Non-contact measurement of spindle stiffness by using magnetic loading device

• A non-contact measurement method of static stiffness for rotating spindles is shown.
• Load–displacement relationship of a constant-position-preload spindle was measured.
• Speed and thermal effects on the stiffness change were clarified quantitatively.
• The thermal effect on the spindle hardening was found to be more dominant.
• Tool interface effect on the stiffness of the spindle system has been shown.

The radial stiffness of a rotating spindle is investigated in this research. A magnetic loading device (magnet loader) that attracts a dummy tool attached to the spindle is developed for this investigation. The dummy tool is designed so that the eddy current generated at higher rotational speed is suppressed. The spindle stiffness was measured with the developed device and compared with the calculated value. From the measurement results, speed and thermal effects on the stiffness were clarified quantitatively.