Showing papers by "Simon S. Park published in 2003"

Receptance coupling for end mills

Abstract: Identification of chatter free cutting conditions, the chatter stability lobes, requires a measurement of the frequency response function (FRF) of each tool mounted on the spindle. This paper presents a method of assembling known dynamics of the spindle–tool holder with an analytically modeled end mill using the receptance coupling technique. The classical receptance technique is enhanced by proposing a method of identifying the end mill–spindle/tool holder joint dynamics, which include both translational and rotational degrees of freedom. The method requires measurement of FRFs with impact tests applied on the spindle–tool holder assembly and blank calibration cylinders attached to the spindle. The spindle and tool holder characteristics are completely identified from the two experiments, and used for the mathematical prediction of FRF for end mills with arbitrary dimensions. The proposed method is experimentally proven and verified in cutting tests.

High frequency bandwidth cutting force measurements in milling using the spindle integrated force sensor system

Abstract: The accurate measurement of forces at the tool tip is required for calibration of cutting force coefficients, adaptive control of maximum cutting forces, detection of tool failure, and monitoring of the force history applied to a workpiece during production. However, the majority of the present sensor systems are not effective due to low frequency bandwidths, limited workpiece size, wiring complexities, and susceptibility to harsh machining environments. To overcome the limitations, the Spindle Integrated Force Sensor (SIFS) system is developed, which can be used in production machines to measure cutting forces by integrating piezoelectric force sensors to the stationary spindle housing. Since the sensors are part of the spindle, the structural dynamics of the spindle assembly directly affect the accuracy and bandwidth of the force measurement. The thesis presents a systematic methodology to compensate the distortions caused by structural dynamic modes of the spindle and tool system. The structural dynamic model between the cutting forces acting on the tool tip and the measured forces at the spindle housing is identified. A disturbance Kalman Filter is designed to remove the influence of structural modes on the force measurements. The frequency bandwidth is increased from 350 H z to 1000 H z by compensating the first three dominant structural modes of the spindle with the proposed sensing and the signal processing method. In addition, the mathematical coupling of Frequency Response Functions (FRFs) of the spindle and arbitrary cutting tool dynamics is proposed and verified using the Receptance