Tài liệu Machine design, tập 84, số 18, 2012

November 22, 2012 A Penton Media Publication Tune in to EngineeringTV.com Reengineering the SNOWMOBILE page 34 HANDLING EMI WITH INDUSTRIAL FIBER OPTICS, page 38 ENERGY-EFFICIENT CASTINGS, page 42 BETTER HEAT SINKS WITH MULTIPHYSICS, page 45 APPLIANCE WIRE GETS A ROLE IN MACHINE BUILDING, page 48 RS# 101 RS# 102 TAILORED. AVNET SOLUTIONS MEET YOUR UNIQUE NEEDS From big to small – we do it all. Even big products begin small, with millions of sizes in between. We see them all. Here at Avnet, no order is too small. Avnet provides products and services to match your needs. No matter the location; whether you are in the new product introduction phase or extending a product’s life. If you need design support, or supply chain assistance – we’re here to help. With Avnet, you determine the scale of interaction – or complexity – and we will support you every step of the way, so it’s a perfect fit! What can we do for you? www.avnetexpress.com Accelerating Your Success!™ 1 800 332 8638 | www.avnetexpress.com | @avnetdesignwire VOLUME 84 ISSUE 18 NOVEMBER 22, 2012 ELECTRICAL/ELECTRONIC TECHNOLOGY GUIDE Safety standard gives Appliance wire is back, but regulations may limit its use. AWM and NFPA compliance APPLIANCE WIRE a new lease on life High-end AWM-style cables are making a comeback in machine wiring providing over 20 years of reliable performance. FEATURES Authored by: Rick Orsini Senior product manager Lapp USA Florham Park, N. J. Edited by Robert Repas [email protected] Key points: • NFPA-79 outlines electrical standards for industrial machinery to protect operators, equipment, and facilities from fire and electrical hazards. • Banned in 2007, AWM may now be used in machine wiring, restrictions permitting. 34 • New permissions may let MTW products that carry a UL TC-ER listing slash installation costs, even over AWM. Rethinking the snowmobile Resources: NFPA 79 Standard, bit.ly/Rbblbv UL Wire and cable flammability testing, bit. ly/TxHTv2 economics for 38 Better industrial fiber optics Plastic optic fiber is a better option than copper wiring for applications plagued by electrical noise. with quartz 42 Casting The casting of synthetic-quartzcomposite mixtures to tolerance uses less energy than casting iron. For a white paper on the NFPA 79 electrical code, scan this code or go to: http://machinedesign. com/whitepaper/ understanding-theelectrical-code-to-becompliant-0501 48 MACHINE DESIGN.com Appliance wire OK’d The key change to NFPA-79 for 2012 involves the ability to use appliance wiring material (AWM), which had been banned since 2007. AWM can be an economical wiring choice compared to higher-performing UL-listed machinetool wire (MTW). But there were several sound reasons behind the AWM ban. For one, some contractors were using AWM incorrectly as part of the building infrastructure. The NEC does not recognize AWM for this type of use. Also, not all AWM products are created equal when it comes to the quality of their insulation layer. The insulation thickness of low-quality commodity cabling varied such that the wire, while meeting its electrical insulation requirements, was not sufficiently flame resistant for use in industrial machines. It’s important to stress that not all AWM suffers from these quality issues. Lapp and other reputable cable manufacturers can and do produce AWM products whose insulation wall thickness is both consistent and adequate for the voltage rating of the cable. High-quality AWM can pass the specified vertical flame tests (FT 1) and can safely be used in industrial machines. Keep in mind, however, that AWM lacks the extra layers of PVC-nylon insulation found in Lapp USA, www.lappusa.com Technology borrowed from motorcycles, snowmobiles, mountain bikes, and snowboards leads to a lighter, more-nimble Personal Snow Vehicle. If you find electrical safety standards confusing, you’re not alone. Many machine builders recently grappled with an ambiguous round of changes to NFPA-79. This is the National Fire Protection Association code that outlines electrical standards for industrial machinery that protects operators, equipment, and facilities from fire and electrical hazards. NFPA-79 is cited extensively in the National Electrical Code (NEC) that governs the electrical wiring of industrial machines. The standard cuts a broad