Page 33 - Manufacturing Engineering and Technology - Kalpakjian, Serope : Schmid, Steven R.

Section 1.3 Design for Manufacture, Assembly, Drsassembly and Service

simulated, analyzed, and tested, rapidly and accurately. The information developed is
stored and can be retrieved, displayed, printed, and transferred anytime and anywhere
within a company’s organization. Design modifications can be made and optimized
(as is often the practice in engineering, especially in the production of large structures)
directly, easily, and at any time.
Computer-aided manufacturing involves all phases of manufacturing, by utilizing
and processing the large amount of information on materials and processes gathered
and stored in the organization’s database. Computers greatly assist in organizing the
information developed and performing such tasks as (a) programming for numerical-
control machines and for robots for material-handling and assembly operations
(Chapter 37), (b) designing tools, dies, molds, fixtures, and work-holding devices
(Parts II, III, and IV), and (c) maintaining quality control (Chapter 36).
On the basis of the models developed and analyzed in detail, product designers then
finalize the geometric features of each of the product’s components, including specifying
their dimensional tolerances and surface-finish characteristics. Because all components,
regardless of their size, eventually have to be assembled into the final product, dimen-
sional tolerances are a major consideration in manufacturing (Chapter 35). Indeed,
dimensional tolerances are equally important for small products as well as for car bodies
or airplanes. The models developed also allow the specification of the mechanical and
physical properties required, which in turn affect the selection of materials. (Section 1.5).

Prototypes. A prototype is a physical model of an individual component or prod-
uct. The prototypes developed are carefully reviewed for possible modifications to
the original design, materials, or production methods. An important and continu-
ously evolving technology is rapid prototyping (RP, see Chapter 20). Using
CAD/CAM and various specialized technologies, designers can now make proto-
types rapidly and at low cost, from metallic or nonmetallic materials such as plastics
and ceramics.
Prototyping new components by means of traditional methods (such as casting,
forming, and machining) could cost an automotive company hundreds of millions of
dollars a year, with some components requiring a year or more to complete. Rapid
prototyping can significantly reduce costs and the associated product-development
times. Rapid-prototyping techniques are now advanced to such a level that they also
can be used for low-volume (in batches typically of fewer than 100 parts) economical
production of a variety of actual and functional parts to be assembled into products.

Virtual Prototyping. Virtual prototyping is a software-based method that uses
advanced graphics and virtual-reality environments to allow designers to view and
examine a part in detail. This technology, also known as simulation-based design,
uses CAD packages to render a part such that, in a 3-D interactive virtual environ-
ment, designers can observe and evaluate the part as it is being drawn and devel-
oped. Virtual prototyping has been gaining importance, especially because of the
availability of low-cost computers and simulation and analysis tools.

l.3 Design for Manufacture, Assembly,
Disassembly, and Service

Design for manufacture (DPM) is a comprehensive approach to integrating the de-
sign process with production methods, materials, process planning, assembly, test-
ing, and quality assurance. DPM requires a fundamental understanding of (1) the