Tài liệu Machine design, tập 84, số 06, 2012

April 19, 2012 A Penton Media Publication Tune in to EngineeringTV.com ENGINEERING SALARY SURVEY Where do you fit in? page 20 SEALED BEARINGS GO GREEN, page 18 PREDICTIVE MODELING FOR BETTER MANUFACTURABILITY, page 44 WHEN PRECISION BELLOWS OUTPERFORM COIL SPRINGS, page 52 Digital Edition Copyright Notice The content contained in this digital edition (“Digital Material”), as well as its selection and arrangement, is owned by Penton Media, Inc. and its affiliated companies, licensors, and suppliers, and is protected by their respective copyright, trademark and other proprietary rights. Upon payment of the subscription price, if applicable, you are hereby authorized to view, download, copy, and print Digital Material solely for your own personal, non-commercial use, provided that by doing any of the foregoing, you acknowledge that (i) you do not and will not acquire any ownership rights of any kind in the Digital Material or any portion thereof, (ii) you must preserve all copyright and other proprietary notices included in any downloaded Digital Material, and (iii) you must comply in all respects with the use restrictions set forth below and in the Penton Privacy Policy and the Penton Terms of Use (the “Use Restrictions”), each of which is hereby incorporated by reference. Any use not in accordance with, and any failure to comply fully with, the Use Restrictions is expressly prohibited by law, and may result in severe civil and criminal penalties. Violators will be prosecuted to the maximum possible extent. You may not modify, publish, license, transmit (including by way of email, facsimile or other electronic means), transfer, sell, reproduce (including by copying or posting on any network computer), create derivative works from, display, store, or in any way exploit, broadcast, disseminate or distribute, in any format or media of any kind, any of the Digital Material, in whole or in part, without the express prior written consent of Penton Media, Inc. To request content for commercial use or Penton’s approval of any other restricted activity described above, please contact the Reprints Department at (888) 858-8851. Without in any way limiting the foregoing, you may not use spiders, robots, data mining techniques or other automated techniques to catalog, download or otherwise reproduce, store or distribute any Digital Material. NEITHER PENTON NOR ANY THIRD PARTY CONTENT PROVIDER OR THEIR AGENTS SHALL BE LIABLE FOR ANY ACT, DIRECT OR INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF OR ACCESS TO ANY DIGITAL MATERIAL, AND/OR ANY INFORMATION CONTAINED THEREIN. 
 
 

 

   


  
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       VOLUME 84 ISSUE 6 APRIL 19, 2012 FASTENING & JOINING TECHNOLOGY GUIDE ion via our Request free informat Web site at Reader Service esign.com/rsc www.machined Authored by: Paul Hazlitt Metal bellows are used for hermetic seals, volume compensators, pressure and temperature sensors, and flexible connectors in countless applications where dependability and long life are critical requirements. Electrodeposited metal bellows, one version of these products, are a viable alternative to metal springs in a variety of mechanical and electrical devices, improving performance and durability while lowering costs. Here’s a look at how they’re made and used. Electrodeposition process Director of Engineering Servometer Cedar Grove, N. J. Edited by Kenneth J. Korane [email protected] Key points: • Metal bellows are extremely sensitive and responsive. • They can be helium leaktight. Electrodeposited bellows are manufactured by first machining an aluminum mandrel to match the internal geometry of the desired bellows. The mandrel is then plated with layers of metal (typically nickel) to the required thickness. • Metals bellows can be made with infinite fatigue life. Resources: Servometer, www.servometer.com RS# 621 Precision bellows have extremely low spring rates, making them a better option than traditional coil springs in many mechanical and electrical devices. FEATURES The tightly controlled deposition process produces walls as thin as 0.0003 in. The ends of the plated mandrel are scored through the plating to expose the aluminum and define the end trim dimensions. Next, caustic chemicals dissolve the aluminum mandrel, leaving behind the thin metal shell. Finally, finishing operations such as coating and testing complete the manufacturing process. This proprietary electrodeposition process turns out helium-leaktight bellows that are highly sensitive, responsive, and reliable. A