A Fourth Industrial Revolution has been proposed, and various research and development activities geared toward the realization of smart factories have become extremely active. In smart factories developed individually within companies, the direction of the development activities is changing drastically. Regarding common technologies, research activities and feasible case study activities that are collaborations among industry, academia, and government and that show consideration and awareness of ecosystems are becoming active.

It has been five years since the IJAT last published a special issue on smart manufacturing. Smart factory technologies are becoming more and more important in the industrial world, not as a temporary boom, but as a steady development. Research on smart factory technologies is progressing, as they are considered to be important technologies in the industrial world, along with Digital Transformation (DX) technologies, among others.

This special issue addresses the latest in advanced research on smart factories. We have received many submissions from researchers at universities, public research institutes, and companies, and we are pleased to publish eight papers. The latest research being published mainly concerns the following five topics:

- Smart and digital twinning of machine tools

- Smart and digital twinning of production systems

- Optimization of production systems using scheduling algorithms

- Optimization of production systems including worker operations

- Optimization of energy consumption for production systems

The results of these studies will serve as a reference for further smart factory technologies in the future.

We deeply appreciate the careful work of all the authors, and we thank the reviewers for their incisive efforts. Without these contributions, this special issue could not have been created. We also hope that this special issue will trigger leading to further advances in smart factories.