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I I I A U i v I i I z. NEIL 0 SCHLA GER, Editor 0 =CMADE Illus trate d An P ro du c t G u i de M a n u fa c tu rin g l NEIL SCHLAGER, GaleResearchinc. to Editor * DETROIT - WASHINGTON, D.C. * LONDON STAFF Neil Schlager, Editor Elisabeth Morrison, Associate Editor Christine Jeryan, Kyung-Sun Lim, Kimberley A. McGrath, Bridget Travers, Robyn V. Young, Contributing Editors Meggin M. Condino, Jeffrey Muhr, Janet Witalec, Contributing Associate Editors Victoria B. Cariappa, Research Manager Maureen Richards, Research Supervisor Donna Melnychenko, Research Associate Jaema Paradowski, Research Assistant Mary Beth Trimper, Production Director Shanna Heilveil, Production Assistant Cynthia Baldwin, Art Director Bernadette M. Gomie, Page Designer Mark C. Howell, Cover Designer Electronic illustrations provided by Hans & Cassady, Inc. of Westerville, Ohio. While every effort has been made to ensure the reliability of the information presented in this publication, Gale Research Inc. neither guarantees the accuracy of the data contained herein nor assumes any responsibility for errors, omissions or discrepancies. Gale accepts no payment for listing; and inclusion in the publication of any organization, agency, institution, publication, service, or individual does not imply endorsement of the editors or publisher. Errors brought to the attention of the publisher and verified to the satisfaction of the publisher will be corrected in future editions. The paper used in this publication meets the minimum requirements of American National Standard for Information (_ Sciences-Permanence Paper for Printed Library Materials, ANSI Z39.48-1984. This publication is a creative work fully protected by all applicable copyright laws, as well as by misappropriation, trade secret, unfair competition, and other applicable laws. The authors and editors of this work have added value to the underlying factual material herein through one or more of the following: unique and original selection, coordinatio; n, expression, arrangement, and classification of the information. All rights to this publication will be vigorously defended. Copyright i 1994 Gale Research Inc. 835 Penobscot Building Detroit, MI 48226-4094 All rights reserved including the right of reproduction in whole or in part in any form. ISBN 0-8103-8907-X ISSN 1072-5091 Printed in the United States of America Published simultaneously in the United Kingdom by Gale Research Intemational Limited (An affiliated company of Gale Research Inc.) 10 9 8 7 6 5 4 3 2 1 i(jp The trademark ITP is used under license. Contents Introduction ................. vii Contributors ................. xi Acknowledgments .......... xiii 1 Aluminum Foil ............... 8 Artificial Limb .............. 14 Aspirin ................... 19 Automobile ................. 24 Automobile Windshield ...... 31 Baking Soda ............... 35 Ball Bearing ................ 39 Bar Code Scanner .......... 44 Baseball ................... 50 Baseball Glove ............. 55 Battery ................... 60 Bicycle Shorts ............... 65 Blood Pressure Monitor ...... 69 Blue Jeans .................. 74 80 Book ................... 86 Brick ................... Bulletproof Vest ............. 91 Candle ................... 96 Carbon Paper...... ....... 100 .105 Cellophane Tape ... .109 Ceramic Tile ....... .114 Chalk ............. .119 Cheese ............ .124 Chewing Gum...... Air Bag ................... ....... ....... ....... ....... ....... Chocolate ................. Coffee .................... Combination Lock ......... Combine .................. Compact Disc ............. 129 134 139 143 148 Compact Disc Player ....... 153 Concrete .................. 158 Cooking Oil ............... 164 Corrugated Cardboard ..... 169 Cutlery ................... 174 Expanded Polystyrene Foam (EPF) .................... 180 Eyeglass Lens ............. 185 File Cabinet ............... 190 Fire Extinguisher ........... 194 Floppy Disk ............... 199 Gold ..................... 204 Golf Cart ................. 209 Grinding Wheel ........... 214 219 Helicopter ................. 223 Jet Engine ................. 230 Laboratory Incubator ....... 236 Laser Guided Missile ....... 242 Laundry Detergent ......... 247 Lawn Mower .............. 252 Light Bulb ................. 256 Light-Emitting Diode (LED) . . 261 Guitar .................... v Lipstick ............... .... 267 Satellite Dish .............. 390 Screwdriver ............... 395 Liquid Crystal Display (LCD) ................ . 272 Seismograph .............. 400 Lubricating Oil ........ ....277 Shaving Cream .............406 Mattress .............. ....281 Soda Bottle ............... 410 Microwave Oven ...... ... . 286 Solar Cell ............... 414 Mirror ................ .... 291 Spark Plug ............... 420 Nail Polish............ .... 297 Stainless Steel ............. 424 Necktie ............... .... 301 Stapler ................430 Optical Fiber.......... .... 305 Stethoscope ............... 434 439 Paint ................. ....310 Sugar ................ Pantyhose............. . 315 Super Glue ............... 444 Peanut Butter.......... .... 320 Thermometer .............. 448 453 326 Tire ............... Pencil ................ Pesticide .............. ....330 Tortilla Chip ............... 458 Porcelain ............. .... 335 Trumpet ............... 464 Postage Stamp ........ .... 340 Umbrella ............... 469 Pressure Gauge ....... .... 345 Washing Machine ......... 473 478 .350 Watch ............... Rayon ................ Refrigerator ........... .... 355 Wind Turbine ............. 482 488 Revolver .............. .361 Wine ............... 494 .367 Wool ............... Rubber Band .......... 500 Running Shoe ......... .... 371 Zipper ............... 376 Zirconium ............... 505 Saddle ............... 509 Salsa ................. .... 381 .Index ............... 385 Sandpaper............ ... .. .... v i Introduction About the Series Welcome to How Products Are Made: An Illustrated Guide to Product Manufacturing. This series provides detailed yet accessible information on the manufacture of a variety of items, from everyday household products to heavy machinery to sophisticated electronic equipment. With step-by-step descriptions of processes, simple explanations of technical terms and concepts, and clear, easy-to-follow illustrations, the series will be useful to a wide audience. In each volume of How Products Are Made, you will find products from a broad range of manufacturing areas: food, clothing, electronics, transportation, machinery, instruments, sporting goods, and more. Some are intermediate goods sold to manufacturers of other products, while others are retail goods sold directly to consumers. You will find products made from a variety of materials, and you will even find products such as precious metals and minerals that are not "made" so much as they are extracted and refined. Organization Every volume in the series is comprised of many individual entries, each covering a single product; Volume 1 includes more than 100 entries, arranged alphabetically. Although each entry focuses on the product's manufacturing process, it also provides a wealth of other information: who invented the product or how it has developed, how it works, what materials it is made of, how it is designed, quality control procedures used, byproducts generated during its manufacture, future applications, and books and periodical articles containing more information. To make it easier for users to find what they are looking for, the entries are broken up into standard sections. Among the sections you will find are: * Background * History * Raw Materials * Design vi i * The Manufacturing Process * Quality Control * Byproducts * The Future * Where To Learn More The illustrations accompanying each entry provide you with a better sense of how the manufacturing process actually works. Uncomplicated and easy to understand, these illustrations generally follow the step-by-step description of the manufacturing process found in the text. Bold-faced items in the text refer the reader to other entries in this volume. Volume 1 also contains an added bonus: approximately ten percent of the entries include special boxed sections. Written by William S. Pretzer, a manufacturing historian and curator at the Henry Ford Museum, these sections describe interesting historical developments related to a product. Finally, Volume 1 contains a general subject index with important terms, processes, materials, and people. Here as in the text, bold-faced items refer the reader to main entries on the subject. Contributors/Advisors The entries in Volume 1 were written by a skilled team of technical writers and engineers, often in cooperation with manufacturers and industry associations. In addition, a group of advisors assisted in the formulation of the series and of Volume 1 in particular. They are: Marshall Galpern Staff Engineer General Motors Corporation Dr. Michael J. Kelly Director Manufacturing Research Center Georgia Institute of Technology Jeanette Mueller-Alexander Reference Librarian/Business Subject Specialist Hayden Library Arizona State University Dr. William S. Pretzer Curator Henry Ford Museum & Greenfield Village v III Diane A. Richmond Head Science and Technology Information Center Chicago Public Library Suggestions Your questions, comments, and suggestions are welcome. Please send all such correspondence to: The Editor How Products Are Made Gale Research Inc. 835 Penobscot Building Detroit, MI 48226 ix Contributors Jim Acton Steve Mathias William L. Ansel Leslie G. Melcer Lawrence H. Berlow L. S. Millberg Douglas E. Betts Robert C. Miller Rick Bockmii/er Dan Pepper Robert A. Cortese Rashid Riaz Blaine Danley Rose Secrest Matthew Fogel Eva Sideman Suzy Fucini Frank Sokolo Theodore L. Giese Edward J. Stone Alicia Haley Peter Toeg David Harris Phillip S. Waldrop Catherine Kolecki Jim Wawrzyniak Greg Ling Glenn G. Whiteside Peter S. Lucking Craig F. Whitlow Barry M. Marton x i Acknowledgments The editor would like to thank the following individuals, companies, and associations for providing assistance with Volume 1 of How Products Are Made: Air Bag: Morton International Incorporated-Automotive Products Division; TRW Vehicle Safety Systems Incorporated. Artificial Limb: Bob Burleson, Southeastern Orthotics & Prosthetics; Jim Colvin, Ohio Willow Wood Company; Douglas Turner, Becker Orthopedic; Al Pike, Otto Bock. Baking Soda: Church & Dwight Company Incorporated; FMC Corporation. Ball Bearing: Thomson Precision Ball Company. Baseball: Scott Smith, Rawlings Sporting Goods Company. Baseball Glove: Bob Clevenhagen, Rawlings Sporting Goods Company; Robby Storey, Nocona Athletic Goods Company. Battery: John Daggett, Rayovac Corporation; Steve Wicelinski, Duracell Incorporated. Bicycle Shorts: Cannondale Manufacturers. Blue Jeans: Bill Dunnahoo, Thomaston Mills Incorporated; Allen Slagle, Bristol Jeans Incorporated. Bulletproof Vest: Al Baker, American Body Armor; Bob Coppage, Progressive Technologies of America; Lester Gray, Keramont Corporation. Carbon Paper: Jim Sellers, NER Data Products Incorporated. Cellophane Tape: Jerry Miron, Skeist Incorporated. Chalk: Roger Taylor, Dixon Ticonderoga Company. Chocolate: Bob Zedik, Chocolate Manufacturers Association. Combination Lock: Master Lock Company. Combine: Dick Corken, John Deere Harvester Division. Compact Disc Player: Sanyo Fisher Company. Corrugated Cardboard: Rod Johnson, Packaging Corporation of America-Containerboard Products Division. Cutlery: Sandra E. Finley, Oneida, Limited. Expanded Polystyrene Foam (EPF): E. S. Clark, University of TennesseeMaterials Engineering Department; Ralph Taylor, Constar International Incorporated. File Cabinet: Phil Bradley, Kwik File Incorporated; Debbie Kniegge, Accuride; K. C. Thomsen, Electro Painters Incorporated. Golf Cart: Textron Incorporated-E-Z Go Division. Laundry Detergent: Larry Byrne, Sr., Byrne Laboratories. Lawn Mower: Dan Ariens, Ariens Company. Optical Fiber: James Bratton, Corning IncorporatedTelecommunications Products Division. Pantyhose: National Association of Hosiery Manufacturers. Peanut Butter: Russell E. Barker, Peanut Butter and Nut Processors Association. Pesticide: Reed Bacon, Bacon Products Corporation. Postage Stamp: Kelly Keough, American Banknote Company. Rubber Band: Michael Halperson, Plymouth Office Supply Company. Running Shoe: Craig Cartley, Athletic Footwear Association. Saddle: John DePietra, Equitation Synergist. Salsa: Caroline Fee, Del Monte Corporation; Lou Rasplicka, Pace Foods Incorporated. Satellite Dish: Jonathan x iii Peschko, Sky