.

For example, Apem specified stiffness and good wear properties for the switch's lever. It found those ingredients in Lubricomp(R) produced by LNP Engineering Plastics, Exton, PA.

"We supplied Lubricomp RFL, an internally lubricated nylon glass-fiber-reinforced 6/6," says Jamie Tebay, Lubricomp product marketing manager. "Adding the glass reinforcing fibers dramatically increased the strength and stiffness, while the internal lubrication ensured low wear around the pivot."

For the spring-loaded pin that runs against the cam, Apem needed a material that combined low wear and low noise generation. To meet these specifications, LNP supplied a combination of materials--Lubricomp RFL and Lubricomp WL, a PTFE-lubricated PBT composite. "PTFE has the lowest coefficient of friction of any known internal lubricant," Tebay notes. "It significantly reduces friction and sear rate, and allows completely grease-free switch operation."

HP unveils NT 'personal workstation'

Chelmsford, MA--Hewlett-Packard has introduced a desktop computer designed for more demanding technical tasks than a conventional PC, but at a lower price than the company's higher-performance PA/RISC workstations.

Built around the 200-MHz Pentium Pro, the Vectra XW Personal Workstation is HP's answer to the rising popularity of Windows/NT machines on the engineering desktop. "The Pentium Pro is approaching in performance the low end of the RISC processors," says Ron McKenzie with HP's Technical Computing Business Unit. Many software firms have already ported to NT or are about to, including Parametric Technology Corp., SDRC, EDS/Unigraphics, Computervision, Dassault, MacNeal-Schwendler, Ansys, and Autodesk.

When to use a "personal workstation?" HP officials say the systems are ideal for working on components or subassemblies; for a full-fledged car or airplane, more powerful computers would be needed. In addition, auto or aerospace suppliers that must install a particular engineering package at a customer's request might find this a more affordable option than a full-blown RISC workstation. Prices range from $9,000 to $11,800, depending on cache, disk size, and whether the system has one or two processors.

Sign up for the Design News Daily newsletter.

You May Also Like