swath across the industrial machinery landscape. It applies to a comprehensive range of machines — everything from machine tools and injection-molding presses to testing machines and packaging lines. It encompasses all of a machine’s electrical and electronic elements operating at 600 V or less. This means that a vast majority of machine power, control, and lighting circuits fall under the scope of NFPA-79. Machine builders complied with the dictates of NFPA-79 for years. But earlier this year the standard underwent revisions that make it more difficult to specify compliant electrical cabling. NOVEMBER 22, 2012 A Krones technician documents the use of AWM in compliance with NFPA-79. One company successfully navigating the shoals of the recent NFPA-79 revisions is Krones Inc., Franklin, Wis., a manufacturer and integrator of packaging lines for food and beverage companies. The company’s engineering team recently found that compliant AWM usage does require a bit of extra effort compared to the automatic compliance found with UL-listed MTW. “Whenever you must implement changes because of an electrical-code change, there’s definitely an engineering-labor factor,” says Mike Nelson, the Krones engineer charged with NFPA-79 compliance. Some of that engineering labor went into researching specific AWM products to see whether they meet the compliance restrictions. Even proper jacket labeling doesn’t answer every compliance question regarding AWM. “You can’t tell whether a product complies just by looking at the cable,” says Nelson. And even more engineering labor went to NFPA-79’s documentation requirements. In all, Nelson estimates that Krones has spent more than 150 engineering man-hours complying with the requirements related to AWM use. And that figure represents just the work done to formulate a compliance strategy. It does not include the technical documentation and drawing changes needed to incorporate the wire into each and every machine. NFPA restrictions. In the case of extremely large machines MTW. This extra insulation allows some types of MTW to such as bottling lines, machine builders and installation pass flame tests (FT 4) more rigorous than those for even contractors can spend dozens of engineering hours and the best AWM. thousands of dollars complying with the documentation Reversing the AWM ban reflected the realities of the requirements. global machinery marketplace in which AWM remains a These documentation needs, while not insurmountwidely used cabling choice. The restrictions imposed by able, must be factored into the cost of wiring the machine. the new NFPA standard attempts to negate the potential In some cases, the added documentation costs can erode drawbacks of AWM. the minor price advantages of some AWM cables. The first restriction states that the AWM must be idenOne way around the concern of documentation is to tified as suitable for the application at hand and must be favor listed MTW. Because it inherently complies with used in accordance with the machine-manufacturer’s inNFPA-79, MTW cabling alleviates the documentation structions. Other restrictions detail cable construction inrequirement and eliminates any residual confusion over cluding minimum conductor count, flame resistance, and whether a given AWM product is approved and properly wall thickness. Compliant AWM cable must carry a jacket labeled. MTW also has a host of technical advantages that print legend that spells out the AWM style number, voltderive from its superior flexibility and resistance to flame, age, temperature rating, and flame rating. The reversal on AWM usage also requires more documentation. For exampl e, m anu f a c tu re rs Certain UL-listed cables meet exposed Another change in the 2012 NFPAmust provide field-instalrun (-ER) specifications, which provide an 79 standard allows exposed cable runs lation information related additional level of protection for these along the structure of the equipment or to the AWM wire with types of applications. Cables meeting -ER in the machine chassis. As long as the exeach machine’s technical requirements are subjected to the same posed cables closely follow the surface documentation. Exposed cable runs for fast installation Easy compliance Given all the cable runs on and around today’s complex industrial machines, the need to do cument AWM usage for