Abstract
A novel method is proposed for measuring the six degrees-of-freedom (DOF) geometric motion errors of a rotary axis based on a polyhedral prism. An error-sensitive unit which consists of a polyhedral prism and a planar reflector, is designed to carry out measurement of all six DOF errors, including the angular positioning error, the tilt motion error around the Y axis, the tilt motion error around the X axis, the radial motion error along the X and Y axes, and the axial motion error along the Z axis. The mathematical error model, including the six DOF geometric motion errors of the rotary axis, the installation errors between the polyhedral prism and the rotary axis, the manufacturing errors of the polyhedral prism, and the position errors of the sensors, are established. The effectiveness of the proposed method and the compensation model was simulated and experimentally verified.
Highlights
Because they possesses the advantages of high efficiency and strong capability in machining complex surfaces [1], multi-axis computerized numerical control (CNC) machine tools are widely used in industrial production such as in the automobile, ship manufacturing, and aerospace industries
A new method based on a polyhedral prism is proposed to simultaneously measure the six DOF geometric motion errors of a rotary axis by using autocollimators and laser displacement sensors
The results simulated by the professional matrix analysis software show that the six DOF motion errors of the target rotary axis after being compensated by our model are essentially equal to the preset errors
Summary
Because they possesses the advantages of high efficiency and strong capability in machining complex surfaces [1], multi-axis computerized numerical control (CNC) machine tools are widely used in industrial production such as in the automobile, ship manufacturing, and aerospace industries. The contact measurement methods include two kinds of methods based on capacitance sensor and circular trajectory, respectively Both of them cannot measure the angular positioning error which is the most important parameter of a rotary axis. The laser collimation method has the advantages of high precision and fast speed, but most existing methods cannot simultaneously measure all six DOF geometric motion errors of a rotary axis; in addition, the measurement device is usually complex and difficult to install, and takes a long time to calibrate. By using photoelectric autocollimators and laser displacement sensors, the full-circle and simultaneous measurement of all six DOF motion errors of a rotary axis can be realized This has the advantages of simple structure, fast measurement speed, and convenient installation. The whole measuring device can simultaneously measure all six DOF geometric motion errors of a rotary axis
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