A trade study is a formal decision-making method that can
be used to solve many complex problems. Trade studies (also called tradeoff
studies or analyses) are used to rank potential design solutions against the
product goals. In the context of this document, the trade study can highlight
the manufacturing advantages and disadvantages of each design concept. Process
maturity, ease of assembly, manufacturing risk, and need for capital equipment
are among the elements considered during the trade studies from the
producibility perspective. The objective is to identify a design solution that
most effectively meets all the product goals.
During the conceptual phase, trade studies can help
identify possible designs that will result in an optimum balance of quality,
functionality, cost, performance, and producibility. Product goals (3.1) and key characteristics (3.2
) may be revisited and changed, as appropriate, based on the
results of the studies.
Ideally, trade studies are conducted according to the
principles of good experimental practice. Two or more design concept strategies
with different values of an independent variable such as size, shape, or weight
are compared using a dependent variable such as speed, energy use, reliability,
or manufacturing process maturity. Tradeoff decisions are more meaningful when
extraneous variables are kept constant or otherwise controlled. Producibility
may be either an independent or dependent variable depending on the
requirements, but it should always be a documented variable. Producibility
measurements can be related to cost, schedule, quality, complexity, and risk.
The trade study's quality depends on the quality of the input data. The results
will be unreliable if the input data comes only from peoples' memories,
estimates, or best guesses. To be viable, trade studies must be based on
Examples of the importance of trade studies in the
product development cycle to producibility are presented in Case Studies 30
through 34 in Appendix D, and Appendix
contains a more detailed presentation
of the tradeoffs considered on a complex cover assembly for a surveillance
system for the U.S. Army.
In areas where a trade study is performed, the IPT will
identify design alternatives and determine rationale in support of design
decisions. Then, working with the customer as a member of the IPT, the team can
modify the product goals - if justified by the data. Further, the documentation
of the alternatives and rationale will provide valuable references should the
issue require revisiting. The tradeoff analysis process allows the IPT to make
optimum decisions, taking into account the goals, the confidence levels of the
trade studies, and the interdependencies among the requirements.
Staff: The IPT should take the lead in the trade studies. Other staff members may be brought in for their expertise. The evaluation should be conducted by the personnel who are most knowledgeable of the details of the product and who are technically qualified to perform the analyses.
Tools and Techniques: A wide range of tools are applicable to the trade study process.
Figure 3.3 lists the tools and techniques included in Appendix F
that can be applied to
this producibility element.