each and every machine represents the most onerous of all the and structural members of the machine, the installation does not require conduit, raceways, or any special hardware. Thanks to reductions in installation time and labor, exposed cable runs can reduce costs dramatically compared to traditional installation methods that need conduit or special mounting hardware. crush and impact tests as armored-type or metal-clad (MC) cables, that lets cables leave the machine area and enter a cable tray without conduit. Keep in mind, though, that not all ULlisted cables meet NFPA requirements, especially lower-priced commodity and rigid products. NOVEMBER 22, 2012 48 Safety standard gives appliance wire a new lease on life CAD/CAM/CAE/FEA builds a better heat sink How Toyota designed a small, efficient heat sink to cool electronic components in its future hybrid vehicles Multiphysics software builds a better heat sink Authored by: Ercan (Eric) Dede Principal Scientist Toyota Research Institute of North America Ann Arbor, Mich. Edited by Leslie Gordon [email protected], Twitter @ LeslieGordon • Engineers designed a smaller and moreefficient heat sink to thermally regulate the electronic components in future Toyota hybrid vehicles. • Numeric simulations generated an optimal cooling channel topology with fluid streamlines in branching channels. • The dual configuration prototype provided higher-performance cooling in an ultracompact package. Resources: Toyota Research Institute of North America, http://tinyurl.com/8kdkq3r It’s no secret that These carmakers are under isometric a lot of pressure to reduce views show the the number, size, and weight of derived hierarchical engine components for better fuel microchannel cold plate economy. In one case, we were tasked with without a jet plate (top) designing a smaller and more-efficient heat and with a jet plate shown transparent for sink to thermally regulate the electronic clarity (bottom). components in Toyota hybrid vehicles. Instead of using typical analytical design methods and trial-and-error physical prototyping, we first used multiphysics software to design and test possible prototypes. Hot under the hood Toyota hybrid vehicles have sophisticated electrical systems in which many power diodes and power semiconductors — such as insulated-gate bipolar transistors — handle power conversion and other applications. These components are standard planar silicon devices measuring a few centimeters on each side. The devices mount on aluminum heat sinks, or cold plates, with channels in which a water-andNOVEMBER 22, 2012 MACHINE DESIGN.com Toyota used multiphysics software to build a better heat sink for its future hybrid vehicles. 45 45 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 MACHINE DESIGN.com NOVEMBER 22, 2012 49 Appliance wiring material, banned in 2007, is now back in service owing to the realities of today’s global machine marketplace. But, its use comes with restrictions. MULTIPHYSICS SOFTWARE Key Points: 2 MACHINE DESIGN.com    ... with 1-ft. cable and 4-wire locking connector SureStep stepping systems provide simple and accurate control of position and speed where open-loop control and cost are considerations. Pulses (or "step" and "direction" signals) from Do-more PLCs, DirectLOGIC PLCs, or other indexers and motion controllers are "translated" by the microstepping drive into precise movement of the stepping motor shaft. The SureStep stepping motors use 2-phase technology with 200 full steps per revolution or 1.8° per full step.  • • • • • • Available in single-shaft and dual-shaft models, starting at $18 Square frame step motor style produces high torque 2-phase bipolar, 4-lead 1.8° per step, 200 Steps per Revolution www.automationdirect.com Standard NEMA Sizes (17, 23, & 34) Go online or call to get complete information, CE Compliant - EN55014-1 (1993) & EN60034-1.5.11 request your free catalog, or place an order. 1-800-633-0405    The SureStep family of motion products also includes microstepping drives with free configuration software, power supplies and cables, all at direct prices that can get you a 1-axis system for as little as $330.50, and 2 axes for just $541. Visit www.automationdirect.com/stepper-systems for specifications and prices. Microstepping Drives Step Motor Power Supplies NEMA Single-Shaft Step Motors Step Motor Extension Cables RS# 103 ON THE COVER DEPARTMENTS An SR-85 Snow Runner from Sierra Snow 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 Silliness at 40 below 10 EDITORIAL STAFF 12 LETTERS 16 SCANNING FOR IDEAS Spindle drive moves with accuracy Filter vent equalizes pressure inside and out 20 REPORTER’S NOTEBOOK 26 LOOKING BACK 33 COMMENTARY What’s up with model-based engineering? 