Machining, Measurement, and Control Laboratory

2 0 0 0    C o n f e r e n c e    P a p e r

Monitoring Cutting Forces in End Milling for Intelligent Machine Tools
Atsushi Matsubara (Kyoto University)
Yoshiaki Kakino (Kyoto University)
Takashi Ogawa (Kyoto University)
Hideo Nakagawa (OKK Co. Ltd.)
Tomonori Sato (Mitsubishi Electric Corp.)

A monitoring method of cutting forces in milling processes is proposed. In drilling and tapping processes, cutting forces can be estimated by monitoring the motor current of the spindle motor and feed drive servo motors. This method cannot be, however, applied to the estimation of smaller cutting forces in milling processes, due to the friction on guideways which varies significantly for different feed conditions. In this project, we present a monitoring method of cutting forces by using high-accuracy displacement sensors installed in a spindle unit. The DC component of the cutting force is estimated by measuring the displacement of the spindle using a simple signal processing technique.

We have been developing machine tools with a learning database and adaptive control schemes of machining processes, which we refer to as intelligent NC (numerically controlled) machine tools. A reliable and economical monitoring method of cutting forces is crucial for adaptive control of machining processes. Cutting force profiles estimated by the present method are compared with actual measurements by a tool dynamometer in order to validate the accuracy and reliability of the proposed monitoring system. Experiments are conducted under milling processes of aluminum, carbon steel, and cast iron materials. It is shown that the monitoring of small and medium scale cutting forces is possible by using the proposed method with a sufficient accuracy.

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