Tài liệu Machine design, tập 84, số 10, 2012

July 19, 2012 A Penton Media Publication Tune in to EngineeringTV.com BASICS OF BALL SPLINES, page 50 RESOLUTION AND ACCURACY IN 3D PRINTING, page 56 FASTER MOLDING WITH HIGH-FLOW POLYCARBONATES, page 72 BETTER WAYS TO ASSEMBLE PEEK PARTS, page 80 Tips & Traps in GD&T Page 68 RS# 101 Motion Control Products HDR Series Starts at $135 Gearboxes Worm Gear Speed Reducers  8 Ratios Available from 5:1 to 60:1  7 Gear Box Sizes from 1.33 to 3.25"  Universally Interchangeable Design for OEM Replacement  Double Bearings Used on Both Shaft Ends Visit omega.com/hdr General Purpose AC Motors, 56C Flange, Single Phase, Fractional and Integral HP General Purpose AC Motors, 56C Frame, Three-Phase, Fractional and Integral HP OMT Series Starts at $125 Permanent Magnet DC Motors OMPM-DC Starts at $ 200 OMAT Series Starts at $115 Visit omega.com/omt_series Visit omega.com/omat_series Visit omega.com/ompm-dc omega.com ® Νο. ® RS# 102 © COPYRIGHT 2012 OMEGA ENGINEERING, INC. ALL RIGHTS RESERVED VOLUME 84 ISSUE 10 JULY 19, 2012 MEDICAL INDUSTRY FOCUS Authored by: Lonny Wolgemuth Senior Medical Market Specialist Specialty Coating Systems Inc. Indianapolis, Ind. Edited by Stephen J. Mraz [email protected] Resources: Specialty Coating Systems Inc., scscoatings. com For more information on parylene coatings, scan this code or go to: http://machinedesign. com/article/coatingadhesion-promoterspecialty-coatingsystems-0609 Many medical devices and their electronics need protection from moisture, chemical contamination, electrical charges, and body fluids. Otherwise, patients and healthcare providers may be put at risk. One way biomedical engineers provide this protection is by encapsulating devices in a conformal coating, one made of a dielectric, or poor conductor of electricity, such as silicone, acrylic, urethane, or epoxy. But one of the best materials for this purpose is parylene. Parylene basics Parylene is the generic name for a series of organic polymers — poly(para-xylylene) polymers — used as coatings. They are polycrystalline and linear in nature, optically clear, and colorless. Parylene coatings have useful dielectric and barrier properties and are chemically inert. Three different types give engineers a range of dielectric and other properties from which to choose. The coatings contain no fillers, stabilizers, solvents, catalysts, or plasticizers, so they are not subject to any leaching, outgassing, Protecting MEDICAL ELECTRONICS with parylene FEATURES This biocompatible conformal-coating material protects medical devices against fluids, chemicals, and stray electrical charges. rotary 50 Exploring ball splines Rotary ball splines can produce submillimeter accuracy. However, the choice of angular-contact or crossed-roller bearings plays a critical role. Parylene coatings are optically clear and do little to change the look or dimensions of the underlying component or part, as demonstrated in this photo of two circuit boards. The top one is coated with parylene, the bottom one isn’t. 20 MACHINE DESIGN.com JULY 19, 2012 or extraction issues. Parylene coatings are also compatible and stable in the presence of bodily fluids and tissues, critical factors in the medical-device industry. Parylene provides dryfilm lubricity with coefficients of friction similar to that of PTFE (Teflon), and dielectric strengths up to 7,000 V at a mil (25 microns) of coating thickness. No other material can be applied as thinly as parylene and provide the same levels of protection. Par ylene withstands all common sterilization methods — steam, ethylene oxide, electron beam, hydrogen peroxide plasma, and gamma radiation. It can be applied to most vacuum-stable materials, including plastics, metals, ceramics, fabrics, paper, and even granular materials. For example, parylene coatings could be applied to microspheres or moisture-absorbent powders. Parylene can be selectively removed with plasma, lasers, or strong abrasion, for instance, to repair devices. Parylene is not soluble in harsh detergents and chemicals; in fact, it protects components from such chemicals. Parylene is not a “hard” coating, so excessive abrasion will remove it. However, most components coated with parylene do not abrade or rub against other parts. If an application does include abrasive contact, it is not a good candidate for parylene. Parylene has been successfully used on implantable electronics such as cardiac-assist devices, neurostimulators, cochlear implants, and pacemakers. It’s also been used to coat nonelectronic medical devices as well, including