Real-time monitoring of workpiece diameter during turning by vision method

The aim of this work is to develop a real-time method of monitoring the diameter of workpiece during the turning process without stopping the lathe. A high-resolution webcam was used as the image acquisition device by capturing the live images of the workpiece being turned with LED light source as light-field backlighting. The images were pre-processed to remove noise and were subjected to sub-pixel edge location to detect the edge of the workpiece using an algorithm coded in MATLAB. The diameter of the workpiece after each pass was determined by subtracting the change in the edge location from the original diameter after applying the correction scale factor. The percentage errors in the workpiece diameter determined by the vision method compared to the manual measurement using a digital calliper were established for three different turning speeds. The vision measurement method was found to be effective in measuring the diameter of the workpiece in real-time during turning within an accuracy of 0.6%.