Study Of The Cylindricity Precision Measurement Technique Based On The Error Separation Method

The error separation technique is the form error precision testing technique developed in 1960s. The fundamental idea of this technique is that, based on the characteristic which measured profile is unchangeable, firstly, using one or multi-probe to measure work-piece and get the measuring signals; secondly, the form error of measured work-piece and the movement error of machine tool or measuring mechanism included in the measuring signals are distinguished, through the proper mathematical manipulation; finally, the form error of the measured work-piece can be acquired. The error separation technique is one of effective methods of improving the testing precision of the shape error. In this paper, based on the fundamental principle of the three-point method roundness error separation technique, the separation of cylindricity error factors and the reconstruction of the measured cylinder profile was intensively studied, and the methods of evaluating the cylindricity form error were discussed. Furthermore, the separation and reconstruction methods of the cylindricity error proposed in this paper were examined by the experiment.Several measurement methods of section roundness based on the error separation technique were discussed. According to the error separation process and results, the characteristic and the application scope were analyzed. The roundness error separation technique based on the three-point method in the aspect of separation roundness error was considered to be sufficient. The roundness error separation procedure based on three-point method was researched systematically. At the same time, the eccentric error motion caused by setting and pure rotation error motion of the rotation axis were separated successfully. The key problem which was incapable of separation between eccentric error motion and pure rotation error motion for a long time was settled out by means of this method. A new kind of algorithm of roundness error separation, namely matrix arithmetic was put forward. The section roundness error was obtained using this algorithm through the direct operating linear equation in stead of the traditional Fourier Transform. The measured section round profiles were reconstructed and the simulation experiment were carried out.The absolute coordinate system centered on the average line of the rotational axis and measuring coordinate system originated on the three sensor intersections were established through analyzing the space motion of the measured cylinder. The section radius error of the measured cylinder, section roundness error and the eccentric error motion of section least square center were separated efficiently, combined with the roundness error separation principle based on the three-point method. At the same time, the radial rotation motion error and the straight motion error of the measuring support were also separated. The reconstruction basis of the measured cylinder profile was analyzed and the reconstruction method of cylinder profile was put forward according to the relationships between the coordinates and the position of the sections.The evaluation method and algorithm of shape error (roundness, plane straightness, space straightness, cylindricity) were discussed. A new kind of algorithm, namely mesh searching method, which can be used to evaluate the roundness error, plane straightness error, space straightness error and cylindricity error, were put forward. With this algorithm, the shape error can be obtained by transferring the distance formula repeatedly and simple judgment without linearzing the distance formula (from point to point or point to line) and choosing optimal direction and step length.A new kind of experimental verification method for the error separation technique, namely self-verifiable method, was brought forward. Using this verification method can judge the correctness of the error separation method by the results of multiple metering, it is unnecessary to apply the other high accuracy instrument to do the contrast test. The cylindricity error separation and reconstruction method proposed in this paper was systematically verified. The experimental results indicate that the instrument error can be more completely separated using the researched method in the paper. So, the precision measurement for the cylindricity error can be realized.