51 ORR ON ENGINEERING The death of e-mail? 52 SOFTWARE REVIEW SolidWorks 2013 makes 3D modeling easier 54 PRODUCT SPOTLIGHT Adhesives & fasteners 56 PRODUCTS Editorial content is indexed in the Applied Science Technology Index, the Engineering Index, SciSearch and Research Alert. 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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. 58 DATA FILES 60 BUSINESS INDEX 61 AD INDEX 62 BUSINESS STAFF 63 BACKTALK 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 NOVEMBER 22, 2012 POSTMASTER: Send change of address notice to Customer Service, MACHINE DESIGN, P.O. Box 2100, Skokie, IL 60076-7800. You Have Big Ideas We Have a Big Catalog 2013 Allied Catalog Over 110,000 products | Over 10,000 new products | Over 300 world-class suppliers New suppliers include Siemens Corporation and FLIR Commercial Systems RS# 104 1.800.433.5700 © Allied Electronics, Inc 2012. ‘Allied Electronics’ and the Allied Electronics logo are trademarks of Allied Electronics, Inc. An Electrocomponents Company. What’s new online machinedesign.com NEW EBOOKS Smart machines: Delivering intelligent maintenance capabilities Rapid technological innovation, demand for customized products, and requirements for more reliably maintained systems are spurring the rise of smart machines. This eBook from National Instruments discusses the different approaches used to track and maintain machine health. New technology for control-panel design This eBook from Eaton offers insights on how to simplify control panel wiring and design. Topics include an overview of traditional panel design; key industry standards; protocols used in industrial networks; and how the SmartWire-DT system speeds commissioning of next-generation machines and control panels. Download these eBooks at http://machinedesign.com/ebook. Simple, low-cost robot The CEO of Rethink Robotics gives an overview of the Baxter robotic platform. The inexpensive, easy-to-use robot is designed for small manufacturers who do short production runs of many different parts. It can be programmed by shop-floor workers and offers humanlike speed, precision, and strength. Learn more at www. engineeringtv.com/video/The-Baxter-RoboticPlatform-for;Only-Engineering-TV-Videos. Selecting potting compounds Electronic and electrical equipment needs potting compound to secure, protect, and insulate components. A Fabrico site, www.fabrico.com/markets-electricalequipment.htm, looks at considerations for evaluating potting materials, including device characteristics, environment, adhesive cure time and expansion rates, and overall costs. It also discusses benefits of materials such as epoxy, polyester, urethane, and silicone. EDITOR’S WEB PICKS Actuator-sizing software 6 A new online sizing program from Tolomatic helps engineers design and specify electric actuators based on motion requirements like length, velocity, and acceleration, as well as orientation, loads, and applied forces. It also lets users select a motor based on parameters such as continuous/peak torque and speed, and add features to the actuator like mounts and switches. It’s compatible with PCs, tablets, and smartphones. Learn more at http://sizeit.tolomatic.com. Oil-cleanliness booklet More than 75% of all hydraulics problems can be linked to dirty oil. Bosch Rexroth has published a 44-page booklet, on oil-resistant paper, that outlines common contaminant sources, the basics of contamination control, key filter properties, tolerances of hydraulic components, and recommended oil-cleanliness levels according to ISO 4406. It also covers monitoring and maintenance strategies to proactively diagnose problems before a failure. Order a free copy at www.boschrexroth-us.com/filter. Enclosure selector Rittal’s Web site (www.rittal-corp.com) helps engineers quickly design, size, and quote enclosures and climatecontrol products. The SmartSelect tool lets users select MACHINE DESIGN.com NOVEMBER 22, 2012 the