05 March 2009

CAD/CAM

The invention: Computer-Aided Design (CAD) and Computer- Aided Manufacturing (CAM) enhanced flexibility in engineering design, leading to higher quality and reduced time for manufacturing The people behind the invention: Patrick Hanratty, a General Motors Research Laboratory worker who developed graphics programs Jack St. Clair Kilby (1923- ), a Texas Instruments employee who first conceived of the idea of the integrated circuit Robert Noyce (1927-1990), an Intel Corporation employee who developed an improved process of manufacturing integrated circuits on microchips Don Halliday, an early user of CAD/CAM who created the Made-in-America car in only four months by using CAD and project management software Fred Borsini, an early user of CAD/CAM who demonstrated its power Summary of Event Computer-Aided Design (CAD) is a technique whereby geometrical descriptions of two-dimensional (2-D) or three-dimensional (3- D) objects can be created and stored, in the form of mathematical models, in a computer system. Points, lines, and curves are represented as graphical coordinates. When a drawing is requested from the computer, transformations are performed on the stored data, and the geometry of a part or a full view from either a two- or a three-dimensional perspective is shown. CAD systems replace the tedious process of manual drafting, and computer-aided drawing and redrawing that can be retrieved when needed has improved drafting efficiency. A CAD system is a combination of computer hardware and software that facilitates the construction of geometric models and, in many cases, their analysis. It allows a wide variety of visual representations of those models to be displayed.Computer-Aided Manufacturing (CAM) refers to the use of computers to control, wholly or partly, manufacturing processes. In practice, the term is most often applied to computer-based developments of numerical control technology; robots and flexible manufacturing systems (FMS) are included in the broader use of CAM systems. A CAD/CAM interface is envisioned as a computerized database that can be accessed and enriched by either design or manufacturing professionals during various stages of the product development and production cycle. In CAD systems of the early 1990’s, the ability to model solid objects became widely available. The use of graphic elements such as lines and arcs and the ability to create a model by adding and subtracting solids such as cubes and cylinders are the basic principles of CADand of simulating objects within a computer.CADsystems enable computers to simulate both taking things apart (sectioning) and putting things together for assembly. In addition to being able to construct prototypes and store images of different models, CAD systems can be used for simulating the behavior of machines, parts, and components. These abilities enable CAD to construct models that can be subjected to nondestructive testing; that is, even before engineers build a physical prototype, the CAD model can be subjected to testing and the results can be analyzed. As another example, designers of printed circuit boards have the ability to test their circuits on a CAD system by simulating the electrical properties of components. During the 1950’s, the U.S. Air Force recognized the need for reducing the development time for special aircraft equipment. As a result, the Air Force commissioned the Massachusetts Institute of Technology to develop numerically controlled (NC) machines that were programmable. A workable demonstration of NC machines was made in 1952; this began a new era for manufacturing. As the speed of an aircraft increased, the cost of manufacturing also increased because of stricter technical requirements. This higher cost provided a stimulus for the further development of NC technology, which promised to reduce errors in design before the prototype stage. The early 1960’s saw the development of mainframe computers. Many industries valued computing technology for its speed and for its accuracy in lengthy and tedious numerical operations in design, manufacturing, and other business functional areas. Patrick Hanratty, working for General Motors Research Laboratory, saw other potential applications and developed graphics programs for use on mainframe computers. The use of graphics in software aided the development of CAD/CAM, allowing visual representations of models to be presented on computer screens and printers. The 1970’s saw an important development in computer hardware, namely the development and growth of personal computers (PCs). Personal computers became smaller as a result of the development of integrated circuits. Jack St. Clair Kilby, working for Texas Instruments, first conceived of the integrated circuit; later, Robert Noyce, working for Intel Corporation, developed an improved process of manufacturing integrated circuits on microchips. Personal computers using these microchips offered both speed and accuracy at costs much lower than those of mainframe computers. Five companies offered integrated commercial computer-aided design and computer-aided manufacturing systems by the first half of 1973. Integration meant that both design and manufacturing were contained in one system. Of these five companies—Applicon, Computervision, Gerber Scientific, Manufacturing and Consulting Services (MCS), and United Computing—four offered turnkey systems exclusively. Turnkey systems provide design, development, training, and implementation for each customer (company) based on the contractual agreement; they are meant to be used as delivered, with no need for the purchaser to make significant adjustments or perform programming. The 1980’s saw a proliferation of mini- and microcomputers with a variety of platforms (processors) with increased speed and better graphical resolution. This made the widespread development of computer-aided design and computer-aided manufacturing possible and practical. Major corporations spent large research and development budgets developing CAD/CAM systems that would automate manual drafting and machine tool movements. Don Halliday, working for Truesports Inc., provided an early example of the benefits of CAD/CAM. He created the Made-in-America car in only four months by using CAD and project management software. In the late 1980’s, Fred Borsini, the president of Leap Technologies in