Link. Screwdriver: Glenn Allen, Stanley Works. Seismograph: Gene Tafra, Spreng-Nethers; Teledyne Incorporated-Geotech Division. Shaving Cream: Leonard Giglio, Contract Packaging Company. Soda Bottle: E. S. Clark, University of Tennessee-Materials Engineering Department; Ralph Taylor, Constar International Incorporated. Solar Cell: Mark Stimson, Siemens Solar Industries Incorporated. Stethoscope: Marc Blitstein, American Diagnostic Corporation; Tom Edmundson, Tycos; Cynthia Runyon, Minnesota Mining and Manufacturing Company (3M). Sugar: Suzanne Arnold, Sugar Association Incorporated. Super Glue: Lou Baccei, Loctite Corporation. Tire: Bill Brown II, Pirelli Armstrong Tire Corporation. Tortilla Chip: Tortilla Industry Association. Trumpet: Cliff Blackburn, Blackburn. Umbrella: Ann Cain, Totes Incorporated; Bob Storey and Manny Dubinsky, Zip Jack Industries, Limited. Washing Machine: Speed Queen Company. Watch: Scott Chou, SEIKO Corporation of America. Wind Turbine: Kerri E. Miller and Robert Sims, U.S. Windpower Incorporated. The historical photographs on pages 25, 51, 81, 175, 225, 257, 321, 454, and 495 are from the collections of Henry Ford Museum & Greenfield Village, Dearborn, Michigan. The cover photograph of a tire is courtesy of AP/Wide World Photos. Finally, the editor would like to thank Hans & Cassady Incorporated of Westerville, Ohio, for providing the electronic illustrations for Volume 1. xiv Air Bag Background An air bag is an inflatable cushion designed turn, fits into the steering wheel for driver'sside applications and above the glove compartment for front passenger applications. to protect automobile occupants from serious injury in the case of a collision. The air bag is part of an inflatable restraint system, also known as an air cushion restraint system (ACRS) or an air bag supplemental restraint system (SRS), because the air bag is designed to supplement the protection offered by seat belts. Seat belts are still needed to hold the occupant securely in place, especially in side impacts, rear impacts, and rollovers. Upon detecting a collision, air bags inflate instantly to cushion the exposed occupant with a big gas-filled pillow. A typical air bag system consists of an air bag module (containing an inflator or gas generator and an air bag), crash sensors, a diagnostic monitoring unit, a steering wheel connecting coil, and an indicator lamp. These components are all interconnected by a wiring harness and powered by the vehicle's battery. Air bag systems hold a reserve charge after the ignition has been turned off or after the battery has been disconnected. Depending on the model, the backup power supply lasts between one second and ten minutes. Since components vital to the system's operation might sit dormant for years, the air bag circuitry performs an internal "self-test" during each startup, usually indicated by a light on the instrument panel that glows briefly at each startup. The crash sensors are designed to prevent the air bag from inflating when the car goes over a bump or a pothole, or in the case of a minor collision. The inflator fits into a module consisting of a woven nylon bag and a breakaway plastic horn pad cover. The module, in In a frontal collision equivalent to hitting a solid barrier at nine miles per hour (14.48 kilometers per hour), the crash sensors located in the front of the car detect the sudden deceleration and send an electrical signal activating an initiator (sometimes called an igniter or squib). Like a light bulb, an initiator contains a thin wire that heats up and penetrates the propellant chamber. This causes the solid chemical propellant, principally sodium azide, sealed inside the inflator to undergo a rapid chemical reaction (commonly referred to as a pyrotechnic chain). This controlled reaction produces harmless nitrogen gas that fills the air bag. During deployment the expanding nitrogen gas undergoes a process that reduces the temperature and removes most of the combustion residue or ash. The expanding gas inflates the bag in less than onetwentieth of a second, splitting open its plastic cover and inflating in front of the occupant. The bag is fully inflated for only one-tenth of a second and is nearly deflated by threetenths of a second after impact. The expanding nitrogen gas inflates the nylon bag in less than one-twentieth (1/20) of a second, splitting open its plastic module cover and inflating in front of the occupant. As the occupant contacts the bag, the nitrogen gas is vented through openings in the back of the bag. The bag is fully inflated for only onetenth (1/10) of a second and is nearly deflated by three-tenths (3/10) of a second after impact. Talcum powder or corn starch is used to line the inside of the air bag and is released from the air bag as it is opened. History The air bag traces its origin to air-filled bladders outlined as early as 1941 and first patented in the 1950s. Early air bag systems 1 How Products Are Made, Volume 1 A typical driver's-side air bag fits neatly on the steering wheel column. In case of a collision, the crash sensor sends an electric spark to the inflator canister, setting off a chemical readion that produces nitrogen gas. The gas expands, inflating the air bag and protecting the driver. Air bag were large and bulky, primarily using tanks of compressed or heated air, compressed nitrogen gas (N2), freon, or carbon dioxide (CO2). Some of the early systems created hazardous byproducts. One particular system used gunpowder to heat up freon gas, producing phosgene gas (COC12)-an extremely poisonous gas. One of the first patents for automobile air bags was awarded to industrial engineer John Hetrick on August 18, 1953. Conceived by Hetrick after a near accident in 1952, the design called for a tank of compressed air under the hood and inflatable bags on the steering wheel, in the middle of the dashboard, and in the glove compartment to protect front seat occupants, and on the back of the front seat to protect rear seat passengers. The force of a collision would propel a sliding weight forward to send air into the bags. Many other inventors and researchers followed suit, all exploring slightly different designs, so that the exact technical trail from 2 the early designs to the present system is impossible to note with certainty. In 1968, John Pietz, a chemist for Talley Defense Systems, pioneered a solid propellant using sodium azide (NaN3) and a metallic oxide. This was the first nitrogengenerating solid propellant, and it soon replaced the older, bulkier systems. Sodium azide in its solid state is toxic if ingested in large doses, but in automotive applications is carefully sealed inside a steel or aluminum container within the air bag system. Since the 1960s, air bag-equipped cars in controlled tests and everyday use have demonstrated the effectiveness and reliability. The Insurance Institute For Highway Safety conducted a study of the federal govemnment's Fatal Accident Reporting System using data from 1985 to 1991, and concluded that driver fatalities in frontal collisions were lowered by 28 percent in automobiles equipped with air bags. According to Air Bag another study conducted in 1989 by General Motors, the combination of lap/shoulder safety belts and air bags in frontal collisions reduced driver fatalities by 46 percent and front passenger fatalities by 43 percent. In response to consumers' increased safety concerns and insurance industry pressure, the federal government has forced automobile manufacturers to upgrade their safety features. First, Department of Transportation (DOT) regulations require all cars, beginning with model year 1990, sold in the United States to be equipped with a passive restraint system. (Passive restraint systems-requiring no activation by the occupant-involve the use of automatic seat belts and/or the use of air bags.) If car manufacturers choose an air bag, then regulations require only a driver's-side system until model year 1994, when air bag-equipped cars must include passive protection on the passenger's side as well. A 1991 law requires driver and passenger air bags in all cars by the 1998 model year and in light trucks and vans by 1999. Ravv MActerials As stated above, an air bag system consists of an air bag module, crash sensors, a diagnostic monitoring unit, a steering wheel connect- ing coil, and an indicator lamp. Both this section and the next ("The Manufacturing Process") will focus on the air bag module itself. An air bag module has three main parts: the air bag, the inflator, and the propellant. The air bag is sewn from a woven nylon fabric and can come in different shapes and sizes depending on specific vehicle requirements. The driver's-side air bag material is manufactured with a heat shield coating to protect the fabric from scorching, especially near the inflator assembly, during deployment. Talcum powder or corn starch is also used to coat the air bag; either substance prevents the fabric from sticking together and makes it easier to assemble. Newer silicone and urethane coated air bag materials require little or no heat shield coating, although talcum powder or corn starch will probably still be used as a processing aid. Preparation of the propellant, the first step in air bag manufacture, involves combining sodium azide and an oxidizer. The propellant is then combined with the metal initiator canister and various filters to form the inflator assembly. The inflator canister or body is made from either stamped stainless steel or cast aluminum. Inside the inflator canister is a filter assembly consisting of a stainless steel wire mesh with ceramic material sandwiched in between. When the inflator is assembled, the filter assembly is surrounded by metal foil to maintain a seal that prevents propellant contamination. 3 How Products Are Made, Volume 1 The propellant, in the form of black pellets, is primarily sodium azide combined with an oxidizer and is typically located inside the inflator canister between the filter assembly and the initiator. The Manufacturing Process Air bag production involves three different separate assemblies that combine to form the finished end product, the air bag module. The propellant must be manufactured, the inflator components must be assembled, and the air bag must be cut and sewn. Some manufacturers buy already-made components, such as air bags or initiators, and then just assemble the complete air bag module. The following description of the manufacturing process is for driver-side air bag module assembly. Passenger-side air bag module assemblies are produced slightly differently. Propellant The propellant consists of sodium azide mixed together with an oxidizer, a substance that helps the sodium azide to burn when ignited. The sodium azide is received from outside vendors and inspected to make sure it conforms to requirements. After inspection it is placed in a safe storage place until needed. At the same time, the oxidizer is received from outside vendors, inspected, and stored. Different manufacturers use different oxidizers. 2 From storage, the sodium azide and the 2oxidizer are then carefully blended under sophisticated computerized process control. Because of the possibility of explosions, the powder processing takes place in isolated bunkers. In the event safety sensors detect a spark, high speed deluge systems will douse whole rooms with water. Production occurs in several redundant smaller facilities so that if an accident does occur, production will not be shut down, only decreased. 3 After blending, the propellant mixture is 3sent to storage. Presses are then used to compress the propellant mixture into disk or pellet form. Inflator assembly 4 The inflator components, such as the Imetal canister, the filter assembly- 4 stainless steel wire mesh with ceramic material inside-and initiator (or igniter) are received from outside vendors and inspected. The components are then assembled on a highly automated production line. 5 The inflator sub-assembly is combined 5with the propellant and an initiator to form the inflator assembly. Laser welding (using C02 gas) is used to join stainless steel inflator sub-assemblies, while friction inertial welding is used to join aluminum inflator sub-assemblies. Laser welding entails using laser beams to weld the assemblies together, while friction inertial welding involves rubbing two metals together until the surfaces become hot enough to join together. 