Digital Image Tool Measuring Machine

It is necessary to develop a cutting tools measurement system with high precision and high efficiency in the NC(numerical control) machining center, so that it can decrease non-production time and improve machining efficiency. In this paper all kinds of cutting tools measurement technology are compared and analyzed before the project of a digital-image cutting tools measurement machine based on digital image processing technology is presented.The digital-image cutting tools measurement machine is made of two-dimension movement platform,optical lighting equipment,CCD imaging unit,digital image processing software module and hardware interface module. The working principle of this system is that an image shooted by CCD camera is transported into the computer through USB interface, then the digital image processing software can measure it precisely, finally the geometrical parameters of cutting tools is outputted through RS-232 interface.Several image processing algorithms are mainly discussed, including cutting tools image binarization,edge detection,contour feature-points extraction,subpixel edge location. Intensity image is segmented to Bi-value image through adopting a method based on maximum between-cluster variance and image morphology compares with classical differential operators in edge detection. A new feature-points extraction algorithm is proposed, which uses least square method fitting contour curve and combines slope,curvature information to extract feature-points. By discussing many subpixel edge location methods in detail, ZOM(zernike orthogonal moments) method,B-spline fitting method and gray center method are adopted and finally the geometrical parameters(lengths,angles,radiuses) of cutting tools are measured in subpixel level.The system software and hardware realization are discussed. All types of possible error sources are analyzed and the actual measurement results are presented. Experiments show the system is capable of realizing quick,accurate,non-contact measurement of cutting tools size and can meet the NC machining need.