coronary and cerebral stents, and catheters. sublimating it directly to a vapor, and then heated again until the dimer cracks into a monomeric vapor. This vapor flows into an ambient-temperature deposition chamber kept at a medium vacuum (0.1 torr) where it spontaneously polymerizes onto all surfaces, forming an ultrathin, uniform film. No curing or additional steps are required. The size of the coating chamber may be an issue if Continued on page 22 A short history of parylene Parylene deposition Parylene coatings are applied using vapor-deposition polymerization (VDP) in a vacuum chamber at room temperature. Film deposition actually takes place on the molecular level, with the coating literally growing one molecule at a time. This lets parylene penetrate and coat small cracks, crevices, and openings, and protect even hidden surfaces in areas where other coating methods such as sprays and brushes cannot reach. Coating thickness is uniform, even on irregular surfaces. And VDP is a clean, self-contained process that uses no additional chemicals. Parylene is deposited as a vapor, so it surrounds the target and perfectly follows its contours, literally encapsulating it. Parylene coatings are ultrathin and pinhole-free. The only raw material used in the coating process is known as dimer. Technicians place the powdered double-molecule dimer into the vaporizing chamber at one end of the coating machine. The dimer is heated, In 1947, Michael Szwarc was pursuing his academic career in physical chemistry at the Univ. of Manchester, England. His interest in the strength of individual chemical bonds led him to investigate a class of aliphatic carbon-hydrogen bonds in which the carbon was directly attached to a benzene ring. While doing so, he heated gases of the simplest compounds having both benzene and carbon — toluene and the xylenes — to high temperatures. He monitored both the decomposition products and rates of decomposition as a function of temperature. With p-xylene only, a tan-colored deposit formed in the cooler reaches of his glassware. The material has been described as a thin, flimsy, tube-shaped mass, “the skin of a small snake.” Szwarc correctly deduced that this film had been formed by polymerizing reaction products of the p-xylene, called p-xylylene. He also noticed the new polymer’s physical properties and chemical inertness. This serendipitous polymerization was the world’s first vapor deposited poly(paraxylyene). Today its purer colorless form is called parylene N. A few years later, William Franklin Gorham at Union Carbide Corp. continued the research on parylene. By 1967, this work led to the availability of a new polymeric coating. “Parylenes” was the term used to describe both a new family of polymers and the vacuum-deposition process for applying them. In fact, Union Carbide developed over 20 types of parylene, but only three were deemed commercially viable. JULY 19, 2012 20 MACHINE DESIGN.com Protecting medical electronics with parylene Parylene coatings give medical devices the dielectric strength to resist stray voltages as well as fluids and gases. for designing 64 Options the best hinge Hinges with spring pins instead of solid pins can lower costs and extend life. CAD/CAM/CAE/FEA Accuracy in SPC leads 68 When engineers astray ADDITIVE The quest for minimizing process variations can lead to parts that are needlessly expensive. go with the flow 72 Polycarbonates A new class of high-flow polycarbonate copolymers meets or exceeds the physical and mechanical properties of traditional materials, and provides better molding characteristics. assembly techniques 80 Advanced for high-performance plastics Engineers switching from metal to plastic need to revisit how they assemble the parts. 2 MACHINE DESIGN.com JULY 19, 2012 21 MANUFACTURING A common mistake is to confuse high resolution with accuracy. In the realm of additive manufacturing, what exactly are the distinctions between accuracy, repeatability, and resolution? Accuracy describes how closely a manufacturing machine’s output conforms to a tolerance within a specified dimensional range. Repeatability captures the equipment’s capability to produce consistent output, time after time. And resolution refers to the smallest measurement the machine can reproduce. These concepts are second nature to designers and manufacturing engineers. Yet, there is a widely held misconception about these measurement concepts as they relate to additive manufacturing. Over the years, some engineers have slid into using resolution attributes — such as layer thickness or dots per inch — as a careless shorthand term for accuracy. 