| It is the important means for high precision, high quality, high efficiency and high benefit of product to measure the geometric positional errors of NC machine tool and a typical three-axis machine centre. There are 21 geometric errors (including three straightness errors of every axis, three angular errors and verticality error among three axes). If only one error is measured after adjusting one time, production efficiency and economic benefit will be influenced greatly. Therefore, it is one of the problems which is concerned by many fields and is not solved completely. Beam drift is one of the serious problems to influence measuring accuracy.In this paper, measuring accuracy is improved further owing to adding the compensation for beam drift. The methods of measuring straightness, roll, pitch and yaw simultaneously and compensating for these parameters is researched. The method is based on the analysis to the relevant references home and abroad. The simultaneously measuring system of five-degree-of-freedom error and compensation is developed. The method for measuring and compensation are verified through a series of theories and experiments.The innovative research achievements achieved in the dissertation are as follows:1. A novel measuring system simultaneously based on laser beam collimation is proposed in this dissertation, and a measuring setup of five-degree-of-freedom is developed. As sensitive elements a retro-reflector, a mirror and a special prism are used to measure straightness in two directions, pitch (yaw).A series of experiments are finished based on the analysis and discussion about the measurement principle of error parameters.2. A method for obtaining and compensating the beam drift is put forward, which is applied to Five-Degree-Of-Freedom (5-DOF) measurement system. The compensating results of beam drift due to laser, mechanical setup and thermal gradient are analyzed. The theoretic anlysis and experimental results indicate that the compensating method proposed in this paper can compensate the beam drift caused by different factors, and the measuring precision is improved.3. The 5-DOF measurement equipment based on common-path compensation for beam drift is set up and various experiments are finished. The feasibility of measurement scheme and the reliability of setup are verified.The problem of disturbance among the geometric parameters and the manufacturing errors of optical elements are analyzed in detail. It is the reason for not compensating for beam drift completely. |