type of product and then specify dimensions, ratings, materials, and other parameters. Results include exact matches and close alternatives, along with product details, drawings, installation videos, and related info. The company’s QuickQuote application creates a bill of material and price estimate. Users can also access the tools on most smartphones and mobile devices. Controls catalog OTTO has published an interactive, 226-page magazinestyle PDF catalog on its switches, grips, joysticks, and control panels. Content includes product data, technical specs, drawings and photos, and a comprehensive military cross-reference. Download a copy, or request a print version, at www.ottoexcellence.com. Structural simulation Ansys will host a free, 1-hr Webinar on November 29 on how to improve simulation processes. The discussion covers large and complex model performance, modeling 3D-composite shapes, customizing processes for structural mechanics, crack modeling, mapping of external data, and contact modeling, as well as better ways to handle finite-element models. Learn more at http://tinyurl.com/cknkp9x. Fastener app PennEngineering has launched the PEMspec app for iPhones and iPads. It lets users access critical installation dimensions for self-clinching, flaring, broaching, surface mount, and weld fasteners. Data includes mounting-hole size, minimum sheet thickness, and installed height above sheet, among other criteria. Users can search by fastener parameters or part number, and the app also contains pertinent links and contact information. Learn more at www.pemnet.com. Your ball screw Your servomotor Our coupling   
   Our ServoClass® couplings have been recently redesigned to enable your actuator to go even faster and achieve the positional accuracy that will take your designs to the next level. Our couplings will do all this with low bearing loads. 3 New sizes now available. Now, size, select and see the right ServoClass® coupling solution for your application with Zero-Max 3D CAD files. Check our FAST deliveries. www.zero-max.com 800.533.1731 © 2010 ZERO-MAX RS# 105 EDITORIAL Silliness at 40 below Many years ago a college classmate of mine told a funny story about his summer job testing communications gear for a defense contractor. He spent his time alternately freezing the radios to –40°C and heating them to 85°C, while operating them to make sure they’d work at these extreme temperatures. Trouble was, most of the radios wouldn’t pass this test. To fix the problem, the contractor had to go through a redesign, which took more than a month, putting the project behind schedule. Once the electronics had been fixed, my buddy drew a lot of overtime running radios in temperature chambers, trying to catch up. In fact, the pace was so hectic that nobody bothered to check the radios at room temperature. You may be able to guess what happened. It was only as things slowed down that QA discovered the revamped radios often sputtered out when operating in ambient temperatures. With that situation in mind, I was amused at a tale told in the memoirs of former General Motors Corp. Vice Chairman Bob Lutz to illustrate some of the whacky design practices he encountered when he joined GM in 2001. He discovered the ashtray of a new Cadillac STS had a lot of spring pressure. When opened, it shot out as though launched from a cannon, and once deployed, was tough to push in with just one finger. This was in contrast to the ashtray on an Acura, which glided open and took a single effortless push to close. Lutz figured the ashtray design in the Cadillac had to be a mistake, so he was flabbergasted when a senior interior-trim engineer said it operated that way on purpose. The reason: So it could meet an internal GM standard that dictated ashtrays had to function after a night spent at –40°F. Lutz says loopy situations like the Cadillac ashtray were not at all uncommon in those days. They arose because GM had a habit of engineering its vehicles for extreme situations. That was a noble idea, but it came at the expense of alienating thousands of GM owners on a daily basis. You might wonder what happened to the –40°F ashtray spec. Lutz says his team eventually eliminated it and 90% of the other sacred but silly engineering do’s and don’ts that had somehow become embedded in GM culture. He also opined that the existence