56 MACHINE DESIGN.com Accuracy in additive manufacturing The color maps reveal that the top part — built on a high-resolution 3D printer — is not as accurate as the bottom part, built using a lower-resolution setting on an FDM system. Purples and reds reveal that the high-res printer produced deviations of ±0.020 in. or more. Greens reveal the FDM-built part is mostly in the ±0.005-in. range. Photo courtesy of T. A. Grimm & Associates Inc. A common mistake is to confuse high resolution with accuracy. JULY 19, 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 Get a big bang for your buck We squeezed the features of our popular TFT 6-inch C-more Micro into a 4-inch package for even more value! Take advantage of the clear and colorful graphics on the TFT color touch screen to create a vibrant and intuitive operator interface. Five programmable function keys give you lots of flexibility. FREE programming software offers the choice of using many built-in objects, such as buttons, bar graphs and data entry keypads. Or import your own custom graphics, and save to libraries for use in multiple projects. Alarm control, recipes and a built-in project simulator are time-saving tools for more complex applications. All these features at a competitive price, in a rugged and reliable package, give you a sweet HMI for even the smallest control system. * The programming software is free when downloaded from the AutomationDirect Web site, or the CD-ROM package can be purchased for $25 (part # EA-MG-PGMSW). < 27165
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4$6,1*5 Also Available Popular protocols/devices supported * All AutomationDirect programmable controllers * Modbus® RTU * Allen-Bradley® DF1 half/full duplex, PLC-5® DF1 and DH485 * Siemens PPI * GE SNPX * Omron Host Link and FINS serial * Mitsubishi MELSEC® 6-inch STN and TFT touch panels 3-inch touch and non-touch panels Optional plug-and-play keypad bezels for 3- and 6-inch models www.automationdirect.com Go online for complete list Go online or call to get complete information, request your free catalog, or place an order. www.automationdirect.com/c-more-micro or www.c-moremicro.com RS# 103 1-800-633-0405 Tips & Traps in GD&T ON THE COVER DEPARTMENTS Cover design by R. L. Rubenking. 8 EDITORIAL A better way to find stand-out engineers 10 EDITORIAL STAFF 12 LETTERS 16 SCANNING FOR IDEAS Modular guarding system protects workers and equipment One serious screwdriver 25 REPORTER’S NOTEBOOK 36 LOOKING BACK 43 SENSOR SENSE Inclination and tilt detectors 44 COMMENTARY The myth of Chinese and Indian engineers 47 INDUSTRIAL DESIGN When symbols are just as important as good design 48 VANTAGE POINT An educated workforce is key to reshoring 86 ORR ON ENGINEERING How to make the path of least resistance work for you 88 SOFTWARE PRODUCTS 90 PRODUCT SPOTLIGHT 4 PRODUCTS DATA FILES AD INDEX BUSINESS INDEX CLASSIFIEDS BUSINESS STAFF BACKTALK MACHINE DESIGN.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. Motors 94 106 108 109 110 110 111 For customized article reprints and permissions please contact: Penton Reprints, 1-888-858-8851, e-mail at [email protected] or visit pentonreprints.com. 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. JULY 19, 2012 POSTMASTER: Send change of address notice to Customer Service, MACHINE DESIGN, P.O. Box 2100, Skokie, IL 60076-7800. Tired of the same routine? Buy a Vac that lasts! Stop throwing your money away on electric vacuum cleaners that are sure to fail. EXAIR vacuums have been engineered to withstand the dust, dirt, chips and liquids common to industrial environments. Ours have no electric motors or other moving parts to clog or wear out. EXAIR’s 30 Day Unconditional Guarantee assures your complete satisfaction. Let our five year “Built To Last” warranty give you the peace of mind that your vacuum will always work and end your trips to the dumpster. Two-Way Drum Pump Chip Vacuum Has No Moving Parts Chip Trapper™ Extends Coolant Life Heavy Duty Vacuum Resists Wear The compressed air powered Reversible Drum Vac™ will quickly fill or empty a 55 gallon drum in 90 seconds. Coolant sumps can be easily refilled, floor spills vacuumed or contaminated liquids transferred to filtration tanks in minutes. Chip Vac™ is powered by compressed air and vacuums chips directly into a 5, 30, 55, and 110 gallon drum. It is easy to move from drum to drum to keep materials separate for recycling. Clean chips from floors, fixtures, work surfaces and machines. The Chip Trapper™ offers a fast, easy way to clean chips, swarf and shavings out of used coolants and other liquids. The Chip Trapper vacuums in the coolant that is filled with debris, traps the solids in a reusable filter bag, and pumps out clean coolant. Heavy Duty Dry Vac™ attaches to an ordinary 30, 55 or 110 gallon opentop drum to turn it into a powerful, industrial duty vacuum cleaner. It has been engineered to vacuum more dry materials in less time than ordinary vacs. Ideal for abrasives. *