bellow’s responsiveness and spring rate are a function of wall thickness. Thus, electrodeposited metal bellows can be produced with low spring rates and, therefore, are capable of significant deflection with a minimal applied force. Couple this with excellent sealing capability yields a bellows that is both sensitive and responsive to changes in pressure. By comparison, springs drawn from standard thickgauge wire require more force to generate the same motion and, by their nature, are not helium leaktight. Rubber and polyurethane bellows are usually quite flexible, but they typically have limited cycle life and sealing capability compared to metal bellows. Mechanically formed (or hydroformed) metal bellows are limited in their minimum wall thickness; they cannot Metal bellows with low spring rates are highly sensitive and responsive. Springs drawn from standard wire require more force to generate the same motion. salaries: staying 20 Engineering ahead of the curve See how you stack up against engineers in other industries and other locales in our annual salary survey. match the thin walls of deposited bellows. As a result, they do not have the same flexibility and responsiveness. Electrodeposited-nickel bellows typically provide just one-fifth to one-tenth the spring rate of hydroformed brass bellows of the same size. The force required to compress them is especially low and stays consistent among bellows of the same size and type. Bellows as spring replacements In electrical devices, springs are commonly used as electrical interfaces for temporary connections. Metal bellows are a reliable alternative to springs in such applications. To increase conductivity, a layer of gold is plated over the bellows to ASTM B488. The actual shape of the bellows is a key factor in the design. Because the signal travels along the walls of the bellows, rather than the circuitous path of a spring, bellows have lower dc resistance, along with minimal self-inductance and insertion loss. This makes bellows well suited for testing electrical circuits. The small size and many available shapes let bellows, acting as electrical contacts, easily pair with through-holes and pads. Soldering the bellows to a probe makes for easier handling during manual testing. For example, a semiconductor-chip maker used a bellows electrical contact to test miniature components as they traveled down an automated production line. The Continued on page 59 Bellows electrical contacts compensate for offsets and vibration when testing electrical components. Metal bellows REPLACE SPRINGS 52 MACHINE DESIGN.com APRIL 19, 2012 APRIL 19, 2012 Our annual survey reveals what irks working engineers and how they feel about their companies and the economy. Precision bellows have extremely low spring rates, making them a better option than traditional coil springs in many mechanical and electrical devices. CAD/CAM What is 46 What is systemsdriven development? SYSTEMSDRIVEN DEVELOPMENT? Building blocks of systems engineering Authored by: Stefan Jockusch Vice President Product Development Mechatronics, Siemens Industry Sector Siemens PLM software Troy, Mich. Edited by Leslie Gordon [email protected] Twitter @LeslieGordon Key points; PLM is the best tool to create a systemsengineering approach for complex products. • Systems engineering involves all stakeholders. • The approach helps eliminate error in complex systems. • The backbone of systems engineering is PLM. Resources: Siemens PLM Software, www.siemens. com/PLM For another feature on “whole-system” design, scan this code or go to: http:// machinedesign. com/article/ engineering-forradical-resourceefficiency-1117 for making 54 Adhesives electrical connections  These are the building blocks of a systemsengineering approach. PLM supports systemdriven product development. Electrically conductive adhesives provide durable bonds with conductive paths to suit a variety of electronics applications. The potential for unintended consequences in today’s complex products makes it increasingly important to tie all aspects of design together. 