Engineering News 7623

Pneumatics moves beyond 'bang bang'

Park Ridge, IL-For decades, engineers have known a basic truth about pneumatics: It's an on-off technology. It's known for fast, simple operation-no mid-stroke positioning, no acceleration profiles, no ultra-precise motion. That's how it earned its moniker as a "bang-bang" technology.

Now, however, that may be changing. A handful of companies have begun offering systems that take pneumatics beyond bang bang. Suddenly, the new systems are challenging electric drives and hydraulics in applications requiring precise linear positioning. "Fifteen years ago, no one in the industry thought it was possible to position a cylinder using air," notes Douglas S. Kelly, vice president of marketing for Mosier Industries, Inc., Brookville, OH. "Now we're doing it at three-thousandths of an inch."

By offering such precise pneumatic drive technology, the new systems open up a raft of potential applications that can't be served by today's conventional pneumatics. Those include: packaging, palletizing, and converting machinery; conveyors; and a host of other systems. Some engineers suggest that the new systems could be used to assemble intricate products such as electric razors, portable tape players, and highly populated PC boards. Rexroth Pneumatics, Lexington, KY, has supplied servo-pneumatic systems for pad printing images on small products, as well as for construction of pneumatic cylinders.

Up to now, such demanding applications haven't been the norm for pneumatics. Most found their greatest use in situations involving clamping, pushing, and braking.

Developing pneumatic systems for the newer breed of applications has been tough, say engineers. Worse, potential customers, particularly in the U.S., have greeted the technology with skepticism, manufacturers say.

The root of the difficulties lies in basic physics. As a power transmission medium, air is difficult to precisely control. It is hundreds of times more compressible than hydraulic oil, and its behavior is inherently non-linear. As a result, engineers have been unable to successfully apply the Proportional Integral Derivative (PID) technology that controls the vast majority of today's industrial systems. The reason: PID technology is essentially linear.

To compensate for that problem, pneumatics engineers have had to design their own control systems from scratch. At Rexroth, engineers developed a numerical controller that incorporates the non-linear nature of pneumatic physics in its algorithms. They've also created their own servopneumatic valve technology. By adjusting in microseconds to changes in the valves, the system precisely controls position and velocity of a load. A $15,000 three-axis system offers an extraordinary positioning resolution of 0.0004 inches, even at top speeds of 12 feet per second. By incorporating a pressure transducer, it also accurately controls force.

At Festo Corp., Hauppauge, NY, engineers have created a family of servopneumatic valves that enable users to control air flow in ways that haven't been possible up to now. Unlike conventional pneumatic valves, the firm's servo valves can shift part-way open when they're energized. Used together with closed-loop control, they allow users to go beyond the realm of on-off operation. As a result, machine designers can now use pneumatics to control such variables as force or acceleration. And they can achieve positioning accuracies down to 0.004 inches.

Not all engineers are convinced that servopneumatics holds all the solutions, however. After exploring servopneumatics, Mosier engineers settled on a low-cost technique that employs a brake to assist in final positioning. Known as the Pneuma-Drive system, it consists of a single axis controller with custom software, position feedback encoder, valve package, and rodless cylinder. The system's brake uses special pads to firmly grip the inner wall of the cylinder chamber. The controller "knows" the required stopping distance of a given load, and incorporates that distance into the positioning process. The system automatically adjusts to changes in friction, load, and external forces. Using a cylinder with a 40-mm bore diameter, Mosier's Pneuma-Drive system can position 300-pound loads within 0.003 inches.

Stateside reluctance. Thus far, acceptance of servopneumatic positioning has been greater in Europe than in the United States, say engineers. "My American database has about 7,000 contacts in it, and probably 80% are not yet open to the idea of servopneumatic positioning," claims one engineer who asked not to be identified. His firm, he says, has placed scores of servopneumatic systems in Europe, but has only about 15 operating in the U.S.

Engineers who have incorporated the technology in their machine designs are now believers, however. "It's fast and extremely repeatable," notes Brian D. Smith, a manufacturing engineer at ITT Automotive in Rochester, NY. ITT employs Rexroth's servopneumatic system in the molding of copper commutators for DC electric motors. "It hits the same spot within a thousandth of an inch all day long, five days a week, three shifts a day, a million-and-a-half cycles a year. It's tough to beat."

Today, the major barrier to the success of pneumatic positioning technology is cost. A linear positioning system currently costs a minimum of three to four times that of conventional pneumatics. On the high end, such systems could run more than stepper motor-based techniques, but less than most servo motor methods. In return for higher cost, however, customers receive levels of accuracy that can be a thousand times greater than those of conventional pneumatics.

