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PLEASE NOTE: The Publications System provided by the Manufacturing Systems Integration Division (MSID) has moved to: http://www.mel.nist.gov/msidlibrary/publications.html. The pages below are maintained for archival purposes only.
Publication summary
Author(s): Rachuri Sudarsan and U. Roy
Publication date: August 2000
Citation: Rachuri Sudarsan and U. Roy: "Information Models for Design Tolerancing: From Conceptual to the Detailed Design," NISTIR 6524, National Institute of Standards and Technology, Gaithersburg, MD, 2000.
Key words: assembly, behavior models, design tolerancing, function, object information architecture, tolerance and synthesis
Availability:
Abstract:
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Tolerance design is the process of deriving a description of
geometric tolerance specifications for a product from a given set of
desired properties of the product. Existing approaches to tolerance
analysis and synthesis entail detailed knowledge of geometry of
assemblies and are mostly applicable during advanced stages of
design, leading to a less than optimal design. During the design
process of assemblies, both assembly structure and associated
tolerance information evolve continuously and significant gains can be
achieved by effectively using this information to influence the design of
an assembly. Any pro-active approach to the assembly or tolerance
analysis in the early design stages will involve making decisions with
incomplete information models. In order to carry out early tolerance
synthesis and analysis in the conceptual product design stage, we
need to devise techniques for representing
function-behavior-assembly models that will allow analysis and
synthesis of tolerances, even with the incomplete data set. A
`function' (what the system is for) is associated with the
transformation of an input physical entity into an output
physical entity by the system. The problem or customer's need,
initially described by functional requirements on an assembly
and associated constraints on the functional requirements
defines the concept of an assembly. This specification of
functional requirements and constraints define a functional
model for the assembly. Many researchers have studied
functional representation (function based taxonomy and
ontology), function to form mapping, and behavior
representation (behavior means how the system/product
works). In a recent paper, we presented a strong need for
comprehensive unction-assembly-behavior (FAB) integrated
model. In this report, we discuss extension of the ideas
presented in our recent paper and explain the integration of
function, assembly, and behavior representation into a
comprehensive information model (FAB models). To do this,
we need to develop appropriate assembly models and
tolerance models that would enable the designer to
incrementally understand the build-up or propagation of
tolerances (i.e., constraints) and optimize the layout, features,
or assembly realizations. This will ensure ease of tolerance
delivery. In an earlier paper, NISTIR-6223, a multi-level
approach called Design for Tolerance [DFT] process was
proposed which enables tolerancing to be addressed at
successive stages of design in an incremental fashion We also
address the effective use of the FAB and DFT model for
design tolerancing, starting from conceptual stage of the design
and continuously evolving throughout the entire design process
to the final detailed design. These models can eventually lead
to tolerance and assembly standards.
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