6 The inflator assembly is then tested and Csent to storage until needed. Air bag 7 The woven nylon air bag fabric is re7ceived from outside vendors and inspected for any material defects. The air bag fabric is then die cut to the proper shapes and sewn, internally and externally, to properly join the two sides. After the air bag is sewn, it is inflated and checked for any seam imperfections. Final assembly of air bag module 8 The air bag assembly is then mounted to Uthe tested inflator assembly. Next, the air bag is folded, and the breakaway plastic horn pad cover is installed. Finally, the completed module assembly is inspected and tested. 9 The module assemblies are packaged in boxes for shipment and then sent to customers. Other components The remaining components of the air l bag system-the crash sensors, the diagnostic monitoring unit, the steering wheel connecting coil, and the indicator lamp-are combined with the air bag module during vehicle assembly. All the components are connected and communicate through a wiring harness. Air Bag Quality Control The quality control aspect of air bag production is, obviously, very important because many lives depend on the safety feature. Two major areas where quality control is critical are the pyrotechnic or propellant tests and the air bag and inflator static and dynamic tests. Propellants, before being inserted into inflators, are first subjected to ballistic tests to pre- dict their behavior. A representative sample of inflators are pulled from the production line and tested for proper operation by a fullscale inflator test, which measures pressurecreated by the generated gas inside a large tank 15.84 or 79.20 gallons (60 or 300 liters)-versus time in milliseconds. This gives an indication of the inflator system's ability to produce an amount of gas at a given rate, ensuring proper air bag inflation. The air bags themselves are inspected for fabric and seam imperfections and then tested for leaks. The air bag parts are die-cut out of woven nylon, sewn together, and riveted. The bag is then carefully folded so that it will fit inside the plastic module cover. Automated inspections are made at every stage of the production process line to identify mistakes. One air bag manufacturer uses radiography (x-rays) to compare the completed inflator against a master configuration stored in the computer. Any inflator without the proper configuration is rejected. The Future The future for air bags looks extremely promising because there are many different applications possible, ranging from aircraft seating to motorcycle helmets. The air bags of the future will be more economical to pro- 5 How Products Are Made, Volume 1 Crash sensors can be located in several spots on the front of the aubmobile. These sensors are connected to the air bag module with a wiring harness. Two other key components of an air bag system are the diagnostic module and the indicator lamp. The diagnosfic module performs a system test each time the car is started, briefly lighting up the indicator lamp mounted on the dashboard. Wiring harness duce and lighter in weight; will involve smaller, more integrated systems; and will use improved sensors. Side-impact air bags are another possibility that would work similar to driver- and passenger-side air bags. Side-impact air bags will most likely be mounted in the car door panels and deployed towards the window during impact to protect the head. Foam padding around the door structure would also be used to cushion the upper body in a side impact. Head and/or knee bolsters (energy absorbing pads) to complement the air bag system are also being investigated. Rear-seat air bags are also being tested but consumer demand is not expected to be high. Aftermarket air bag systems-generic systems that can be installed on any vehicle already built-are not currently available. Since the effectiveness of an air bag depends on its sensors recognizing if a crash is severe enough to trigger deployment, a system must be precisely tuned to the way a specific car model behaves in a crash. Still, companies are exploring the future possibility of producing a modified air bag system for retrofit. A hybrid inflator is currently being tested that uses a combination of pressurized inert gas (argon) and heat from a propellant to significantly expand the gas's volume. These systems would have a cost advantage, since less propellant could be used. Air bag manufacturers are also developing systems that would eliminate the sodium azide propellant, which is toxic in its undeployed form. Work 6 Indicator lamp Crash sensors Diagnostic module is also underway to improve the coatings that preserve the air bag and facilitate its opening. Eventually the bags may not need coatings at all. In the future, more sophisticated sensors called "smart" sensors will be used to tailor the deployment of the air bag to certain conditions. These sensors could be used to sense the size and weight of the occupant, whether the occupant is present (especially in the case of passenger-side air bags where deployment may be unnecessary if there are no passengers), and the proximity of the driver to the steering wheel (a driver slumped over the steering wheel could be seriously injured by an air bag deployment). Where To Learn More Periodicals Chaikin, Don. "How It Works-Airbags," Popular Mechanics. June, 1991, p. 81. Frantom, Richard L. "Buckling Down on Passenger Safety," Design News. October 2, 1989, pp. 116-118. Gottschalk, Mark A. "Micromachined Airbag Sensor Tests Itself," Design News. October 5, 1992, p. 26. Grable, Ron. "Airbags: In Your Face, By Design," Motor Trend. January, 1992, pp. 90-91. Air Bag Haayen, Richard J. "The Airtight Case for Air Bags," Saturday Evening Post. November, 1986. Reed, Donald. "Father of the Air Bag," Automotive Engineering. February, 1991, p. 67. Sherman, Don. "It's in the Bag," Popular Science. October, 1992, pp. 58-63. Spencer, Peter L. "The Trouble with Air Bags," Consumers' Research. January, 1991, pp. 10-13. -Glenn G. Whiteside 7 Aluminum Foil The preference for aluminum in flexible packaging has become a global phenomenon. In Japan, aluminum foil is used as the barrier component in flexible cans. In Europe, aluminum flexible packaging dominates the market for pharmaceutical blister packages and candy wrappers. Background Aluminum foil is made from an aluminum alloy which contains between 92 and 99 percent aluminum. Usually between 0.00017 and 0.0059 inches thick, foil is produced in many widths and strengths for literally hundreds of applications. It is used to manufacture thermal insulation for the construction industry, fin stock for air conditioners, electrical coils for transformers, capacitors for radios and televisions, insulation for storage tanks, decorative products, and containers and packaging. The popularity of aluminum foil for so many applications is due to several major advantages, one of the foremost being that the raw materials necessary for its manufacture are plentiful. Aluminum foil is inexpensive, durable, non-toxic, and greaseproof. In addition, it resists chemical attack and provides excellent electrical and nonmagnetic shielding. Shipments (in 1991) of aluminum foil totaled 913 million pounds, with packaging representing seventy-five percent of the aluminum foil market. Aluminum foil's popularity as a packaging material is due to its excellent imperTneability to water vapor and gases. It also extends shelf life, uses less storage space, and generates less waste than many other packaging materials. The preference for aluminum in flexible packaging has consequently become a global phenomenon. In Japan, aluminum foil is used as the barrier component in flexible cans. In Europe, aluminum flexible packaging dominates the market for pharmaceutical blister packages and candy wrappers. The aseptic drink box, which uses a thin layer of aluminum foil as a barrier against oxygen, light, and odor, is also quite popular around the world. 8 Aluminum is the most recently discovered of the metals that modem industry utilizes in large amounts. Known as "alumina," aluminum compounds were used to prepare medicines in ancient Egypt and to set cloth dyes during the Middle Ages. By the early eighteenth century, scientists suspected that these compounds contained a metal, and, in 1807, the English chemist Sir Humphry Davy attempted to isolate it. Although his efforts failed, Davy confirmed that alumina had a metallic base, which he initially called "alumium." Davy later changed this to "aluminum," and, while scientists in many countries spell the term "aluminium," most Americans use Davy's revised spelling. In 1825, a Danish chemist named Hans Christian 0rsted successfully isolated aluminum, and, twenty years later, a German physicist named Friedrich Wohler was able to create larger particles of the metal; however, Wohler's particles were still only the size of pinheads. In 1854 Henri Sainte-Claire Deville, a French scientist, refined Wo1hler's method enough to create aluminum lumps as large as marbles. Deville's process provided a foundation for the modem aluminum industry, and the first aluminum bars made were displayed in 1855 at the Paris Exposition. At this point the high cost of isolating the newly discovered metal limited its industrial uses. However, in 1866 two scientists working separately in the United States and France concurrently developed what became known as the Hall-Heroult method of separating alumina from oxygen by applying an electrical current. While both Charles Hall and PaulLouis-Toussaint Heroult patented their discoveries, in America and France respectively, Hall was the first to recognize the financial potential of his purification process. In 1888 Aluminum Foil he and several partners founded the Pittsburgh Reduction Company, which produced the first aluminum ingots that year. Using hydroelectricity to power a large new conversion plant near Niagara Falls and supplying the burgeoning industrial demand for aluminum, Hall's company-renamed the Aluminum Company of America (Alcoa) in 1907-thrived. H6roult later established the Aluminium-Industrie-Aktien-Gesellschaft in Switzerland. Encouraged by the increasing demand for aluminum during World Wars I and II, most other industrialized nations began to produce their own aluminum. In 1903, France became the first country to produce foil from purified aluminum. The United States followed suit a decade later, its first use of the new product being leg bands to identify racing pigeons. Aluminum foil was soon used for containers and packaging, and World War II accelerated this trend, establishing aluminum foil as a major packaging material. Until World War II, Alcoa remained the sole American manufacturer of purified aluminum, but today there are seven major producers of aluminum foil located in the United States. Rcaw Materials Aluminum numbers among the most abundant elements: after oxygen and silicon, it is the most plentiful element found in the earth's surface, making up over eight percent of the crust to a depth of ten miles and appearing in almost every common rock. However, aluminum does not occur in its pure, metallic form but rather as hydrated aluminum oxide (a mixture of water and alumina) combined with silica, iron oxide, and titania. The most significant aluminum ore is bauxite, named after the French town of Les Baux where it was discovered in 1821. Bauxite contains iron and hydrated aluminum oxide, with the latter representing its largest constituent material. At present, bauxite is plentiful enough so that only deposits with an aluminum oxide content of forty-five percent or more are mined to make aluminum. Concentrated deposits are found in both the northern and southern hemispheres, with most of the ore used in the United States coming from the West Indies, North America, and Australia. Since bauxite occurs so close to the earth's surface, mining procedures are relatively simple. Explosives are used to open up large pits in bauxite beds, after which the top layers of dirt and rock are cleared away. The exposed ore is then removed with front end loaders, piled in trucks or railroad cars, and transported to processing plants. Bauxite is heavy (generally, one ton of aluminum can be produced from four to six tons of the ore), so, to reduce The Bayer process of refining bauxite consists of four steps: digestion, clarification, precipitation, and calcination. The result is a fine white powder of aluminum oxide. 