Engineering News 7683Engineering News 7683

Motion-control suppliers
help cut design time

Newton, MA--Wrestling with engineering decisions on which motor to specify--like similar decisions with other components--is getting easier. The reason: supplier involvement.

To get mechanical engineers to the next time-critical project faster, more firms bring suppliers into the design cycle early. For the vendor's part, especially if quality and price are a wash, they tout software, integration, and application services to make them stand out from the competition. Here's a look at how some suppliers go all out to help engineers meet their design goals.

Teach the machine. Rory Kelly, senior project engineer, was brought on-board Oakdale, CA-based Haeger Inc. to automate its 824 series insertion machines. Haeger, builds about 400 fastener insertion machines per year. To maintain its market position, automation was critical.

Kelly decided to farm out the hardware and software integration to a supplier to free some time to start specifying the next project. After corresponding with 150 vendors, he chose Westamp Inc. (Chatsworth, CA). Kelly issued the purchase or-der at the end of June 1996; the completed ma-chine arrived in Chicago at the end of August. "We wanted the machine ready for IMTS '96," Kelly explains. Westamp convinced him they could accomplish this. A proven track record and the ability to dedicate resources night and day won the bid. "We brought the prototype to IMTS without prior testing," Kelly notes. "I turned it on and it performed well."

Haeger's customers, mainly automotive and appliance manufacturers, use the 3-axis press to insert self-clinching fasteners into various sheet metal products. They require flexibility and fast, easy changeovers from one product to the next. "When Westamp finished integrating the controller, OI, and software, we could teach the machine ourselves. Programming, accomplished by moving the machine into position and pushing the teach button, was fast and easy," Kelly says.

Other motion-control suppliers follow suit. For example, Michael Gigl, technical group leader at Green Bay, WI-based Paper Converting Machine Co. (PCMC), needed motor-sizing software and guaranteed field support. Indramat (Hoffman Estates, IL) incorporated Gigl's suggestions into its Winsize software to meet his motor and drive needs.

PCMC, a custom builder of capital equipment, used hand calculations and conservative engineering assumptions to spec motors before Winsize. The rule was oversize when in doubt, says Gigl. "Motor sizing is more critical now," he adds, "We work from minimal information, such as web speed, roll sizes, and gearing, then estimate performance requirements."

After entering requirements into Winsize, the software provides different motor sizes and drive combinations to obtain the desired torques. "I look for commonalities and oversize where practical to minimize the number of different parts," Gigl explains. He then enters new specs, and runs another iteration to ensure performance. "To get the design right the first time requires many iterations. Winsize lets us do iterations faster," he notes.

"I can spec closer and fine tune the design more than traditional sizing methods. I don't have to second guess the issued part. I know it will work, because the program gives accurate and conservative numbers," reports Gigl.

Matched sets. While motor sizing is critical to many applications, stability presents more problems for highly-dynamic (fast acceleration/deceleration) systems. If coupling, bearing, or structure designs aren't stiff enough, they could excite the mechanism, decreasing performance. "Filtering or fine-tuning problems like this are usually beyond our expertise," explains Gigl. "That's where Indramat's (for information FAX 630-462-1346) experienced servo support proves essential."

Guaranteeing such support usually requires buying matched motor/amplifier sets from a single source. Firms such as Cleveland Machine Controls (CMC) (for information, FAX 216-360-4790) market performance-matched motor/am-plifier sets, but will test non-CMC amplifiers to support its motors, says Jay Greyson, vice president and general manager for CMC's Torque Systems Division (Billerica, MA).

For maximum performance, servo-based controls require matched components, and smooth integration. A mismatched component could decrease the investment's value, and lower anticipated quality and productivity gains. A November 1996 Design News market insight study on industrial controls and drives reports that 84% of design engineers have some problems with motion-control applications. "Much of this difficulty stems from a lack of performance-matched motor/amplifier sets," says Greyson.

A poorly matched motor and amplifier can decrease servo performance and impact system reliability. As the inner loop of nested-loop control systems, the current loop governs bandwidth for the velocity and position loops. It's the last thing a mechanical engineer wants to mess around with in a motion system. CMC offers Motion Master, a simulation package designed to save engineering time, effort, and reduce the chance of such errors. "It puts years of servo-sizing application experience into the designer's hands," says Greyson.

Greg Selke, president of Multitech Inc. (West Chester, PA), has worked with several different vendors' products. "MotionMaster is the most advanced," he explains. "In about half an hour, depending on system complexity, the motion system is clearly defined and documented."

