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TECHNICAL PAPERS

A Comparative Study Of Tolerance Analysis Methods

[+] Author and Article Information
Zhengshu Shen

Design Automation Lab, Department of Mechanical and Aerospace Engineering, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ 85287-6106, USAzhengshu.shen@asu.edu

Gaurav Ameta

Design Automation Lab, Department of Mechanical and Aerospace Engineering, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ 85287-6106, USAgaurav.ameta@asu.edu

Jami J. Shah1

Design Automation Lab, Department of Mechanical and Aerospace Engineering, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ 85287-6106, USAjami.shah@asu.edu

Joseph K. Davidson

Design Automation Lab, Department of Mechanical and Aerospace Engineering, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ 85287-6106, USAj.davidson@asu.edu

1

To whom correspondence should be addressed.

J. Comput. Inf. Sci. Eng 5(3), 247-256 (May 16, 2005) (10 pages) doi:10.1115/1.1979509 History: Received June 30, 2004; Revised May 16, 2005

This paper reviews four major methods for tolerance analysis and compares them. The methods discussed are: (1) one-dimensional tolerance charts; (2) parametric tolerance analysis, especially parametric analysis based on the Monte Carlo simulation; (3) vector loop (or kinematic) based tolerance analysis; and (4) ASU Tolerance-Map® (T-Map®) (Patent pending; nonprovisional patent application number: 09/507, 542 (2002)) based tolerance analysis. Tolerance charts deal with worst-case tolerance analysis in one direction at a time and ignore possible contributions from the other directions. Manual charting is tedious and error prone, hence, attempts have been made for automation. The parametric approach to tolerance analysis is based on parametric constraint solving; its inherent drawback is that the accuracy of the simulation results are dependent on the user-defined modeling scheme, and its inability to incorporate all Y14.5 rules. The vector loop method uses kinematic joints to model assembly constraints. It is also not fully consistent with Y14.5 standard. The ASU T-Map® based tolerance analysis method can model geometric tolerances and their interaction in truly three-dimensional context. It is completely consistent with Y14.5 standard but its use by designers may be quite challenging. The T-Map® based tolerance analysis method is still under development. Despite the shortcomings of each of these tolerance analysis methods, each may be used to provide reasonable results under certain circumstances. Through a comprehensive comparison of these methods, this paper will offer some recommendations for selecting the best method to use for a given tolerance accumulation problem.

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Copyright © 2005 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

The tolerance analysis maze (see Ref. 1)

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Figure 2

Rules for setting up the charting coordinate system

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Figure 3

Identify the stack path for 1D chart

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Figure 4

Separate configurations for maximum and minimum stackup in an assembly

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Figure 5

Nonlinear tolerance analysis via the Monte Carlo Simulation (see Ref. 1)

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Figure 6

Parametric analysis directly using 2D constraint model in CAD (see Ref. 1)

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Figure 7

Feature simplification in an abstracted feature-parameter model (see Ref. 1)

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Figure 8

Metric relations between the entities in an abstracted feature-parameter model (see Ref. 1)

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Figure 9

Parametric approach to a simple assembly example

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Figure 10

The T-Map® for the tolerance zone on the rectangular bar in Fig. 1

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Figure 11

The tolerance zone for a rectangular bar with a size tolerance t

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Figure 12

Tolerance-Maps (a) for part 1, (b) for Part 2, (c) for the assembly (Minkowski sum of (a) and (b)), shown at a larger scale to enhance detail, (d) for the desired function and (e) p′q′ section of the fit of functional and accumulation T-Map®.

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