9 How Products Are Made, Volume 1 Continuous casting is an altemafive to melting and casting aluminum. An advantage of continuous casfing is that it does not require an annealing (heat treatment) step prior to foil rolling, as does the melting and casting process. the cost of transporting it, these plants are often situated as close as possible to the bauxite mines. The Mcanufacturing Process Extracting pure aluminum from bauxite entails two processes. First, the ore is refined to eliminate impurities such as iron oxide, silica, titania, and water. Then, the resultant aluminum oxide is smelted to produce pure aluminum. After that, the aluminum is rolled to produce foil. Refining-Bayer process The Bayer process used to refine bauxite comprises four steps: digestion, clarification, precipitation, and calcination. During 10 the digestion stage, the bauxite is ground and mixed with sodium hydroxide before being pumped into large, pressurized tanks. In these tanks, called digesters, the combination of sodium hydroxide, heat, and pressure breaks the ore down into a saturated solution of sodium aluminate and insoluble contaminants, which settle to the bottom. 2 The next phase of the process, clarifica- 2tion, entails sending the solution and the contaminants through a set of tanks and presses. During this stage, cloth filters trap the contaminants, which are then disposed of. After being filtered once again, the remaining solution is transported to a cooling tower. 3 In the next stage, precipitation, the aluminum oxide solution moves into a large silo, where, in an adaptation of the Deville Aluminum Foil method, the fluid is seeded with crystals of hydrated aluminum to promote the formation of aluminum particles. As the seed crystals attract other crystals in the solution, large clumps of aluminum hydrate begin to form. These are first filtered out and then rinsed. ROLLING Coolant/ Lubricant Foil is produced from aluminum stock by rolling it between heavy rollers. Rolling produces two natural finishes on the foil, bright and matte. As the foil emerges from the rollers, circular knives cut it into rectangular pieces. A Calcination, the final step in the Bayer refinement process, entails exposing the aluminum hydrate to high temperatures. This extreme heat dehydrates the material, leaving a residue of fine white powder: aluminum oxide. Smelting 5 Smelting, which separates the aluminum- 5oxygen compound (alumina) produced by the Bayer process, is the next step in extracting pure, metallic aluminum from bauxite. Although the procedure currently used derives from the electrolytic method invented contemporaneously by Charles Hall and PaulLouis-Toussaint Heroult in the late nineteenth century, it has been modernized. First, the alumina is dissolved in a smelting cell, a deep steel mold lined with carbon and filled with a heated liquid conductor that consists mainly of the aluminum compound cryolite. 6 Next, an electric current is run through 6the cryolite, causing a crust to form over the top of the alumina melt. When additional alumina is periodically stirred into the mixture, this crust is broken and stirred in as well. As the alumina dissolves, it electrolytically decomposes to produce a layer of pure, molten aluminum on the bottom of the smelting cell. The oxygen merges with the carbon used to line the cell and escapes in the form of carbon dioxide. 7 Still in molten form, the purified alu7minum is drawn from the smelting cells, transferred into crucibles, and emptied into furnaces. At this stage, other elements can be added to produce aluminum alloys with characteristics appropriate to the end product, though foil is generally made from 99.8 or 99.9 percent pure aluminum. The liquid is then poured into direct chill casting devices, where it cools into large slabs called "ingots" or "reroll stock." After being annealedheat treated to improve workability-the ingots are suitable for rolling into foil. An alternative method to melting and casting the aluminum is called "continuous casting." Aluminum web This process involves a production line consisting of a melting furnace, a holding hearth to contain the molten metal, a transfer system, a casting unit, a combination unit consisting of pinch rolls, shear and bridle, and a rewind and coil car. Both methods produce stock of thicknesses ranging from 0.125 to 0.250 inch (0.317 to 0.635 centimeter) and of various widths. The advantage of the continuous casting method is that it does not require an annealing step prior to foil rolling, as does the melting and casting process, because annealing is automatically achieved during the casting process. Rolling foil 8 After the foil stock is made, it must be Oreduced in thickness to make the foil. This is accomplished in a rolling mill, where the material is passed several times through metal rolls called work rolls. As the sheets (or webs) of aluminum pass through the rolls, they are squeezed thinner and extruded through the gap between the rolls. The work rolls are paired with heavier rolls called backup rolls, which apply pressure to help maintain the stability of the work rolls. This helps to hold the product dimensions within tolerances. The work and backup rolls rotate in opposite directions. Lubricants are added to facilitate the rolling process. During this I 1 How Products Are Made, Volume 1 rolling process, the aluminum occasionally must be annealed (heat-treated) to maintain its workability. The reduction of the foil is controlled by adjusting the rpm of the rolls and the viscosity (the resistance to flow), quantity, and temperature of the rolling lubricants. The roll gap determines both the thickness and length of the foil leaving the mill. This gap can be adjusted by raising or lowering the upper work roll. Rolling produces two natural finishes on the foil, bright and matte. The bright finish is produced when the foil comes in contact with the work roll surfaces. To produce the matte finish, two sheets must be packed together and rolled simultaneously; when this is done, the sides that are touching each other end up with a matte finish. Other mechanical finishing methods, usually produced during converting operations, can be used to produce certain patterns. 9 As the foil sheets come through the 9 rollers, they are trimmed and slitted with circular or razor-like knives installed on the roll mill. Trimming refers to the edges of the foil, while slitting involves cutting the foil into several sheets. These steps are used to produce narrow coiled widths, to trim the edges of coated or laminated stock, and to produce rectangular pieces. For certain fabricating and converting operations, webs that have been broken during rolling must be joined back together, or spliced. Common types of splices for joining webs of plain foil and/or backed foil include ultrasonic, heatsealing tape, pressure-sealing tape, and electric welded. The ultrasonic splice uses a solid-state weld-made with an ultrasonic transducer-in the overlapped metal. Finishing processes For many applications, foil is used in combination with other materials. It can be coated with a wide range of materials, such as polymers and resins, for decorative, protective, or heat-sealing purposes. It can be laminated to papers, paperboards, and plastic films. It can also be cut, formed into any shape, printed, embossed, slit into strips, sheeted, etched, and anodized. Once the foil is in its final state, it is packaged accordingly and shipped to the customer. 12 Quality Control In addition to in-process control of such parameters as temperature and time, the finished foil product must meet certain requirements. For instance, different converting processes and end uses have been found to require varying degrees of dryness on the foil surface for satisfactory performance. A wettability test is used to determine the dryness. In this test, different solutions of ethyl alcohol in distilled water, in increments of ten percent by volume, are poured in a uniform stream onto the foil surface. If no drops form, the wettability is zero. The process is continued until it is determined what minimum percent of alcohol solution will completely wet the foil surface. Other important properties are thickness and tensile strength. Standard test methods have been developed by the American Society For Testing and Materials (ASTM). Thickness is determiined by weighing a sample and measuring its area, and then dividing the weight by the product of the area times the alloy density. Tension testing of foil must be carefully controlled because test results can be affected by rough edges and the presence of small defects, as well as other variables. The sample is placed in a grip and a tensile or pulling force is applied until fracture of the sample occurs. The force or strength required to break the sample is measured. The Future The popularity of aluminum foil, especially for flexible packaging, will continue to grow. Four-sided, fin-sealed pouches have gained wide popularity for military, medical, and retail food applications and, in larger sizes, for institutional food service packs. Pouches have also been introduced for packaging 1.06 to 4.75 gallons (4-18 liters) of wine for both retail and restaurant markets, and for other food service markets. In addition, other products continue to be developed for other applications. The increase in popularity of microwave ovens has resulted in the development of several forms of aluminum-based semi-rigid containers designed specifically for these ovens. More recently, special cooking foils for barbecuing have been developed. However, even aluminum foil is being scrutinized in regard to its environmental "friendli- Aluminum Foil ness." Hence, manufacturers are increasing their efforts in the recycling area; in fact, all U.S. foil producers have begun recycling programs even though aluminum foil's total tonnage and capture rate is much lower than that of the easy-to-recycle aluminum cans. Aluminum foil already has the advantage of being light and small, which helps reduce its contribution to the solid waste stream. In fact, laminated aluminum foil packaging represents just 17/lOOths of one percent of the U.S. solid waste. For packaging waste, the most promising solution may be source reduction. For instance, packaging 65 pounds (29.51 kilograms) of coffee in steel cans requires 20 pounds (9.08 kilograms) of steel but only three pounds (4.08 kilograms) of laminated packaging including aluminum foil. Such packaging also takes up less space in the landfill. The Aluminum Association's Foil Division is even developing an educational program on aluminum foil for universities and professional packaging designers in order to help inform such designers of the benefits of switching to flexible packaging. Aluminum foil also uses less energy during both manufacturing and distribution, with inplant scrap being recycled. In fact, recycled aluminum, including cans and foil, accounts for over 30 percent of the industry's yearly supply of metal. This number has been increasing for several years and is expected to continue. In addition, processes used during foil manufacturing are being improved to reduce air pollution and hazardous waste. Where To Learn More Books Aluminum Foil. The Aluminum Association. 