Tài liệu Machine design, tập 84, số 07, 2012

May 10, 2012 A Penton Media Publication Tune in to EngineeringTV.com Better ways to catch the WIND page 42 A MAGNETIC BRAKE WITHOUT COGGING OR NONLINEARITIES, page 16 ULTRAPRECISE MACHINING HOLDS SUBMICRON TOLERANCES, page 56 SOFTWARE ANALYZES BEARING PERFORMANCE, page 60 DIMENSIONAL TOLERANCES SIMPLIFY ENGINEERING TASKS, page 64 High-speed counting The DL205 micromodular PLC is an industry workhorse, time-tested in some of the toughest industrial settings. Installed in thousands of applications, its wide range of I/O and communication options ensure you’ve got the tools you need to do the job. And our direct prices, 30-day money-back guarantee and FREE award-winning technical support are all standard features that make that job a little easier! DISCRETE: Choose from 25 discrete modules that support AC, DC and relay I/O types. All modules have removable terminal blocks for easy wiring and module replacement. Our newest DC output module performs electronic short circuit protection. ANALOG: 19 analog modules offer interfaces to current and voltage signals, as well as thermocouples and RTDs. Connect devices such as process transmitters, proportional valves and AC drives. CHECK OUT OUR PRICES ON PLC MODULES PLC modules HIGH-SPEED/MOTION: Counter modules include a simple counting input module or a high-speed input/pulse output module for interfacing to stepper or servo drives. Using our SureServo or SureStep motion systems with the DL205 gives you a very cost-effective motion control system. COMMUNICATIONS: The DL205 series makes Ethernet communications easy and inexpensive. Get fast peer-to-peer access to HMI, other PLCs and PCs on the factory floor at one of the lowest costs per node in the industry. DirectLOGIC DL205 Allen-Bradley CompactLogix Discrete Modules AC 16-pt. input DC 16-pt. input DC 16-pt. output Isol. relay 8-pt. out $135.00 $91.00 $99.00 $100.00 $282.80 $240.38 $314.11 $289.87 Analog Modules 4-channel input (current) 4-channel thermocouple in 8-channel output (voltage) $201.00 $301.00 $271.00 $485.81 $986.77 (6-ch) $1,454.40 Communications Ethernet interface $301.00 $783.00 * All prices are U.S. published prices. Prices and specifications may vary by dealer and configuration. AutomationDirect prices are from April 2012 Price List. Allen-Bradley prices are based on www.rockwellautomation.com/en/e-tools 2/20/12. www.automationdirect.com/plcs Test-drive the software for FREE! Our fully functional PC-DS100 programming package can create and download programs to all our DirectLOGIC PLCs (max 100 words runtime; unlimited programming package PC-DSOFT5 is $395). Download the software online at: http://support.automationdirect.com/downloads.html RS# 101 www.automationdirect.com Go online or call to get complete information, request your free catalog, or place an order. 1-800-633-0405 High Accuracy Pressure Transducers Insta Pricent ! Design Your Own Custom Transducer Online `^VX Over a Million Combinations with 1-Week Delivery! RT`^ T`_WZ XRU +)(+$
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,*$& ",*-3*  omega.com R No. ® RS# 102 VOLUME 84 ISSUE 7 MAY 10, 2012 ELECTRICAL/ELECTRONIC Authored by: Robert Repas Associate Editor Key points: • Embedded systems take on the disguise of ordinary devices, not computers. • Industrial trends tend to mirror those in the consumer space. • One critical missing aspect is a simple programming method for the embedded system. Resources: Microchip Technology Inc., www.microchip. com National Instruments, www.ni.com Texas Instruments, www.ti.com WinSystems, www.winsystems.com FEATURES Xilinx, www.xilinx.com A Development cycles have shortened dramatically. So much so that there is no longer enough time to devise computer-powered applications starting with a standalone computer or processor. Consequently, computer and chipmakers have added new and more-powerful functions into the silicon of a computer chip. The result heralds the advent of computerized platforms comprised of a processor, a communication interface, and I/O functions targeting specific end-use categories such as mobile phones, computer graphics, and industrial control. One of the earliest examples of such a single-purpose design is the PC/104, a single-board computer architecture about the size of a 3.5-in. floppy disk that had stackable accessory boards to fit numerous application needs. As small as the PC/104 system is, some applications required even-smaller processors. Stepping down in size, the system-on-module (SOM) and system-on-chip (SOC) combined all aspects of the single-board computer into a single module or integrated-circuit form. SOMs take the individual dies of multiple devices such as a processor, memory, and I/O, and mount them onto a common substrate material. The tighter integration has led to smaller but more-powerful systems in the form