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

Abstract

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 production 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 production cost and the reduction of structural strength due to the introduction of joints. A multiobjective genetic algorithm is utilized 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 case study with two aluminum space frame automotive bodies is presented to demonstrate that not all types of component sharing are economically justifiable under a certain production scenario.

Decomposition-Based Assembly Synthesis for Structural Stiffness and Dimensional Integrity

“…Assembly synthesis is a process of determining the optimal components set through the decomposition of the end product design prior to the detailed component design phase [2]. As an extension of our past researches on the decomposition-based assembly synthesis [2][3][4][5][6][7], this paper introduces a method for determining the components set of aluminum space frame (ASF) vehicle bodies using pre-analyzed joint libraries defined at each potential joint location. The uniqueness of the present work is the simultaneous consideration of stiffness, manufacturing and assembly cost [4,5] and dimensional integrity [3,7] , which are considered separately in our previous work, under a unified framework based on joint libraries.…”

“…Conventional DFA/DFM methods assume the pre-determined components with given geometries and, therefore, are limited to the design improvements by locally modifying the given geometries. Decomposition-based assembly synthesis [2][3][4][5][6][7], on the other hand, emphasizes the determination of components prior to the detailed design stages. Starting with no prescribed components, the method decomposes the component geometry so the optimal components set and joint configurations best achieving the design criteria on each component and joint, as well as the assembles product.…”

“…Starting with no prescribed components, the method decomposes the component geometry so the optimal components set and joint configurations best achieving the design criteria on each component and joint, as well as the assembles product. The criteria attempted in the previous work includes structural strength [2], structural stiff ness [4,5], component modularity [6], and dimensional integrity [3,7].…”

Assembly Synthesis for Stiffness, Dimensional Adjustability and Manufacturability

“…Assembly synthesis has been defined by Yetis and Saitou [1] as the decomposition of the end product design prior to the detailed component design phase in the systematic ways. This paper integrates our previous works on the decomposition-based assembly synthesis methods [2][3][4][5][6], by considering the stiffness, the manufacturing / assembly cost [3,4], and the dimensional integrity [2,6] altogether in finding optimal assembly syntheses. To solve the optimization problem posed with multiple objectives, a multi-objective genetic algorithm (GA) [7] with a direct crossover operator [8,9] is used.…”

“…To solve the optimization problem posed with multiple objectives, a multi-objective genetic algorithm (GA) [7] with a direct crossover operator [8,9] is used. The GA synthesizes candidate assembly designs by selecting joints from a predefined set of joint types (i.e., joint library [5]) for predefined potential locations, thus defining component set, deciding the beam cross sections and welding thickness where joints are assigned. Then all objectives are evaluated for each candidate assembly design.…”