Theoretical And Experiment Research On Motion Error Identification Of Nc Machine Tools Based On Multi-step Identification Method

Machining accuracy is directly influenced by the quasi-static errors of a machine tool. A revised multi-step identification method of error component based on geometric synthetic error modeling, measurement of 3-axis and 4-axis NC machine tool by using a cross grid encoder is proposed in this paper. Precision of NC machine tools will be analyzed in this paper systematically. What's more, error modeling, measurement and identification of NC machine tools will be also analyzed in this paper.Firstly a revised synthetic error model of 21 geometric error components of the 3-axis NC machine tools and 29 geometric error components of the 4-axis NC machine tools are developed. Also the mapping relationship between the error component and radial motion error of round work piece manufactured on the NC machine tools are deduced. Aiming to overcome the solution singularity shortcoming of traditional error component identification method, a new multi-step identification method of error component by using the cross grid encoder measurement technology is proposed based on the kinematic motion error model of NC machine tool. Finally the experimental validation of the above modeling and identification method is carried out in the 3-axis CNC vertical machining center Cincinnati 750 Arrow and 4-axis NC machine tool MAHO 600C.For 3-aixs NC machine tools, the entire 21 error components have been successfully measured by the above method. The whole measuring time of 21 error components is cut down to 1–2 h because of easy installation, adjustment, operation and the characteristics of non- contact measurement. It usually takes days of machine down time and needs an experienced operator when using other measuring methods.In order to validate the method proposed above, a comparison experiment is performed on the same machining center by Heidenhain VML182 linear measurement system. Result shows that the multi-step identification method have a good identification precision and is very suitable for'on machine'measurement.