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- - A worker sets up a computer controlled profiling machine that cuts complex parts out of aluminum, steel, and titanium. The program of instructions for making a part is usually generated on ~ separate CAM system, then transferred to the machine's computer, which can store programs for dozens of parts. 8 _ ~ ~ ~ ~ ____ ~ ~ ~e.~" - ~ .~ __ .................~ .~. ~ _ ,.,.. __ --I-__-~ - ·-a_ - Hidden behind factory walls throughout the world, . another industrial revolution ............................................................................................. . ~1 . -- i ~s un 0 cling arounc t Ale computer. It is changing industry as profoundly as power machinery did in the eighteenth century and mass production, typified by the assembly line, did early this century. Computer-aided design and computer- aided manufacturing-CAD and CAM- have already increased speed and efficiency for many manufacturers. They are improving the quality of products while decreasing the time to take them from idea to market. And they are giving manufacturers the flexibility to respond to an ever-changing market. Essentially, CAD covers the use of computers on the design side of a product while CAM refers to their use on the manu- facturing side. On the design side, engineers use computer graphics to design the new part or product. Other engineers use analyti- cal programs to determine whether the part, as it is designed, will hold up under the stress of actual use. Drafters use computer- ized devices to add detail to the design and produce the final drawings. On the manufac- turing side, computers help engineers write instructions for the automatic tools that will create the part. Small computers on the machines themselves allow the machines to be quickly changed from producing one part to making another. Small computers have also spread to other areas of the factory, controlling manufacturing processes, operating robots that move pieces from one machine to another, and guiding automatic carts that move materials, parts, and finished products around the plant. Modern CAD and CAM systems began appearing on the market around 1970, I following the marriage of CAD and CAM computer programs to minicomputers in the $100,000 range. Previously they were limited to a few large manufacturers of aircraft, autos, and textiles who wrote their own CAD and CAM programs and ran them on mainframe computers that often cost a million dollars or more. The roots of CAD and CAM reach back to two Air Force programs in 1949. CAD hardware the machines began with efforts to build an air defense system by linking radar to computers, whose data were displayed on video screens. At the same time, the forerunner of CAM software programs to run the hardware began with the creation of punched tapes to operate numerically controlled (NC) machines. These machines cut, drill, and perform other tasks according to instructions fed into their control units on a punched paper tape. Tapes for the first generation of commercial NC machines were laboriously punched by hand. After the creation of a computer E N G I N E E ~ I N G A N ~ F H E A D VA ~ C E M E N T O F H U M ~ N W E ~ FA R E
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,jili my' IUtf^~ ~ '''I '~ programming language called APT, for Automatically Programmed Tools, tapes were generated on mainframe computers. Modern CAM really began in 1969 with the appearance on the market of a less complex language, called Compact II, for programming NC machines. Before then, companies produced their NC tapes by hand, made them with APT on a mainframe computer, or sent the work to be done on a time-sharing basis on an out-of-house mainframe. Compact II was initially a time- sharing service. But later the program was sold to run on a minicomputer, further reducing the cost of the service. With such a CAM system, an engineer could quickly write a program to produce a part, press a button, and the computer would punch out the correct instructions on an NC tape. The tape was taken to the NC machine to make the part. Today, even easier languages have been introduced for programming NC machines. In some systems, the tapes have been eliminated by hooking the programming ~ computer directly to the machine tool. And I many NC machines have small computers that store several programs for producing different parts. Computer-aided design has sparked its own revolution within the broader move- ment toward factory computerization. Like the telescope and the microscope, CAD systems have opened up new worlds of understanding to the engineers who design, analyze, and test today's sophisticated products. CAD is applied to nearly every large or complex engineering project under- taken today, from designing modern jumbo jets to planning energy-efficient buildings. It was, for example, extensively used in designing Stars ~ Stripes, the racing yacht that won the America's Cup competition held in Australia in 1987. And CAD is absolutely essential for designing the tiny I circuits in microprocessors and other inte- grated-circuit chips that mn most electronic devices. The second wave of the CAD revolution rose In 1981 with the introduction of single- user CAD workstations. Workstation computers are powered by microprocessors and generally have more computing power C O M P U T E R - A I D E D D E S I G N A N D M A N U FA C T U R I N G The screen of a CAD/CAM system illustrates the complex tool path that a milling machine must follow to create the curving surface of an impeller blade for a jet engine. 19
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and graphics capability than personal computers, which are also based on micro- processors. However, a workstation costs about one-tenth as much as a minicomputer. Today, the price of some workstations is under $10,000, and their power equals that of most minis. Modern CAD did not spring full grown into existence. It began as a drawing aid for e~ A microprocessor is designed with the aid of an electronic CAD system. Using this program, an engineer can quickly design an electronic circuit by placing and connecting symbols of components on the screen. The computer automatically adds the details to the final design. l ~ . . ..~ An engineer uses a workstation and a mechanical CAD program to design a new wheel hub assembly. 