In the past few years, functional modeling approach has also proven to be suitable for tooling design such as injection mould design [17, 18], though the application is still in its infancy stage. However, no literature exists so far applying functional modeling technique in die structure design. Hence in this paper we hope to utilize the advantages of functional modeling approach to provide conceptual support for die structure design, with which, various functional reasoning techniques should be integrated to develop a comprehensive functional structure of die design object.

3. A  COMPREHENSIVE  FUNCTIONAL  MODELING

FRAMEWORK

3.1. Functional relationships

In functional modeling, various functional relationships between functions and structures should be elaborated in order to develop a comprehensive functional model. Three critical types of relations, i.e., decomposed into, realized by, and supported by relations are defined in this paper.

F1

Decomposed into

F11 F12 F13

Supported by Realized by

F111 S11

Supported by

F112

Figure 1. Functional relationships between functions and structures.

Decomposed into relation: This relation indicates a function is decomposed into simple sub-functions. Referring to figure 1, a main function F1: Perform the stamping operation is decomposed into simple sub-functions F11: Form the stamping part, F12: Strip the stamping part, and F13: Eject the stamping part.

Realized by relation: This relation indicates a function is realized by a physical structure through a mapping between them. Referring to figure 1, the function F11: Form the stamping part is realized by a physical structure S11: Punches.

Supported by relation: This relation depicts the dependency of one function (or structure) on other functions that provide supporting roles. In other words, if needed supportive functions are not provided, their supported function (or structure) may not be fully actualized. Referring to figure 1, the function F11: Form the stamping part that directly influences the immediate achievement of the purpose is supported by a supportive function F111: Support the stamping part that is not responsible for the immediate achievement of the purpose but affects soundness of achievement of the purpose. In other words, the function F11 may only be fully actualized due to the presence of the supportive function F111. Similarly, the structure S11: Punches may only be fully actualized due to the presence of another supportive function F112: Guide the punches. Incorporation of supportive function was borrowed from Multilevel Flow Modeling (MFM) based reasoning approach [19] from different views of modeling space, though in a more generic, lower level functional context, facilitates generation of a comprehensive functional model.

3.2. A functional modeling framework with various functional reasoning paths

Figure 2 shows the features of the proposed functional modeling framework that consists of two layers, namely function layer and structure layer. The function layer defines some functions necessary to compose other functions, or support other functions (or structures). The structure layer describes the underlying physical embodiments of the

Function layer

Reasoning F1

path type I

Reasoning F2

path type II F21