46 MACHINE DESIGN.com Imagine this scenario: You are driving a brand new luxury car. At a toll station, you accidentally open the rear power window instead of the front window and forget to close it. As the car accelerates, an annoying wind throb can be heard coming from the back. You try to close the window from the driver control but the window doesn’t move. You slow the car down, the throb stops, and suddenly you can close the window. At the dealership, they can’t find anything wrong with the car. This happens to a number of consumers so the issue eventually makes it to the carmaker’s development department. The engineers reproduce the problem and determine the cause: a safety feature, a touchless sensor, prevents the windows from closing when obstructed. This feature is meant to keep kids, who like to put their hands APRIL 19, 2012 46 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 APRIL 19, 2012 53 Metal bellows replace springs 52 glimpse into the 26 Aengineering workplace MACHINE DESIGN.com Whether you need 3-potentiometer simplicity, a high horsepower range, or proven energy saving operation, AutomationDirect has a soft starter series for your applications. 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 ON THE COVER DEPARTMENTS Photo illustration by R. L. Rubenking For customized article reprints and permissions please contact: Penton Reprints, 1-888-858-8851, e-mail at [email protected] or visit pentonreprints.com. 8 EDITORIAL More hiring, less anxiety 10 EDITORIAL STAFF 12 LETTERS 16 SCANNING FOR IDEAS Roller-screw actuators use almost any motor Sealed bearing cartridges are green and can handle the load 20 REPORTER’S NOTEBOOK 34 LOOKING BACK 40 COMMENTARY Form should follow function, and more 42 INDUSTRIAL DESIGN “Speaking” design 44 OEM SERVICES Predictive modeling can help manufacturers 60 FASTENING & JOINING PRODUCTS 64 ORR ON ENGINEERING Seven ways to improve your inner engineering game 66 SOFTWARE PRODUCTS 68 PRODUCT SPOTLIGHT Controls & drives 70 80 83 85 86 87 PRODUCTS DATA FILES AD INDEX BUSINESS INDEX BUSINESS STAFF BACKTALK 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. 4 MACHINE DESIGN.com APRIL 19, 2012 POSTMASTER: Send change of address notice to Customer Service, MACHINE DESIGN, P.O. Box 2100, Skokie, IL 60076-7800. Solutions you can trust. Brands you can trust. Rex® Falk® Link-Belt® Thomas® TableTop® Rexnord solutions are not just about a transaction. To support your business, Rexnord delivers what’s needed to run a successful operation, including: t
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Installation, testing, maintenance and repair What’s new online machinedesign.com FREE WEBCAST: STRUCTURAL THERMOSET COMPOUNDS  TECHNOLOGY AND APPLICATIONS THURSDAY, APRIL 26, 2012, 2:00 EDT This detailed presentation will cover hybrid resins and glass reinforcements used for molding compounds that are specifically designed for high-performance industrial applications. IDI Composites International presents information on resin formulations and thermoset compound manufacturing; Owens Corning discusses fiberglass-reinforcement technology. Learn more and register at http://machinedesign.com/training. Hot products from Design West Engineering TV highlights the hottest new products from DESIGN West 2012, including the BeagleBone from Texas Instruments, the FSLBOT robot from Freescale, and the LabView Robotics Starter Kit from National Instruments. View the video at www.engineeringtv.com/video/DESIGN-West-2012Showcase-03;Only-Engineering-TV-Videos. Motor sizing tool Medical-applications site Oriental Motor has a new online tool for sizing motors. Users supply parameters such as the basic type of application, loads, friction coefficients, ball/leadscrew size, factors related to transmission belts and pulleys, and device orientation. The program then calculates torque, speed, stopping accuracy, and system inertia. Find it at www.orientalmotor.com. Mouser Electronics has launched its new Medical Applications training site to help design engineers keep up to date on medical electronics, regulatory considerations, and medical-design trends. It highlights devices ranging from telehealth monitors and digital stethoscopes to infusion pumps and pulse oximeters. It also includes videos and design guides. Learn more at www.mouser.com/medical. EDITOR’S WEB PICKS Plastics awards 6 The Society of Plastics Engineers is taking nominations for its annual Automotive Innovation Awards. It recognizes technical achievements by vehicle engineers, as well as innovative parts that provide benefits such as reducing weight and cost or increasing safety. Learn more at http:// speautomotive.com/inno. FEA and motor efficiency Cobham Technical Services has a new Web site (www. motor-design-software.com) that helps engineers understand how FEA can improve motor performance and efficiency. It explains the basics of electromagnetic FEA software and covers topics such as magnetic gearing and linear motion. Machine-safety book The updated Fluid Power Safety for Machine Guarding book is available from Ross Controls. The book reflects the latest safety standards