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www.exair.com @EXAIR What’s new online machinedesign.com Free eBook: Electric linear actuators, hydraulic systems, and manual operation Recent advances in motion-control technology have given design engineers many options to meet their needs for speed, precision, and other requirements. However, these developments have also complicated the process for determining the most appropriate hardware and controls. This eBook, sponsored by Linak, discusses important criteria to consider when facing motion-related problems. It’s designed to aid OEM engineers in selecting the most-appropriate technology for a given application. Learn more at http://machinedesign.com/ebook/news/electriclinear-actuators-hydraulic-systems-manual-operation-0523. Hand gestures control PCs, TVs PointGrab’s hand-gesturerecognition technology lets designers integrate 3D gesture control into devices such as tablets, laptops, and smart TVs that have built-in cameras. It’s based on sophisticated hand-shape and motion-detection algorithms working with a standard 2D camera. A company expert explains how the software works and how it can be incorporated into your next design. See the episode at www.engineeringtv.com/video/ PointGrab-Gesture-Control-Softw. EDITOR’S WEB PICKS Tubing and hose guide 6 NewAge Industries has updated its buying guide with 20 tips on choosing plastic and rubber tubing and reinforced hose. It offers advice on critical aspects of tubing and hose selection, such as temperature, corrosion resistance, flexibility, pressure and vacuum requirements, and reuse. Get a free copy at www. newageindustries.com/inforeq.asp. CAD models Zero-Max’s downloadable 3D CAD models of motion-control components, previously for Internet Explorer users, are now compatible with Firefox and Chrome Web browsers. Intended to aid engineers when configuring a system, product models include flexible and servo-shaft couplings, overhung load adapters, gearboxes, torque limiters, and linear actuators. Download the models at www. zero-max.com. MACHINE DESIGN.com Free Webinar: Pitfalls of global compliance TÜV Rheinland will host a free Webinar, August 7, on key issues related to global compliance. It will address common challenges that prevent companies from reaching global markets and discuss design concerns, choosing vendors, and legal requirements. Learn more at www.tuv. com/us. Sealing site Garlock has revamped its Web site (www.garlock.com) with a focus on seals and related hardware for aerospace, chemical processing, pharmaceutical, industrial, and pulpand-paper applications. It includes an extensive archive of technical articles; product info on compression packings, diaphragms, gaskets, hydraulic components, and expansion joints; and a technical section with engineering tools, product selectors, and training resources. The site is also compatibile with mobile phones and tablets. JULY 19, 2012 WATCH PRODUCT OVERVIEW AND TUTORIAL VIDEOS AT YOUR CONVENIENCE AutomationDirect’s Learn Web site features industrial-control product overviews and tutorials. Topics range from PLCs and HMI to motion control and sensors. Recent Kickstart video uploads include: WERMA stack lights — See the full line of stack-light components and how they are assembled; a wide variety of visual and audible devices are completely configurable. Digital counter/ timer/tach — Compact DIN-rail-mount unit offers multiple modes for flexibility. Foot switches with metal guards – Use heavy-duty foot switches for controls on rotating or spinning machinery. NITRA pneumatic components — Overview of newly added brass fittings, quick-disconnect air couplings, and blow guns. For a complete list of videos, visit http://learn.automationdirect. com or www.youtube.com/ automationdirect. Become a subscriber and get alerts when new videos are uploaded. IT’S MOTION CONTROL VERSUS MOTHER NATURE ON CENTRE COURT. ©2010 Moog. All rights reserved. RS# 106 WHEN IT COMES TO HIGH PERFORMANCE MOTION CONTROL, MOOG EXPERTS ARE THERE. When design engineers sought the best way to control the new retractable roof at Wimbledon’s famed Centre Court, they