Application of Measurement Method of Sequential Points to Parts with High Accuracy

序贯两点法(STP)是本实验室发明的一种能够同时测量机床十字工作台和十字滑板或被加工零件运动直线度的方法。该装置由两个位移传感器组成，它们固定在十字台上，检测横向滑块或机械零件相对于物体的相对位移。通过在普通车床或大型卧式铣床上的基础研究，证实了该方法的重复精度很好，测量的稳定性优于惠普公司的激光测量系统，并应用于测量精度为亚微米量级的直线度。随着超精密加工技术的发展，对直线度的测量要求也越来越高。由于分辨率为0.01m的电容式位移传感器的出现，STP法有望实现更精确的直线度测量。用该方法和激光系统测量了直线度。在激光系统的情况下，结果的波动很大。结果表明，用STP法可以稳定地获得0.1m量级的直线度，且重复精度较好。在此过程中，提出了一种新的算法，该算法可以得到十字台和十字滑块的直线度独立描述的结果，而工作台的旋转运动对测量精度的影响则留作未来的评估问题。

Sequential two points (STP) method which was invented in head investigator's laboratory was able to measure the straightness of the motion of cross table of machine tool and that of the cross slide or the machined parts simultaneously. The apparatus consists of two displacement sensors which are hold by the cross table and detect the relative displacement to the objective as the cross slide or the machine parts. According to the basic research used for an engine lathe or the large horzontal milling machine, it was confirmed that repetetive accuracy of the method is very good, the stability of the mesurement by this method is better than that by laser system sold by Hewlett Packard Ltd. The method was applied to measure the straightness whose order of the accuracy is sub-micron meter. The needs for measurument of this accuracy is increased as the super precision machining has been developed.It is expected that more accurate mesurement of the straightness might be possible by the STP method due to the appearance of advanced type of displacement sensor in terms of capacitance which gas the resolution of 0.01 m. In this research an x-y table which was supported by static air pressure was used as the objective. The straightness was measurued by this method and by the laser system. fluctuation for the resutls was so large in case of the laser system. It was made obvious that the straightness with order of 0.1 m could be satably obtained by good repetitive accuracy by the STP method. In the procedure a new algorithm, which is possible to obtain the results in terms of independent description of the both straightness for the cross table and for the cross slide, was proposed.Influence of the rotational motion of the table on the measured accuracy are left as the future problem to be evaluted.