such as ANSI B11.0-2010, ANSI/PMMI B155.1-2010, and ANSI B11.19-2010, and also covers a wide range of important safety issues, such as risk assessment, control integrity, and press counterbalance. Download or order a free hard copy at www.rosscontrols.com. MACHINE DESIGN.com APRIL 19, 2012 Innovation award The German Engineering Federation (VDMA) and Messe München International will recognize forward-looking technology with the bauma Innovation Award. Categories include machinery, components, research, and design. Deadline for entries is August 31, and winners will be announced at next year’s bauma trade fair for construction and mining equipment. Learn more at www.baumainnovation-award.com. Energy-savings calculator Colfax Fluid Handling has a new online Energy Savings Calculator for oil and gas-industry pump applications. The calculator, found at www.colfaxcorp. com/oil-gas, permits head-to-head comparisons between centrifugal and rotary positivedisplacement pumps in both single and multipump applications. Users supply flow, pressure, viscosity, electricity costs, and pump type and efficiency, and the program projects annualized energy cost savings. Technology by THE INNOVATORS (IÀFLHQW $XWRPDWLRQ ` Increased precision and quality through synchronization and real-time capabilities ` Reduced costs through scalability and design freedom – PC-based or embedded ` Investment security through openness and full compatibility ` Increased productivity throughout the entire life cycle through intelligent service and diagnostic functions ` Space-savings through compact systems and decentralized topologies RS# 105 Perfection in Automation www.br-automation.com EDITORIAL More hiring, less anxiety Newswire headlines scream that hiring is back in a big way on college campuses. So for our annual salary-survey issue, it seems appropriate to check out this thesis for new engineering grads. The schools we talked to report that prospects for engineers joining the workforce are indeed brighter than they have been in recent years, though some engineering disciplines are in hotter demand than others. “We have seen a 20% increase in on-campus job interviews from last year,” says Georgia Tech Career Services Director Ralph Mobley. “In 2011, 64.2% of our engineering graduates said they had a job lined up by our May commencement. It is a little early to tell how that will go this year, but I think we will beat that figure based on interview activity.” But more hiring hasn’t yet translated into bigger paychecks. “My overall sense is that salaries aren’t going up,” says Mobley. “The median salary in 2011 was $63,000. Though, if we have another year like this one, that figure is likely to rise.” Mobley also says disciplines in the highest demand at Georgia Tech include chemical engineering, computer engineering, and computer science. At the University of Texas at Austin, getting hired hasn’t been a problem for most new engineers even during the economic downturn, but most couldn’t afford to be choosy about employment. “Our low point for recruiting was during 2009 and 2010, but even then, our students were accommodated at about a 90% rate. They just didn’t have as many offers,” says U of T at Austin Career Center Director Michael Powell. “Last year recruiting went up about 20% across the board and students got more opportunities for full-time employment and internships. This year is similar, though the increase in recruiting visits isn’t as large.” Powell says more than 94% of U of T at Austin engineering grads who wanted employment had found jobs six months after graduation last year, and he expects that percentage to rise a bit for the school’s 1,400 newly graduated engineers this year. Finally, interesting statistics emerge from U of T at Austin’s tally of starting salaries for its 2010-11 graduates. The top earner was someone with an MS in engineering management who walked away with a salary of $150,000. The lowest was $38,000 for a postdoc position that went to a biomedical Ph.D. There was a tie for the highest BS-level salary: It was $105,000, earned by both an electrical engineer and a petroleum engineer. A confirmation that these sorts of salaries aren’t out of the ordinary comes from Cornell University College of Engineering Career Services Mark Savage. “Computer-science majors can walk away with multiple offers,” he says. “A few have gotten six-figure salaries. On average, those graduates probably earn $15,000 more than those in other engineering areas.” All in all, only 2% of Cornell’s 2011 graduating class of engineers (about 1,500) who wanted jobs were