1981. Periodicals "Barrier Qualities Stimulate Aluminum Foil Packaging Growth," FoilPak News. The Aluminum Association. Fall, 1992. "The Best Ways to Keep Food Fresh: A Roundup of the Most Effective and Most Economical Wraps, Bags, and Containers," Consumer Reports. February, 1989, p. 120+. Gracey, Kathryn K. "Aluminum in Microwaves," Consumers' Research Magazine. January, 1989, p. 2. "Promote Even Cookery with Foil," Southern Living. December, 1987, pp. 130131. -L. S. Millberg 13 Artificial Limb The most exciting development of the twentieth century hos been the development of myoelectric prosthetic limbs. Myoelectricity involves using electrical signals from the potient's orm muscles to move the limb. Background Artificial arms and legs, or prostheses, are intended to restore a degree of normal function to amputees. Mechanical devices that allow amputees to walk again or continue to use two hands have probably been in use since ancient times, the most notable one being the simple peg leg. Surgical procedure for amputation, however, was not largely successful until around 600 B.c. Armorers of the Middle Ages created the first sophisticated prostheses, using strong, heavy, inflexible iron to make limbs that the amputee could scarcely control. Even with the articulated joints invented by Ambroise Pare in the 1500s, the amputee could not flex at will. Artificial hands of the time were quite beautiful and intricate imitations of real hands, but were not exceptionally functional. Upper limbs, developed by Peter Baliff of Berlin in 1812 for below-elbow amputees and Van Peetersen in 1844 for above-elbow amputees, were functional, but still far less than ideal. The nineteenth century saw a lot of changes, most initiated by amputees themselves. J. E. Hanger, an engineering student, lost his leg in the Civil War. He subsequently designed an artificial leg for himself and in 1861 founded a company to manufacture prosthetic legs. The J. E. Hanger Company is still in existence today. Another amputee named A. A. Winkley developed a slip-socket below-knee device for himself, and with the help of Lowell Jepson, founded the Winkley Company in 1888. They marketed the legs during the National Civil War Veterans Reunion, thereby establishing their company. Another amputee named D. W. Dorrance invented a terminal device to be used in the place of a hand in 1909. Dorrance, who had 14 lost his right arm in an accident, was unhappy with the prosthetic arms then available. Until his invention, they had consisted of a leather socket and a heavy steel frame, and either had a heavy cosmetic hand in a glove, a rudimentary mechanical hand, or a passive hook incapable of prehension. Dorrance invented a split hook that was anchored to the opposite shoulder and could be opened with a strap across the back and closed by rubber bands. His terminal device (the hook) is still considered to be a major advancement for amputees because it restored their prehension abilities to some extent. Modified hooks are still used today, though they might be hidden by realisticlooking skin. The twentieth century has seen the greatest advances in prosthetic limbs. Materials such as modern plastics have yielded prosthetic devices that are strong and more lightweight than earlier limbs made of iron and wood. New plastics, better pigments, and more sophisticated procedures are responsible for creating fairly realistic-looking skin. The most exciting development of the twentieth century has been the development of myoelectric prosthetic limbs. Myoelectricity involves using electrical signals from the patient's arm muscles to move the limb. Research began in the late 1940s in West Germany, and by the late sixties myoelectric devices were available for adults. In the last decade children have also been fitted with myoelectric limbs. In recent years computers have been used to help fit amputees with prosthetic limbs. Eighty-five percent of private prosthetic facilities use a CAD/CAM to design a model Artificial Limb Plaster cast 4 Making the socket Vacuum of the patient's arm or leg, which can be used mold from which the new limb can be shaped. Laser-guided measuring and fitting is also available. to prepare a Raw Materials The typical prosthetic device consists of a custom fitted socket, an internal structure (also called a pylon), knee cuffs and belts that attach it to the body, prosthetic socks that cushion the area of contact, and, in some cases, realistic-looking skin. Prosthetic limb manufacture is currently undergoing changes on many levels, some of which concern the choice of materials. A prosthetic device should most of all be lightweight; hence, much of it is made from plastic. The socket is usually made from polypropylene. Lightweight metals such as titanium and aluminum have replaced much of the steel in the pylon. Alloys of these materials are most frequently used. The newest development in prosthesis manufacture has been the use of carbon fiber to form a lightweight pylon. Certain parts of the limb (for example, the feet) have traditionally been made of wood (such as maple, hickory basswood, willow, poplar, and linden) and rubber. Even today the feet are made from urethane foam with a wooden inner keel construction. Other materials commonly used are plastics such as polyethylene, polypropylene, acrylics, and polyurethane. Prosthetic socks are made from a number of soft yet strong fabrics. Earlier socks were made of wool, as are some After a plaster cost of the amputee's stump is made, a thermoplastic sheet is vacuum-formed around this cast to form a test socket. In vacuum-forming, the plastic sheet is heated and then placed in a vacuum chamber with the cost (or mold). As the air is sucked out of the chamber, the plastic adheres to the cast and assumes its shape. After testing, the permanent socket is formed in the some way. 15 How Products Are Made, Volume 1 modem ones, which can also be made of cotton or various synthetic materials. Physical appearance of the prosthetic limb is important to the amputee. The majority of endoskeletal prostheses (pylons) are covered with a soft polyurethane foam cover that has been designed to match the shape of the patient's sound limb. This foam cover is then covered with a sock or artificial skin that is painted to match the patient's skin color. The Manufacturing Process Prosthetic limbs are not mass-produced to be sold in stores. Similar to the way dentures or eyeglasses are procured, prosthetic limbs are first prescribed by a medical doctor, usually after consultation with the amputee, a prosthetist, and a physical therapist. The patient then visits the prosthetist to be fitted with a limb. Although some parts-the socket, for instance-are custom-made, many parts (feet, pylons) are manufactured in a factory, sent to the prosthetist, and assembled at the prosthetist's facility in accordance with the patient's needs. At a few facilities, the limbs are custom made from start to finish. Measuring and casting Accuracy and attention to detail are I important in the manufacture of prosthetic limbs, because the goal is to have a limb that comes as close as possible to being as comfortable and useful as a natural one. Before work on the fabrication of the limb is begun, the prosthetist evaluates the amputee and takes an impression or digital reading of the residual limb. 2 The prosthetist then measures the lengths of relevant body segments and determines the location of bones and tendons in the remaining part of the limb. Using the impression and the measurements, the prosthetist then makes a plaster cast of the stump. This is most commonly made of plaster of paris, because it dries fast and yields a detailed impression. From the plaster cast, a positive model-an exact duplicate-of the stump is created. Making the socket 3 Next, a sheet of clear thermoplastic is 3heated in a large oven and then vacuum- 16 formed around the positive mold. In this process, the heated sheet is simply laid over the top of the mold in a vacuum chamber. If necessary, the sheet is heated again. Then, the air between the sheet and the mold is sucked out of the chamber, collapsing the sheet around the mold and forcing it into the exact shape of the mold. This thermoplastic sheet is now the test socket; it is transparent so that the prosthetist can check the fit. 4 Before the permanent socket is made, the prosthetist works with the patient to ensure that the test socket fits properly. In the case of a missing leg, the patient walks while wearing the test socket, and the prosthetist studies the gait. The patient is also asked to explain how the fit feels; comfort comes first. The test socket is then adjusted according to patient input and retried. Because the material from which the test socket is made is thermoplastic, it can be reheated to make minor adjustments in shape. The patient can also be fitted with thicker socks for a more comfortable fit. 1 5 The permanent socket is then formed. 5Since it is usually made of polypropylene, it can be vacuum-formed over a mold in the same way as the test socket. It is common for the stump to shrink after surgery, stabilizing approximately a year later. Thus, the socket is usually replaced at that time, and thereafter when anatomical changes necessitate a change. Fabrication of the prosthesis 6 There are many ways to manufacture the of a prosthetic limb. Plastic pieces-including soft-foam pieces used as liners or padding-are made in the usual plastic forming methods. These include vacuumforming (see no. 3 above), injecting molding -forcing molten plastic into a mold and letting it cool-and extruding, in which the plastic is pulled through a shaped die. Pylons that are made of titanium or aluminum can be die-cast; in this process, liquid metal is forced into a steel die of the proper shape. The wooden pieces can be planed, sawed, and drilled. The various components are put together in a variety of ways, using bolts, adhesives, and laminating, to name a few. 6parts 7 The entire limb is assembled by the pros7thetist's technician using such tools as a torque wrench and screwdriver to bolt the Artificial Limb A typical artiFicial limb, in this case an above-the-knee prosthesis. The foam cover is covered with artificial skin that is pointed to match the patient's natural skin color. prosthetic device together. After this, the prosthetist again fits the permanent socket to the patient, this time with the completed custom-made limb attached. Final adjustments are then made. Physical Therapy Once the prosthetic limb has been fitted, it is necessary for the patient to become comfortable with the device and learn to use it in order to meet the challenges of everyday life. At the same time, they must learn special exercises that strengthen the muscles used to move the prosthetic device. When the patient has been fitted with a myoelectric device, it is sometimes true that the muscles are too weak to effectively signal the device, so again the muscles are exercised to strengthen them. Some new amputees are trained to wash the devices-including the socksdaily, and to practice getting them on and off. A patient fitted with an artificial arm must learn to use the arm and its locking device as well as the hand. If the amputee lost an arm due to an accident and is subsequently fitted with a myoelectric device, this is relatively easy. If the loss of the limb is congenital, this is difficult. An instruction system has been developed to teach amputees how to accomplish many small tasks using only one hand. Some patients fitted with an artificial leg also undergo physical therapy. It typically takes a new amputee 18-20 weeks to learn how to walk again. Patients also learn how to get in and out of bed and how to get in and out of a car. They learn how to walk up and down hill, and how to fall down and get up safely. Quality Control No standards exist for prosthetic limbs in the United States. Some manufacturers advocate instituting those of the International Standards Organization of Europe, particularly because U.S. exporters of prosthetic limbs to Europe must conform to them anyway. 1 7 How Products Are Made, Volume 1 Others believe these regulations to be confusing and unrealistic; they would rather see the United States produce their own, more reasonable standards. Lack of standards does not mean that prosthetic limb manufacturers have not come up with ways to test their products. Some tests evaluate the strength and lifetime of the device. For instance, static loads test strength. A load is applied over a period of 30 seconds, held for 20 seconds, then removed over a period of 30 seconds. The limb should suffer no deformation from the test. To test for failure, a load is applied to the limb until it breaks, thus determining strength limits. Cyclic loads determine the lifetime of the device. A load is applied two million times at one load per second, thus simulating five years of use. Experimental prosthetic limbs are usually considered feasible if they survive 250,000 cycles. The Future Many experts are optimistic about the future of prosthetic limbs; at least, most agree that there is vast room for improvement. A prosthetic limb is a sophisticated device, yet it is preferably simple in design. The ideal prosthetic device should be easy for the patient to learn how to use, require little repair or replacement, be comfortable and easy to put on and take off, be strong yet lightweight, be easily adjustable, look natural, and be easy to clean. Research aims for this admittedly utopian prosthetic device, and strides have been made in recent years. Carbon fiber is a strong, lightweight material that is now being used as the basis of endoskeletal parts (the pylons). In the past it was used primarily for reinforcement of exoskeletal protheses, but some experts claim that carbon fiber is a superior material that will eventually replace metals in pylons. One researcher has developed software that superimposes a grid on a CAT scan of the stump to indicate the amount of pressure the soft tissue can handle with a minimum amount of pain. By viewing the computer model, the prosthetist can design a socket 1 8 that minimizes the amount of soft tissue that is displaced. An experimental pressure-sensitive foot is also in the works. Pressure transducers located in the feet send signals to electrodes set in the stump. The nerves can then receive and interpret the signals accordingly. Amputees can walk more normally on