Ultimately, engineers expect pneumatic positioning systems to match the best electric technology. And much of the performance that was once considered impossible has already been achieved. "All of a sudden you find pneumatics in very sophisticated applications requiring precise positioning," notes Joachim Scholz, vice president of sales for Festo Corp. "We're talking about random positioning, not just in-out or on-off. We're adding servo controls that provide the capability of ramping, speeding up, or slowing down in mid-stroke. Those are things pneumatics couldn't do in the past."

Rival digitizing-tablet makers join forces

Austin, TX-Summagraphics Corp. is teaming up with rival Kurta Corp. to jointly develop digitizing-tablet products and technologies, the two companies announced.

"This is a strategy that has already been utilized in many other market segments and is clearly needed in ours," says Michael Bennett, Summagraphics president and CEO. "Combining both companies' strengths in engineering and manufacturing will provide the end user with the best overall applications solutions."

"Working together gives us the opportunity to capitalize on our synergies and fuse the best of both to create a new force in the digitizer marketplace," adds Kurta CEO Bruce Moeller. The companies expect to unveil details of their first collaborative efforts at upcoming trade shows and industry conferences.

Summagraphics is known for its SummaSketch digitizing tablets, as well as plotters and printers. Kurta, based in Phoenix, manufactures desktop graphics tablets and large-scale digitizers; it is affiliated with Mutoh Industries of Japan.

Summagraphics recently announced two cordless, pressure-sensitive graphics tablets, SummaFlex and Summa Expression. The 18- x 24-inch SummaFlex, about the size of a standard desktop blotter, can be rolled out and left in place not only as a tablet, but permanent desktop work surface. Summa Expression is a smaller (6x8-inch) version for users with limited work space.

Design News awards engineering achievement

Chicago-Celebrating the best and brightest minds in the engineering world, the Design News Engineering Awards Banquet honored three distinguished professionals in the field: inventor Jerome Lemelson, voted by Design News readers as the 1995 "Engineer of the Year"; Lester Davis of Cray Research, who accepted the Special Achievement Award; and Amar Bose of Bose Corp., who won the Quality Award.

Nevada-based inventor Lemelson has received nearly 500 U.S. patents in his career. Only Thomas Edison and Edwin Land have more. His inventions span such fields as robots, material handling, consumer electronics, and medical devices.

"It's difficult to think of a product that does not relate in some way to one of Jerry Lemelson's inventions," notes Design News Editorial Director Larry Maloney, one of the hosts of the eighth annual gala. "The man has averaged a patent a month for 40 years-and at 71 is still going strong."

In accepting the award, Lemelson spoke out against changing the U.S. patent system to satisfy trading partners. "We must commit resources to programs that promote invention and protect intellectual property rights," he said. "This country's founders were more commited to invention than the current Congress."

Lester Davis, who recently retired as the chief operating officer of Cray Research, Inc., is one of the prime movers in the field of supercomputers and this year's Special Achievement Award winner.

Since the company's founding, Davis has played a key role in every major machine it has built. He served as chief engineer on the widely successful Cray-1, introduced in 1976. He then guided Cray's technical efforts on a string of even more successful machines-from the X-MP to the recently introduced Triton.

Davis echoed one of Lemelson's themes when accepting his award: encouraging young people to choose a career in engineering.

The third award winner, Amar Bose, founded Bose Corp., the company that captured the annual Design News Quality Award. Richard Paynting, Bose's director of product development, accepted the award on his behalf. Designing and manufacturing award-winning sound systems, Bose Corp. continues to be a leading acoustics innovator. Behind the company's success is a multilayer quality program that includes extensive use of Total Quality Management concepts.

Saturn coupe offers practical vogue

Newton, MA-A single word describes the new Saturn SC2 coupe: Inexpensive.

The '95 SC2 begins at $13,815. But even at $17,540, the loaded version Design News tested behaved like a more-expensive car. Standard dual airbags and power four-wheel-disc brakes matched with optional ABS, traction control, a/c, and cruise control leave little to be desired. Conveniences include power locks and windows and a rear-window defogger with automatic shut-off.

Not mere bells and whistles, these options qualify the car as fully appointed. More importantly, the SC2 handles well. At a curb weight of 2,389 lbs (1,084 kg), the SC2 is nimble and sure-footed in city driving. A welded steel frame and beefed-up front stabilizer contribute to a pleasing stiffness in handling.

While the l.9 leader, single-overhead-cam, four-cylinder engine is no powerhouse, a new multi-port fuel injection system adds 15 horsepower in "95 for a total output rating of 124. And what the engine lacks in brute strength it makes up for in fuel efficiency and low emissions.

