油套管螺纹关键参数的三坐标测量方法

螺纹参数的精确测量对油套管接头的设计开发和加工制造有重要作用。为了对螺纹关键参数进行精确测量,研发了油套管螺纹中径和螺距的测量方法。建立了测量空间坐标系,在每个螺纹牙侧面进行两处采点测量,给出了测点的直线方程,结合直线间距离算法,得到了螺纹中径线与螺纹牙的交点,利用最小二乘法对交点数据进行拟合,建立了交点与螺纹中径线的几何关系及其数学模型,推导出了中径和螺距的计算公式。以油管螺纹接头为例进行了螺纹中径及螺距的测量试验和应用,并将测量值和实际值进行了对比。对比结果表明,各螺纹牙中径和螺距测量精度高,误差不超过1%。该三坐标测量方法的提出为未知理论螺距和牙型角的螺纹测量提供了新方法。

Coordinate Measurement Method for Key Parameters of Tubing and Casing Thread

The accurate measurement of thread parameters plays an important role in the design,development,manufacturing of tubing and casing joints.In order to accurately measure the key parameters of the thread,the measuring method of the middle diameter and pitch of the tubing and casing thread was developed.A measuring space coordinate system was established.Two points were measured on the side of each thread tooth.The straight line equation of the measuring point was given.Combined with the distance algorithm between the straight lines,the intersection point of the thread middle diameter line and the thread tooth was obtained.The least square method is used to fit the intersection point data.The geometric relationship and mathematical model of the intersection point and the thread middle diameter line was established.The formulas for the middle diameter and pitch are derived.Taking the tubing thread joint for case study,the measurement test and application of the thread middle diameter and pitch are carried out,and is compared with the actual value.The comparison results show that the measurement accuracy of the middle diameter and pitch of each thread is high,with an error no more than 1%,which verifies that the proposed method has high measurement accuracy and small error.The proposed measurement method provides a new method for measuring thread with unknown theoretical pitch and thread angle.