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Title: Capturing design rationale within a CAD environment
Authors: Chan, Chiu-cheung
Degree: Ph.D.
Issue Date: 2009
Abstract: Effective reuse of design information and knowledge is vital to today's globalised competitive manufacturing environment. Preliminary investigation into this subject through discussion with practising mechanical design engineers showed that majority of their day-to-day design tasks were dealing with modifications and changes to existing designs and they faced challenges in understanding these existing designs, especially in the context of reusing them. The objective of this research is to better understand and effectively reuse existing designs. Further research through empirical studies showed that mechanical design engineers today spent a significant amount of time using computer-based tools like Computer Aided Design (CAD) systems for their design task. Parametric featured-based three-dimensional (3D) CAD systems have been developed not only for creating 3D models and 2D drawings but have also included some design intent capturing capability for enhancing design reuse. However, the analysis of a collection of 3D models created by different engineers showed that engineers used varying combinations of modelling approaches to create the same model. This signified that current 3D CAD systems with built-in design intent capturing capability are not sufficient to be used to capture design rationale for ease of reuse. A design rationale capturing approach integrated as an extension to a 3D CAD system is needed. In this dissertation, a 'Product-centric Dimension-driven' approach is developed to capture, maintain and share design rationale within a CAD environment. This approach attempts to capture design rationale by linking design decisions and constraints to design dimensions. Models that represent the design decision process ('Design Decision Model') and product model ('Product Model') were proposed to support this approach. The 'Design Decision Model' is used to represent the decision making by means of how the product evolves from its initial specifications into its final design. The 'Product Model' represents the product and its evolution during the design process. These two Models, covering the 'Product-centric' part of the approach, naturally share a common basic element - design dimensions - which lay down the foundation for the 'Dimension-driven' part of the approach. The 'Dimension-driven' design rationale capturing method targets to handle the dimensions on engineering drawings, may it be paper drawings or electronic 2D/3D drawings. Through analysing dimensions on production drawings or 3D computer models, a design dimension digraph bearing the design rationale can be constructed. The dimension digraph then connects the 'Product Model' to the 'Design Decision Model' to allow tracking of design constraints. This approach supports capturing both in a forward and a backward manner. In a forward manner, this approach captures design rationale when the design engineer starts to place a design dimension on a 3D model or a 2D drawing. In a backward manner, design dimensions on drawings can be systematically back tracked to design decisions and constraints. The proposed approach is independent of the product being developed and independent of the design process being employed. Although this approach is best integrated as an extension to a history-based 3D solid modelling system to capture and share design rationale, the underlying principles can be applied independently as a general approach.
Subjects: Hong Kong Polytechnic University -- Dissertations.
Computer-aided design.
Computer-aided engineering.
CAD/CAM systems.
Pages: 269 p. : ill. ; 30 cm.
Appears in Collections:Thesis

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