of these disconnected-from-the-real-world practices was a “testimony to a culture that was inwardly focused in pursuit of its own goals, with the customer left out of the equation.” I would put it a little differently than Lutz did. Both in the case of the bad radios and with the ashtrays that operated superbly only at –40°C, the designers had lost sight of the trade-offs they were making. There is a lesson here for any engineer who’d like to avoid having something they designed be the butt of jokes, or who doesn’t want their work to wind up as a humorous incident in someone else’s memoir. — Leland Teschler, Editor RS# 106 NOVEMBER 22, 2012 75D61CD Actuatorline has all the precision you need – and won’t keep you waiting s QUICK DELIVERY TIMES s WEB-BASED DESIGN TOOLS s LIVE TECHNICAL SUPPORT SC 60 with 500mm of travel ROBOT 130 with 2 meters of travel Learn Fast Design Fast For data sheets, application guides and white papers, visit our Technical Resource Center at www.actuatorline.com Contact one of our applications engineers for help selecting an Actuatorline module. Call 1.877.976.5566 RS# 107 VISIT US AT IMTS BOOTH #E-4351 EDITORIAL STAFF EDITOR Leland E. Teschler [email protected] MANAGING EDITOR Kenneth J. Korane [email protected] SENIOR EDITORS Leslie Gordon [email protected] Stephen J. Mraz [email protected] ASSOCIATE EDITORS Lindsey Frick [email protected] Robert J. Repas, Jr. [email protected] RS# 108 INDUSTRY COVERAGE: AUTOMOTIVE, PACKAGING, MEDICAL Stephen J. Mraz CAD/CAM, MANUFACTURING Leslie Gordon ELECTRICAL, ELECTRONICS Robert J. Repas, Jr. FASTENING & JOINING, MATERIALS Lindsey Frick FLUID POWER Kenneth J. Korane MECHANICAL 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. RS# 109 EDITORIAL PRODUCTION Denise Greco Editorial Production Manager Randall L. Rubenking Art Director MITRPAK Power Transmission Products 38 River Road, Uxbridge, MA 01569 Tel: 508-278-2422 • Fax: 800-346-0018 • 800-648-7725 www.mitrpak.com 10 Lindsey Frick Kenneth J. Korane MACHINE DESIGN.com 1300 E. 9th St. Cleveland, OH 44114-1503 NOVEMBER 22, 2012 TM micro fasteners Ideal for today’s compact electronics f*DPLQJ+DQG+HOG'HYLFHVf1RWHERRNV f&HOO6PDUW3KRQHVf7DEOHW&RPSXWHUV  1(: 7RVHHRXUFRPSOHWHOLQHRIPLFUR3(0IDVWHQHUV DQGFDSDELOLWLHVJRWRRXUZHEVLWHDQGFOLFNRQWKH PLFUR3(0EXWWRQ PLFUR3(0706HOI&OLQFKLQJ 7DFN3LQj)DVWHQHUV{'HVLJQHGIRU 6KHHWWR6KHHW$WWDFKPHQW  f f f f 5HSODFHVVFUHZVZHOGVDQGDGKHVLYHV $WWDFKHVWRSVKHHWVDVWKLQDVPP} &OLQFKHVLQWREDVHSDQHODVKDUGDV +5%+% 7DSHUHGDQGLQWHUIHUHQFHILWPLQLPL]HKROH WROHUDQFHLVVXHV Locating pins Surface mount nuts/spacers *RWRZZZSHPQHWFRPDQGVHOHFWWKHSURGXFWOLWHUDWXUHWDE WRYLHZPLFUR3(0706HOI&OLQFKLQJ7DFN3LQ70EXOOHWLQ Standoffs/spacers Inserts for plastics Low profile head screws 70 YEARS OF EXCELLENCE www.pemnet.com 1942-2012 RS# 110 382R ©2012 LETTERS Anyone for ethics? Unfortunately, ethics went out the window in the U. S. many years ago with the advent of our “instant” society (“Where Did Ethics Go?” Sept. 6). Everyone wants everything they can possibly need and dream of without waiting or working for it, all at the expense of others. This problem is more prevalent here in the U. S. than in Europe, Asia, or the Caribbean countries. It is most likely the fault of parents who let others raise their kids and advertising wonks. And it doesn’t matter what the profession is, it is all about greed. Randy Scott I have worked in the engineering field for more than 40 years. I am now in business for myself as a forensic mechanical engineer doing accident reconstruction for attorneys and insurance companies. Part of my job involves testifying in court on civil and criminal cases where I have been amazed at what some engineers will say under oath to prove a case for their clients. Sometimes they testify to accident scenarios that violate the laws of physics. Some engineers testifying are registered professional engineers and are theoretically bound to follow the “Engineers Code of Ethics.” But they don’t. How can they look in the mirror and not cringe at what they see? Why do people try to beat the system? Do they really think the “easy way” is the best way? It’s pretty simple, and somewhat trite, but honesty is always the best policy. Harold A. Schwartz Smaller can be better Yes, small sample sizes have more outliers, but there is more to the story (“Bad Math for Fixing Bad