Structure Analysis And Research On Drive System Thermal Error Model Of θFXZ Type Cmms

Coordinate measuring machines (CMMs) are dispensable and important measuring equipments in modern industrial inspection, quality control and manufacture. which are high efficiency precision measuring systems. The technology of CMMs represents the level of both modern measuring and manufacture technology. CMMs are expected to complete measuring assignment more precisely and quickly. Because of the improvement of CMMs'precision and speed, the CMMs error model, which is based on the rigid body model and low-speed operation state, can't commendably describe the additional error induced by the CMMs'non-rigid body and dynamic characteristic. The high operating speed results in a large temperature rise of drive system which consists of ball-screw and linear rolling guide, and brings on thermal error which can't be ignored.This paper presents the analysis and study of non-rigid body structure deformation, dynamic and thermal characteristic, and drive system thermal error modeling based on the CMMs withθFXZ structure. The main research works include:1. Basing on the non-rigid body model of CMMs, an additional deformation error item was introduced for measuring system with special structure. Non-rigid body model, the error expression form and the error analysis method of the specific CMMs were defined. According to the study above, experiment was designed to calibrate the error by laser interferometer. Finally, the error compensation was carried out to improve the CMMs'precision.2. In term of the ball screw drive system, the heat transfer differential equation of screw was established and solved according to boundary value in cylinder coordinate. The temperature response superposition was analyzed in different heat sources. Analyzing the screw temperature distribution of single heat source, theory model and actual temperature rise of screw was combined. The subsection modeling idea was proposed and a screw temperature field subsection model was built. The model got an expected result in screw temperature field prediction of single heat source and double heat sources.3. The CMMs'dynamic characteristic and temperature characteristic were deeply analyzed according to location error induced by different operating conditions and temperature rise of drive system. The influence on CMMs'location error of different operating conditions and drive system temperature variation were analyzed to provide important references for research of spatial location error compensation.4. The key parts temperature and drive system thermal error were analyzed in different operating conditions. It was found that the thermal error values are close while the temperature values of CMMs'key parts in different experiments make a large difference. In term of the phenomenon, the key parts temperature and operating condition are both considered during the thermal error modeling process. The model was built by artificial neural network and compared with the model built only considering the temperature. The result showed that the thermal error model built based on the modeling idea achieved a higher predicting precision.