The paper describes a novel framework for an Assembly-Oriented Design (AOD) approach as a new functional part of the Product Lifecycle Management (PLM) strategy, by considering product design and assembly sequence planning phases concurrently. Integration issues of product lifecycle into the product development process have received much attention over the last two decades, especially at the detailed design stage. The main objective of the research is to define assembly sequence into preliminary design stages by introducing and applying assembly process knowledge in order to provide an assembly context for the product development process, particularly for product structuring. The proposed framework highlights a novel algorithm based on a mathematical model integrating boundary conditions related to DFA rules, engineering decisions for assembly sequence and the product structure definition. This framework has been implemented in a new system called PEGASUS considered as an AOD module for a PLM system. A case study of applying the framework to a Catalytic-Converter and Diesel Particulate Filter sub-system, belonging to an exhaust system from an industrial automotive supplier, is introduced to illustrate the efficiency of the proposed AOD methodology. The work described has not been submitted elsewhere for publication, in whole or in part, and all the authors listed have approved the manuscript that is enclosed. Cover Letter *Cover LetterAn Assembly-Oriented Design Framework for Product Structure Engineering and Assembly Sequence Planning _______________________________________________________________________________________________ Abstract:The paper describes a novel framework for an Assembly-Oriented Design (AOD) approach as a new functional part of the Product Lifecycle Management (PLM) strategy, by considering product design and assembly sequence planning phases concurrently. Integration issues of product lifecycle into the product development process have received much attention over the last two decades, especially at the detailed design stage. The main objective of the research is to define assembly sequence into preliminary design stages by introducing and applying assembly process knowledge in order to provide an assembly context for the product development process, particularly for product structuring. The proposed framework highlights a novel algorithm based on a mathematical model integrating boundary conditions related to DFA rules, engineering decisions for assembly sequence and the product structure definition. This framework has been implemented in a new system called PEGASUS considered as an AOD module for a PLM system. A case study of applying the framework to a Catalytic-Converter and Diesel Particulate Filter sub-system, belonging to an exhaust system from an industrial automotive supplier, is introduced to illustrate the efficiency of the proposed AOD methodology.

The recent decades have witnessed the booming of additive manufacturing (AM), or 3D printing, not only in conventional areas, such as aviation, [1] automobile [2] and construction, [3] but also in various emerging fields, such as electronics, [4] biomedical engineering [5] and soft robotics. [6] The reason is the growing capability of AM to fabricate complex structures, which are challenging to be realized by traditional machining methods. In this advancement, the material library of 3D printing is no longer limited to static materials for structural construction and has expanded to active materials or stimuli-responsive materials, such as shape memory polymers, [7] hydrogels, [8] magnetic soft materials [9] and liquid crystal elastomers (LCEs), [10] driven by the growing need for soft robots, [10h,11] biomedical devices, [5,8a] smart wearable devices, [12] etc. The active nature of stimuli-responsive materials adds the dimension of time to 3D printing and leads to the emerging 4D printing. [8a,13] Among active materials for 4D printing, LCEs are appealing candidates due to their large, reversible and rapid actuation through a nematic-isotropic phase transition upon external stimuli, such as heat, [14] light, [10a,b,15] humidity [16] and electric fields. [17] LCEs are a class of soft active materials that inherit both the entropic elasticity of elastomers and the molecular anisotropy of liquid crystals (or mesogens). The actuation relies on the mesogen alignment, [18] which can be achieved by mechanical stretching, [19] surface shearing [10g] or external fields. [20] 3D/4D printing methods have been developed to fabricate LCE-based structures and align the mesogens. Direct ink writing (DIW) has been explored for printing LCEs. [11,15,21] In DIW, mesogens are aligned along the printing path when the LCE ink is extruded out of the syringe through the nozzle. Different inks have been developed for both high-temperature printing [10c,21a,c] and room-temperature printing. [21d,22] In addition, functionally graded LCEs were achieved by varying printing parameters, [10d,21c,g,23] such as printing temperature, printing speed and nozzle size. Although 3D structures, such as pinecone and saddle-shaped structures, [21c] can be achieved by 2D structures via different actuation strains between layers, the layer-by-layer manner of material deposition in DIW makes LCEs to be printed on the build platform or the previous layers.Liquid crystal elastomers (LCE) are appealing candidates among active materials for 4D printing, due to their reversible, programmable and rapid actuation capabilities. Recent progress has been made on direct ink writing (DIW) or Digital Light Processing (DLP) to print LCEs with certain actuation. However, it remains a challenge to achieve complicated structures, such as spatial lattices with large actuation, due to the limitation of printing LCEs on the build platform or the previous layer. Herein, a novel method to 4D print freestanding LCEs on-the-fly by using laser-assisted DIW w...

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