In-process roundness measurement system for cylindrical machine parts of small diameter w|th run-out error compensation

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An objective of our study is to develop an in-process measurement system which can evaluate both the roundness of turned cylindrical part and the rotational error of lathe spindle, Cylindrical parts to be measured are smaller than 2 mm in diameter and the target measurement accuracy of the system is the range of sub-micrometer. The Developed system is composed of measurement instrument, signal processing equipment and data analysis system. The measuring instrument of the developed system consists of three optical sensing units. Each unit has a parallel light beam and twin photo diodes to detect the asymmetrical beam power distribution, A cylindrically turned work is set within the crossing of the three light beams, where two of them are orthogonal. The work displacement perpendicular to each beam axis can be detected from the difference signal of the related twin photo diodes. Then the run-out locus of the work can be drawn as a Lisajous figure using the two orthogonal sensing units.As … More to the roundness measurement of the work itself, so-called V-block method was adopted. The two sensing units may be regarded as an optical virtual V-block and the remaining sensing unit as a tangential type displacement sensor.The measurement experiment was carried out with turned cylindrical part of 1mm in diameter at 300 rpm. As a result, the roundness profile by developed system is in rough agreement with the roundness profile by commercial instrument in undulation per revolution (UPR). The form error which was included in the run-out locus was effectively compensated. The run-out locus before the compensation was the square locus which was similar to simulation result, when small cylindrical part which mainly contains amplitude of 3rd UPR were used. Then, the value of radial circular run-out was 1.24μn. As a result of compensation using the measured roundness profile, the square corner became round, and the value of circular run-out decreased to 0.71μm. Consequently, it was able to be confirmed that the developed system was the run-out error measuring system in which the roundness profile of the cylindrical part did not influence in the run-out locus. Less