Design And Experimental Testing Of Optical Tool Presetting And Measuring Machine Of Ultra-precision Turning Lathe

In the field of ultra-precision machining, the dimension error of the part is in the submicron, and the surface roughness reaches the nanometer level. In order to develop the processing quality of the workpiece, the new technologies are continually applied and the research of tool alignment accuracy is increased. Because tool alignment accuracy will directly determine the quality of the product, and is the first condition to realize ultra-precision machining.When the single-point diamond turning tool is used for machining spherical or aspherical optical parts and molds, the tool alignment error in the horizontal and the height and the measurement error of the tool nose radius will directly affect the size and surface shape accuracy of the workpiece. Optical tool presetting and measuring machine is based on computer vision measurement technology, which utilizes industrial camera to acquire cutting tool image and processes the acquisition image, and then get the arc radius and center coordinates of the tool nose and other parameters to pre-tuning the tool, to realize precise tool aligning and tool arc radius measurement. Therefore, in the paper it is discussed with the design and measurement algorithm research of the optical tool presetting and measuring machine, and concrete work done in the following aspects:1. In view of the positioning error caused by reciprocation in the auto focus, a second phase focused search strategy was proposed, which used in the autofocus module of the optical tool presetting and measuring machine, and improved the search speed and accuracy.2. According to the characteristics of the tool nose image,research and Analysis the image processing algorithms, which include image preprocessing, pixel and subpixel edge detection, line detection, image mosaic and characteristic parameters acquisition, to determine the image processing algorithms which can meet the tool alignment accuracy precision and real-time requirement.3. Based on the application requirements of the project, the overall architecture of the optical tool presetting and measuring machine and the software system are designed, to realize the automatic tool alignment of optical tool presetting and measuring machine.4. Aim at the existing chessboard size can’t meet the high magnification microscopy of the optical tool presetting and measuring machine, Zhang.Z. Y’s calibration method that use virtual checkerboard is proposed, to realize the inner parameters calibration of optical tool presetting and measuring machine.5. Deeply study the homography matrix and the transformation theory between the coordinate system, and achieve the relative positional relationship between the optical tool presetting and measuring machine and machine tool coordinate system, and then access to the tool nose position in the machine tool coordinate system, to realize tool precisely positioning in the machine.6. Experiment and error analysis. The positioning accuracy of Y direction and XZ plane is verified through experiments on Nanotech 350FG machine tool to validate the effectiveness of the method in this paper.