of self-contained devices that can drop into any piece of equipment for a specific purpose. Examples of these devices include digital signal processors (DSPs), network interface and communication services, and even complete computing platforms. Computers-on-modules (COMs) are a subset of SOMs that integrate an entire computer on a single modular device. While still considered as embedded systems, the versatility of their general-purpose computer lets COMs handle more functions with a single package than typical of the other embedded approaches. The push to make systems still smaller has freed chipmakers to form all devices onto a single die, the SOC. Instead of individual IC dies of discrete components mounted to a substrate, all devices are etched onto a single die of silicon or other suitable material. But there is a problem with this approach. Many design teams may use the same SOC or SOM as the basis of a product. When those design teams compete with one another, it is sometimes difficult to come up with final designs that are distinctively different from those of competitors. So most design teams augment the SOC or SOM with additional discrete components and programmable logic. For example, field-programmable gate arrays (FPGAs) let design teams add specialized process- ing, improve performance, and future-proof the design with the ability to update the logic at any time during development or even after they have deployed the embedded system. FPGAs have always been used as the “glue” logic that ties various parts of the system together. But as their performance rose while power and cost dropped, FPGAs took on the additional task of handling signal processing. Today FPGAs perform the functions of digital filters, process Fast-Fourier Transforms (FFTs), and provide the logic needed for proportional-integral-derivative (PID) control loops, among many other things. Most times these processes take place in parallel with the computing side of the system, boosting processing speed while giving more deterministic control of the application. The addition of FPGAs to embedded systems has become so common that new SOC releases now contain both a complete microprocessor and an FPGA in a single package. One example being released in 2012 is the Zynq-7000 Extensible Processing Platform (EPP) from Xilinx, San Jose. The Zynq integrates a dual-core ARM Cortex-A9 processor with a Xilinx 7 Series programmable FPGA and an industry-standard AXI interface. The combination gives embedded design teams the ability to Reconfigurable processors hold the key to future products using embedded systems. SOFTWAREDEFINED FUTURE 42 for Better alternatives for wind power Innovative new designs for wind turbines promise to cure problems ranging from noisy props to poor efficiency in moderate breezes. 52 embedded controls 52 MACHINE DESIGN.com National Instruments LabView graphicalinterface software is one of the first to adopt a noncode approach to writing application programs, relying on operational block diagrams to program the system. MAY 10, 2012 MAY 10, 2012  52 A software-defined future for embedded controls The future of embedded computing includes devices with more power, features, and simpler programming systems. OEM SERVICES of 56 Fundamentals ultraprecision machining It no longer takes exotic machining to hold submicron tolerances. the essentials 60 Analyzing of bearing performance Software that examines bearing fundamentals leads to better designs. with 64 Working dimensional tolerances Understanding the nuances of tolerances makes life easier for engineers. 73 MACHINE DESIGN’s LITERATURE EXPRESS Fundamentals of ultraprecision machining It no longer takes exotic machining to hold submicron tolerances. Ultraprecision machining (UPM) comes from the optics industry so not many designers are familiar with the process. However, the technology has the potential to revolutionize the way manufacturers, in general, finish parts or make fine-featured patterns. First, recall that “high precision” in traditional machining generally refers to tolerances in the single-digit micron range. In inch units, machinists talk about holding “tenths” (ten-thousandths of an inch, or 0.0001 in.). And the best conventional machining and grinding machines typically get Ra values no better than 0.1 μm. In contrast, ultraprecision machining provides accuracy an order of magnitude better by holding submicron tolerances. UPM also obtains surface finish Ra values better than 0.5 nm. When using diamond tooling on nonferrous materials, UPM produces yet more-impressively smooth finishes. Ametek Precitech, in Keene, N. H., manufactures UPM equipment and has provided the benchmark for this technology. Precitech’s machine layout resembles that of standard equipment, but the details make all the difference. Programming input resolution, the precision level of