turned to Moog. The result was an innovative all-electric installation that provides 148 axes of control via high performance electric actuators, servo motors, servo drives, closed-loop controls and software. Now, more than 1,100 metric tons (1,212 tons) of steel and 5,200 square meters (17,060 square feet) of fabric move swiftly and safely to prevent rain delays. Moog’s combination of motion control expertise and world-class solutions can make the difference for you too—no matter what industry you’re in. For more information call 866-580-7610. How can we improve your machine design? View our Wimbledon video at http://info.moog.com/wimbledon/1 WHAT MOVES YOUR WORLD moog.com/industrial EDITORIAL A better way to find stand-out engineers There are K pegs. Each peg can hold discs in decreasing order of radius when looked from bottom to top of the peg. There are N discs, which have radius 1 to N. Given the initial configuration of the pegs and the final configuration of the pegs, output the moves required to transform from the initial to final configuration ... What you see above is part of a sample problem found on Facebook’s Web site. Programmers looking for work at Facebook often start out by submitting code to solve puzzlers like this one. Code that impresses the Facebook crowd earns you a job interview over the phone. If that goes well, you’ll find yourself in Facebook’s Menlo Park, Calif., facilities for an in-person evaluation. Facebook says it has uncovered some of its most-able software engineers just by using its Web site to ask for solutions to programming brain-teasers. Whatever your opinion of Facebook social media, you have to give that company credit for coming up with an inexpensive way of finding good engineers. Its methods stand in direct contrast to the practice of asking riddlelike questions that have nothing to do with the job at hand, an interviewing technique popularized by Google and adopted by several other high-tech companies. Employers, though, increasingly seem to be coming around to the idea that responses to off-the-wall questions may say something about an applicant’s quick-wittedness, but don’t really reveal much about how that person will get a job done. So some organizations are now trying to find the real qualities that predict good work performance. And many of them have concluded these qualities have little to do with academic credentials or job resumes. Engineering employers that still depend on brain-teasers to find technical talent might learn a few things from George Anders, a former Wall Street Journal writer and book author. A lot of traditional talent-scouting systems don’t work, he claims. Anders studied several professions to see how the best employers found new hires who would likely turn into first-rate employees. He summarized his findings in a book called The Rare Find. Two of the groups he examined had an interesting insight: The Teach for America project and the U. S. Army Special Forces both looked for evidence of one trait in particular — resilience. Teach for America sends teachers into low-income communities. It figures educators who find success there must persist in the face of problems that might crush less-committed individuals. So among other things, TFA is on the lookout for applicants who struggled in their first year of college but persevered and eventually earned higher grades year after year. Similarly, Army Special Forces drill sergeants these days aren’t particularly impressed by candidates who do the most pushups or crank out fast times for two-mile runs. They are more interested in who performs well with little sleep during team problems where it’s important to think like a soldier. Guys who excel at pull-ups are still eliminated from the program if they get moody or hostile when things don’t go their way. I’d argue that resilience is just as important for many engineering tasks as it is for teaching disadvantaged kids or gaining trust in a remote village. But it doesn’t come up in many job interviews because hiring managers find it easier to pull out a few head-scratcher problems than to spend time making a frank assessment about what a job really entails. — Leland Teschler, Editor RS# 107 JULY 19, 2012 Providing custom products and value-added assemblies based on the most successful miniature pneumatic line in the world! Wire leads to be 7” + 1/8” with crimped terminal 10258333-2 “Cleaned for Oxygen Service” internal components Stainless Steel coil housing 5-volt coil less than 0.5 watt Brass base (no plating needed) FKM seals Mounting holes 1/2” max Toggle-operated