Additive manufacturing can be used to construct complex structures and facilitate the design of an overall structure by adding materials layer-by-layer to form parts. Additive manufacturing technology has been widely used in the automotive, electronics, aerospace, and medical fields and plays a crucial role.

However, during the additive manufacturing process, parts with overhangs are often encountered and cannot be successfully printed without considering the overhangs. For traditional 2.5-axis 3D printers, two methods are used to solve the problem of overhanging structures that cannot be printed. One method involves adding support structures below the area with the overhanging structures, and the other requires achieving self-support of the structures through structural optimization. Adding support structures can prevent warping and reduce the structural deformation of a part. However, this method increases the production time and material costs. In addition, further postprocessing is required to remove unwanted support structures, which is time-consuming and affects the surface accuracy of the part. Therefore, it is important to achieve self-support of a printed part to reduce the material cost, printing time, and postprocessing time.

We summarize the research progress in structural self-supporting design for additive manufacturing. First, the principle of the structural self-supporting design of additive manufacturing is summarized, and the research progress in the self-supporting design of the overall structure of additive manufacturing parts and the self-supporting design of additive manufacturing infill structures are reviewed. Based on different structural optimization methods, it is further divided into structural self-supporting design using continuum structural topology optimization, discrete structural topology optimization, and shape optimization. Next, the advantages and disadvantages of each method are analyzed. Finally, solutions to improve computing efficiency and structural performance are discussed, along with future application scenarios and research priorities.

Additive manufacturing of structural self-supporting designs is critical for saving printing time and material, but it has not been systematically reviewed. This paper first summarizes the structural self-supporting design principle of additive manufacturing and reviews the research progress of the self-supporting design of the overall structure of the part, which is divided into three parts: research progress in structural self-supporting design based on continuum structure topology optimization, discrete structural topology optimization, and shape optimization. Previous studies were mainly based on continuum structure topology optimization, and the research progress in structural self-supporting design based on continuum structure topology optimization is presented in four parts: research progress in structural self-supporting design using the SIMP method and its improved version, the level set method, the BESO method, and feature-driven optimization. Subsequently, the research progress in the self-supporting design of additive manufacturing infill structures is reviewed. Finally, self-supporting designs of additive manufacturing structures are summarized and discussed. The structural self-supporting design of additive manufacturing is still in its infancy, and the following prospects are proposed to further develop this field.

(1) Perform 3D case extensions. Despite the rapid development of structural self-supporting design, the proposed method is still in its infancy and has been mainly applied to 2D cases based on the “rule of thumb” of printable overhang angles. Therefore, the extension to 3D cases still requires further investigation.

(2) Improve the computational efficiency of sensitivity. Previous studies were mainly based on continuum structure topology optimization, and topology optimization design has problems, such as large design variables, which often leads to high computational costs owing to the excessive number of elements in the sensitivity calculation design. Therefore, it is necessary to improve the sensitivity calculation method and increase calculation efficiency.

(3) Comprehensive consideration of the overhang feature constraints, printing direction, and topological layout. Compared with considering only the overhang angle constraint, a comprehensive consideration can further reduce the loss of structural performance. Moreover, the threshold value of the overhang angle often depends on the direction of printing. Therefore, in future research, the integrated consideration of printing direction and topological layout should be the focus.

(4) Combine self-support with other structural properties. During the melting and solidification of metallic materials printed by additive manufacturing, residual stresses and deformations are typically induced, resulting in printing failure or a decrease in strength and dimensional accuracy. Therefore, considering a self-supporting design that considers the residual stress and deformation of the structure is an important direction for future development. In addition, lightweight design is required in the aerospace field and should be considered in combination with light weight during the self-supporting design process.