Engineers can expect new motion-control technologies to provide added flexibility, performance, improved accuracy, reliability, and diagnostics only if integrated appropriately. As motion-control options grow, and engineers get busier, suppliers will continue to be there to help engineers meet their design goals.

What this means to you

Motor/amplifier specification

..Here's a look at what's involved when specifying motors and amplifiers, according to Jim Woodward, application manager for Copley Controls Corp., Westwood, MA.

Assume motor and load inertia are equal, and double load inertia in your calculations. Determine maximum speed and acceleration.

Share your experience

Solved a tough design problem recently? Tell us about it. Design News is looking for short stories on how our readers are using new tools and components to make design breakthroughs. We want to know the problems you faced, the tradeoffs you made, the tools you used, and the lessons you learned that can benefit other engineers.

We'll give you a by-line and run a picture of you, your design team, and the end product.

This is a great opportunity to share your knowledge and experience with others, and to learn from them.

Send the details to Paul Teague, Chief Editor, Design News, 275 Washington St., Newton, MA 02158. E-mail: [email protected]

Recycled magnesium can yield quality castings

Detroit, MI--According to a paper presented at the annual conference of the SAE by Senior Researcher Andrew G. Haerle of Dow Corp., tests showed no differences in final die-cast properties between virgin metal and argon-refined recycled material. Haerle's paper also details the impact of varying non-metallic inclusion (NMI) content in recycled magnesium on machining, corrosion, paint adhesion, and basic mechanical properties.

Automotive manufacturers have hesitated to use recycled material because of concerns over residual NMI contamination. Present in small quantities even in virgin alloy, NMIs generally degrade performance.

Dow announced last year that a simple, inexpensive light-reflectance method can measure NMIs and serve as a quality indicator. "Wider acceptance of recycled alloy depends on two things: the ability to quickly and reliably measure NMI content in recycled material, and a better understanding of the relationship between NMIs and die-cast performance," says Haerle. Dow's light-reflectance technique can give the rapid feedback needed to ensure product quality. "With state-of-the-art refining," says Haerle, "recycled materials can be argon-refined to the same cleanliness as virgin metal."

Coatings chemically bond to surfaces

Eden Prairie, MN--A patented bonding technology called PhotoLink uses light activation to produce covalent bonds between proprietary photoreagents and almost any carbon-containing substrate, according to the developer, BSI Corp. This method of immobilizing reagents on a substrate controls random, intra-matrix crosslinking, creating stable surface properties. PhotoLink coatings enhance the properties of materials used in medical device applications.

One example of a PhotoLink coating is a low-friction coating. Medical-grade polymers, such as those used in catheters, generally exhibit reductions in surface friction of 50 to 90% once coated. The coating is typically 200 to 500 nm thick, with thickness largely determined by control of the coating solution's concentration and the method of coating application.

Covalent bonds make PhotoLink coatings very durable in clinical settings. Also, low-friction coatings reduce cell damage and tissue irritation. Except for some perfluoropolymers, PhotoLink coatings are not substrate-dependent. More than one coating can be used on a substrate. If a product combines one reagent that produces a low-friction surface and another that reduces clot formation, the product will wind up with a slippery coating that reduces the risk of clotting.

Most PhotoLink reagents come as water-based solutions and require no hazardous solvents. Light activation requires less than three minutes, and employs commercially available light sources. The coatings usually exhibit long shelf lives because of the covalent nature of the bond between substrate and coating.

Technology soothes audio-lovers' ears

St. Paul, MN--In the discriminating world of high-end audio, maximum sound performance is everything. That's why developments in vibration control and sound damping technology have caught the eye of both equipment manufacturers and do-it-yourself audiophiles.

One such technology from the 3M Vibration Control Products Group incorporates a thin stainless-steel constraining layer with a layer of viscoelastic polymer. The stainless steel adds stiffness to the applied area, while the polymer dissipates the vibration energy.

The application, not unlike 3M polymers specified for military and aerospace damping, should prove ideal for many amplifiers, compact-disc players, pre-amps, and speakers. The technology's damping characteristics--in which the constraining layer remains rigid while the polymer absorbs the vibration--help produce improved sound, especially in audio systems that use vacuum tubes where resonance may create a problem.

"Mechanical vibration can cause audible degradation in high-quality audio equipment," explains Harry Straub, market development supervisor for 3M's Vibration Control unit. "Audio engineers and designers are always looking for methods to improve their products. We feel this technology offers them that advantage."

The 3M material, part of the viscoelastic family of high-energy dissipative polymers, is a pressure-sensitive adhesive that's easy to apply. It comes in thicknesses from 1 to 15 mils.