manual by-pass valve in base Integrated needle valve for precise flow control CUSTOM er s n o i t u l o s RS# 108 Clippard Instrument Laboratory, Inc. Cincinnati, OH 1-877-245-6247 www.clippard.com/customsolutions WASHERS & STAMPINGS EDITORIAL STAFF EDITOR Leland E. Teschler [email protected] MANAGING EDITOR Kenneth J. Korane [email protected] FREE CATALOG & BROCHURE Call 1-888-WASHERS 1-888-927-4377 • [email protected] 612-729-9365 • FAX 612-729-8910 SENIOR EDITORS Leslie Gordon [email protected] Stephen J. Mraz [email protected] ASSOCIATE EDITORS Lindsey Frick [email protected] Robert J. Repas, Jr. [email protected] WWW.BOKERS.COM/MD RS# 109 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 Lindsey Frick Kenneth J. Korane EDITORIAL PRODUCTION Denise Greco Editorial Production Manager Randall L. Rubenking Art Director 1300 E. 9th St. Cleveland, OH 44114-1503 10 MACHINE DESIGN.com RS# 110 JULY 19, 2012 Medical equipment requires high performance motors. Moog Silencer™ series brushless DC ŵŽƚŽƌƐŽīĞƌƵŶŝƋƵĞĚĞƐŝŐŶƐƚŚĂƚĚĞůŝǀĞƌƌĞƐƵůƚƐhůƚƌĂƋƵŝĞƚĨƵŶĐƟŽŶĂůŝƚLJƐŵŽŽƚŚŽƉĞƌĂƟŽŶ ĂƚǀĂƌŝŽƵƐƐƉĞĞĚƐĂŶĚƚŚĞĂĚǀĂŶƚĂŐĞŽĨŚŝŐŚƚŽƌƋƵĞĂƚĂůŽǁĐŽƐƚ >ĞĂƌŶŵŽƌĞĂďŽƵƚDŽŽŐƐƐŽůƵƟŽŶƐĨŽƌportable oxygen concentrators and other medical ĚĞǀŝĐĞƐ^ƚĂŶĚĂƌĚĂŶĚĐƵƐƚŽŵŵŽƚŽƌŵŽĚĞůƐĂƌĞĂǀĂŝůĂďůĞǁŝƚŚŽƉƟŽŶƐŽŶƚĂĐƚƵƐƚŽĚŝƐĐƵƐƐ Brushless DC Motor Features: LJŽƵƌĂƉƉůŝĐĂƟŽŶ  >ŽǁŶŽŝƐĞůŽǁǀŝďƌĂƟŽŶ  ŽŵƉĂĐƚƐŝnjĞ Looking for more?  ,ŝŐŚƌĞůŝĂďŝůŝƚLJ ^ĐĂŶƚŽǀŝĞǁŵŽƚŽƌƐƉĞĐŝĮĐĂƟŽŶƐ  >ŽŶŐůŝĨĞ  ,ŝŐŚĞĸĐŝĞŶĐLJ DŽƟŽŶdĞĐŚŶŽůŽŐLJ#&ŝďĞƌKƉƟĐƐ#ůĞĐƚƌŽŶŝĐ^LJƐƚĞŵƐ нϭϱϰϬϱϱϮϯϬϭϭဒϬϬϯϯϲϮϭϭϮ;h^3ŵĐŐΛŵŽŽŐĐŽŵ www.moog.com/components RS# 111 LETTERS Almost united on unions I read with amusement the letters sent to you concerning the question of engineers joining a union (“ Time for Engineers to Think About Unionizing? Jan. 19). I was in an engineering union several decades ago. It was for a large railroad-car manufacturer in the Rust Belt, which is no longer in business. (No, the union didn’t bring it down.) As a designer and engineer-in-training, I was required to join the union based on my job description. It was a good learning experience on why engineers and unions don’t mix. I won’t go into details of the office culture or issues with having hourly and salary workers combined. The issue that I had at the time and still do today is that the union had many constricting work rules on how you get promoted and how people advance within the organization. Professionals or not, you were treated differently if you were in the union. I found the whole process to be nonproductive and inefficient for getting work done. I was denied advancement, not based on experience or productivity, but on years of service. Union people didn’t go to lunch with nonunion. The entire culture was counter to the teamwork environment required in the engineering profession. During the summers, while attending college, I worked in a manufacturing plant that was also unionized. I can honestly say that the hourly union plant job had more job satisfaction than did engineers in the unionized office. My opinion is that there is no place for a union in the office environment, let alone the engineering profession. Joseph C. Dominick There can be a period in an engineer’s career in which the individual is too young to retire but old enough that a change 12 MACHINE DESIGN.com Engineers still unified on some things Readers convey their dislike of engineering unions, although one offe r s a m o re - o p t i m i s t i c v i e w. B u t r e a d e r s a r e speaking with one voice to criticize modern design and the fact that form no longer follows function. They also seem to agree that sustainability standards will do more harm than good. We’ll see. of employment is difficult or the potential loss of benefits is too great. Management can take advantage of this situation by withholding salar y increases. Membership in a union could be advantageous in this situation, and a union could also provide assistance against dismissal before eligibility to retire. In my own career, I benefitted from a union I did not even belong to. The factory employees were represented by the United A u t o Wo r k e r s U n i o n , w h i c h negotiated ear ly retirement, health-care benefits, and vacation and holiday times. The same benefits were then granted by management to salaried employees. Thus, there was no union of salaried employees who had no protection against age discrimination or arbitrary dismissal. R Bruce Hopkins No form and too much function As an industrial designer, I appreciated your recent commentary (“Form Should Follow Function, and More,” April 19). I suggest that