the machine inputs, is 0.01 nm for linear and 0.026 arc-sec for angular position. Workpiece spindle speeds hit 18,000 rpm and milling spindles rotate at 15,000 or 50,000 rpm. Workpiece positional accuracies of 1 micron linear and ±2 arc-sec are standard and — because these errors are repeatable — software compensation can be used to reduce them by a factor of 10. The company’s machines have a solid foundation made with a sealed granite base that provides physical and thermal stability. Mounted on pneumatic isolators, the base remains protected from external excitation including footfalls, road traffic, and nearby mechanical equipment. In addition, the UPM machines have an axis stiffness as high as 875 N/μ as well as Adaptive Control Technology (ACT), which analyzes feedback, including disturbances. ACT also provides active cancellation (analogous to noise-canceling headsets) that continually 56 MACHINE DESIGN.com  Ultra Precision three-axis diamond turning creates a toric with a sine-wave pattern in brass. Final surface is produced without postpolishing. MAY 10, 2012 56 Access our Reader Service Web site to quickly find and request information on the products and services found in the pages of MACHINE DESIGN. www.machinedesign.com/rsc 2 MACHINE DESIGN.com MAY 10, 2012 MACHINE DESIGN.com 53 C-more operator touch panels offer: D
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'# # www.automationdirect.com/c-more REMOTE ACCESS AND CONTROL BUILT-IN www.automationdirect.com No Additional Hardware required. The C-more Remote Access feature resides in all panels with Ethernet support, and requires no option modules. Access real-time data or initiate an action on a control system from anywhere, any time. (Requires software and firmware version 2.4 or later*, and an Go online or call to get complete information, request your free catalog, or place an order. 1-800-633-0405 Ethernet C-more panel) C-more touch panel line-up: * Software and firmware are downloadable for authorized customers from: www.automationdirect.com 6-inch STN grayscale 6-inch TFT 65,538 colors 8-inch TFT Starting at: Starting at: $1,081 $432 $540 RS# 103 10-inch TFT 12-inch TFT $1,727 $2,051 15-inch TFT $2,484 ON THE COVER Altaeros Energies’ proofof-concept model for an airborne turbine platform. DEPARTMENTS 8 EDITORIAL The wind industry needs more inventors 10 EDITORIAL STAFF 12 LETTERS 16 SCANNING FOR IDEAS Magnetic brake’s microcontroller eliminates cogging and nonlinearity Compact stepper-motor actuator fits the bill 20 26 33 34 REPORTER’S NOTEBOOK LOOKING BACK SENSOR SENSE COMMENTARY Union or not, engineers’ salaries are about the same 36 BERKE ON SAFETY Bad stretching can defeat good design 38 VANTAGE POINT Why aren’t more manufacturers embracing sustainable metalworking? — Doug Watts 40 INVENTOR’S CORNER Lockbox secures software dongles 68 MECHANICAL TECH GUIDE PRODUCTS 72 SOFTWARE REVIEW Merging medical imagery with CAD 82 SOFTWARE PRODUCTS 84 PRODUCT SPOTLIGHT Engineered materials 86 92 93 94 94 95 4 PRODUCTS BUSINESS INDEX AD INDEX CLASSIFIEDS BUSINESS STAFF BACKTALK MACHINE DESIGN.com For customized article reprints and permissions please contact: Penton Reprints, 1-888-858-8851, e-mail at [email protected] or visit pentonreprints.com. Editorial content is indexed in the Applied Science Technology Index, the Engineering Index, SciSearch and Research Alert. Microfilm copies available from National Archive Publishing Company (NAPC), 300 N. Zeeb Rd., P.O. Box 998, Ann Arbor, MI 48106-0998, Ph: 734-302-6500 or 800-420-NAPC (6272), extension 6578. Permission to photocopy is granted for users registered with the Copyright Clearance Center (CCC) Inc. to photocopy any article, with the exception of those for which separate ownership is indicated on the first page of the article, provided that the base fee of $1.25 per copy of the article, plus $.60 per page is paid to CCC, 222 Rosewood Dr., Danvers, MA 01923 (Code No. 0024-9114/12 $1.25 + .60). Subscription Policy: MACHINE DESIGN is circulated to research, development, and design engineers primarily engaged in the design and manufacture of machinery, electrical/electronic equipment, and mechanical equipment. To obtain a complimentary subscription see our Web page at submag.com/sub/ mn. For change of address fill out a new qualification form at submag.com/sub/mn. Printed in U.S.A., Copyright © 2012. Penton Media, Inc. All rights reserved. MACHINE DESIGN (ISSN 0024-9114) is published semimonthly except for a single issue in January, February, June, July, and December by Penton Media, Inc., 9800 Metcalf Ave., Overland Park, KS 66212. Paid subscriptions include issues 1-18. Issue No. 19 (OEM Handbook and Supplier Directory) is available at additional cost. Rates: U.S.: one year, $139; two years, $199;. Canada/Mexico: one year, $159; two years, $239; All other countries: one year, $199; two