The Axiomatic Approach to Design

The creative process of mapping the FRs in the functional domain to DPs in the physical domain is not unique; the solution varies with a designer’s knowledge base and creative capacity. As a consequence, solution alternatives may vary in their effectiveness to meet the customer’s needs. The axiomatic approach to design is based on the premise that there are generalizable principles that form the basis for distinguishing between good and bad designs.
Suh (1990) identi ed two design axioms by abstracting common elements from a body of good designs, including products, processes, and systems. The rst axiom is called the Independence Axiom.
It states that the independence of functional requirements (FRs) must be always maintained, where FRs are de ned as the minimum set of independent functional requirements that characterize the design goals.The second axiom is called the Information Axiom, which states that among those designs that satisfy the Independence Axiom the design that has the highest probability of success is the best design. During the mapping process (for example, mapping from FRs in the functional domain to DPs in the physical domain), the designer should make correct design decisions using the Independence Axiom. When several designs that satisfy the Independence Axiom are available, the Information Axiom can be used to select the best design.
Axioms are general principles or self-evident truths that cannot be derived or proven to be true;
however they can be refuted by counterexamples or exceptions. Through axioms such as Newton’s laws and the laws of thermodynamics, the concepts of force, energy, and entropy have been de ned. One of the main reasons for pursuing an axiomatic approach to design is the generalizability of axioms, which leads to the derivation of corollaries and theorems. These theorems and corollaries can be used as design rules that precisely prescribe the bounds of their validity because they are based on axioms. The following corollaries are presented in Suh (1990).
Corollary 1:
(Decoupling of Coupled Designs)
Decouple or separate parts or aspects of a solution if FRs are coupled or become interdependent in
the designs proposed.
Corollary 2:
(Minimization of (FRs)
Minimize the number of FRs and constraints.
Corollary 3:
(Integration of Physical Parts)
Integrate design features in a single physical part if FRs can be independently satis ed in the proposed
solution.
Corollary 4:
(Use of Standardization)
Use standardized or interchangeable parts if the use of these parts is consistent with FRs and
constraints.
Corollary 5:
(Use of Symmetry)
Use symmetrical shapes and/or components if they are consistent with the FRs and constraints.
Corollary 6:
(Largest Tolerance)
Specify the largest allowable tolerance in stating FRs.
Corollary 7:
(Uncoupled Design with Less Information)
Seek an uncoupled design that requires less information than coupled designs in satisfying a set of FRs.
The ultimate goal of axiomatic design is to establish a science base for design and improve design
activities by providing the designer with a theoretical foundation based on logical and rational thoughtprocesses and tools.

Nam P