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

Abstract

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 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 non-destructively with localized heat [1, 2], 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 number, locations and sizes of heating areas, which realize the release of snaps with minimum heat, compliance, and tolerance stack-up. The motion and structural requirements are considered constraints. Screw Theory is utilized to pre-calculate a set of feasible types and orientations of locators and snaps that are examined during optimization. The optimization problem is solved using Multi Objective Genetic Algorithm (MOGA) coupled with structural and thermal FEA. The method is applied on two case studies. The Pareto-optimal solutions present alternative designs with different trade-offs between the design objectives while meeting all the constraints.