years, $299. Cost for back issues are U.S. $10.00 per copy plus tax, Canada $15.00 per issue plus tax, and Int’l $20.00 per issue. Product Locator, $50.00 plus tax. Prepaid subscription: Penton Media (MACHINE DESIGN), P.O. Box 2100, Skokie IL 60076-7800. Periodicals Postage Paid at Shawnee Mission, Kans., and at additional mailing offices. Can GST #R126431964. Canadian Post Publications Mail Agreement No.40612608. Canada return address: Pitney Bowes, P.O. Box 25542, London, Ont., N6C 6B2. Digital subscription rates: U.S.: one year, $69; two years, $99;. Canada/Mexico: one year, $79; two years, $119; All other countries: one year, $99; two years, $149. MAY 10, 2012 POSTMASTER: Send change of address notice to Customer Service, MACHINE DESIGN, P.O. Box 2100, Skokie, IL 60076-7800. The Truth About Compressed Air! If you think compressed air is too expensive and noisy - read this. The facts will surprise you! Compare these Blowoffs Facts about Blowers There are a variety of ways to blow the water from the bottles shown in the photo below, but which method is best? To decide, we ran a comparison test on the same application using four different blowoff methods: drilled pipe, flat air nozzles, Super Air Knife (each using compressed air as a power source), and a blower supplied air knife (using an electric motor as a power source). Each system consisted of two twelve inch long air knives. The following comparison proves that the EXAIR Super Air Knife is the best choice for your blowoff, cooling or drying application. Energy conscious plants might think a blower to be a better choice due to its slightly lower electrical consumption compared to a compressor. In reality, a blower is an expensive capital expenditure that requires frequent downtime and costly maintenance of filters, belts and bearings. Here are some important facts: The goal for each of the blowoff choices was to use the least amount of air possible to get the job done (lowest energy and noise level). The compressed air pressure required was 60 PSIG which provided adequate velocity to blow the water off. The blower used had a ten horsepower motor and was a centrifugal type blower at 18,000 RPM. The table at the bottom of the page summarizes the overall performance. Since your actual part may have an odd configuration, holes or sharp edges, we took sound level measurements in free air (no impinging surface). Drilled Pipe Blower Air Knife This common blowoff is very inexpensive and easy to make. For this test, we used (2) drilled pipes, each with (25) 1/16" diameter holes on 1/2" centers. As shown in the test results below, the drilled pipe performed poorly. The initial cost of the drilled pipe is overshadowed by its high energy use. The holes are easily blocked and the noise level is excessive - both of which violate OSHA requirements. Velocity across the entire length was very inconsistent with spikes of air and numerous dead spots. The blower proved to be an expensive, noisy option. As noted below, the purchase price is high. Operating cost was considerably lower than the drilled pipe and flat air nozzle, but was comparable to EXAIR’s Super Air Knife. The large blower with its two 3" (8cm) diameter hoses requires significant mounting space compared to the others. Noise level was high at 90 dBA. There was no option for cycling it on and off to conserve energy like the other blowoffs. Costly bearing and filter maintenance along with downtime were also negative factors. Flat Air Nozzles EXAIR Super Air Knife As shown below, this inexpensive air nozzle was the worst performer. It is available in plastic, aluminum and stainless steel from several manufacturers. The flat air nozzle provides some entrainment, but suffers from many of the same problems as the drilled pipe. Operating cost and noise level are both high. Some manufacturers offer flat air nozzles where the holes can be blocked - an OSHA violation. Velocity was inconsistent with spikes of air. The Super Air Knife did an exceptional job of removing the moisture on one pass due to the uniformity of the laminar airflow. The sound level was extremely low. For this application, energy use was slightly higher than the blower but can be less than the blower if cycling on and off is possible. Safe operation is not an issue since the Super Air Knife can not be deadended. Maintenance costs are low since there are no moving parts to wear out. Filters must be replaced every one to three months. Belts must be replaced every three to six months. Typical bearing replacement is at least once a year at a cost near $1000. G
Blower bearings wear out quickly due to the high speeds (17-20,000 RPM) required to generate effective airflows. G
Poorly designed seals that allow dirt and moisture infiltration and environments above 125°F decrease the one year bearing life. G