An aluminum block, polymer body panels, new composite fuel rail, and tuned composite air-induction system boost mileage to a respectable 24 mpg city, 34 mpg highway EPA rating.

Also new for '95 is a cast-aluminum intake manifold. The design uses an integrated coolant passage for heating during cold weather to improve emissions performance. The car meets California and Federal Tier 1 emissions regulations.

To compete in a segment that includes the Dodge Neon, the Ford Escort, and the Nissan Sentra, Saturn engineers emphasized practical design. The re-designed instrument panel has fewer parts for easier assembly, and boasts a removable upper to service components behind the panel. Saturn engineers claim the design also reduces squeaks.

The SC2 isn't perfect. In the name of safety, small horn buttons are given short shrift beside the airbag. And the sporty profile comes at a price-although there is a rear seat, passengers more than five feet tall would be ill-advised to use it for long trips. But overall, this stylish little car is at home on the road.

CATIA expands its horizons

-Sharon Machlis, Senior Editor

Charlotte, NC-CATIA-one of the world's most popular CAD/CAM software packages-is about to move out of its IBM-only environment.

The latest CATIA release now runs on Hewlett-Packard HP 9000 workstations, marking the first time CATIA will be available on a non-IBM platform. A version of the software is in the works to run on Silicon Graphics workstations as well.

"That is big news," says Bruce Jenkins at Daratech, a Cambridge, MA, research and consulting firm. "We think that will drive a lot of new growth for them." While this year's overall software revenues are expected to rise 16.2%, Daratech predicts CATIA growth will soar 30%.

The move comes in a marketplace where users are increasingly demanding flexibility in running different brands of hardware and software together. "Many users have told us they are more comfortable with a multi-vendor environment," Jenkins says. Even customers who have no plans to switch from IBM equipment will be more likely to buy CATIA now that it gives them the option to change in the future.

CATIA Version 4 Release 1.4 offers what Dassault calls "single-system images," allowing users to pass data between IBM and HP workstations with no "translations" needed. It also supports emerging STEP (Standard for the Exchange of Product model data) protocols to allow easier movement of CAD drawings among different types of hardware and software.

The move is already winning new customers. "The commitment to open CATIA to multivendor hardware platforms like Silicon Graphics was a major prerequisite for our decision to use CATIA for car-body design and car manufacturing," said Dr. Trac Tang with Volkswagen AG.

Dassault Systems of France, the developer of CATIA, was the last major CAD vendor to keep with a single-platform hardware strategy, marketing the package through IBM.

"It's notable that CATIA achieved the position of second-largest CAD revenue generator after Autodesk running on a single hardware platform," Jenkins said. Now, he adds, its prospects are even brighter.

Refreshment stands meet requirements nationwide

Charleston, IL-Everybody has seen those all-too-familiar refreshment stands at beaches, fairs, and other events. And many people have joked about owning one. But for those who may be serious, Ice Deli(TM) Refreshment Centers has made the start-up process a little simpler. The company manufactures ready-built, ready-to-open refreshment stands that serve "Snoballs"-a shaved ice and flavoring mixture.

The refreshment stands can be easily transported and are totally self-contained-the only equipment needed is an electrical hook-up and a "gray" water drain outlet. That may sound simple; but for Ice Deli Refreshment Centers, designing the stands wasn't that easy.

The company had to develop a unit that would meet varying codes and requirements across the country, including the ability to withstand 120-mile-per-hour hurricane winds in Florida. State electrical codes demanded that all dictated load centers be placed on the exterior of the building, so the company needed an enclosure and breakers that could be placed in this position and still operate in harsh environmental conditions.

The solution: Cutler-Hammer's C-H 100R Load Center in a NEMA 3R weather-proof enclosure. Says Doug Cochran, a consultant on the Ice Deli design: "We checked with several companies and discovered that only Cutler-Hammer could give us what we wanted in a stock, off-the-shelf unit."

Another concern in the stand design was heat generated in enclosures from constant exposure to sunlight and possible corrosion from salt water. To avoid failures caused by breakers constantly tripping, the company chose Cutler-Hammer's magnetic thermal-trip breakers. "These were the only breakers that could stand up to that type of punishment," Cochran claims. A Cutler-Hammer disconnect switch was also used on the roof-mounted air-conditioning units.

Polymer helps hush conveyor

Grand Rapids, MI-Engineers at Rapistan Demag Corp. have improved their roller-conveyor technology using high-performance polymers and fibers. Driven by a belt, the new conveyor runs faster than comparable accumulation conveyors with only half the noise, according to the manufacturer.

