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Research Papers

Toward Automatic Tolerancing of Mechanical Assemblies: Assembly Analyses

[+] Author and Article Information
Prashant Mohan, Payam Haghighi, Prabath Vemulapalli, Nathan Kalish, Jami J. Shah, Joseph K. Davidson

Design Automation Lab,
Arizona State University,
Tempe, AZ 85287

Contributed by the Computers and Information Division of ASME for publication in the JOURNAL OF COMPUTING AND INFORMATION SCIENCE IN ENGINEERING. Manuscript received July 28, 2014; final manuscript received September 3, 2014; published online October 7, 2014. Editor: Bahram Ravani.

J. Comput. Inf. Sci. Eng 14(4), 041009 (Oct 07, 2014) (14 pages) Paper No: JCISE-14-1241; doi: 10.1115/1.4028592 History: Received July 28, 2014; Revised September 03, 2014

Generating geometric dimensioning and tolerancing (GD&T) specifications for mechanical assemblies is a complex and tedious task, an expertise that few mechanical engineers possess. The task is often done by trial and error. While there are commercial systems to facilitate tolerance analysis, there is little support for tolerance synthesis. This paper presents a systematic approach toward collecting part and assembly characteristics in support of automating GD&T schema development and tolerance allocation for mechanical assemblies represented as neutral B-Rep. First, assembly characteristics are determined, then a tentative schema is determined and tolerances allocated. This is followed by adaptive iterations of analyses and refinement to achieve desired goals. This paper will present the preprocessing steps for assembly analysis needed for tolerance schema generation and allocation. Assembly analysis consists of four main tasks: assembly feature recognition (AFR), pattern detection, directions of control, and loop detection. This paper starts with identifying mating features in an assembly using the computer-aided design (CAD) file. Once the features are identified, patterns are determined among those features. Next, different directions of control for each part are identified and lastly, using all this information, all the possible loops existing in an assembly are searched.

Copyright © 2014 by ASME
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Figures

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Fig. 2

Assembly preprocessing modules and data flow

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Fig. 1

High level architecture

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Fig. 3

Common assembly feature types

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Fig. 4

Assembly feature definition for pin-blind hole

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Fig. 5

Geometric constraint dialog box

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Fig. 6

Algebraic constraint dialog box

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Fig. 7

Cam Follower assembly (courtesy RECON services)

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Fig. 11

Interfacing feature patterns

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Fig. 8

Assembly sequence for cam follower assembly

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Fig. 9

Liaison graph in (a) graphical and (b) textual format

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Fig. 10

Modified face adjacency graphs for AFR

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Fig. 19

Algorithm flow chart

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Fig. 13

A part with cylindrical faces only

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Fig. 14

DoC extraction process

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Fig. 15

“ANC 101” sample part

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Fig. 16

DoC output that identifies seven directions of control for the ANC101 part

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Fig. 21

Monocoque hull of a landing craft

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Fig. 18

Sample loops for cam follower assembly

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Fig. 20

Cam follower assembly loops

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