Many bearings can not be replaced in the field, resulting in downtime to send the assembly back to the manufacturer. Blowers take up a lot of space and often produce sound levels that exceed OSHA noise level exposure requirements. Air volume and velocity are often difficult to control since mechanical adjustments are required. To discuss an application, contact: EXAIR Corporation 11510 Goldcoast Drive Cincinnati, Ohio 45249-1621 (800) 903-9247 Fax: (513) 671-3363 email: [email protected] www.exair.com/45/423b.htm The Super Air Knife is the low cost way to blowoff, dry, clean and cool. RS# 104 Blowoff Comparison Comp. Air Type of blowoff SLPM Horsepower Required Sound Annual Approx. Annual Purchase Level Electrical Maintenance Price dBA Cost* Cost First Year Cost PSIG BAR SCFM Drilled Pipes 60 4.1 174 4,924 35 91 $50 $4,508 $920 $5,478 Flat Air Nozzles 60 4.1 257 7,273 51 102 $208 $6,569 $1,450 $8,227 Blower Air Knife 3 0.2 N/A N/A 10 90 $5,500 $1,288 $1,500 $8,288 Super Air Knife 60 4.1 55 1,557 11 69 $518 $1,417 $300 $2,235 *Based on national average electricity cost of 8.3 cents per kWh. Annual cost reflects 40 hours per week, 52 weeks per year. What’s new online machinedesign.com FREE WEBCAST: OPTIMIZE MACHINE PERFORMANCE WITH THE LATEST SERVOTUNING TECHNOLOGY May 24, 2012, 2:00 ET This Webinar by Yaskawa will first present some of the latest servotuning technologies, including advance autotuning, vibration suppression, and model following, along with the particular strengths of each. The discussion will then examine how these methods can solve specific application challenges, when one technique is preferred over another, and cases where a combination of techniques provides the best results. Servotuning can help simplify designs, improve throughput and performance, increase component life, and reduce machine commissioning time. Learn more and register at http://machinedesign. com/training. Ball-shaped robot EDITOR’S WEB PICKS Engineers from STMicroelectronics show off the Sphero, a small robot that looks like a baseball. It houses a motor, drive, battery, MEMS sensors and, via Bluetooth, uses an iPad for steering and control. Learn more and watch it roll at www.engineeringtv.com/video/ Fun-Applications-for-STMicroele. 6 Application note on wireless LAN Metric mechanical-drive products A new Agilent application note, “Wireless LAN at 60 GHz,” discusses in detail the proposed IEEE 802.11ad guidelines for devices that would provide up to 7 Gbps throughput using approximately 2 GHz of spectrum at 60 GHz over a short range. It addresses the requirements and challenges of the higher data throughput needed to support today’s “unwired office.” Download a copy at www.agilent.com/find/WLAN. Stock Drive Products/Sterling Instrument’s new D805 Metric Catalog includes detailed specs and information on more than 40,000 drive components, including timing belts, pulleys, clamps, bearings, gearheads, couplings, and vibration mounts, many of which are RoHS compliant. The 1,264-page catalog also contains a comprehensive 233-page technical data section. Download or request a hard copy at www.sdp-si.com/D805/ D805cat.htm. Capping-clutch Web site Warner Electric’s new Web site, www.cappingclutch.com, provides a comprehensive resource for improving bottle-capping operations. The site covers magnetic headsets that provide consistent torque control; fixed, quick connect, and mechanical chucks; and stainless-steel antirotation knives. Content includes product information, design features, brochures, catalogs, application profiles, and video links — covering applications from milk cartons and bottled water to ketchup and motor oil. MACHINE DESIGN.com YouTube training channel Wago Corp.’s new YouTube channel features more than 30 stepby-step training and product support videos that cover a broad spectrum of content on electrical interconnections and automation. Topics range from basic terminalblock marking to commissioning a Bluetooth RF transceiver, remote I/O EtherNet/IP fieldbus, and CoDeSys programming. The videos include instructional text, letting users follow along with their own computer. Access the channel at www.wago.us MAY 10, 2012 UPCOMING WEB EVENTS WATCH PRODUCT OVERVIEW AND TUTORIAL VIDEOS AT YOUR CONVENIENCE AutomationDirect’s YouTube channel features industrial-control product overviews and tutorials. Recent uploads include: Field wirable connectors — Two helpful videos on the components and how to wire them. Temperature controllers — Overview of standalone process/temperature controllers with universal signal inputs. Soft starters — Features of soft starters that can help save energy and increase motor reliability. NFPA pneumatic cylinders — Features and applications for the latest addition to the NITRA pneumatic-cylinder family. For a complete list of videos, visit www.youtube.com/ automationdirect. Become a subscriber and get alerts when new videos are uploaded.