still looking six months after graduation. Savage calls hiring in the mechanical-engineering area “stable.” But he thinks hiring is “lagging” in civil engineering because many civil-engineering projects get funded by states, and many states have no money. “I think it will come back eventually because of infrastructure needs,” he says. But all things considered, “We are not seeing a lot of hiring anxiety among students,” he says. “It’s certainly nothing like what it was in 2009.” — Leland Teschler, Editor RS# 106 APRIL 19, 2012 RS# 107 EDITORIAL STAFF EDITOR Leland E. Teschler [email protected] MANAGING EDITOR Does your gear drive mesh properly? Not all do. MITRPAK drives are precision made. You can feel the difference. MITRPAK features include: • Stainless steel shafts • Double-shielded ball bearings • Factory optimized gear mesh • Hardened spiral • Adjustable locknuts in place of • Completely sealed bevel gears spacers and retaining rings • Lubricated for life U.S. and metric right angle, three-way, and counter-rotating gear drives in stock and guaranteed to ship in 24 hours. For complete specifications and CAD files, log onto www.mitrpak.com, or call toll free, 800-648-7725. Kenneth J. Korane [email protected] SENIOR EDITORS Leslie Gordon [email protected] Stephen J. Mraz [email protected] ASSOCIATE EDITOR MITRPAK Power Transmission Products 38 River Road, Uxbridge, MA 01569 Tel: 508-278-2422 • Fax: 800-346-0018 • 800-648-7725 www.mitrpak.com Robert J. Repas, Jr. [email protected] RS# 108 INDUSTRY COVERAGE For An Angle Sensor That Works Around Your Application… Rotary angle measurement just got better. With Novotechnik’s RFA4000 Series touchless position sensor you can measure through air or through non-magnetic materials. Just attach a magnetic pick-up to your rotating application and mount the sensor nearby. AUTOMOTIVE, PACKAGING, MEDICAL Stephen J. Mraz CAD/CAM, MANUFACTURING Leslie Gordon Go Touchless. ELECTRICAL, ELECTRONICS Robert J. Repas, Jr. FLUID POWER, MECHANICAL Kenneth J. Korane RFA4000 Series sensors are extremely thin and compact with dimensions of 30x30x7 mm. The sensors are fully encapsulated for operation in tough environments. EDITORIAL PRODUCTION Other specifications include: • Electrical measurement range to 360° • Unlimited mechanical life • Update rate of 5,000 measurements/s • Repeatability of 0.1° • 12-bit resolution • Independent linearity to ±0.5% • Single and redundant versions Denise Greco Editorial Production Manager Randall L. Rubenking Art Director For complete RFA4000 information, visit www.novotechnik.com/rfa Novotechnik U.S., Inc. 155 Northboro Road • Southborough, MA 01772 Telephone: 508-485-2244 Fax: 508-485-2430 10 MACHINE DESIGN.com RS# 109 APRIL 19, 2012 1300 E. 9th St. Cleveland, OH 44114-1503 PELICAN TM TRUST YOUR TECHNOLOGY TO OURS Mission Critical Custom Case Engineering Harnessing our global resources, Pelican-Hardigg Advanced Case Solutions™ develops custom case solutions using a multidisciplinary process under the industry’s most experienced project management team. Driven by your product’s specifications, usage and environmental analysis, these custom case solutions can provide you with the highest level of Mission Critical confidence in the field – guaranteed. RS# 110 www.pelicanoem.com/md PELICAN PRODUCTS , INC. 23215 Early Avenue, Torrance, CA 90505 866.628.9890 (TOLL FREE) Q 310.326.4700 Q FAX 310.326.3311 All trademarks are registered and/or unregistered trademarks of Pelican Products, Inc., its subsidiaries and/or affiliates. LETTERS Thanks, but no to unions The recent commentary (“Time for Engineers to Think About Unionizing?” Jan. 19) is right about one thing; engineers do have a reputation for individualism and shy away from unions. But do unions offer better pay and benefits? For the most part, they do. However, I look at unions as placing a cap on my earnings. I can produce results and earn a higher wage in a nonunion company. Also, as a former union employee (U. S. Steel Workers), I was unable to perform even the easiest multitasking job. I could only do one thing at a time, which was inefficient and boring to say the least. This was not an option for someone who likes to create. In my position today within a large organization of 25,000 employee’s worldwide, I feel like an entrepreneur as I can respond to various situations without fearing reprisal from colleagues concerned only with job preservation and working at a minimal pace. Besides, unions are notorious for protecting less-thanqualified or derelic t workers simply because they are union members. I’ll take my chances in the