Milling force measurement using a constrained motion dynamometer with compensation

This paper describes milling force measurement using a low-cost constrained motion dynamometer (CMD). Comparisons are made to force measurement using a commercial dynamometer. The CMD structural dynamics are used to determine the milling force using in-process dynamic displacement of the CMD. Cutting force measurements are presented for three workpiece materials: aluminum, steel, and titanium alloys. For each workpiece material, the time domain displacement is converted to the frequency domain, a filter is produced by inverting the CMD frequency response function (FRF), and the displacement is used to calculate the cutting force. An algorithm is also presented to compensate for CMD FRF variation with workpiece height. It is demonstrated that the CMD offers an accurate low-cost alternative to a commercially available system.