Machine tools usually consume more energy in cooling systems than in spindle motors. This is largely because circulation pumps in the cooling systems are continuously powered to measure the temperature of spindle motors. In this paper, energy saving algorithms are proposed, which modify this behavior of the circulation pumps in such a way that the circulation pumps run only when it is likely that the information on the temperature is critical to bang-bang control of compressors in cooling systems. A mathematical model is established that explains heat transfer phenomena near the spindle motors. The power consumptions are measured for individual components in a machine tool, and the parameters that appear in the mathematical model are estimated. Computer simulations are performed with the estimated parameters, and the results are compared with the experimental ones. It turns out that a large amount of energy can be saved by using the proposed method.
