Research Papers: Design for Manufacturing

Design for Disassembly With High-Stiffness Heat-Reversible Locator-Snap Systems

[+] Author and Article Information
Mohammed Shalaby

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

Kazuhiro Saitou1

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


Corresponding author.

J. Mech. Des 130(12), 121701 (Nov 06, 2008) (7 pages) doi:10.1115/1.2991134 History: Received November 18, 2007; Revised June 14, 2008; Published November 06, 2008

Recent legislative and social pressures have driven manufacturers to consider effective part reuse and material recycling at the end of product life at the design stage. One of the key considerations is to design and use joints that can disengage with minimum labor, part damage, and material contamination. This paper presents a unified method to design a high-stiffness reversible locator-snap system that can disengage nondestructively with localized heat, and its application to external product enclosures of electrical appliances. The design problem is posed as an optimization problem to find the locations, numbers, and orientations of locators and snaps as well as the number, locations, and sizes of heating areas, which realize the release of snaps with minimum heating area and maximum stiffness while satisfying any motion and structural requirements. The screw theory is utilized to precalculate a set of feasible orientations of locators and snaps, which are examined during optimization. The optimization problem is solved using the multi-objective genetic algorithm coupled with the structural and thermal finite element analysis. The method is applied to a two-piece enclosure of a DVD player with a T-shaped mating line. The resulting Pareto-optimal solutions exhibit alternative designs with different trade-offs between the structural stiffness during snap engagement and the area of heating for snap disengagement. Some results require the heating of two areas at the same time, demonstrating the idea of a lock-and-key.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Different snap-fit types: (a) nondisassemblable and disassemblable snaps, (b) prone to accidental disassembly, and ((c) and (d)) affecting the aesthetic appeal (5)

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Figure 2

(a) Part geometry (only one part shown), coordinates of vertices of the mating polygon, and feasible region for heating. ((b)–(e)) Locators and snaps in library.

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Figure 3

Examples of two different locator and snap orientations

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Figure 4

Simplified model of the case assembly of a DVD player

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Figure 5

FE model of the lower part of the assembly showing edges and the feasible heating region

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Figure 6

(a) Heating area in the flattened feasible heating subregion S1R−S5R and (b) corresponding heating area in 3D

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Figure 7

Pareto-optimal solutions for the case study

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Figure 8

Optimum solution with minimum heat area (solution 1)

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Figure 9

Optimum solution with minimum symmetric heat area (solution 7)

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Figure 10

Solution 7 response to one sided heating: (a) area 1 is heated and (b) area 2 is heated

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Figure 11

CAD drawing for the optimized DVD player model (solution 1): (a) top part and (b) base part

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Figure 12

CAD drawing for the optimized DVD player model (solution 7): (a) top part and (b) base part



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