Investigation Into Geometrical Accuracy Optimal Distribution Of High-precision Horizontal Machining Centers

In this paper,a systematic study on the optimal allocation method of geometric accuracy for precision horizontal machining center is carried out.The geometric error modeling,interval sensitivity analysis and optimal allocation of geometric accuracy are deeply studied.The research results are applied to assembly process of ?2000/800 H four-axis precision horizontal machining center that is produced by Beijing Precision Machinery & Engineering Research Co.,LTD,which has made a certain degree of guidance effect on assembly.The full text has made the following achievements:In the aspect of geometric error modeling method: a general model of spatial error of a precision horizontal machining center is established based on multi-body system theory.An ideal stationary matrix,an ideal motion characteristic matrix,a static error characteristic matrix and a motion error characteristic matrix are deduced by homogeneous coordinate transformation.The space error model of whole machine is established by the matrix multiplication.Taking a typical horizontal machining center ?2000/800 H as an example,the generality and validity of the above modeling methods are verified The geometric error modeling method has the characteristics of normalization,programming,less constraints and is convenient for computer programming.In the research of interval sensitivity analysis: the interval sensitivity analysis is studied based on the interval theory,and the interval expansion factor is defined.The interval sensitivity of the position error sources,the interval sensitivity of the angle error sources and the maximum interval sensitivity for the entire region are respectively defined with the Abbe error taken into account.Taking the error model of ?2000/800 H horizontal machining center as the research object,the law of interval sensitivity of each geometric error source to space error is studied fully,obtaining the maximum interval sensitivity for the entire region of the geometric error source to the space error.This study provides geometric accuracy allocation weights for the study of optimal allocation of geometric accuracy.In the research of optimal allocation methods of geometric accuracy: an optimal allocation method of geometric accuracy is proposed based on interval optimization theory.An interval optimization model for the optimal allocation of geometric accuracy is established with the interval width of 21 geometric error sources as the design variables,the deviation of the diagonal positioning system of the whole space body not exceeding 25 ?m as the constraint,the maximum interval sensitivity for the entire region of 21 geometric error sources to the space error as allocation weights and the interval width of 21 geometric error source to be maximized as the design goal.The genetic algorithm is used to solve the interval optimization model.Range of geometric error sources tolerance achieves the maximum in the premise of meeting the machine space accuracy.Based on the results of the accuracy allocation,a simulation is conducted under the cases of both the fixed values and the interval values of the geometric errors,indicating the accuracy satisfaction rates are 98.9 % and 87.4 % respectively,which verifies the rationality of the optimization result and the correctness of the accuracy allocation method fully.