Decomposition-Based Assembly Synthesis of Multiple Structures for Minimum Manufacturing Cost

[+] Author and Article Information
Onur L. Cetin1

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125

Kazuhiro Saitou2

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125kazu@umich.edu

No branch involving more than four beams are assumed in the structures.


Currently a post-doctoral research fellow, Engineering Design Centre, Cambridge University, UK.


Corresponding author.

J. Mech. Des 127(4), 572-579 (Sep 06, 2004) (8 pages) doi:10.1115/1.1897409 History: Received June 30, 2003; Revised September 06, 2004

An extension of decomposition-based assembly synthesis for structural modularity is presented where the early identification of shareable components within multiple structures is posed as an outcome of the minimization of estimated manufacturing costs. The manufacturing costs of components are estimated under given production volumes considering the economies of scale. Multiple structures are simultaneously decomposed, and the types of welded joints at component interfaces are selected from a given library, in order to minimize the overall manufacturing cost and the reduction of structural strength due to the introduction of joints. A multiobjective genetic algorithm is used to allow effective examination of trade-offs between manufacturing cost and structural strength. A new joint-oriented representation of structures combined with a “direct” crossover is introduced to enhance the efficiency of the search. A preliminary case study with two simplified aluminum space frame automotive bodies is presented to demonstrate that not all types of component sharing are economically justifiable under a certain production scenario.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Fabrication costs for several automobile body structures (from (18))

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Figure 2

Example of two beam-based product variants

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Figure 11

Decomposed structures at point D in Fig. 7

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Figure 3

Example of decomposition of the product variants in Fig. 2. The selected weld types are shown as numbers with the arrows indicating which beam is welded onto another. The identified sharable components are annotated with s.

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Figure 4

Joint types of (a) two-beam intersection (types 0-2) and (b) three-beam intersection (types 3–14). The arrows indicate which beam is welded onto another. Note that three-beam intersection must be always decomposed since branching beams cannot be manufactured with extrusion.

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Figure 5

(a) infeasible component with an out-of-plane bend and (b) feasible components without out-of-plane bends

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Figure 6

Example aluminum space frame structures under global bending condition. (a) structure 1: compact vehicle subject to downward force P1=895kg and (b) structure 2: midsize vehicle with P2=1770kg.

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Figure 7

Pareto optimal solutions for scenarios 1: (v1,v2)=(30,000,30,000), scenario 2: (v1,v2)=(90,000,30,000) and 3: (v1,v2)=(90,000,90,000)

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Figure 8

Decomposed structures at point A in Fig. 7

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Figure 9

Decomposed structures at point B in Fig. 7

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Figure 10

Decomposed structures at point C in Fig. 7



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