20 as_ drafters and developed along two parallel paths. One led through electronic design, and the other through mechanical design. In the electronics industry, the great problem facing engineers in the late 1960s was the design of increasingly smaller and more complex integrated circuits on tiny silicon chips. NC machines had been devel- oped for cutting the stencil-like masks used in etching circuit patterns onto chips. But instructions for the machines were still calculated and punched into the tapes by hand. In 1970 one of the first commercial electronic CAD systems, called Design Assistant, appeared on the market. It consist- ed of a minicomputer, screen, sketch pad, and keyboard plus software. The engineer drew the circuit on the pad, watching the design appear on the screen. After correcting mistakes, the engineer pressed a button, and instructions for cutting the design were punched into an NC tape. This early CAD system sold for about $150,000. But just two years later, improved versions were selling for half that price. In the mid-1970s, new electronic CAD programs for "design rule check" came to the market. They not only copied the circuit pattern but also told the engineer whether the patterns were too close together or violated any other design rules. In the early 1980s, even more intelligent programs were developed. Called "performance models," they could tell a design engineer what would happen when electric signals flowed through the circuit and point out flaws in the design. Today, no self-respecting engineer would design a circuit without performance modeling. One of the first modern CAD systems for mechanical design arrived in 1971 on the heels of electronic CAD. It was really a drafting aid that consisted of a drawing table, computer, screen, and plotting arm that digitized its movements: that is, translated them into digital electronic signals. By moving the plotter to different points on the table and telling the computer what to draw between them, a draftsman could copy a design into the computer while watching it materialize on the screen. After correcting the design, the draftsman pressed a button, and the plotting arm automatically redrew the design on a clean piece of paper. Called Interact I, this mechanical CAD system ran on a minicomputer with four terminals and cost around $375,000. The early mechanical CAD systems could draw points, lines, circles, arcs, and symbols in two dimensions but with no mathematical idea of what they were doing. By 1973 more intelligent programs were developed that could not only create three- dimensional figures on the computer screen but understood the geometry and mathemat- ics associated with them. These were wire- frame models like the 3-D figures engineers traditionally drew. More important than creating 3-D design models, though, was the intelligence of such a CAD program. Using a mathematical model of the design in its data base, it could answer questions from the engineer: How long is that line? What is the area of this plane? Where is the center of gravity? And if, for example, the engineer tried to put a 2- inch piece in a space 1.75 inches wide, the CAD program would reply that the piece was 0.25 inch too long. It was smart enough to calculate and draw a new line through a model if the engineer so requested. It could also calculate a section, in effect slicing the model in two so the engineer could see how ~ E N G ~ N E E R ~ N G A N D T H E A D VA N C E M E N T O F H U M A N W E ~ FA R E
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parts fit together inside the design. And it could turn the model to be viewed from different angles. This was not just a drafting device but a true CAD system that helped an engineer design a part. The newer mechanical CAD programs were also intelligent enough to perform simple analyses on the design, to see how it would hold up under the stress of actual use. They could also prepare a design for more complex analysis by dividing the model into the hundreds or thousands of geometrical shapes that formed it. The data were then sent to analytical engineers who tested the design on powerful mainframe computers. This preparation, which the CAD program did in seconds, would have taken engineers hundreds of hours to do by hand. In the late 1970s, computer models of solid objects came onto the market. These were even better for analysis than 3-D wire- frame models. Nevertheless, since there are so many variables in designing a mechanical part, mechanical CAD systems today are only beginning to reach the level of perfor- mance modeling that electronic CAD systems achieved nearly a decade ago. However, programs are being developed that allow engineers to analyze mechanical systems for a large number of variables. For example, engineers soon could be able to model the performance of a mechanical system as complex as a commercial power plant. CAD programs of the late 1970s also began linking to CAM systems on the manufacturing side of factories, eliminating the need for many paper design drawings and reducing the time manufacturing engineers need to write instruction programs for the NC machines that make the parts. Previously, engineers had to study the paper drawings in order to calculate tool move- ments. These CAD systems, however, could simulate the movement of a cutting tool around the design model in order to deter- mine the necessary tool movements. These were not only determined more quickly using CAD models, they were also more accurate. In the future, engineers will seek ways to use CAD and CAM more effectively. Today CAD programs are linked to CAM systems in only a small number of factories. On the design side of factories, separate CAD systems often exist independently in design, drafting, and engineering departments. Drawings are still often carried from one office to another, where it may take 50 to 100 hours to enter the data into another comput- er system. On the manufacturing side, computers are only slowly being applied to tasks that they could perform faster and more effectively. In addition, many factories could greatly increase their productivity by joining isolated computerized systems into integrated networks. Such computer- integrated manufacturing, or CIM, has begun in a few factories, and some of the results have been spectacular. For example, the highly integrated use of computerized systems at one company that manufactures motor-starter components helps it produce and ship the parts in less than 24 hours, a job that used to take about 15 days. Another challenge in computerizing the manufacturing process lies in integrating f~,~Y ~ _ ^. it',\ ,~ . . ,. , ~ . , `, ~. ~i, ,,, ~ , '"HI" i. ~ ',. at_ ~ ' me, ° ~ilium, I' '/; r~;; -~ computers throughout the company, not just at an individual factory. Such a CIM network might include finance, market forecasting, material ordering, customer service, and stocking, as well as CAD and CAM. Current debate swirls around how to integrate the computers whether to design one big network or to integrate computers only where and when it becomes necessary. Too much integration could flood and slow the network with needless data. Computers have found an indispensable role to play in manufacturing through CAD, CAM, and other automated systems. No one really disagrees. How big a role they will play, and when, are the real questions for the future. C O M P U T E R - A ~ D E D D E 51 G N A N D M A N U FA C T U R I N G I An engineer uses a mechanical CAD program to analyze stress on the lifting arm in the design of an automobile jack assembly. The program creates a solid model of the device, top. It uses a mesh to divide the lifting arm into small "finite elements" that are analyzed for stress individually, center The program then uses color coding to indicate varying levels of stress throughout the component, telling the I engineer where to strengthen the design, bottom. 21
Representative terms from entire chapter: