This book contains research papers that were accepted for presentation at the 15th International Conference on Interdisciplinarity in Engineering-INTER-ENG 2021, which was held on October 7-8, 2021, in the city of Targu Mures, Romania. The general scope of the conference "Innovative aspects of Industry 4.0 concepts aimed at consolidating the digital future of manufacturing in companies" is proposing a new approach related to the development of a new generation of smart factories grounded on the manufacturing and assembly process digitalization. It is related to advance manufacturing technology, lean manufacturing, sustainable manufacturing, additive manufacturing, and manufacturing tools and equipment. It is a leading international professional and scientific forum of great interest for engineers and scientists who can read in this book research works contributions and recent developments as well as current practices in advanced fields of engineering.