Prototyping is a tool used for assessing
form-fit-and-function of a product and for visualizing aesthetic quality.
Prototyping techniques can also be used to create molds for full-scale
production. Through use of a prototype, a designer can get feedback on design
information and initial part acceptance for further use in optimizing the design
and/or the manufacturing process(es). Prototyping is used to check design
features and complexity and is helpful in tradeoff studies. The use of
prototyping begins in the preliminary design step and continues into the early
stages of the final design step. The ability to quickly transform a design into
a three-dimensional solid model or prototype can significantly streamline the
design and product development process, while substantially reducing costs.
Product prototyping falls into two categories: virtual
and physical. Virtual prototyping, more commonly referred to as modeling and
simulation (discussed in more detail in Appendix F.1.13
), is a software-based
engineering technique that entails computer modeling a product and then
simulating and visualizing its behavior in three-dimensional, real-world
operating conditions. Modeling and simulation enables the refining and
optimizing of the design through iterative design studies and is of use as a
preliminary step to physical prototyping.
Physical prototype fabrication is a test of a product
design. Physical prototyping is used to test fabrication feasibility, check
feature designs, and test material and product properties. Physical prototype
fabrication falls into three categories: subtractive, compressive, and additive
Subtractive Process: In a subtractive process, a block of material is carved out to produce
the desired shape. Most conventional prototyping processes fall into the
subtractive category. Subtractive processes normally used to fabricate
prototypes include milling, turning, and grinding.
A compressive process forces a semi-solid or liquid material into the desired
shape, in which it is then induced to harden or solidify. Compressive processes
include casting, molding, and powder metallurgical processes. Compressive
processes tend to be the most time-consuming of physical prototyping processes.
They require the production of a mold and cannot be used to produce high aspect
ratio features. Compressive process prototypes can be produced with a wide
variety of materials, but care must be taken to ensure 100% dense products if
physical testing of the prototype is desired.
Additive Process: An additive process builds an object by joining particles or layers
of raw material. The new rapid prototyping technologies (discussed in more
detail in Appendix F.1.17
) are additive processes. The integration of rapid prototyping
into the compressive process category has resulted in the capability to more
rapidly generate patterns from which molds are made. In general, prototypes
produced using rapid prototyping cannot be used for physical testing of the
design but can be used to check design features and complexity issues.
In addition to product prototyping, processes can be
prototyped. While more often referred to as process verification or process
trials, process prototyping is conducted to gain insight into whether a process
can be utilized in the production of a particular product or product line and to
optimize process parameters for the production of that product. Although it is
very similar to product prototyping, the emphasis is on the process - process
verification and process optimization. Process verifications are often performed
as part of the trade studies in integrated product and process development. They
are also performed, as the design matures, on any intended production process
for parameter development or optimization. Verifying process capabilities
through process prototyping can help reduce the risks associated with committing
to production and investing in tooling and fixtures for an untested process or a
new part design. Production benefits resulting from process verifications
include the production of more accurate parts, a reduction in rework and scrap,
cost savings, and, possibly, the avoidance of a deleterious impact to
Alting, L., & Boothroyd, G. (1994). Manufacturing Engineering Processes. Marcel Dekker.
Fellers, W.O., & Hunt, W.W. (1994). Manufacturing Processes for Technology. New York: Prentice-Hall
Haas, R., & Teixeira, A. A. (1995). Virtual Prototyping: Virtual Environments and the Product Design Process. Chapman & Hall.
Ostwald, P. F., & Munoz, J. (1996). Manufacturing Processes and Systems. New York: Wiley & Sons.
Wood, L. (1992). Rapid Automated Prototyping: An Introduction. New York: Industrial Press.
Wright, J. R., & Helsel, L. D. (1996). Manufacturing Processes. Delmar Publishers.