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.
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.
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