Additive manufacturing (AM) is defined as the manufacture of three-dimensional tangible products by additively consolidating two-dimensional patterns layer by layer. In this review, we introduce four fundamental conceptual pillars that support AM technology: the bottom-up manufacturing factor, computer-aided manufacturing factor, distributed manufacturing factor, and eliminated manufacturing factor. All the conceptual factors work together; however, business strategy and technology optimization will vary according to the main factor that we emphasize. In parallel to the manufacturing paradigm shift toward mass personalization, manufacturing industrial ecology evolves to achieve competitiveness in economics of scope. AM technology is indeed a potent candidate manufacturing technology for satisfying volatile and customized markets. From the viewpoint of the innovation technology adoption cycle, various pros and cons of AM technology themselves prove that it is an innovative technology, in particular a disruptive innovation in manufacturing technology, as powder technology was when ingot metallurgy was dominant. Chasms related to the AM technology adoption cycle and efforts to cross the chasms are considered.

1. Introduction
2. Additive Manufacturing
3. Metal Additive Manufacturing
4. Four Conceptual Factors in AM Fundamental
5. Efforts to Cross Chasms in AM Technology Adoption
6. Concluding Remarks
Acknowledgements
References

• Hanshin Choi(Incheon Regional Division, Korea Institute of Industrial Technology)
• Wonsik Lee(Incheon Regional Division, Korea Institute of Industrial Technology)
• Jong Min Byun(Department of Materials Science & Engineering, Hanyang University)
• Su-Ryong Bang(Department of Materials Science & Engineering, Hanyang University)
• Young Do Kim(Department of Materials Science & Engineering, Hanyang University) Corresponding author