the new device because they can feel the ground and adjust their gait appropriately. Another revolutionary development in the area of prosthetic legs is the introduction of an above-knee prosthesis that has a built-in computer that can be programmed to match the patient's gait, thereby making walking more automatic and natural. Where To Learn More Books Forester, C. S. Flying Colours. Little, Brown, 1938. Sabolich, John. You're Not Alone. Sabolich Prosthetic and Research Center, 1991. Shurr, Donald G. and Thomas M. Cook. Prosthetics and Orthotics. Appleton and Lange, 1990. Periodicals Abrahams, Andrew. "An Amazing 'Foot' Puts Legless Vet Bill Demby Back in the Ballgame," People Weekly. April 4, 1988, p. 119. Hart, Lianne. "Lives that Are Whole," Life. December, 1988, pp. 112-116. Heilman, Joan Rattner. "Medical Miracles," Redbook. May, 1991, p. 124+. "A Helping Hand for Christa," National Geographic World. November, 1986, p. 10. "Off to a Running Start," National Geographic World. August, 1991, pp. 29-3 1. -Rose Secrest Aspirin Background Aspirin is one of the safest and least expensive pain relievers on the marketplace. While other pain relievers were discovered and manufactured before aspirin, they only gained acceptance as over-the-counter drugs in Europe and the United States after aspirin's success at the tum of the twentieth that cause pain and inflammation. Since then, scientists have made further progress in understanding how aspirin works. They now know, for instance, that aspirin and its relatives actually prevent the growth of cells that cause inflammation. History century. Today, Americans alone consume 16,000 tons of aspirin tablets a year, equaling 80 million pills, and we spend about $2 billion a year for non-prescription pain relievers, many of which contain aspirin or similar drugs. Currently, the drug is available in several dosage forms in various concentrations from .0021 to .00227 ounces (60 to 650 milligrams), but the drug is most widely used in tablet form. Other dosage forms include capsules, caplets, suppositories and liquid elixir. Aspirin can be used to fight a host of health problems: cerebral thromboses (with less than one tablet a day); general pain or fever (two to six tablets a day; and diseases such as rheumatic fever, gout, and rheumatoid arthritis. The drug is also beneficial in helping to ward off heart attacks. In addition, biologists use aspirin to interfere with white blood cell action, and molecular biologists use the drug to activate genes. The wide range of effects that aspirin can produce made it difficult to pinpoint how it actually works, and it wasn't until the 1970s that biologists hypothesized that aspirin and related drugs (such as ibuprofen) work by inhibiting the synthesis of certain hormones The compound from which the active ingredient in aspirin was first derived, salicylic acid, was found in the bark of a willow tree in 1763 by Reverend Edmund Stone of Chipping-Norton, England. (The bark from the willow tree-Salix Alba-contains high levels of salicin, the glycoside of salicylic acid.) Earlier accounts indicate that Hippocrates of ancient Greece used willow leaves for the same purpose-to reduce fever and relieve the aches of a variety of illnesses. Today, Americans alone consume 16,000 tons of aspirin tablets a year, equaling 80 million pills, and we spend about $2 billion a year for nonprescription pain relievers, many of which contain aspirin or similar drugs. During the 1800s, various scientists extracted salicylic acid from willow bark and produced the compound synthetically. Then, in 1853, French chemist Charles F. Gerhardt synthesized a primitive form of aspirin, a derivative of salicylic acid. In 1897 Felix Hoffmann, a German chemist working at the Bayer division of I.G. Farber, discovered a better method for synthesizing the drug. Though sometimes Hoffmann is improperly given credit for the discovery of aspirin, he did understand that aspirin was an effective pain reliever that did not have the side effects of salicylic acid (it bumed throats and upset stomachs). Bayer marketed aspirin beginning in 1899 and dominated the production of pain relievers until after World War I, when Sterling Drug bought German-owned Bayer's New 1 9 How Products Are Made, Volume 1 WEIGHING Active ingredient Lubricant Corn starch I, DRY SCREENING The first three steps in aspirin manufacture: weighing, mixing, and dry screening. Mixing can be done in a Glen Mixer, which both blends the ingredients and expels the air from them. In dry screening, small batches are forced through a wire mesh screen by hand, while larger batches can be screened in a Fitzpatrick mill. York operations. Today, "Aspirin" is a registered trademark of Bayer in many countries around the world, but in the United States and the United Kingdom aspirin is simply the common name for acetylsalicylic acid. The manufacture of aspirin has paralleled advancements in pharmaceutical manufacturing as a whole, with significant mechanization occurring during the early twentieth century. Now, the manufacture of aspirin is highly automated and, in certain pharmaceutical companies, completely computerized. While the aspirin production process varies between pharmaceutical companies, dosage forms and amounts, the process is not as complex as the process for many other drugs. In particular, the production of hard aspirin tablets requires only four ingredients: the 20 active ingredient (acetylsalicylic acid), starch, water, and a lubricant. corn Raw Materials To produce hard aspirin tablets, corn starch and water are added to the active ingredient (acetylsalicylic acid) to serve as both a binding agent and filler, along with a lubricant. Binding agents assist in holding the tablets together; fillers (diluents) give the tablets increased bulk to produce tablets of adequate size. A portion of the lubricant is added during mixing and the rest is added after the tablets are compressed. Lubricant keeps the mixture from sticking to the machinery. Possible lubricants include: hydrogenated vegetable oil, stearic acid, talc, or aluminum stearate. Scientists have performed considerable investigation and research to isolate the Aspirin most effective lubricant for hard aspirin tablets. Chewable aspirin tablets contain different diluents, such as mannitol, lactose, sorbitol, sucrose, and inositol, which allow the tablet to dissolve at a faster rate and give the drug a pleasant taste. In addition, flavor agents, such as saccharin, and coloring agents are added to chewable tablets. The colorants currently approved in the United States include: FD&C Yellow No. 5, FD&C Yellow No. 6, FD&C Red No.3, FD&C Red No. 40, FD&C Blue No. 1, FD&C Blue No. 2, FD&C Green No. 3, a limited number of D&C colorants, and iron oxides. ents meet pre-determined specifications for the batch size and dosage amount. Mixing 2 The corn starch is dispensed into cold 2purified water, then heated and stirred until a translucent paste forms. The corn starch, the active ingredient, and part of the lubricant are next poured into one sterile canister, and the canister is wheeled to a mixing machine called a Glen Mixer. Mixing blends the ingredients as well as expels air from the mixture. 3 The mixture is then mechanically sepa- 3rated into units, which are generally from The Manufacturing Process Aspirin tablets are manufactured in different shapes. Their weight, size, thickness, and hardness may vary depending on the amount of the dosage. The upper and lower surfaces of the tablets may be flat, round, concave, or convex to various degrees. The tablets may also have a line scored down the middle of the outer surface, so the tablets can be broken in half, if desired. The tablets may be engraved with a symbol or letters to identify the manufacturer. Aspirin tablets of the same dosage amount are manufactured in batches. After careful weighing, the necessary ingredients are mixed and compressed into units of granular mixture called slugs. The slugs are then filtered to remove air and lumps, and are compressed again (or punched) into numerous individual tablets. (The number of tablets will depend on the size of the batch, the dosage amount, and the type of tablet machine used.) Documentation on each batch is kept throughout the manufacturing process, and finished tablets undergo several tests before they are bottled and packaged for distribution. The procedure for manufacturing hard aspirin tablets, known as dry-granulation or slugging, is as follows: Weighing The corn starch, the active ingredient, and the lubricant are weighed separately in sterile canisters to determine if the ingredi- 7/8 to 1 inches (2.22 to 2.54 centimeters) in size. These units are called slugs. Dry screening 4 Next, small batches of slugs are forced x through a mesh screen by a hand-held stainless steel spatula. Large batches in sizable manufacturing outlets are filtered through a machine called a Fitzpatrick mill. The remaining lubricant is added to the mixture, which is blended gently in a rotary granulator and sifter. The lubricant keeps the mixture from sticking to the tablet machine during the compression process. Compression 5 The mixture is compressed into tablets _either by a single-punch machine (for small batches) or a rotary tablet machine (for large scale production). The majority of single-punch machines are power-driven, but hand-operated models are still available. On single-punch machines, the mixture is fed into one tablet mold (called a dye cavity) by a feed shoe, as follows: * The feed shoe passes over the dye cavity and releases the mixture. The feed shoe then retracts and scrapes all excess mixture away from the dye cavity. * A punch-a short steel rod-the size of the dye cavity descends into the dye, compressing the mixture into a tablet. The punch then retracts, while a punch below 2 1 How Products Are Made, Volume 1 This drawing illustrates the principle of compression in a single-punch machine. First, the aspirin mixture is fed into a dye cavity. Then, a steel punch descends into the cavity and compresses the mixture into a tablet. As the punch retracts, another punch below the cavity rises to eject the tablet. COMPRESSION Compress - I3 n H Eject the dye cavity rises into the cavity and ejects the tablet. * As the feed shoe returns to fill the dye cavity again, it pushes the compressed tablet from the dye platform. On rotary tablet machines, the mixture runs through a feed line into a number of dye cavities which are situated on a large steel plate. The plate revolves as the mixture is dispensed through the feed line, rapidly filling each dye cavity. Punches, both above and below the dye cavities, rotate in sequence with the rotation of the dye cavities. Rollers on top of the upper punches press the punches down onto the dye cavities, compressing the mixture into tablets, while roller-activated punches beneath the dye cavities lift up and eject the tablets from the dye platform. Testing 6 The compressed tablets are subjected to a 6tablet hardness and friability test, as well 22 as a tablet disintegration test (see Quality Control section below). Bottling and packaging 7 The tablets are transferred to an auto/mated bottling assembly line where they are dispensed into clear or color-coated polyethylene or polypropylene plastic bottles or glass bottles. The bottles are topped with cotton packing, sealed with a sheer aluminum top, and then sealed with a plastic and rubber child-proof lid. A sheer, round plastic band is then affixed to the circular edge of the lid. It serves as an additional seal to discourage and detect product tampering. 