Non-Contact Device for Measuring Frequency Response Functions of CNC Machine Tools
The frequency response function (FRF) of a CNC machine tool is composed of tool/toolholder/spindle dynamics, and plays an important role in determining the stability of high speed machining processes. This paper details the design, development and operational verification of a non-contacting, controllable, electromechanical actuator (EMA) for measuring the FRFs of tools mounted in CNC milling machines. Although standard modal testing methods are available and provide similarly accurate results, these test procedures are difficult to perform in machine shop environments and can require expensive equipment. The EMA developed as part of this research extends the capabilities of the NIST “best speeds device” to provide controllable, non-contacting excitation for modal tests on machine tools. This EMA device offers the advantages of being accurate, easy to use, and applicable to a wide variety of tools and operating conditions.