3M has worked with major manufacturers of high-end audio equipment in a variety of applications. Wadia Digital, River Falls, WI, will use the product in a new CD player to be introduced soon.

"These products allow better vibration control than previous materials," says Jim Kinne, Wadia's director of engineering. "This allows us to achieve our goal--creating better sounding CD players--better sonic value."

Alpha chip targets PCs

Hudson, MA--Long a leader in microprocessor performance, Digital Semiconductor's Alpha chip will soon be appearing in PCs. By offering high performance, Windows compatibility, and PC price points, Digital hopes to take a bite out of In-tel's market.

Digital officials estimate that a PC using the 466-MHz version and featuring 32 Mbytes RAM, 2.4-Gbyte hard drive, 8x CD-ROM drive, and a 15-inch monitor could sell for $2,600. Look for systems based on the new chip in June.

Initial processor speeds will be 400 to 533 MHz. The 500-MHz part achieves 15 SPECint95 and 19 SPECfp95 (measures of integer and floating-point performance, re-spectively), according to company estimates. Desktop per-formance for the 64-bit RISC processor is given as 2.1 BIPS (billion instructions per second), thanks in part to four instruction pipelines.

Alpha runs Windows NT, which boasts more than 1,800 native applications including AutoCAD and MicroStation. It is also fully compatible with x86 WIN16 and WIN32 applications by running FX!32 translation software.

"When you attempt to go after the PC market with a non-x86 processor, there are always barriers," says Dean McCarron, a principal analyst for Mercury Research, Scottsdale, AZ. "Digital has taken a lot of steps to reduce those barriers, for example, having the FX!32 software and of-fering pretty substantial performance to induce people to switch processor families. It has a chance for reasonable success."

The 21164PC has a 30% smaller die than the 21164, mostly due to removing the level 2 cache from the chip, says Pippa Jollie, 21164PC product manager for Digi-tal Semiconductor. "We in-creased the cache to 96 kbits and moved it to the board." Digital also beefed up the on-chip level 1 cache to 8 kbytes for data and 16 kbytes for instructions.

Debuting in the 21164PC Alpha are 13 motion-video instructions that speed calculations of multimedia data. Company officials say they will enable such applications as full-frame-rate DVD (digital video disk) playback and high-quality video conferencing in software.

Second sources for the microprocessor include Mitsubishi Electric, which helped in its design, and Samsung. Samples are available now; production volumes will come on line in the third quarter. VLSI Logic is a second source for the core logic, whose single-chip implementation helps improve a PC's data throughput and reduce cost.

Digital expects to be selling standard ATX form-factor PC motherboards based on the Alpha 21164PC for less than $1,000. Samples will be available in the second quarter, with volume shipments in the third quarter.

Sprocket and belt design eliminates maintenance

Montgomery, AL--Aiming to provide maintenance-free operation for powered live conveyors, Interroll Inc. (Wilmington, NC) now offers an alternative to chain-driven live-roller (CDLR) conveyor systems: POLYCHAIN(R) belt drive rollers that use sprockets in conjunction with synchronous belts.

"CDLR systems have long presented a range of problems: chains that stretch and break, power transmission lag, high maintenance costs, and messy lubrication," says Michael Cordle, conveyor components product manager at Interroll. The POLYCHAIN drive roller's nylon sprocket/synchronous belt drive arrangement eliminates these issues, he says.

When a chain breaks on a CDLR system, lengths of chain must be removed to fix the break. With a belt system, only the one broken belt need be replaced, he says. Using belts also enables the conveyors to run faster, and they do not require lubrication. Plus, the nylon sprocket/synchronous belt drive eliminates sprocket wear.

That's the reason the Montgomery, AL facility of HK Systems's Unit Handling Group switched to POLYCHAIN rollers. The facility makes palletizers, which bring in products from a conveyor, form a stacking pattern, and drop the accumulated material onto a pallet.

Previously, the company's systems used plain rollers and a padded chain. Underneath the chain was an air bladder. To make the rollers convey and stop, pressure in the bladder was increased and decreased. When the company began designing systems for higher-speed applications, several problems arose. Heat generated from the increased speed melted the pads on the chains, and air bladders began leaking.

"We needed something that would better endure the heat and wear," says Cynthia Reinhardt, mechanical engineer at HK Systems.

Now, many of the company's systems use roller-to-roller drives with POLYCHAIN rollers. Not only do the POLYCHAIN rol-lers assist speed and maintenance, they improve overall performance. "The POLYCHAIN rollers gave us the drive we needed, and they handle well," says Reinhardt. "Plus, noise has been greatly reduced compared to our padded chain systems."