Math Scores,” Aug. 23). Home schooling represents the smallest of schools, and homeschooled kids have average scores in the 88th percentile on standard12 MACHINE DESIGN.com Ethics are dead? A couple of readers bemoan the lack of ethics in practically every facet of American life. Others debate whether Steve Jobs’ management style would work at NASA. And one reader wonders about our privacy and cloud computing. ized tests without the enormous budgets of public schools and in spite of (or perhaps because of ) most parents lacking education degrees. Not all home-schooling parents are in it just to get their children a good education. Some parents are more interested in religious indoctrination and some appear to be ducking the responsibility of getting their kids to school every day. I became a home-schooling parent when I saw that children in many overseas schools, especially in Asia, were about two years ahead of American kids in math by 4th grade. I figured that my children were going to have to compete with those kids when they grew up, so I took on the rather large responsibility of teaching them at home. I remember asking a public-school teacher why they didn’t assign more homework. The response was that the parents would complain. Funding ever more assistants and fewer students per school is not going to fix the problems of public education. Plus, it ignores two extremely serious problems: The lack of parental involvement, which would change if all parents paid part of the cost out of pocket; and the cultural sense of entitlement that everyone deserves an easy, effortless life courtesy of the government. When the government subsidizes something we get more of it. Subsidizing idleness, teenage motherhood, and recreational degrees that don’t lead to produc- NOVEMBER 22, 2012 tive jobs erases the work ethic that made this country great. Karl Oberstramm Get off of my cloud I’m concerned over privacy in “the cloud.” I am no expert on this topic, just someone who has seen Facebook, Google, and other e-mail providers “data mine” everything that passes through their hands. Supposedly no personally identifying data is ever mined, but how many pieces of a jigsaw puzzle have to be present before the final piece can easily be deduced? It’s already frightening how much Google knows and what advertising clout they have attained. I use Google as an example, but the same principle applies to similar online organizations and to governments. If I have heard correctly, the U. S. government, for example, is building an ambitious project to record everything in the U. S. that goes on in the Internet. So am I right to be downright frightened of storing my employer’s engineering information in “the cloud”, where I will have no real control over who might see it? David Rensle Running NASA Apple-style By your example, Steve Jobs let the project run off the rails and then chewed out the development team after development had reached a crisis (“If Steve Jobs RS# 111 LETTERS Had Run the Mars Rover Project,” Sept. 20). Only then did he take corrective action. The NASA results might have been the same with Steve Jobs present. It depends on how much micromanaging (or project oversight) Jobs was capable of. NASA made its decisions and lived with the consequences. Managers there thought they had managed the risks. It takes proactive checks to prevent projects from running off the rails. Even Steve Jobs didn’t do that. I think your analogy is faulty. Stephen McDonald A wise manager taught me early in my career that if you fire everyone who makes a mistake you are soon left with only those folks who are not doing anything at all. David Leahy I agree with whoever said Steve Jobs was the last American busi- nessman who knew what he was doing, so I doubt he would have any interest in landing an SUV on Mars. But if he did, he’d have the right people in the right places at the right times. You don’t keep underachieving employees on your payroll. Get rid of the people who do it wrong and promote/hire those who do it right. The replacements automatically learn from their predecessors mistakes. Or they, too, become predecessors. Frank Blankenship Curing those ethanol blues My problem with ethanol started out with my RV and some equipment I store for winter. The 10% ethanol/gas blend attracts water in the atmosphere. This fact