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Research Papers

High-Stiffness, Lock-and-Key Heat-Reversible Locator-Snap Systems for the Design for Disassembly

[+] Author and Article Information
Mohammed Shalaby

 General Electric-Global Research Center, 1 Research Circle, Niskayuna, NY 12309shalaby@ge.com

Kazuhiro Saitou

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

J. Mech. Des 131(4), 041005 (Mar 23, 2009) (9 pages) doi:10.1115/1.3087529 History: Received August 10, 2008; Revised December 24, 2008; Published March 23, 2009

Driven by the moral sense of obligation, legislative and social pressures, manufacturers now consider effective part reuse and material recycling at the end of product life at the design stage. It is a key consideration to use joints that can disengage with minimum labor, part damage, and material contamination. This paper extends our previous work on the design of high-stiffness reversible locator-snap system that can disengage nondestructively with localized heat (Shalaby and Saitou, 2006, “Optimal Heat-Reversible Snap Joints for Frame-Panel Assembly in Aluminum Space Frame Automotive Bodies,” Proceedings of the LCE2006: The 13th CIRP International Conference on Life Cycle Engineering, Leuven, Belgium, May 31–Jun. 2, pp. 411–416; Shalaby and Saitou, 2008, “Design for Disassembly With High-Stiffness, Heat-Reversible Locator-Snap Systems,” ASME J. Mech. Des., 130(12), p. 121701) to include (1) modeling for tolerance stack-up and (2) lock-and-key concept to ensure that snaps only disengage when the right procedure is followed. The design problem is posed as an optimization problem to find the locations, numbers, and orientations of locators and snaps, and the locations and sizes of heating areas, to release the snaps with minimum heat, compliance, and tolerance stack-up. The motion and structural requirements are considered constraints. Screw theory is employed to precalculate the set of feasible types and orientations of locators and snaps that are examined during optimization. Multi-objective genetic algorithm coupled with structural and thermal finite element analysis is used to solve the optimization problem. The method is applied on two case studies. The Pareto-optimal solutions present alternative designs with different trade-offs between the design objectives.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Assembly and disassembly of heat-reversible snap: (a) before assembly, (b) push, (c) lock, (d) heat, (e) pull apart, and (f) unlock

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Figure 2

Double-latch snap: (a) locked, (b) unlocked, and ((c) and (d)) insufficient and excessive unlocking displacement, respectively

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Figure 3

(a) Part geometry, coordinates of vertices of mating polygon, and feasible region for heating and ((b)–(e)) locators and snaps in library

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Figure 4

Example of feasible locator/snap orientations

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Figure 5

Tolerance stack-up example: (a) ideal case and response to dimensional variations, (b) v1 for a locator at a distance d1, and (c) v1 for a locator at a distance d2

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Figure 6

Examples double-latching snap attachments with snaps attached to part B: part A bulges outward when heated ((a) and (b)) and part A bulging inward when heated ((c) and (d))

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Figure 7

Flowchart of the NSGA-II (30)

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Figure 8

Geometric crossover: (a) parent p1, (b) parent p2, (c) child c1, and (d) child c2

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Figure 9

Simplified model of the rhombus enclosure casing

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Figure 10

(a) CAD model for the lower enclosure only with the four sides of the rhombus numbered S1,…,S4 and (b) flattened 2D surfaces of the rhombus

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Figure 11

3D Pareto front for the case study

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Figure 12

Optimum solution with minimum heat/cool area

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Figure 13

CAD drawing for the solution with minimum heat/cool area

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Figure 14

Optimum solution with maximum distance between locators constraining same DOFs

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Figure 15

CAD drawing for the solution with maximum distance between locators constraining same DOFs

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Figure 16

Simplified model of a flat panel TV: (a) front bezel, (b) steel frame with LCD screen, and (c) rear panel

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Figure 17

TV front enclosure with apparent edges highlighted

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Figure 18

Front view of the front TV bezel two heating areas identified using polar coordinates

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Figure 19

Measuring locator and snap stiffness: (a) z-direction constraining locator and snap, (b) y-direction constraining locator, and (c) x-direction constraining locator

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Figure 20

Spider-web diagram for Pareto-optimal solutions

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Figure 21

Solution with minimum local heat/cool area

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Figure 22

Schematic CAD drawing for the solution with minimum local heat/cool area

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Figure 23

Solution with maximum distance between locators that constrain the same DOF

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Figure 24

Schematic CAD drawing for solution with maximum distance between locators that constrain the same DOF

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