| Error compensation is one of effective ways to improve the accuracy of NC machine. This thesis is aimed to explore the technology of error identification and error modeling among technologies of error compensation.The thesis develops a new method for error parameter identification based on ten displacement measurement line, in which the Laser Doppler Interferometer is used to examine displacement error of ten particular lines of NC machine center. Thus all of the twenty-one geometrical error parameters are identified in the machine center. In comparison with other methods, this method gets rid of unsound assumptions, has fewer lines to measure and makes beam path easy to adjust. It is easy to operate and very effective.The object on which the thesis studies is V-60A NC vertical machine center with three axes. All of the geometric error parameters are identified by means of ten displacement measurement line, the mechanical structure of NC machine center is simplified, and introducing dynamics of multi-body systems, topological structure analysis is made, and considering the actual condition of the machine center, a geometric error calculating model of space is built. Through the model, the rules of error moving from the machine host to the cutting tool and object are analysis. Through the model and the geometric error parameters, space errors between the cutting tool's actual position and the ideal position in spatial discrete are calculated; by means of making polynomial interpolation in the space errors, the orbit of errors changing between the cutting tool and the object is simulated when the flat of the object is processed in the machine center. Based on the error changing rules, through correcting the NC manufacturing procedures, the machine's geometric errors are compensated. In the processing the actual object, the accuracy of the NC machine center improve about 65% after being compensated. A satisfying success has been attained. |
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