nonunion masses any day and protect my hard-earned money from being used by union management to support their wealthy lifestyle and political interests that are not always in tune with the average union worker. Unions are a racket, just like a ny o t h e r o rg a n i z a t i o n w i t h power. They want to preserve the power within their small group of people. They are not necessarily looking out for the workers as they should be. Mike Zupkofska Odd job interview If I caught one of my managers asking those type of questions (“How to Ace an Engineering Job Interview,” Jan. 19), I would escort them to the door. If you want to 12 MACHINE DESIGN.com Unions, interviews, and worker shortages Readers don’t like unions, don’t care for off-target questions during job interviews, and don’t fully believe there’s a shortage of engineers or skilled workers in the U. S. Those readers who do agree that the U. S. lacks skilled workers, point the finger at companies that refuse to do any employee training or pay commensurate wages and an education system that tries to get everyone into college. see how an employee performs, give them the rundown on a current problem you are facing and see how they approach it. Make sure to emphasize that there are no right or wrong answers. Watch them and talk to them, periodically picking their brain, while they work out a solution. This will give you a glimpse into their capacity to think, their creativity, aptitude in working with your company ’s product, and their temperament. Plus, I always walk away from such interviews having learned something new. L.A. Margagliano M a ny ye a r s a g o, I w a s i n te r viewed by a HR type who seemed to me to be smug and pompous. He asked if I was a plodder. I told him that if I were a plodder, I would have gone into human resources. I didn’t get the job. David Hunt It seems the only purpose such questions fulfill is to take a measure of just how many stupid, asinine, and totally irrelevant-toactual performance questions a candidate is willing to tolerate. This can be a useful skill as an engineer. Paul Richter APRIL 19, 2012 No skilled U. S. workers and engineers? The lack of qualified engineers and designers has nothing to do with academics (“Why does the U. S. lack skilled workers?” Blog entry). U. S. manufacturer’s don’t pay and education costs are rivaling the housing bubble. Hence, the cream of the crop use their engineering degrees to work on Wall Street where they can make a living wage. Want proof, you say? At my company, there are newly minted MIT graduate engineers who are forced to share a two-bedroom apartment among three renters. Lawrence Margagliano I used to think the dumbingdown of public-school systems was a result of misguided but good intentions. But things are becoming so bad you have to wonder if it isn’t intentional. The biggest threat to a king’s power is not posed by other kings, but rather his subjects becoming fit to rule themselves. Perhaps this is all a ploy to mitigate the threat that an educated and capable (i.e., independent and criticalthinking) pubic pose to those who want to rule them. I doubt it is really intended to dumb ev- One Cable to Rule Them All! 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XXXDJDPJMDPN LETTERS eryone down, but it does make you wonder if there isn’t a grain of truth in there somewhere. Mark Willis As a former teacher, it seems to me that what we in the U. S. need to learn is that it’s a waste of time and energy to try to turn all highschool students into college students. Instead, we need to take a more European approach in which high schoolers are put into tracks based on their capabilities, aptitudes, and desires. That way, some go to college and others pursue vocational training. Each student gets what they need to be successful and will be ready to enter the workforce. And don’t forget those in jobs using vo-tech skills can earn just as much or more than those with jobs requiring college degrees. Just look at teachers compared to plumbers or electricians. The problem with our current system is that the schools try to prepare ever yone for college. The fact is that on average only 10 to 20% of high-school grads continue on to college, and only 10% of those make it through college. In other words, our current system works for 1 to 2% of the students. You would think someone, especially educators, would realize this and change it. Another contributing problem is that most current high schools don’t teach basic personal-finance skills. Guess what the number one reason is for quitting college? Finances. Erika E. You’ve