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A Scheme for Transformation of Tolerance Specifications to Generalized Deviation Space for Use in Tolerance Synthesis and Analysis

Published

Author(s)

H Wang, N Pramanik, Utpal Roy, Sudarsan Rachuri, Ram D. Sriram, Kevin W. Lyons

Abstract

Traditionally tolerances for manufactured parts are specified using symbolic schemes as per ASME or ISO standards. To use these tolerance specifications in computerized tolerance synthesis and analysis, we need an information model to represent the tolerances. Tolerance specifications have been modeled as a class with its attributes and methods [ROY01]. Tolerances essentially impose restrictions on the possible deviation of features from its nominal size/shape. These variations of shape/size could be thought of as deviations of a set of generalized coordinates defined at some convenient point on the feature. Any tolerance specification for the feature would impose some kind of restrictions or constraints on these deviation parameters. These constraints would, in general, define a bounded region in the deviation space. In this paper, we present a method for converting tolerance specifications as per MMC (Maximum Material Condition) / LMC (Least Material Condition) / RFS (Regardless of Feature Size) material conditions for standard mating features (planar, cylindrical, and spherical) into a set of inequalities in a deviation space. This is useful for representing feature deviations nominal shapes. We utilize virtual condition boundaries1 (VCB) as well as tolerance zones (as the case may be) for these mappings. For the planar feature, these relations are linear and the bounded space is diamond shaped. For all other cases, the mapping is a set of nonlinear inequalities. The mapping transforms the tolerance specifications into a generalized coordinate frame as a set of inequalities. These are useful in tolerance synthesis and analysis, as well as in assemblability analysis in the generalized coordinate system (deviation space). In this paper, we also illustrate the mapping procedures with an example.
Citation
Ieee Journal Of Robotics And Automation

Keywords

Deviation Space, Mapping, Tolerance Analysis, Tolerance Synthesis

Citation

Wang, H. , Pramanik, N. , Roy, U. , Rachuri, S. , Sriram, R. and Lyons, K. (2002), A Scheme for Transformation of Tolerance Specifications to Generalized Deviation Space for Use in Tolerance Synthesis and Analysis, Ieee Journal Of Robotics And Automation (Accessed May 29, 2023)
Created June 30, 2002, Updated October 12, 2021