Research on Measuring Method of Thread Pitch Diameter Based on Machine Vision
The thread pitch diameter is an important parameter to measure the thread manufacturing accuracy.When measur-ing the thread based on machine vision,the thread profile is obtained,not the specific thread diameter value.In order to improve the efficiency of machine vision in detecting thread pitch diameter,an extended virtual three ball thread pitch diameter measure-ment method was proposed.This method took the threaded shaft section image obtained by machine vision as the data source,rota-ted and corrected the acquired axis section image,calculated the ideal needle center coordinates of each tooth profile on the shaft section,and used the geometric relation and the three ball method to obtain the center diameter value.Taking the thread plug gauge M48×1.5-5g6h as the object,the pitch diameter measured by the extended virtual three ball method was compared with that of the length measuring instrument and the thread comprehensive measuring instrument.The experimental data show that the standard deviation of the pitch diameter measured by this method is 51.1％lower than that of the length measuring instrument,which is equivalent to the comprehensive thread measuring instrument.The measuring efficiency is 1.3 times higher than that of the length measuring instrument and 1.4 times that of the comprehensive thread measuring instrument,which provides an efficient and reliable measuring method for machine vision to measure the thread pitch diameter.
extended virtual three ball methodthread pitch diametermachine visionrotation correction
NETL
NSTL
万方数据