                 
 
          
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   !" RS# 106 EDITORIAL The wind industry needs more inventors Next time your TV viewing habits include watching the Cleveland Indians playing at home, keep an eye out for the ballpark’s newly installed wind turbine. It is an innovative design, but it’s only there because the Indians didn’t have to pay for much of it. Cleveland’s vice president of ballpark operations recently admitted that the club used grants, subsidies, and other spiffs — i.e., other people’s money — to justify the installation. The few kilowatts of power it will generate are an insignificant percentage of what the ballpark consumes. You can’t blame the Indians for taking advantage of “free money.” But the process by which they came to install a wind turbine is a snapshot of the unhealthy situation that characterizes the wind industry: Unless installed by hobbyists, most wind turbines are built only because of subsidies, not because of economic feasibility. Consider the comments of the Texas State Energy Conservation Office a few years ago which conceded, “For wind farms being installed today, the production tax credit is still the main driver of economic viability.” The PTC is a corporate tax credit for several renewable sources, including wind, which credits 2.2¢/kW-hr for electricity generated by wind power. Wind producers have even been known to pay users to take their energy just so they can get the PTC. If there was ever an energy source in need of technological progress to be economically viable, it is wind power. That is why we devoted a few pages in this issue to looking at novel designs for wind turbines. Readers will note none of these ideas come from mainstream wind-turbine manufacturers. Turbine makers today seem to act a little like Detroit automakers of the 1970s and 80s: Despite criticism of their designs, they’d rather push the models already in their brochures than go back to the drawing board to come up with something better. The wind-turbine designs we highlight are products of independent inventors who have noted the many difficulties of commercial wind-turbine architectures. In particular, they have tried to devise ways of fielding wind turbines that are less costly and more reliable than those that occupy wind farms today. A case in point is the wind turbine now adorning the Indians’ home field. Designed by Dr. Majid Rashidi of Cleveland State University, it is a noncommercial prototype that uses a cylindrical structure with a helical shape to deflect wind into small-scale turbines on its sides. This lets Rashidi’s turbines begin turning in light breezes that wouldn’t budge the blades on most other designs. They are essentially noiseless thanks to diffuser rings that reduce the wind currents traveling along the blades. And the design uses inexpensive materials that are easy to find and relatively simple to assemble. Proponents of the wind industry have predicted dire consequences if legislators fail to extend wind’s production tax credit. But their arguments begin to sound like those of automakers and their Armageddon-like pronouncements about CAFE standards decimating their industry. Windturbine makers would be better served listening to some of the inventors who want to make wind power practical without spending other people’s money to subsidize it. — Leland Teschler, Editor RS# 107 MAY 10, 2012 Intelligent fans for smart savings. Most axial fans of the “compact class” use the old shaded-pole motor AC technology, despite its poor efficiency compared to DC technology. The barrier to improvement was that DC technology couldn’t be operated directly from the AC mains supply. A solution is now available with i-Maxx technology from ebm-papst. The i-Maxx retains the mounting dimensions of the equivalent AC fans and is capable of operating on AC mains power around the world. There is no simpler way to save energy. Learn more at info.ebmpapst.us/i-maxx the engineer’s choice RS# 108 Digital Pressure Gauge 3$7 (17 EDITORIAL STAFF (' t

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FODMPTVSF Email: [email protected] www.adsens.net 18310 Bedford Cir., Industry, CA 91744-5971 USA TEL: 626-854-2773 FAX: 626-854-8183 ASSOCIATE EDITOR Robert J. Repas, Jr. [email protected] RS# 109 INDUSTRY COVERAGE We’ve Covered All The Angles -Without Contact AUTOMOTIVE, PACKAGING, MEDICAL Stephen J. Mraz CAD/CAM, MANUFACTURING Leslie Gordon ELECTRICAL, ELECTRONICS Robert J. Repas, Jr. With more than a thousand different series, models, sizes, and options there is a Novotechnik non-contact rotary position sensor to match your application, and there’s one very good reason to choose Novotechnik: A level of precision that’s unmatched in the industry. Whether you’re looking for non-contacting, or even touchless, single-turn, or multi-turn rotary position sensors, Novotechnik has the sensor you need. They are all detailed in our 96-page rotary position sensor catalog. For your free copy, contact Novotechnik. Setting A Higher Standard: • Operating lives to: unlimited movements • Independent linearity to ± 0.3º • Resolution to 0.09º • Repeatability to <0.03% of signal range • Maximum rotating speed to: unlimited rpm • Sealed to protection class IP 69 • Absolute measurements to 360º • Housing diameters from 13 mm FLUID POWER, MECHANICAL Kenneth J. Korane EDITORIAL PRODUCTION Denise Greco Editorial Production Manager Randall L. Rubenking Art Director Novotechnik U.S., Inc. 155 Northboro Road Southborough, MA 01772 Tel: 508-485-2244 • Fax: 508-485-2430 For complete information, visit www.novotechnik.com/ncr 1300 E. 9th St. Cleveland, OH 44114-1503 10 MACHINE DESIGN.com RS# 110 MAY 10, 2012 Lubriplate® %"