Michigan, brought various products to market in record time through the use of CAD/CAM. In the early 1980’s, much of theCAD/CAMindustry consisted of software companies. The cost for a relatively slow interactive system in 1980 was close to $100,000. The late 1980’s saw the demise of minicomputer-based systems in favor of Unix work stations and PCs based on 386 and 486 microchips produced by Intel. By the time of the International Manufacturing Technology show in September, 1992, the industry could show numerous CAD/CAM innovations including tools, CAD/CAM models to evaluate manufacturability in early design phases, and systems that allowed use of the same data for a full range of manufacturing functions. Impact In 1990, CAD/CAM hardware sales by U.S. vendors reached $2.68 billion. In software alone, $1.42 billion worth of CAD/CAM products and systems were sold worldwide by U.S. vendors, according to International Data Corporation figures for 1990. CAD/ CAM systems were in widespread use throughout the industrial world. Development lagged in advanced software applications, particularly in image processing, and in the communications software and hardware that ties processes together. A reevaluation of CAD/CAM systems was being driven by the industry trend toward increased functionality of computer-driven numerically controlled machines. Numerical control (NC) software enables users to graphically define the geometry of the parts in a product, develop paths that machine tools will follow, and exchange data among machines on the shop floor. In 1991, NC configuration software represented 86 percent of total CAM sales. In 1992, the market shares of the five largest companies in the CAD/CAM market were 29 percent for International Business Machines, 17 percent for Intergraph, 11 percent for Computervision, 9 percent for Hewlett-Packard, and 6 percent for Mentor Graphics. General Motors formed a joint venture with Ford and Chrysler to develop a common computer language in order to make the next generation of CAD/CAM systems easier to use. The venture was aimed particularly at problems that posed barriers to speeding up the design of new automobiles. The three car companies all had sophisticated computer systems that allowed engineers to design parts on computers and then electronically transmit specifications to tools that make parts or dies. CAD/CAM technology was expected to advance on many fronts. As of the early 1990’s, different CAD/CAM vendors had developed systems that were often incompatible with one another, making it difficult to transfer data from one system to another. Large corporations, such as the major automakers, developed their own interfaces and network capabilities to allow different systems to communicate. Major users of CAD/CAM saw consolidation in the industry through the establishment of standards as being in their interests. Resellers of CAD/CAM products also attempted to redefine their markets. These vendors provide technical support and service to users. The sale of CAD/CAM products and systems offered substantial opportunities, since demand remained strong. Resellers worked most effectively with small and medium-sized companies, which often were neglected by the primary sellers of CAD/CAM equipment because they did not generate a large volume of business. Some projections held that by 1995 half of all CAD/CAM systems would be sold through resellers, at a cost of $10,000 or less for each system. The CAD/CAM market thus was in the process of dividing into two markets: large customers (such as aerospace firms and automobile manufacturers) that would be served by primary vendors, and small and medium-sized customers that would be serviced by resellers. CAD will find future applications in marketing, the construction industry, production planning, and large-scale projects such as shipbuilding and aerospace. Other likely CAD markets include hospitals, the apparel industry, colleges and universities, food product manufacturers, and equipment manufacturers. As the linkage between CAD and CAM is enhanced, systems will become more productive. The geometrical data from CAD will be put to greater use by CAM systems. CAD/CAM already had proved that it could make a big difference in productivity and quality. Customer orders could be changed much faster and more accurately than in the past, when a change could require a manual redrafting of a design. Computers could do automatically in minutes what once took hours manually. CAD/ CAM saved time by reducing, and in some cases eliminating, human error. Many flexible manufacturing systems (FMS) had machining centers equipped with sensing probes to check the accuracy of the machining process. These self-checks can be made part of numerical control (NC) programs. With the technology of the early 1990’s, some experts estimated that CAD/CAM systems were in many cases twice as productive as the systems they replaced; in the long run, productivity is likely to improve even more, perhaps up to three times that of older systems or even higher. As costs for CAD/ CAM systems concurrently fall, the investment in a system will be recovered more quickly. Some analysts estimated that by the mid- 1990’s, the recovery time for an average system would be about three years. Another frontier in the development of CAD/CAM systems is expert (or knowledge-based) systems, which combine data with a human expert’s knowledge, expressed in the form of rules that the computer follows. Such a system will analyze data in a manner mimicking intelligence. For example, a 3-D model might be created from standard 2-D drawings. Expert systems will likely play a pivotal role in CAM applications. For example, an expert system could determine the best sequence of machining operations to produce a component. Continuing improvements in hardware, especially increased speed, will benefit CAD/CAM systems. Software developments, however, may produce greater benefits. Wider use of CAD/CAM systems will depend on the cost savings from improvements in hardware and software as well as on the productivity of the systems and the quality of their product. The construction, apparel, automobile, and aerospace industries have already experienced increases in productivity, quality, and profitability through the use of CAD/CAM. A case in point is Boeing, which used CAD from start to finish in the design of the 757.

