An on-line approach for energy efficiency monitoring of machine tools

Machining processes cause measurable impacts on environment due to substantial amounts of energy consumption. Enhancing energy efficiency of machine tools can significantly improve the environmental performance of machining systems. For this reason, an on-line energy efficiency monitoring system is necessary. Most conventional approaches monitored the energy efficiency by directly measuring cutting power with torque sensors or dynamometers. In contrast, we propose a new on-line approach without using any torque sensor or dynamometer which leads to a decreased implementation cost. The energy efficiency monitoring model of this approach is constructed based on an energy consumption model of machine tool. Then the entire machine-tool energy consumption can be divided into two parts, i.e. constant energy consumption and variable energy consumption. The former is measured in advance and stored in database, and the latter is derived from cutting power that can be estimated on-line according to power balance equation and additional load loss function. The additional load loss function can be identified off-line through input power and cutting power of the machine-tool spindle. Several experiments are performed on a CNC machine tool CJK6136 and the results show the effectiveness of the proposed method.