8 The bottles are then labeled with product 8information and an expiration date is affixed. Depending on the manufacturer, the bottles are then packaged in individual cardboard boxes. The packages or bottles are then boxed in larger cardboard boxes in preparation for distribution to distributors. Aspirin Finished aspirin tablets often have a line "scored" down the center so that the tablet can be broken into two parts with ease. Quality Control Maintaining a high degree of quality control is extremely important in the pharmaceutical manufacturing industry, as well as required by the Food and Drug Administration (FDA). All machinery is sterilized before beginning the production process to ensure that the product is not contaminated or diluted in any way. In addition, operators assist in maintaining an accurate and even dosage amount throughout the production process by performing periodic checks, keeping meticulous batch records, and administering necessary tests. Tablet thickness and weight are also controlled. Once the tablets have been produced, they undergo several quality tests, such as tablet hardness and friability tests. To ensure that the tablets won't chip or break under normal conditions, they are tested for hardness in a machine such as the Schleuniger (or Heberlein) Tablet Hardness Tester. They are also tested for friability, which is the ability of the tablet to withstand the rigors of packaging and shipping. A machine called a Roche Friabilator is used to perform this test. During the test, tablets are tumbled and exposed to repeated shocks. Another test is the tablet disintegration test. To ensure that the tablets will dissolve at the desirable rate, a sample from the batch is placed in a tablet disintegration tester such as the Vanderkamp Tester. This apparatus consists of six plastic tubes open at the top and bottom. The bottoms of the tubes are covered with a mesh screen. The tubes are filled with tablets and immersed in water at 37 degrees Fahrenheit (2.77 degrees Celsius) and retracted for a specified length of time and speed to determine if the tablets dissolve as designed. Where To Learn More Books HIJSA'S Pharmaceutical Dispensing, 6th edition, Mack Publishing Company, 1966. History of Pharmacy, 4th edition, The American Institute of History of Pharmacy, 1986. An Introduction to Pharmaceutical Formulation, Pergamon Press, 1965. Mann, Charles C. The Aspirin Wars: Money, Medicine & One Hundred Years of Rampant Competition. Alfred A. Knopf, Inc. 1991. Remington's Pharmaceutical Sciences, 17th edition, Mack Publishing, 1985. Periodicals Draper, Roger. "A Pharmaceutical Cinderella (History of Aspirin)," The New Leader. January 13, 1992, p. 16. Weissmann, Gerald. "Aspirin," Scientific American. January, 1991, pp. 84-90. Wickens, Barbara. "Aspirin: What's in Name?," Maclean's. July 16, 1990, p. 40. a Greg Ling 23 Automobile The development of the electric automobile will owe more to innovative solar and aeronautical engineering and advanced satellite and radar technology than to traditional automotive design and construction. The electric car will have no engine, exhaust system, transmission, muffler, radiator, or spark plugs. It will require neither tuneups nor gasoline. Background ups in the production process as faster workers overtook slower ones. In Detroit in 1913, In 1908 Henry Ford began production of the Model T automobile. Based on his original Model A design first manufactured in 1903, the Model T took five years to develop. Its creation inaugurated what we know today as the mass production assembly line. This revolutionary idea was based on the concept of simply assembling interchangeable component parts. Prior to this time, coaches and buggies had been hand-built in small numbers by specialized craftspeople who rarely duplicated any particular unit. Ford's innovative design reduced the number of parts needed as well as the number of skilled fitters who had always formed the bulk of the assembly operation, giving Ford a tremendous advantage over his competition. he solved this problem by introducing the first moving assembly line, a conveyor that moved the vehicle past a stationary assembler. By eliminating the need for workers to move between stations, Ford cut the assembly task for each worker from 2.5 minutes to just under 2 minutes; the moving assembly conveyor could now pace the stationary worker. The first conveyor line consisted of metal strips to which the vehicle's wheels were attached. The metal strips were attached to a belt that rolled the length of the factory and then, beneath the floor, returned to the beginning area. This reduction in the amount of human effort required to assemble an automobile caught the attention of automobile assemblers throughout the world. Ford's mass production drove the automobile industry for nearly five decades and was eventually adopted by almost every other industrial manufacturer. Although technological advancements have enabled many improvements to modern day automobile assembly operations, the basic concept of stationary workers installing parts on a vehicle as it passes their work stations has not changed drastically over the years. Ford's first venture into automobile assembly with the Model A involved setting up assembly stands on which the whole vehicle was built, usually by a single assembler who fit an entire section of the car together in one place. This person performed the same activity over and over at his stationary assembly stand. To provide for more efficiency, Ford had parts delivered as needed to each work station. In this way each assembly fitter took about 8.5 hours to complete his assembly task. By the time the Model T was being developed Ford had decided to use multiple assembly stands with assemblers moving from stand to stand, each performing a specific function. This process reduced the assembly time for each fitter from 8.5 hours to a mere 2.5 minutes by rendering each worker completely familiar with a specific task. Ford soon recognized that walking from stand to stand wasted time and created jam- 24 Rsw Materials Although the bulk of an automobile is virgin steel, petroleum-based products (plastics and vinyls) have come to represent an increasingly large percentage of automotive components. The light-weight materials derived from petroleum have helped to lighten some models by as much as thirty percent. As the price of fossil fuels continues to rise, the preference for lighter, more fuel efficient vehicles will become more pronounced. Automobile Design Introducing a new model of automobile generally takes three to five years from inception to assembly. Ideas for new models are developed to respond to unmet pubic needs and preferences. Trying to predict what the public will want to drive in five years is no small feat, yet automobile companies have successfully designed automobiles that fit public tastes. With the help of computer-aided design equipment, designers develop basic concept drawings that help them visualize the proposed vehicle's appearance. Based on this simulation, they then construct clay models that can be studied by styling experts familiar with what the public is likely to accept. Aerodynamic engineers also review the models, studying air-flow parameters and doing feasibility studies on crash tests. Only after all models have been reviewed and accepted are tool designers permitted to begin building the tools that will manufacture the component parts of the new model. The M a n u f a c t u r i n g Process Components The automobile assembly plant represents only the final phase in the process of manufacturing an automobile, for it is here that the components supplied by more than 4,000 outside suppliers, including company-owned parts suppliers, are brought together for assembly, usually by truck or railroad. Those parts that will be used in the chassis are delivered to one area, while those that will comprise the body are unloaded at another. 1 Chassis 2 The typical car or truck is constructed from the ground up (and out). The frame forms the base on which the body rests and from which all subsequent assembly components follow. The frame is placed on the assembly line and clamped to the conveyer to prevent shifting as it moves down the line. From here the automobile frame moves to component assembly areas where complete front and rear suspensions, gas tanks, rear axles and drive shafts, gear boxes, steering box components, wheel drums, and braking systems are sequentially installed. 3 An off-line operation at this stage of production mates the vehicle's engine with its transmission. Workers use robotic arms to install these heavy components inside the engine compartment of the frame. After the engine and transmission are installed, a 25 How Products Are Made, Volume 1 On automobile assembly lines, much of the work is now done by robots rather than humans. In the first stages of automobile manufacture, robots weld the floor pan pieces together and assist workers in placing components such as the suspension onto the chassis. worker attaches the radiator, and another bolts it into place. Because of the nature of these heavy component parts, articulating robots perform all of the lift and carry operations while assemblers using pneumatic wrenches bolt component pieces in place. Careful ergonomic studies of every assembly task have provided assembly workers with the safest and most efficient tools available. Body 4 Generally, the floor pan is the largest s body component to which a multitude of panels and braces will subsequently be either welded or bolted. As it moves down the assembly line, held in place by clamping fixtures, the shell of the vehicle is built. First, the left and right quarter panels are robotically disengaged from pre-staged shipping 26 containers and placed onto the floor pan, where they are stabilized with positioning fixtures and welded. 5 The front and rear door pillars, roof, and Jbody side panels are assembled in the same fashion. The shell of the automobile assembled in this section of the process lends itself to the use of robots because articulating arms can easily introduce various component braces and panels to the floor pan and perform a high number of weld operations in a time frame and with a degree of accuracy no human workers could ever approach. Robots can pick and load 200-pound (90.8 kilograms) roof panels and place them precisely in the proper weld position with tolerance variations held to within .001 of an inch. Moreover, robots can also tolerate the Automobile PAINT BODY smoke, weld flashes, and gases created during this phase of production. As the body moves from the isolated Vweld area of the assembly line, subsequent body components including fully assembled doors, deck lids, hood panel, fenders, trunk lid, and bumper reinforcements are installed. Although robots help workers place these components onto the body shell, the workers provide the proper fit for most of the bolt-on functional parts using pneumatically assisted tools. Paint 7 Prior to painting, the body must pass 7through a rigorous inspection process, the body in white operation. The shell of the vehicle passes through a brightly lit white room where it is fully wiped down by visual inspectors using cloths soaked in hi-light oil. Under the lights, this oil allows inspectors to see any defects in the sheet metal body panels. Dings, dents, and any other defects are repaired right on the line by skilled body repairmen. After the shell has been fully inspected and repaired, the assembly conveyor carries it through a cleaning station where it is immersed and cleaned of all residual oil, dirt, and contaminants. As the shell exits the cleaning station it 8goes through a drying booth and then through an undercoat dip-an electrostatically charged bath of undercoat paint (called the E-coat) that covers every nook and cranny of the body shell, both inside and out, with primer. This coat acts as a substrate surface to which the top coat of colored paint adheres. After the E-coat bath, the shell is again dried in a booth as it proceeds on to the final paint operation. In most automobile assembly plants today, vehicle bodies are spray-painted by robots that have been programmed to apply the exact amounts of paint to just the right areas for just the right length of time. Considerable research and programming has gone into the dynamics of robotic painting in order to ensure the fine "wet" finishes we have come to expect. Our robotic painters have come a long way since Ford's first Model Ts, which were painted by hand with a brush. 9 The body is built up on a separate assembly line from the chassis. Robots once again perform most of the welding on the various panels, but human workers are necessary to bolt the parts together. During welding, component pieces are held securely in a jig while welding operations are performed. Once the body shell is complete, it is attached to an overhead conveyor for the painting process. The multi-step painfing process entails inspection, cleaning, undercoat (electrostatically applied) dipping, drying, topcoat spraying, and baking. Once the shell has been fully covered V with a base coat of color paint and a clear top coat, the conveyor transfers the bodies through baking ovens where the paint is cured at temperatures exceeding 275 degrees Fahrenheit (135 degrees Celsius). 