Thermal growth control techniques for motorized spindles

A motorized high speed spindle has very complicated dynamics consisting of non-stationary and speed-related thermal characteristics. Several studies have been reported with different designs to control or monitor spindle’s thermal growth with limited results. However, the thermal growth is critical to the “zero tolerance” requirement of high speed machining technology (HSM) in different range of speed or material machining.This paper proposes a direct displacement measuring system, which is a great improvement compared with other inaccurate readings using a traditional thermo-coupler, to accurately monitor and compensate the thermal growth associated with motorized high speed spindles. This direct displacement measuring system optimizing a high speed synchronous feedback system will meet the tolerance and performance required in HSM applications. Based on the introduction of Foucault current, this study develops a design for an accurate thermal growth.