| Popis: |
Thread gauges are widely used to obtain the values of complex parameters of thread surfaces. The virtual pitch thread diameter (VPTD) is the main standard complex thread accuracy figure. In practice, limit gauges are still applied to determine the value of this parameter. Despite the extensive use of coordinate measuring machines (CMMs), such machines have not replaced limit gauges for thread control still. One of the problems faced in thread control using CMM is the accurate determination of thread longitudinal axis. Earlier, the author has published studies aimed at determining thread axis based on the average values of the coordinates of point clouds for the starting and ending thread areas. The presented paper considers another approach to determine thread axis—the application of regression. The research results show that the case if the thread axis is the straight-line regression provides better results for small angles of axis rotation relative to the CMM coordinate system. However, if axis angular deviations increase, the previous method of axis determination is preferable. The paper presents research results for the cases that thread axis is a circle arc or a sine wave. In addition, the case that thread axis is a curved line in three dimensions is considered. Both axis determination methods have certain advantages in specific cases. |
