Build orientation optimization for lightweight lattice parts production in selective laser melting by using a multicrite
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Additive manufacturing has enabled the development of lightweight lattice structures, which are widely used in orthopedic implant, aerospace and filtration fields. The traditional method of optimizing part build orientation has been unable to meet the demand for lightweight lattice parts. This paper proposes a novel method to obtain an optimum build orientation for lightweight lattice parts based on selective laser melting by considering two factors at a time, namely processability of lattice structures and the surface quality of functional features. First, the overhang structure area model for the evaluation of the processability of lattice structures is established; then, mesh segmentation and feature level classification of the lightweight part frame are carried out. On this basis, the adaptive feature roughness model for the evaluation of the surface quality of functional features is established; finally, a multicriteria genetic algorithm is used to solve the build orientation optimization problem of lightweight lattice parts to obtain a Pareto optimal set.
Introduction The lattice structures (cellular structures or porous structures) have the characteristics of lightweight and high strength. It has been widely used in lightweight manufacturing fields, such as medical implants and aerospace. There are many traditional fabrication methods of lattice structures is developed, such as three-dimensionally formed perforated sheets [1] and filament winding [2]. With the development of metal additive manufacturing technology [3,4], this method is increasingly used in the fabrication of lattice structures. Lewis et al. [5] and Dalia et al. [6] introduced some case studies for using lattice structures for orthopedic implants. Lattice structures can be used to reduce stress shielding and enhance osseointegration. Vasiliev et al. [7] presented the information about manufacturing processes, design analysis methods, mechanical performances of the unit cells and application of anisotropic composite lattice structures to aerospace field. Lightweight lattice parts have been applied in many fields, but there are still many key problems that have not been completely solved, such as the optimization of build orientation, the selection of unit cells and heat treatments. The build orientation directly affects the stability of the manufacturing process, the
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processability of lattice structures and the surface quality of functional features. When the unit cell’s strut with an inclined angle α ≤ 35°, the warpage deformation happened. The smaller the inclined angle, the worse the quality of the lattice structures [8]. Horizontal struts should be avoided during fabrication, unless the applied load after fabrication can be properly supported by other struts [9]. Generally, lightweight lattice parts consist of a frame and lattice structures. Many functional features are distributed among the frame, such as assembly surfaces or working surfaces. When selecting a suitable build orientation, the surface qu
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