An air-powered actuator controls contact between the rubber drive belt and the rollers. This mechanism has eight components injection molded from DuPont's Delrin(R) acetal resin.

"These parts operate more quietly than equivalent metal parts," says Riccardo Schiesser, engineering manager for Rapistan Demag. "Consistently close molding tolerances prevent rattling."

To bring the conveyor belt against the rollers, pressurized air flows through a manifold to an actuator, causing the actuator diaphragm to expand upward against a shoe. The shoe, which has the belt guides snapped into it, pushes the moving belt up against the rollers to drive them.

"For the shoe assembly, the low friction and wear resistance of the polymer are especially important properties because the moving belt rides on it," adds Schiesser.

For best compatibility, the belt is reinforced with Kevlar(R) aramid fiber for high strength and minimal stretching. The inside of the belt is smooth so it can glide over the Delrin-comprised contact shoes, while the outside has a high friction surface to drive the conveyor rollers.

Actuator parts are designed for ease of assembly and disassembly, the company notes. The air actuator and manifold snap-fit into the bracket, and the bracket is held in openings in the conveyor side rails by molded-in spring hooks.

As a result, the conveyor is not only quiet, but also provides flexible installation using a minimum of parts, according to Schiesser.

Rapistan Demag rates the Model 1278 conveyor for handling shipping cartons or packages weighing 0.5 lbs to 200 lbs at speeds from 50 to 250 ft/min.

Sensors ensure safety, cut costs

The sensing and assembly of aerosol cans in a potentially explosive environment can be difficult and extremely expensive. In an aerosol plant, every stage of production in which the aerosol propellant is present must be made intrinsically safe. Traditionally, this has meant placing sensors and controls in large, bulky, explosion-proof enclosures to contain any possible explosions. But Banner Engineering, Minneapolis, MN, now has an alternative.

The company's NAMUR sensors are intrinsically safe and can perform virtually every sensing function on the assembly line, eliminating the need for bulky enclosures. Most cable sealing and explosion-proof conduit can be eliminated as well, saving significant time and expense.

In a typical aerosol can application, a wide-angle diffuse sensor directed between the guide rails can note passing cans, replacing a proximity sensor that could potentially be false-triggered by the metal rail. Spray pipes can be detected using a diffuse mode bifurcated glass fiber-optic sensor looking down at the can from the top.

NAMUR through-beam fiber-optic sensors can monitor delivery of spray pipes to the assembly area, and shut down the assembly conveyor if the supply runs out. The same type of sensor can detect the presence of the spray nozzle and whether it is properly seated. Through-beam fiber-optic sensors can also check for the presence of a cap; while convergent sensors can monitor the cap supply.

Banner claims its NAMUR technology can save companies thousands of dollars in purchased product cost, as well as hundreds of hours of engineering, installation, and maintenance time.

Quickdraw 3D delivers workstation graphics to Macs

Cupertino, CA-Macintosh computers have long been popular with graphics professionals. With the introduction of Quickdraw(TM) 3D, Apple Computer (Cupertino, CA) intends to make the Mac a more powerful contender in the 3-D CAD arena as well.

"Our goal was to make 3-D just another data type on the Macintosh," explains John Alfano, digital space product manager for Apple. "And in order to do that we've got to get people at some level to agree on a robust file format."

That file format, 3DMF (3-D metafile), lies at the core of the Quickdraw 3D standard. It supports not only three-dimensional geometry but also appearance information such as lighting, shading, phong illumination, NURBS surfaces, and rendering-essentially all the information that comprises a particular scene.

The 3DMF format gives users the ability to move data, seamlessly, from program to program- even from the 3D world to the 2D world.

"What this means is that you'll be able to copy 3-D data right out of your CAD application and put it into your desktop publishing application,' says Bruce Morgan, vice president of sales and marketing at Spatial Technologies (Boulder, CO). Morgan's company is the developer of ACIS, a geometric toolkit that forms the basis of 3-D modeling systems from more than 250 vendors including Autodesk and MacNeal-Schwendler.

Quickdraw 3D exploits the capabilities of Motorola's Power PC processor and will run only on Power Macintosh computers. Applications will have to be rewritten to support the new interface. And while hardware-based acceleration of graphics functions isn't required, Quickdraw 3D will take advantage of industry-standard PCI cards. "For $400, you will be able to get an acceleration card for this," says Alfano.

The interface eliminates file-translation hassles while still allowing vendors to write proprietary extensions for 3DMF files. Quickdraw 3D for Windows will appear about six months after the official Mac introduction sometime this summer.

Ultimately, Quickdraw 3D may provide the Macintosh with a path into the formerly exclusive domain of high-end workstations.