taken a corporate manager ’s statement about a lack of skilled workers as gospel and ran with it. Perhaps you could investigate if a “shortage” actually exists. Our firm gets over 600 qualified applicants every time we have an entry-level apprenticeship opening, absolutely unheard of ever before. And the part-time worker at Home Depot that sells me conduit fittings is a mechanical engineer with 18 years experience. (His previous company shut down its U. S. operations.) Unemployment is at record highs. There appears to be little evidence indicating a lack of skilled U. S. workers, but plenty of evidence pointing to a cover story trying to justify giving U. S. jobs to other countries. Perhaps, as one previous letter writer said, the problem developed when pure greed and ambition re placed skill, responsibility and plain old common sense as job requirements for managers and corporate bigwigs. Barb Daniels Aerotech Motion Controllers Deliver: High Performance Motion Composer Advanced controls for superior contouring, in-position stability, move and settle, and velocity control Reduced Setup Time Integrated calculators and extensive diagnostics Automation 3200 Ease of Use PLC Soloist One software environment: .NET, C, G code, LabVIEW® or AeroBasic™ Industries Ensemble Automation, Data Acquisition, Fieldbus, Vision and PLC Laser processing Target tracking Stencil cutting Beam steering Wire bonding Dispensing Stent manufacturing Packaging Grinding Case erectors Sensor testing Web applications Dedicated to the Science of Motion Aerotech, Inc., 101 Zeta Drive, Pittsburgh, PA 15238 Ph: 412-963-7470 • Fax: 412-963-7459 • Email: [email protected] www.aerotech.com AH0510H_CSG RS# 112 14 MACHINE DESIGN.com APRIL 19, 2012 Aerotech Worldwide United States • Germany • United Kingdom • Japan • China • Taiwan • France A n atomy of the HUCK BOBTAIL ® Strength is in its DNA. Engineered for the maximum level of reliability, the BobTail® HuckBolt® offers 5 to 10 times the fatigue strength of conventional nuts and bolts. Its shallow thread and large root radius increase fatigue strength. And full metal-tometal contact between the collar wall and the bolt threads eliminates the gap that you find with ordinary nuts and bolts; the kind of gap that can lead to loosening under vibration intensive conditions. Ultimate strength and vibration resistance. It’s engineered into every BobTail HuckBolt. FULL METAL-TO-METAL CONTACT ELIMINATES GAPS TRANSVERSE VIBRATION COMPARISON CLAMP (LBF-THOUSANDS) 25 Once vibration begins, clamp load quickly decays with nuts and bolts, while it holds constant with the BobTail . 20 BOBTAIL 15 10 NUT 5 0 0 50 AND 100 time (SECONDS) ® afsindustrial.com/bobtail 800-388-4825 RS# 113 BOLT 150 200 250 SCANNING FOR IDEAS Edited by Stephen J. Mraz Roller-screw actuators use almost any motor Provisions to mount any motor NPT ports The new K Series actuators from Exlar, Chanhassen, Minn. (www.exlar.com), mount to most types of motor and are available in several configurations and price points. They also have dimensions and form factors consistent with ISO metric pneumatic cylinders, so they make good replacements for air cylinders, as well as hydraulic ones. The actuators’ corrosion-resistant, anodized aluminum housings are sealed to provide IP65 protection. The units operate in temperatures up to 175°F. The standard rod is nickel-plated steel with a 304 SS rodend insert, which reportedly gives the rod excellent wear characteristics. Mounting options include front and rear flange, rear clevis and eye, adjustable side trunnion, end angles, and foot mounts. For roller screw versions, the maximum rated input is 5,000 rpm, with speeds ranging from 9.8 to 32.8 ips. The maximum allowable force ranges from 675 to 1,800 lb-in. There are four levels in the K Series. The KT Series is for high loads and cycle rates. The KX Series provides high performance in a range of demanding applications. The KM Series, like KT and KX Series, use roller screws, but the KM actuators are the most economical of the roller-screw actuators. The KA Series use an Acme screw and works well in applications that position and hold a load. RS# 401 16 MACHINE DESIGN.com APRIL 19, 2012 Limit switch can be mounted on any side Sealed output rod Several rod ends are available Roller screw Belt and pulley drive with built-in tensioner or in-line mount available r formation via ou Request free in Web site at ice rv Se er Read c design.com/rs ww w.machine Standard cylinder mounts and T-slots for adding mounting attachments on all sides

    
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