Tool condition monitoring using laser diffraction for rotating cutters

With the increasing use of Computer Numerical Control (CNC), there is a growing need for reliable on-line tool condition monitoring systems that are capable of sensing worn or broken tools. A tool condition monitoring system not only prevents losses owing to spoilt jobs but also minimizes premature tool replacement. In the long run, it helps to reduce manufacturing costs, increase machine tool utilization, optimize cutting conditions and build a reliable and intelligent manufacturing system.;This thesis presents a new method of tool condition monitoring for machining processes that employ rotating cutters, such as milling and drilling. It focusses on end-milling cutters but it can be extended to other types of rotating cutters as well.;The method used for tool wear measurement is based on laser diffraction. As a coherent laser light source passes through a slit, which is formed between a reference edge and the cutting edge of the cutter, a characteristic diffraction pattern is obtained. The luminous pattern of light consists of a number of fringes. The image can be captured by a CCD camera and various image processing techniques are employed to determine the fringe spacing. The fringe spacing is mathematically correlated to the width of the slit and accordingly, can be used to calculate the tool wear.;A prototype measurement system was designed and fabricated. Experiments were conducted and good results were obtained. Comparing the mechanical and optical measurements methods, the maximum error was only 16%. This method proved to be a reliable tool wear measurement method even for low values of the tool wear.