| Machine tools is the basic of machining. Multi-axis CNC machine tools and especially the five-axis CNC machine tools or above are the most efficient ways to processing the large complex shaped parts. Five-axis CNC machine tools represent the highest level of manufacturing, but also signs the manufacturing capabilities and scientific and technological level of the country.Precision is one of the main indicator of CNC machine tools performance. Generally, there are two basic methods to improve the precision of CNC machine tools, error prevention and error compensation. Error prevention method has significant limitations, the economic costs usually to be expensive. Error compensation method can reduce the Manufacturing cost of instruments and equipment, it also has very significant economic benefits, so it rapidly develop and promote in the manufacturing industry.Establish CNC machine tools space error model and accurately measure the CNC machine tool's various error is one of the key problems to realize error compensation. The main contributions of the paper are:First, introduction the ball bar structure and the detection principle and briefly describe the geometric error identification based on the Ball bar detection principle. Including comprehensive error modeling bases on the homogeneous coordinate transformation method, ball bar detection geometry and thermal error separation principle, and ball bar ball seat installation error separation method. It points out the advantage of ball bar than the general machine tools detection tools.Second, the error modeling analysis of the CNC machine tools. Analysis the structure of the CNC machine tools, description the feature relationship between the two adjacent moving body. Definition body coordinate system, sports reference coordinate system, etc between adjacent body of the characteristics transformation matrix when have errors. Base on this, use the coordinate transformation matrix represents the relationship, and abstract the complex relationships between entities to matrix relationship in mathematical. Shows the expression of error model, this provide a theoretical basis for the modeling of error.Third, the movement error identification and experiment of the five-axis machine tools base on ball bar, design a test program of five-axis machine tools motion errors to separate sports errors and simulate results to prove the validity of the model, and use ball bar field experiment,data collection,data processing and calculation,get the machine tools'actual value error.Finally, relative to traditional application displacement sensor test spindle drift error method, the experimental method is used to test the spindle drift error.The paper has a certain reference value for the error detection and analysis of CNC machine tools and the error compensation technology. It also provides some practical effect for the user of error analysis and precision detection of their machine tools. |
