Research On Geometric Error Identification Method Of Five-axis Machining Center

Five-axis machining center is the mother machine of modern manufacturing industry.With its advantages of high precision,high efficiency and the ability to process complex parts,it has been widely used in the fields of aerospace,marine,automotive mold and high-precision instruments.The development of these industries has put forward higher requirements for machine tool accuracy.In this paper,in order to accurately obtain the set error of the five-axis machining center,a series of studies are carried out in the following aspects: the optical path calibration process of measure the linear axis of NC machine tools with laser interferometer,the spatial geometric error modeling of five-axis machining center,the geometric error analysis and error identification of the rotary axis,which can quickly and accurately identify the errors of the machine tool.The main work of this paper includes:1)In terms of measuring the geometric errors of the three linear axes of a five-axis machining center,in order to quickly calibrate the optical path of the laser interferometer,combined with the analysis of the error elements in the optical path,the homogeneous coordinate transformation matrix is used to construct the optical path model.This paper presents a new method of adjusting light path quantitatively.Using the moving distance of the measured axis of the machine tool and the relation between the fixed distance from the center of the light target to the quartile point on the edge of the light target and the movement distance of the measured axis.The corresponding error model is established to solve the eight deviations of the light path affected by the three components of the laser emitter,the spectroscope and the reflector can be solved,so as to quickly quantified and calibrate the laser optical path.2)In terms of measuring the geometric errors of the two rotation axes in the five-axis machining center,a new method based on a ball bar system,which only involves the synchronous motion of the two rotation axes is proposed to detect the geometric errors of the two rotation axes independent of the position.Based on the multi-body system theory and the topological structure of the multi-body system,the spatial error model of the five-axis machining center is established.In the process of simulating the synchronous movement of the two rotation axes of the machine tool,the pose of the DBB forms a space semi-conical surface.The deviation error in the cone trajectory is captured by the cue meter.Using DBB to capture the trajectory deviation error in the cone trajectory.The asynchronous problem between the synthesis speed of spindle tool cups and the sampling rate of DBB in the coordinated movement of B-axis and C-axis is solved,so as to truly reflect the error of the machine tool.The space error measurement simulation platform of five-axis machine tool was developed based on MATLAB,and the geometric error irrelevant to position was simulated with the simulation model and compared with the measurement results.The residual error accounted for 8.76% of the total error after compensating the geometric error irrelevant to the position,which greatly improved the overall accuracy of the five-axis machining center.3)In evaluating the error distribution of the five-axis machining center,a new method based on multi-body system theory and sensitivity analysis is proposed to identify the key geometric errors of the two rotation axes in the five-axis machining center.Considering the random characteristics of geometric errors,Monte Carlo method is used to sample error parameters.The spatial error model of B and C double rotating axes in five-axis machining center is used.A new mathematical model is established based on Sobol sequence.Sobol sensitivity analysis index was used to identify the key geometric errors of the five-axis machining center.