1 27 How Products Are Made, Volume 1 The body and chassis assemblies are mated near the end of the production process. Robotic arms lift the body shell onto the chassis frame, where human workers then bolt the two together. After final components are installed, the vehicle is driven off the assembly line to a quality checkpoint. After the shell leaves the paint area it is ready for interior assembly. Interior assembly The painted shell proceeds through the interior assembly area where workers assemble all of the instrumentation and wiring systems, dash panels, interior lights, seats, door and trim panels, headliners, radios, speakers, all glass except the automobile windshield, steering column and wheel, body weatherstrips, vinyl tops, brake and gas pedals, carpeting, and front and rear bumper fascias. Next, robots equipped with suction 12cups remove the windshield from a shipping container, apply a bead of urethane sealer to the perimeter of the glass, and then place it into the body windshield frame. Robots also pick seats and trim panels and transport them to the vehicle for the ease and efficiency of the assembly operator. After passing through this section the shell is given a water test to ensure the proper fit of door panels, glass, and weatherstripping. It is now ready to mate with the chassis. Mate The chassis assembly conveyor and body shell conveyor meet at this 13the 28 stage of production. As the chassis passes the body conveyor the shell is robotically lifted from its conveyor fixtures and placed onto the car frame. Assembly workers, some at ground level and some in work pits beneath the conveyor, bolt the car body to the frame. Once the mating takes place the automobile proceeds down the line to receive final trim components, battery, tires, antifreeze, and gasoline. 1 4 The vehicle can now be started. From here it is driven to a checkpoint off the line, where its engine is audited, its lights and horn checked, its tires balanced, and its charging system examined. Any defects discovered at this stage require that the car be taken to a central repair area, usually located near the end of the line. A crew of skilled trouble-shooters at this stage analyze and repair all problems. When the vehicle passes final audit it is given a price label and driven to a staging lot where it will await shipment to its destination. Quality Control All of the components that go into the automobile are produced at other sites. This means the thousands of component pieces that comprise the car must be manufactured, Automobile tested, packaged, and shipped to the assembly plants, often on the same day they will be used. This requires no small amount of planning. To accomplish it, most automobile manufacturers require outside parts vendors to subject their component parts to rigorous testing and inspection audits similar to those used by the assembly plants. In this way the assembly plants can anticipate that the products arriving at their receiving docks are Statistical Process Control (SPC) approved and free from defects. Once the component parts of the automobile begin to be assembled at the automotive factory, production control specialists can follow the progress of each embryonic automobile by means of its Vehicle Identification Number (VIN), assigned at the start of the production line. In many of the more advanced assembly plants a small radio frequency transponder is attached to the chassis and floor pan. This sending unit carries the VIN information and monitors its progress along the assembly process. Knowing what operations the vehicle has been through, where it is going, and when it should arrive at the next assembly station gives production management personnel the ability to electronically control the manufacturing sequence. Throughout the assembly process quality audit stations keep track of vital information concerning the integrity of various functional components of the vehicle. This idea comes from a change in quality control ideology over the years. Formerly, quality control was seen as a final inspection process that sought to discover defects only after the vehicle was built. In contrast, today quality is seen as a process built right into the design of the vehicle as well as the assembly process. In this way assembly operators can stop the conveyor if workers find a defect. Corrections can then be made, or supplies checked to determine whether an entire batch of components is bad. Vehicle recalls are costly and manufacturers do everything possible to ensure the integrity of their product before it is shipped to the customer. After the vehicle is assembled a validation process is conducted at the end of the assembly line to verify quality audits from the various inspection points throughout the assembly process. This final audit tests for properly fitting panels; dynamics; squeaks and rattles; functioning electrical components; and engine, chassis, and wheel alignment. In many assembly plants vehicles are periodically pulled from the audit line and given full functional tests. All efforts today are put forth to ensure that quality and reliability are built into the assembled product. The Future The development of the electric automobile will owe more to innovative solar and aeronautical engineering and advanced satellite and radar technology than to traditional automotive design and construction. The electric car has no engine, exhaust system, transmission, muffler, radiator, or spark plugs. It will require neither tune-ups nor-truly revolutionary-gasoline. Instead, its power will come from alternating current (AC) electric motors with a brushless design capable of spinning up to 20,000 revolutions/minute. Batteries to power these motors will come from high performance cells capable of generating more than 100 kilowatts of power. And, unlike the lead-acid batteries of the past and present, future batteries will be environmentally safe and recyclable. Integral to the braking system of the vehicle will be a power inverter that converts direct current electricity back into the battery pack system once the accelerator is let off, thus acting as a generator to the battery system even as the car is driven long into the future. The growth of automobile use and the increasing resistance to road building have made our highway systems both congested and obsolete. But new electronic vehicle technologies that permit cars to navigate around the congestion and even drive themselves may soon become possible. Turning over the operation of our automobiles to computers would mean they would gather information from the roadway about congestion and find the fastest route to their instructed destination, thus making better use of limited highway space. The advent of the electric car will come because of a rare convergence of circumstance and ability. Growing intolerance for pollution combined with extraordinary technological advancements will change the global transportation paradigm that will carry us into the twentyfirst century. 29 How Products Are Made, Volume 1 Where To Learn More Books Abernathy, William. The Productivity Dilemma: Roadblock to Innovation in the Automobile Industry. Johns Hopkins University Press, 1978. Gear Design, Manufacturing & Inspection Manual. Society of Manufacturing Engineers, Inc., 1990. Hounshell, David. From the American System to Mass Production. Johns Hopkins University Press, 1984. Lamming, Richard. Beyond Partnership: Strategies for Innovation & Lean Supply. Prentice Hall, 1993. Making the Car. Motor Vehicle Manufacturers Association of the United States, 1987. Mortimer, J., ed. Advanced Manufacturing in the Automotive Industry. Springer-Verlag New York, Inc., 1987. Mortimer, John. Advanced Manufacturing in the Automotive Industry. Air Science Co., 1986. Nevins, Allen and Frank E. Hill. Ford: The Times, The Man, The Company. Scribners, 1954. Seiffert, Ulrich. Automobile Technology of the Future. Society of Automotive Engineers, Inc., 1991. Sloan, Alfred P. My Years with General Motors. Doubleday, 1963. Periodicals "The Secrets of the Production Line," The Economist. October 17, 1992, p. S5. - Rick Bockmiller 30 Automobile Windshield Background Glass is a versatile material with hundreds of applications, including windshields. Glass has a long history and was first made more than 7,000 years ago in Egypt, as early as 3,000 B.C. Glass is found in a natural state as a by-product of volcanic activity. Today, glass is manufactured from a variety of ceramic materials (main components are oxides). The main product categories are flat or float glass, container glass, cut glass, fiberglass, optical glass, and specialty glass. Automotive windshields fall into the flat glass category. There are more than 80 companies worldwide that produce automotive glass, including windshields. Major producers in the United States include PPG, Guardian Industries Corp., and Libby-Owens Ford. According to the Department of Commerce, 25 percent of flat glass production is consumed by the automotive industry (including windows) at a total value of approximately $483 million. In Japan, 30 percent of flat glass goes to the automotive industry, valued at around $190 billion in 1989. Major Japanese flat glass manufacturers include Asahi Glass Co., Central Glass Co., and Nippon Sheet Glass Co. Little growth is expected for the flat glass industry overall in both countries. Germany has a more positive outlook, with high growth rates expected from the automotive industry. Glass windshields first appeared around 1905 with the invention of safety glass-glass tempered (tempering is a heat treatment) to make it especially hard and resistant to shattering. This type of windshield was popular well into the middle of the century, but it was eventu- ally replaced by windshields made of laminated glass-a multilayer unit consisting of a plastic layer surrounded by two sheets of glass. In many countries, including the U.S., auto windshields are required by law to be made of laminated glass. Laminated glass can bend slightly under impact and is less likely to shatter than normal safety glass. This quality reduces the risk of injury to the automobile's passengers. Rawv Materials Glass is composed of numerous oxides that fuse and react together upon heating to form a glass. These include silica (SiO2), sodium oxide (Na2O), and calcium oxide (CaO). Raw materials from which these materials are derived are sand, soda ash (Na2CO3), and limestone (CaCO3). Soda ash acts as a flux; in other words, it lowers the melting point of the batch composition. Lime is added to the batch in order to improve the hardness and chemical durability of the glass. Glass used for windshields also usually contains several other oxides: potassium oxide (K20 derived from potash), magnesium oxide (MgO), and aluminum oxide (AI203 derived from feldspar). A bi-layer windshield has been developed that consists of one sheet of glass joined to a single sheet of polyurethane. Unique features of this windshield include ultraviolet resistance, selfhealing of scratches, weight savings, more complex shapes, increased safety due to retention of glass splinters, and anti-fog capability. The Manufacturing Process The raw materials are carefully weighed I in the appropriate amounts and mixed together with a small amount of water to prevent segregation of the ingredients. Cullet (broken waste glass) is also used as a raw material. 2 Once the batch is made, it is fed to a 2large tank for melting using the float 31 How Products Are Made, Volume 1 The glass for automible windshields is made using the float glass process. In this method, the raw material is heated to a molten state and fed onto a bath of molten tin. The glass literally floats on top of the fin; because the fin is perfectly flat, the glass also becomes flat. From the float chamber, the glass passes on rollers through an oven (the "annealing lehr"). After exiting the lehr and cooling to room temperature, the glass is cut to the proper shape and tempered. glass process. First, the batch is heated to a molten state, and then it is fed into a tank called the float chamber, which holds a bath of molten tin. The float chamber is very large-from about 13 feet to 26.25 feet (4 to 8 meters wide and up to almost 197 feet (60 meters) long; at its entrance, the temperature of the tin is about 1,835 degrees Fahrenheit (1,000 degrees Celsius), while at the exit the tin's temperature is slightly cooler-1,115 degrees Fahrenheit (600 degrees Celsius). In the float chamber, the glass doesn't submerge into the tin but floats on top of it, moving through the tank as though on a conveyor belt. The perfectly flat surface of the tin causes the molten glass also to become flat, while the high temperatures clean the glass of impurities. The decreased temperature at the exit of the chamber allows the glass to harden enough to move into the next chamber, a furnace. 3 After the glass exits from the float cham- 3ber, rollers pick it up and feed it into a special furnace c