Sensitivity Analysis in Ball Bar Measurement of Three-Dimensional Circular Movement Equivalent to Cone-Frustum Cutting in Five-Axis Machining Centers

Abstract

The present paper describes the sensitivity coefficient of measurement in the three-dimensional circular interpolation movement that is equivalent to cone-frustum cutting in five-axis machining centers with a tilting rotary table. The sensitive direction of a ball bar having a one-dimensional displacement sensor is parallel to its telescopic bar. In the present paper, the ratio of the measurement value to the actual error is defined as the sensitivity coefficient of measurement. The sensitivity coefficient of each axis is calculated by changing the apex angle and location of the cone-frustum. Different trajectories are obtained according to the attitude of the ball bar. This is due to the resulting variation in the sensitivity coefficient of the ball bar. If the ball bar is set parallel to the base circle of the cone-frustum, and if the center of the cone-frustum is positioned away from the centerline of the rotary table (in the positive direction of the linear axis that is perpendicular to the tilting axis of the table), the trajectory can be obtained appropriately.

Keywords

• five-axis machining center
• cone-frustum
• sensitivity coefficient
• ball bar measurement
• half apex angle