Additive manufacturing (AM), also known as 3D printing, is a technology that  produces  three-dimensional parts  layer  by  layer from a material. AM has existed at various levels of sophistication for decades. However, it has only recently caught the widespread attention of industries  and  policy  makers  thanks  to  technological breakthroughs and advancements in the past decade that allow full-scale metallic  components and  structures to be  made to high standards. No longer solely a prototyping technology, AM is now being used for the production of series components for the most demanding applications. It is definitely a disruptive—if not revolutionary—manufacturing technology, as it totally  changes the traditional way of making products. The biggest advantage of this technology is its capacity to make parts with any free form, thus paving the way for free and complex part design. Components and integrated structures with complex designs that would not  have  been  possible  just a  few  years  ago  can  now be made according to various requirements. The net-shape manufacturing capacity of AM allows a considerable saving of materials, conventional thermomechanical processing, and machining processes, making it an environmentally friendly manufacturing technology.  These  are  the  main  reasons  why  AM  is  increasingly attracting attention and making  a  great  impact  on  a  number of industries such as the aerospace, military, nuclear, and medical  industries.  While  significant  advances  have  been  made in  AM,  there  are  also  a  number  of  challenges  that  need  to  be addressed for the future development of this technology. These include heat source-material interaction, defect formation mechanisms, microstructural control, process monitoring  and  control, and so forth. In general, as a smart, digital, and environmentally friendly manufacturing technology, AM represents the trend for future manufacturing technology development and is expected to play an increasingly important role in high-end product manufacturing and in promoting global economic development. In-depth scientific study and technological innovations are the key for this technology to be developed to a new level.

This special issue of Engineering on AM presents nine papers from selected experts all over the world and serves as a source of useful information on new developments in fundamental scientific research, technological innovation, and new applications of additively manufactured metals, plastics, and biomaterials. The papers in this special issue focus on the following topics: ① thermodynamic and kinetic mechanisms for AM, ② modeling and simulation of selective laser melting (SLM) and electron beam melting (EBM), ③ 3D printing of shape memory alloys, ④ 3D printing for medical phantoms and regenerated tissues/organs applications, ⑤ servo systems for precision AM, and ⑥ AM-driven innovative design.

We appreciate the contributions of all  the  authors,  reviewers, and editorial board members and thank them for their great efforts and constructive suggestions that helped to bring this special issue to a successful completion.