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Publication summary

Author(s): Kevin Lyons, Venkat Rajan and Raj Sreerangam

Publication date: September 1997

Citation: Kevin Lyons, Venkat Rajan and Raj Sreerangam: "Representations and Methodologies for Assembly Modeling," NISTIR 6059, National Institute of Standards and Technology, Gaithersburg, MD, 1997.

Key words: assembly modeling, representations, constraints, design methods and models

Availability:

  • A paper copy of this document is available by contacting Kristy Thompson [web,email]
Abstract:
Most products are assemblies of components. The number of components can range from a few tens to a few millions. Design of electro-mechanical assemblies involves the description of the constraints between a group of parts that allows them to behave in the desired fashion. This includes the description of the relatie motion between components, fit requirements, and joint strength requirements. While some of these cosntraints are generated during the conceptual design stage, additional details are developed during the preliminary and detailed design stages. Any such information generated during a previous level of the design needs to be captured and propagated to the next lower level of design. In this research, a thorough study is conducted of representations and methodologies available for assembly modeling during the various stages of design. The objective is to evaluate, and, if necessary, extend the current STEP representations dealing with assemblies. The study indicates that the current notion of assembly modeling is limited both in the existing research literature and commercial CAD implementations. Therefore, a set of three representations are developed to support the conceptual, preliminary and detailed design phases. Constraint propagation and verification methodologies are also developed to link information between the representations. The relevance of the representations and methodologies to downstream activities such as assembly analysis and planning are discussed. The impact of the proposed representations on the STEP standard is also discussed. A prototype Assembly Modeling System (AMS) has been developed in which the constraint verification methodology has been implemented. Case studies demonstrating the operation of this system are also described.

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