anyone involved in the design of any product that people use read two books from the 70s. One is How Things Don’t Work, JULY 19, 2012 and the other is Design for the Real World. Both books deal with the same issues we need to deal with today. By the way, we have a 2005 German car purchased two years ago. We are still trying to figure out all of the technology/gadgets in the car. My son has the same type of German car, but his is a 2010. He will be trading it in this year for a new one. He is a top engineering manager working for one of the top computer manufacturers, and he still hasn’t figured out all the gimmicks and features of this German driving machine. But he paid for all of them. There is no evidence of a human-factors approach in these two cars, just lots of interesting things to look at and play with, but hardly functional or germane to driving. And who has the time to figure out all of this? If I buy something, no matter what, I want to use it, not have to go back to college for two years and take another 60 credits, just to repeat the exercise the next time I buy a car. As my teachers used to say: M ake it simple enough for a 10-year old to figure out. Manuel de Sa 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 I just read your commentary and now I think we are wired similarly. I agree with all your comments. At my firm, we are always talking about form following function and to design for use, not looks. Cars today get too cluttered because so many automakers are competing to have the most “options” for mass marketing. I told my spouse the other day that if I could, I would get our next company vehicle with a hand-crank starter. Less to go wrong, no batteries, and those cheap magnetos used to work pretty well. All kidding aside, I enjoy controlling the functions of driving. It’s not that difficult to clutch and shift and hand crank the windows up and down, especially when there’s little physical work to do while sitting there anyway. Larry Kooiker Sustainability = Scam? I want to thank you for your commentary on sustainability (“Do We Need a Sustainability Standard? March 22). Unfortunately, I think you are preaching to the choir. I appreciate your perspective, but the idea of a sustainability standard just sounds too good to those politically correct nonproductive meddling by nonproducers. They firmly believe we all, but especially everybody else, will just have to buck le down and throw more money at another nonproblem (until it dies from suffocation under its own weight). By then, of course, two new great sounding ideas will have covered it up, and all the money that can be squeezed from the last idea will be taken. The small companies that can’t afford the extra cost and the drag of more bureaucracy will have closed up shop. Remember when efficiency meant doing more with less, when economical meant costing less? Some day that common sense will again prevail. In the meantime, keep up the good work. Wayne A. Strand I do a lot of presentations about Reduce, Recycle, and Reclaim and I paraphrase another engineer (her name escapes me). She wrote: “I cannot design anything green. Everything will consume resources. I can make my designs greener, so they consume less resources both when built and when they run.” Randy Mountcastle Make the Switch. It’s time for a change. So make the switch to Nason and say goodbye to switches that almost work. With Nason, you’ll get exactly what you want when you create your own quality bi-metal temperature switch. And once you make the perfect combination, we’ll send you a free sample, so you’ll know before you order that it fits your application to a T. Make your own switch using the widest range of electrical connections in the industry. Watch “Making the Switch” on YouTube. www.youtube.com/NasonPTC MACHINE DESIGN.com JULY 19, 2012 Don’t forget to request your own sample: http://nasonptc.com/switch_form 800.229.4955 • www.nasonptc.com .com Check out our TT switches online and see how easy making the switch can be. http://nasonptc.com/ttswitch RS# 113 14 Each switch is preset and 100% are tested— a feature unique to Nason. Make the switch to Nason, and make yourself a perfect switch. A n atomy of the HUCK 360 ® ® PROBLEM : CONVENTIONAL THREAD BOLT NUT TRANSVERSE VIBRATION TRANSVERSE V I B R A T I O N C O M P ARISON Gap between the threads allows for transverse movement. CLAMP (LBF-THOUSANDS) 25 20 HUCK 36 0 15 OTHER VIBRA TIONRESISTANT NUT DESIG NS 10 5 0 0 50 100 time 150 200 SOLUTION : HUCK 360 250 No gap exists. Threads are locked (SECON D S ) BOLT Once vibration begins, clamp