was hammered home as I pumped 2 gallons of water from my 200-gallon fuel tank on my boat. It was also evident in the Spring when I found that the float valve on my lawnmower rusted, even after draining it for the winter. Fortunately, I found a station that sells ethanol-free gas. These can be found at www.puregas.org. And Washington state now lets marine stations sell only ethanol-free gas. The real surprise came when I started using ethanol-free gas in my car and truck. The truck (a 2005 F 150) was getting 13 mpg around town and the spark plugs were black. In Feb. of this year, I started using ethanol-free gas in the truck. Within two tanks, it was getting 14.5 mpg, and the new plugs are running tan. Since then, the mileage has been 14.5 to 15 mpg, which is an 11 to 15% improvement. This might be an isolated case, but it seems a rigorous test needs to be done. Erik A. Larsen TM 14 MACHINE DESIGN.com NOVEMBER 22, 2012 RS# 112 A n atomy of the HUCK 360 ® ® PROBLEM: CONVENTIONAL THREAD BOLT NUT TRANSVERSE VIBRATION TRANSVERS E V I BRATION COMPARISON Gap between the threads allows for transverse movement. CLAMP (LBF-THOUSANDS) 25 20 H U C K 3 60 15 O T H E R V I B R AT I O N R E S I S T AN T NUT DESIGNS 10 5 0 0 50 100 ti m e 150 200 SOLUTION: HUCK 360 250 (SECONDS) BOLT Once vibration begins, clamp load quickly decays with nuts and bolts, while it holds constant with the Huck 360. RS# 113 NUT No gap exists. Threads are locked preventing any movement. SCANNING FOR IDEAS Edited by Stephen J. Mraz Spindle drive moves with accuracy The BS22-1.5 spindle drive from MICROMO, Clearwater, Fla. (www. micromo.com), a member of the Faulhaber Group, uses ball screws to generate highly accurate linear motion. The stainless-steel drive is accurate to within 5 μm or less over its entire length of travel. The motor connects to the ball screw through a backlash-free coupling that is part of the ball screw. The screw is 126.5-mm long, and the standard stroke measures 94 mm. Pitch is 1.5 mm. Axial load capacities are to 519 N (dynamic) and 475 N (static). The device can handle input speeds up to 5,000 rpm and still maintain its accuracy. RS# 401 Motor Motor flange Clutch housing with duplex ball bearings Spindle thread Spindle nut with fastening screw thread For a white paper on gearhead construction and use, scan this code or go to: http:// machinedesign.com/ whitepaper/gearheadconstruction-and-use-0911 16 MACHINE DESIGN.com NOVEMBER 22, 2012 r formation via ou Request free in Web site at ice Reader Serv c design.com/rs ww w.machine COMPLETE ENGINEERING SOLUTIONS Start here. "The navigation and ordering process are easy to work. Thanks." – Richard, Newark element14 customer At Newark element14, all your engineering needs come together in one source—vast product range from world-class brands, fast online search, seamless purchasing tools, resources and services, one-on-one support, and a community of experts. Here, you’ll find simpler, smarter and faster ways to do business. HOW MAY WE HELP YOU TODAY? COMMUNITY: element14.com WEBSITE: newark.com PHONE: 1.800.463.9275 LEARN MORE: newark.com/together RS# 114 SCANNING FOR IDEAS Filter vent equalizes pressure inside and out Electronic enclosures are often sealed against water and contaminants, but this can lead to pressure differentials between the interior and exterior that cause problems. For example, lower pressure inside the enclosure can pull water and air in, damage the seals, and wreak havoc on the electronics. To prevent this problem, engineers at W.L. Gore & Associates Inc., Elton, Md. (www.gore.com/protectivevents), developed a protective vent, the PolyVent D3, that lets air pass in and out, but keeps water, dust, insects, and debris from getting in. The vent has a press-fit width of 2.5 mm and gas-flow capacity of 7 ml/min. The housing is polypropylene and contains an ePTFE membrane. This membrane lets gases pass through while keeping out contaminants. The vent works in temperatures from –4 to 212°F. The vent takes up no space inside enclosures and its low-profile exterior portion reduces the risk of damage from technicians who service the enclosure. RS# 402 18 RS# 115 MACHINE DESIGN.com NOVEMBER 22, 2012 Liquid and particles kept out Polyester backing Polypropylene housing Air and gas molecules pass in and out through the membrane ePTFE membrane RS# 116