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Computers offer the possibility of reintegrating these fragmented
functions into a single, smoothly operating, manufacturing system with
reduced total manufacturing costs and turnaround times, and improved
quality. Computer-integrated manufacturing (CIM) in a manufacturing
enterprise occurs when:
· all the processing functions and related managerial functions
are expressed in the form of data,
· these data are in a form that may be generated, transformed,
used, moved, and s tared by computer technology, and
· these data move freely between functions in the system
throughout the life of the product,
with the objective that the enterprise as a whole have the information
needed to operate at maximum effectiveness.
The computer has been used in manufacturing for years. Perhaps
its most common early use was in controlling machine tools--first
offline, via punched tapes, and then online, via direct numerical
control (DNC). The computer has been used successfully in a variety
of applications for communication of data among a limited number of
manufacturing functions. A number of companies have focused their
activities on two broad areas:
~ computer-aided design (CAD), which applies the computer to the
creation, modification' and evaluation of product design, and
· computer-aided manufacturing (CAM), which applies the computer
to the planning, control, and operation of a production facility.
Of the countless interactions required in a fully integrated
manufacturing system, the interface between engineering design and
production--that is' between CAD and CAM--is currently a major
s tumbling block in achieving computer integration. In the movement of
a product from initial concept to finished form, the organizational
division between engineering design and production has been, until
very recently, the most clear-cut and accepted. As a result' efforts
to bridge this interface have lagged progress in the computer
integration of applications within those areas.
The CAD/CAM interface, though presenting a great challenge to
integration, should not be separated from other problems in developing
a CIM system. Examining only the CAD/CAM interface could perpetuate
the existing fragmentation. This report will emphasize the interface
between engineering design and production, but within the context of
the integration of a broader range of data and functions necessary to
optimize a factory's operation.
THE CONSEQUENCES OF COMPUTER-INTEGRATED MANUFACTURING
The computer can provide manufacturing with two powerful, never-
before-available capabilities:
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· flexible, data-driven automation--for example, the choice of a
DNC program as a function of the part to be processed
· online decision-making algorithms--the ability to determine
system status, generate alternatives, and choose the best one, based
on objective criteria
The computer has the potential to provide these capabilities not
only for limited portions of manufacturing activity ~ but also for the
entire manufacturing system. This use of the computer is producing
what is being called the computer-integrated manufacturing system,
portrayed generally in Figure 1.
In today's manufacturing environment in the United States, both
managers and engineers often treat manufacturing as a unidirectional
system in which data and information flow only downstream, from
product design to production to shipping. Realization of the
potential offered by CIM requires a data handling system that assures
free access to data (though not necessarily to change data) and the
flow of data among all parts of a manufacturing system. Included in
this data flow is information on the customer's expectations as well
as information on design and production of the product.
Information in a CIM system is extracted from fully automated
segments of a process for use in controlling ~ planning, or modifying
inputs into the process. Thus, a system having an objective and a
means of detecting deviations from that objective can take corrective
action to decrease the deviation. This technique is commonly called
"feedback" control.
Information from segments that depend wholly or partially on human
judgment is made completely available to the user, and computer
facilities for simulation and prediction are available. This is
neither "feed forward" nor "feed back," but concurrent perception of
all factors entering a decision. Until this free flow of information
is accepted, the CAD/CAM interface will remain a barrier.
The path in Figure 1 labeled "cost and capabilities" is directed
at improving cost-effectiveness by enabling both design and manufac-
turing engineers to evaluate the consequences of each alternative
design concept and each decision on production methods. The
"performance" path will incorporate quality control in the system.
A GLIMPSE AT THE INTEGRATED FACTORY OF THE FUTURE
Full CIM has not been realized in practice anywhere in the world,
although many systems have major elements in operation. For instance,
flexible manufacturing systems (EMS) have many of the characteristics
of CIM applied to production. One FMS is described in Appendix B.
From a pro Section of ache operation of present systems, it is possible
to envision what the factory of the future may be like.
A product will be designed using an iterative dialog between the
design engineer and a computer. The designer will supply the design
concepts and requirements and do the creative work. The computer will
supply standard design elements and other stored, experience-based
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information and perform the design calculations. During this design
process, the computer will constantly retrieve and evaluate informa-
tion on the manufacturing costs and capabilities of the equipment and
processes required to produce each of the alternatives conceived by
the designer. The computer will assist the engineer in achieving a
design alternative that is the best compromise among product cost,
quality, durability, and producibility.
Concurrently, production planning will use the same data to choose
the proper equipment and processes, sequence of operations, and
operating conditions for manufacturing the product. This numerical
information in turn will be used to control the array of machines and
equipment that will produce the parts and assemble the product. These
machines and equipment will be capable of automatically adjusting the
operating conditions, handling parts, selecting tooling, and carrying
out a variety of fabrication processes and assembly. The machines
will be self-regulating as a consequence of information provided to
the control system through the path labeled "performance" in Figure 1.
This system will continually receive information about the actual
performance of the equipment and processes and compare it with the
"ideal" performance planned in the earlier phase. Should performance
begin to depart from the plan, the system will override the original
instructions, adjust the operating conditions of the machines and
processes to compensate, and automatically reschedule as necessary.
The machines and equipment will have self-diagnostic and predic-
tive capabilities. Should an impending malfunction be projected, they
will take appropriate corrective action, including automatic replace-
ment of defective modules in the system. Further, the machines will
conduct automatic, in-process inspection of the product at each stage
so that any impending deviations from the original specifications can
be automatically corrected and the product held within prescribed
tolerances. In a computer-integrated manufacturing system, quality
means the prevention of problems, not detection and correction. Thus,
every final assembled product will conform with the original design
concepts and requirements. This ideal system will also incorporate
data for updating product design.
GETTING TO CIM
It is difficult to justify new technology by traditional cost-
benefit methods. The costs are current and easily measured, while the
benefits are often realized in the future and not easily quantified.
CIM, in particular, is very difficult to quantify because its benefits
are dispersed through the entire organization, do not necessarily
occur on a uniform, consistent basis, and frequently depend on the
transformation of raw data into useful information. The value of the
information added by CIM is highly dependent on the perspective of the
individual.
In its attempt to document the benefits of CIM to firms that
pioneered its use, the Committee found that much of that information
was proprietary. Clearly, the firms that use CIM consider it a
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competitive advantage. In at least one industry, computer manufactur-
ers, CIM has become a competitive necessity. Many firms are using an
integrated approach to design of their product and the process by
which it is to be produced. The main tool for the integration of the
various design processes is a central engineering data base. Propri-
etary systems are used to integrate all of the design processes from
technology insertion, logic design (both logic and fault simulation).
and physical design through to inputs to fabrication and assembly.
The same data base is used throughout the hierarchy of the design
process.
In the early 1980s, with the advent of electronic designer work
stations, local area networks consisting of sets of microcomputers
available to the design engineers were added to the in-house systems.
Over the past several years, companies have integrated the data bases
available on these local area network nodes with the central engi-
neering data bases. Integration of these data ~ ~
and money by reducing the amount of rework
rework was
intervention
-
,
oases saved both time
required. In some cases,
virtually eliminated because of the elimination of human
in the various elements of product design.
NOTE S
1. Joseph Harrington, Jr., Understanding the Manufacturing Process
(New York and Basel: Marcel Dekker, 1984~.
Frederick W. Taylor,
(New York and London:
The Principles of Scientific Management
Harper and Brothers. 19113. See also.
for example, Daniel Nelson, Frederick W. Taylor and the Rise of
Scientific Management (Madison: University of Wisconsin Press,
1980).
Representative terms from entire chapter:
engineering design
