Machining, Measurement, and Control Laboratory

On the Monitoring of Cutting Forces in End Milling Processes
-- An Estimation Method based on Geometrical Combination of Force Vectors of Servo Motors and a Spindle Motor --

Soichi Ibaraki (Kyoto University)
Masahiro Sakahira (Kyoto University)
Hidenori Saraie (Mori Seiki Co., Ltd.)
Atsushi Matsubara (Kyoto University)
Yoshiaki Kakino (Kyoto University)

This paper presents a scheme to estimate cutting forces in end milling without using any additional sensors. An external disturbance can be estimated by monitoring the armature current in servo motors. It is, however, often subject to high friction on guideways, particularly in a stationary direction, which makes it difficult to estimate the disturbance in an accurate and stable manner. On the other hand, the armature current in a spindle motor is less affected by the friction, although only the tangential component of cutting force can be estimated. This paper proposes an estimation scheme of all the components of cutting force by geometrically combining force vectors given by servo motor and spindle motor currents. The accuracy and practical applicability of the proposed scheme are validated by experimental case studies, where the cutting force control for end milling processes is implemented based on the proposed estimation scheme.
Key Words:   process monitoring, cutting force estimation, end milling, engagement angle, motor loads.