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"/2+-' Lubriplate’s Advanced, 100% Synthetic, NSF H-1 Registered Lubricants Include... PGO-FGL Series – Polyalkylene Glycol (PAG)-Based, Synthetic, Helical and Worm Gear Fluids. SFGO Ultra Series – 100% Synthetic, Polyalphaolefin (PAO)-Based, High-Performance, Super Multi-Purpose Fluids For A Variety of Applications Including Gearboxes, Bearings, Pumps, Chains, Hydraulic Systems and Air Compressors. SSO-FG Series – 100% Synthetic Lubricants For Can Closing and Seaming Equipment. SYNXTREME FG-Series – Synthetic, High-Performance, Calcium Sulfonate Complex, Food Machinery Greases. ISO HTCL-FG Series – 100% Synthetic, Ester-Based, Oven Chain Lubricants. ISO 21469 9001 Compliant Registered RS# 111 Backed By: Lubriplate ® ESP Extra Services Package For more information contact Ellen Girard, LUBRIPLATE’s 
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4 Training LETTERS Them kids I graduated from college 30 years ago, and about every two years after that, I read at least one article about college graduates being unprepared for the workforce (“Old Codgers Always Gripe About ‘the Kids,’” March 8). The articles are usually written by academics from places like the Social Science Research Council. But they just want to extract more education funding from the government. If the premise of the articles is true, however, then it is an embarrassment to academia to advertise such poor student preparedness, considering the astronomical salaries and benefits teachers and professors receive. The argument that college graduates are not prepared for the workforce also comes from managers in all industries. When asked about this issue, one discovers that managers expect new hires to jump in and know all the systems and procedures of their company. This is too much to expect from any new hire, especially from recent college graduates. I find that some engineering managers have even higher expectation from new college graduates. They expect them to know and have experience in all advanced manufacturing processes, in addition to being able to jump in and create new designs. As you pointed out, the idea that new college grads are not being properly educated to join the workforce will be around for a long time, along with other myths espoused by academia such as the one that says engineers lose half their knowledge every five years after graduating from college. Twelve of the engineering textbooks that I used in my studies 30 years ago are still in print today. What new laws of physics are new engineers learning, making the old engineers obsolete? Please do not publish such absurd ideas without real proof. G. Harris 12 MACHINE DESIGN.com Kids and baseball: They never change The establishment, to use an old 60s term, is always harping on the college grads, complaining they aren’t as educated or qualified as they themselves were at that age. But one reader points out that the older generation never seems to take responsibility for educating and training those college grads. In another vein, readers agreed with Ken Korane’s satiric plea for Congress to mandate strike-zone-detection technology for major-league baseball. Getting more U. S. engineering jobs As a long-time reader of your magazine, I can remember many variations on one topic being debated repeatedly in your editorials and letters: the deterioration of the labor market in the U. S. for engineers. Anyway you look at the situation, it becomes clear that the root cause of the problem is the loss of manufacturing in the U. S. causing the reduction in demand for materials and services. This trend has been going on for more than two decades, and it is time we admit that globalization is not working for us and will never work in our favor. Most of the calls to level the playing field with tax cuts and incentives are just more smoke and mirrors sponsored by corporations already making billions of dollars despite the deterioration of the take-home pay and standard of living of American engineers and workers in general. There is no silver bullet or a simple solution to decades of failed industrial policies, but a fair-trade policy that protects American jobs is required to stop, or at least slow, the further deterioration of our labor market. Name withheld by request MAY 10, 2012 Quality not quantity I recall having a related discussion with engineering educators about 10 years ago (“Deconstructing Engineering Education,” Leland Teschler’s Blog, Feb. 22). A few years before that, around 1997, many universities essentially junked a full year of engineering curriculum to squeeze in a full year of “design courses.” I asked educators how they managed to still teach the essentials and get it all done in four years of coursework. They said they got rid of overlap by combining parts of classes to eliminate several separate classes. It seems they didn’t see the value in courses that repeated some materials, but in a different approach. Many critics of current engineering education seem to have a single complaint: “Engineering courses are too hard!” But then, they are supposed to be hard. That’s what produces great engineers. Engineers have an awesome responsibility to society; repetition and “hard” are absolutely necessary to produce those great engineers that we need. “More engineers” is not a worthwhile goal, while “the best engineers in the world” is the only goal worth pursuing. Scott Prost-Domasky All the Tools you Need for Embedded Measurements and Control, in one rugged box. Q Graphical Software Q Custom Triggering Q Sensor Connectivity Q Actuator Connectivity Q Signal Analysis Q Embedded Storage Q Control Algorithms Q Industrial Networks Q Custom Timing Q Expansion Systems The NI CompactRIO hardware platform can handle your embedded measurement and control applications, and do it in a way that outperforms other off-the-shelf systems so you don’t have to spend time developing a custom solution. The range of high-quality measurements, coupled with an extremely rugged design and the ability to modify the hardware using NI LabVIEW system design software, gives you all the benefits of customization with the convenience of an off-the-shelf platform. >> To learn more about CompactRIO, visit ni.com/compactRIO 800 891 2755 RS# 112 ©2012 National Instruments. All rights reserved. CompactRIO, LabVIEW, National Instruments, NI, and ni.com are trademarks of National Instruments. Other product and company names listed are trademarks or trade names of their respective companies. 