Towards greener machine tools - A review on energy saving strategies and technologies

The imbalance between energy supply and demand is expected to keep increasing, with the manufacturing sector being responsible for about one-third of world energy consumption. Hence, concerns about energy-efficient and environmentally benign manufacturing process have become an emerging issue. This paper suggests a novel hierarchy of energy saving technologies for machine tools, mainly for machining. Cutting is a widely used traditional process, and accounts for a large portion of energy consumption in machine tool sectors. A novel hierarchy is suggested, from the perspective of a single device manager, in accordance with the level of application. Technologies and strategies were compiled from research project reports, journal and conference articles, energy policies, etc. They were then rearranged in respective levels in the suggested hierarchy. Theories and technologies in the assessment and modeling of energy characteristics were reviewed, and general strategies on micro process planning were discussed at the software-based optimization level. Then, technologies for control and cutting improvement, such as novel lubrication and assisted machining systems, were introduced, and their effects were presented. Finally, improvement of hardware components and design rules for the environment were reviewed. Future market demands have clearly drawn more attention to energy efficiency, and the energy consumption of machine tools should be more accurately modeled and controlled. Loss and unnecessary operation of partial components should be minimized. From the perspective of energy efficiency, machine tools are expected to become more compact and lightweight. Operators and manufacturers need to understand both the process and hardware for greener machine tools.