A Study On 3-PUU Parallel Coordinate Measuring Machine Error

Over the past two decades parallel mechanism has been in-depth researched and extensive applied in the fields of robotics and machine tools with its small motion inertia, high stiffness, average error effects and other unique advantages, and some of them has achieved commercialization, but its application in testing and measuring field can not be found frequently, a novel parallel coordiante measurng machine is developed with 3-PUU parallel mechanism, comparing to orthogonal CMM’s shortcomings,some errors analysis will be focused in this paper.First of all,Positive and negative solution measurement model of the coordinate measuring machine is established according to the basic theory of parallel mechanism. The straightness error model is established based on the theoretical measurement model, and Abbe error propagation model is established based on the total differential theory. The concrete measures used in the design, manufacture and assembly of the prototype are introduced and the main error source of instrument is analyzed briefly.Then,on the impact problem of slider motion straightness error and angular motion error on the accuracy of the instrument in parallel measuring machine, principle and approach of slider motion straightness error influence on the measurement accuracy of the instrument is analyzed,and then slider angular motion error and the characteristics of Abbe error caused by angular motion is analyzed.Finally,the original data of straightness error and Abbe error is obtained through experiment, and 27 feature points are selected to analyze the effects of two kinds of errors on the overall precision of the instrument respectively.The analysis results show that:the slide motion straightness error and angular motion error has greatest impact of measurement precision on the Y direction, minimal impact on the direction of X, which reflects the mathematical connotation of error averaging effect from another angle, and reveals the transmission characteristics of slider angular motion error in parallel mechanism.