05312 LETTERS One problem with keeping students in engineering is that they do not relate what they are learning in early courses to practical engineering. What is needed is more hands-on experience early in the curriculum to show them the need for what they are learning. Lawrence Mann Strike zone technology and a new pi In reference to your commentary (Mandating Innovation, Feb. 9): I have been advocating the use of modern technology to determine and police the strike zone in major-league baseball. Umps have needed it for many years now. I want to explode when I hear the argument that doing so would remove the “human element” from the game. Only when the players are robots will such a statement be true. Removing hu- man error from calling balls and strikes is long overdue. Frank C. Maffei I recall a small hometown game yea r s a g o w h e n t h e u m p i r e called a strike on my father when the ball bounced off the front edge of the plate. The ump’s argument was that as the ball went by the batter, it was in the strike zone. My father was deep in the batter’s box. As it turned out, the ump had a substantial bet on the game. Maybe umpires could be rigged with cameras so we could all see exactly what they see. Sort of an instant replay. And the ump could review the pitch before making the call. All in all, I don’t support adding high tech to baseball. Over the course of nine innings, it usually all balances out. Carl Junior When I was at Purdue, there was a story making the rounds that the Indiana legislature discussed passing a law that would mandate that pi equal three, since the real value was too hard to remember. Buck I’ve heard rumors the new Corporate Average Fuel Economy (CAFE) mandate will include an antigravity provision that vehicle manufacturers must meet by 2050. Ellen Hellman Correction In the March 22 Looking Back item, “Rough-water power boats,” the sentence “Speed is 20 knots with an 180-hp outboard,” should have read, “Speed is 20 knots with an 18-hp outboard. — Editor RS# 113    
        
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()' RS# 114 SCANNING FOR IDEAS Edited by Stephen J. Mraz Magnetic brake’s microcontroller eliminates cogging and nonlinearity Magnetic brakes have suffered from hysteresis, cogging, and low-power Outer stator output for over 30 years. And they Inner stator have lacked linearity, so users had to more than double the input signal to double the output force of the brake. To solve these problems, engineers at Magnetic Brake Systems, Camarillo, Calif. (www.magbrakesystems. com), designed a new Ball bearings type of magnetic brake. It uses a microcontroller to ensure output torque is linear with input sigCoil nals, regardless of whether the control signal is increasing or decreasing. Shaft The same microcontroller eliminates cogging Vent hole which, on some magnetic brakes, can be as high as 25% of the brake’s maximum torque. The microcontroller ensures that within Drag ring 500 msec after the input signal goes to Impeller zero, cogging disappears — and with no rotation of the brake drag ring. The brakes can exert constant tension instead of constant torque, which is useful for unwinding wire or films from variable-diameter feed rolls. To do this, the microcontroller monitors the radius of the feed roll by measuring dissipate 4,700 W for 10 sec; on a conthe time between pulses created by tinuous basis, it can dissipate 1,700 W Hall-effect devices and magnets on the at 8,000 rpm. The brakes come with feed spindle and metering roller. outside diameters ranging from 1.5 to The brakes use an internal, centrifu12 in., and handle 4,000 to 20,000 rpm. The brakes are powered by a 24-V gal cooling fan and ventilation slots r formation via ou Request free in Web site at power supply. to keep the brakes cool. For example, ice rv Se Reader RS# 401 the MBL-5.5, with a 5.5-in. OD, can m/rsc hinedesign.co ww w.mac 16 MACHINE DESIGN.com MAY 10, 2012 N OW I T H I N K I N 3 D. AND MY DESIGNS JUST KEEP GET TING BET TER. With our Dimension ® 3D Printer, I know my model will represent my idea exactly. And that makes it easier to improve my design with each iteration. Our Dimension is right here in the office, and that helps us get our products to market faster. The Dimension models we create are made in ABS, so they’re also tough and durable. Overall, Dimension gives me an amazing sense of freedom—and creativity. Find out more at www.dimensionprinting.com/macd4 ©2012 Stratasys, Inc. RS# 115 SCANNING FOR IDEAS Compact stepper-motor actuator fills the bill NEMA-17 or 23 stepper motor with preloaded ball bearings Antirotation collar Anodizedaluminum housing Wiper seal Polished stainlesssteel shaft Acme or ball nut with optional antibacklash feature Bidirectional endof-stroke-seal The Digit, a stepper-motor actuator from Ultra Motion, Cutchogue, N. Y. (www.ultramotion.com), is based on an in-line design that couples the motor directly to the leadscrew. This makes for a compact package, one that measures 5.4-in. long when equipped with a NEMA-176 motor and about 6.6-in. long when a NEMA-23 stepper mo- tor is used. Coupling the motor to the leadscrew with an Acme or ball nut gives the actuator more accuracy and a longer life. Repeatability of the Digit is ±0.00004 in., and resolution is 0.00004 in./step. The device can exert up to 400 lb of force and move at up to 15 ips. RS# 402 O-ring seal For another article on Ultra Motion actuators, scan this code or go to http://machinedesign. com/article/modularactuator-meets-flexibledemands-0108 How do you identify the correct tray cables for your next application? ©2012 TURCK RS# 116 askTURCK.com