load quickly decays with nuts and bolts, while it holds constant with the Huck 360. RS# 114 NUT preventing any movement. SCANNING FOR IDEAS Edited by Stephen J. Mraz Modular guarding system protects workers and equipment Factory owners don’t want workers interfering with conditions and situations. For example, standard 6-ftequipment. Nor do they want them injured. To keep tall walls can be expanded to tower 30-ft high, and workers safely away from moving machinery and roofs can be added if needed to keep out trespassers inventory that shouldn’t be disturbed, engineers or animal pests. at Wireway Husky Corp., Denver, N. C. (www. Matrix Guard can also be used in warehouses, wirewayhusky.com), have developed the modular residences, and communications installations, Matrix Guard line of products. as well as retail establishments and The OSHA-approved doors, walls, posts, restaurants. connectors, latches, and other accessories are RS# 401 r formation via ou designed to work together and assemble quickly Request free in Web site at er Service ad Re and easily. A new chalice bolt, a nonremovable-type c design.com/rs ww w.machine fastener used on the panels, also meets European and Canadian safety standards. Cable-tray And enclosures or walls can be easily guide for use expanded or changed to meet new Glass or Lexan panel for clear views with Unistrut or Cablofil cablemanagement systems Double tunnel doors Line post Solid-steel panel for maximum protection 2 × 2-in. welded eight-gauge wire with reinforcing flute for extra strength Half-sized mesh panel Swinging door Mesh guard panel 2.5-in.2 oversized foot plate Standard slide-bolt lock, but other standard and custom locks are available, including interlock mounting brackets. 16 MACHINE DESIGN.com JULY 19, 2012 "I am so pleased with your wide selection and availability of products.” – Newark element14 customer COMPLETE ENGINEERING SOLUTIONS Start here. Newark element14 connects you to the brands and products engineers trust from bench to board. Our direct relationships with world-class brands means you get access and information first, with our engineers actively sourcing global and niche manufacturers to provide you with the best choices. Technology, services and solutions start at Newark element14. HOW MAY WE HELP YOU TODAY? COMMUNITY: element14.com WEBSITE: newark.com PHONE: 1.800.463.9275 LEARN MORE: newark.com/together RS# 115 SCANNING FOR IDEAS This is one serious screwdriver Machine builders and other manufacturers can now acquire a ready-to-go, preprogrammed, modular screw-driving machine, the Viper MBC from Visumatic Industrial Products, Lexington, Ky. (www.visumatic.com). And though it’s said to be the fastest screw-driving module available, installing up to six screws in 5 sec, it can also install nuts, bolts, pins, clips, brass rings, and barbed darts. Viper uses a Visumatic 94 feeder to deliver screws and other fasteners directly to the tooling tip. Other screw-installing robots fall in the pick-andplace category. This means the robotic arm spends time getting the fastener and then returning to the work area. Viper eliminates this wasted time. Viper uses a SCARA robot to handle motion because, as its full name suggests (Selective Compliant Assembly Robot Arm), it is selectively compliant. So it is stiff in the vertical direction, which helps when installing screws and pushing parts together, but a bit compliant in the horizontal plane, which lets it compensate for less-than-perfect alignments between the tooling tip and the hole for the screw. The Viper also features zero-offset mounting for the screw-driving portion. This is a change from conventional designs where mounting points are located beyond the extreme end of the robot, which creates an exaggerated cantilever effect. This means screw-tightening torque transfers directly to the robot’s extended joints, and the tooling payload is magnified by the moment arm and applied to the joints as well. With the Viper, joints three and four do not see any tightening forces, and they carry only one-third the weight of the tooling. This leads to faster motions, lon18 MACHINE DESIGN.com JULY 19, 2012 Gearbox Screwdriver with torqueangle control SCARA robot Quick disconnect for maintenance Zero-offset quill mount Independent “Z” stroke and bit stroke Tooling tip holds screw ger robot life, and repeatable assembly with consistent quality. The lack of offset also simplifies setup by eliminating complex calculations to account for any offset. The Viper has a working envelope of at least 7,000 in.3, and an NST traceable axis. RS# 402