Buna rubber

The invention: The first practical synthetic rubber product developed, Buna inspired the creation of other other synthetic substances that eventually replaced natural rubber in industrial applications. The people behind the invention: Charles de la Condamine (1701-1774), a French naturalist Charles Goodyear (1800-1860), an American inventor Joseph Priestley (1733-1804), an English chemist Charles Greville Williams (1829-1910), an English chemist A New Synthetic Rubber The discovery of natural rubber is often credited to the French scientist Charles de la Condamine, who, in 1736, sent the French Academy of Science samples of an elastic material used by Peruvian Indians to make balls that bounced. The material was primarily a curiosity until 1770, when Joseph Priestley, an English chemist, discovered that it rubbed out pencil marks, after which he called it “rubber.” Natural rubber, made from the sap of the rubber tree (Hevea brasiliensis), became important after Charles Goodyear discovered in 1830 that heating rubber with sulfur (a process called “vulcanization”) made it more elastic and easier to use. Vulcanized natural rubber came to be used to make raincoats, rubber bands, and motor vehicle tires. Natural rubber is difficult to obtain (making one tire requires the amount of rubber produced by one tree in two years), and wars have often cut off supplies of this material to various countries. Therefore, efforts to manufacture synthetic rubber began in the late eighteenth century. Those efforts followed the discovery by English chemist Charles GrevilleWilliams and others in the 1860’s that natural rubber was composed of thousands of molecules of a chemical called isoprene that had been joined to form giant, necklace- like molecules. The first successful synthetic rubber, Buna, was patented by Germany’s I. G. Farben Industrie in 1926. The success of this rubber led to the development of many other synthetic rubbers, which are now used in place of natural rubber in many applications.From Erasers to Gas Pumps Natural rubber belongs to the group of chemicals called “polymers.” Apolymer is a giant molecule that is made up of many simpler chemical units (“monomers”) that are attached chemically to form long strings. In natural rubber, the monomer is isoprene (dimethylbutadiene). The first efforts to make a synthetic rubber used the discovery that isoprene could be made and converted into an elastic polymer. The synthetic rubber that was created from isoprene was, however, inferior to natural rubber. The first Buna rubber, which was patented by I. G. Farben in 1926, was better, but it was still less than ideal. Buna rubber was made by polymerizing the monomer butadiene in the presence of sodium. The name Buna comes from the first two letters of the words “butadiene” and “natrium” (German for sodium). Natural and Buna rubbers are called homopolymers because they contain only one kind of monomer. The ability of chemists to make Buna rubber, along with its successful use, led to experimentation with the addition of other monomers to isoprene-like chemicals used to make synthetic rubber. Among the first great successes were materials that contained two alternating monomers; such materials are called “copolymers.” If the two monomers are designated Aand B, part of a polymer molecule can be represented as (ABABABABABABABABAB). Numerous synthetic copolymers, which are often called “elastomers,” now replace natural rubber in applications where they have superior properties. All elastomers are rubbers, since objects made from them both stretch greatly when pulled and return quickly to their original shape when the tension is released. Two other well-known rubbers developed by I. G. Farben are the copolymers called Buna-N and Buna-S. These materials combine butadiene and the monomers acrylonitrile and styrene, respectively. Many modern motor vehicle tires are made of synthetic rubber that differs little from Buna-S rubber. This rubber was developed after the United States was cut off in the 1940’s, during World War II, from its Asian source of natural rubber. The solution to this problem was the development of a synthetic rubber industry based on GR-S rubber (government rubber plus styrene), which was essentially Buna-S rubber. This rubber is still widely used.Buna-S rubber is often made by mixing butadiene and styrene in huge tanks of soapy water, stirring vigorously, and heating the mixture. The polymer contains equal amounts of butadiene and styrene (BSBSBSBSBSBSBSBS). When the molecules of the Buna-S polymer reach the desired size, the polymerization is stopped and the rubber is coagulated (solidified) chemically. Then, water and all the unused starting materials are removed, after which the rubber is dried and shipped to various plants for use in tires and other products. The major difference between Buna-S and GR-S rubber is that the method of making GR-S rubber involves the use of low temperatures. Buna-N rubber is made in a fashion similar to that used for Buna- S, using butadiene and acrylonitrile. Both Buna-N and the related neoprene rubber, invented by Du Pont, are very resistant to gasoline and other liquid vehicle fuels. For this reason, they can be used in gas-pump hoses. All synthetic rubbers are vulcanized before they are used in industry. Impact Buna rubber became the basis for the development of the other modern synthetic rubbers. These rubbers have special properties that make them suitable for specific applications. One developmental approach involved the use of chemically modified butadiene in homopolymers such as neoprene. Made of chloroprene (chlorobutadiene), neoprene is extremely resistant to sun, air, and chemicals. It is so widely used in machine parts, shoe soles, and hoses that more than 400 million pounds are produced annually. Another developmental approach involved copolymers that alternated butadiene with other monomers. For example, the successful Buna-N rubber (butadiene and acrylonitrile) has properties similar to those of neoprene. It differs sufficiently from neoprene, however, to be used to make items such as printing press rollers. About 200 million pounds of Buna-N are produced annually. Some 4 billion pounds of the even more widely used polymer Buna-S/ GR-S are produced annually, most of which is used to make tires. Several other synthetic rubbers have significant industrial applications, and efforts to make copolymers for still other purposes continue.