Cutting tool form compensaton system and method

In a computer-controlled machining apparatus having a controller and including a cutting tool and a workpiece holder which are movable relative to one another along a preprogrammed path during a machining operation for effecting a cut in a workpiece held by the workpiece holder wherein the preprogrammed path of relative movement between the cutting tool and workpiece holder is based upon an assumed size and shape of the cutting edge of the cutting tool and the controller includes a database including criteria relating to the assumed size and shape of the cutting edge, the improvement comprising:

• means for obtaining an image of the cutting edge of the cutting tool at a preselected stage of a marching operation;
• means for generating information relating to the actual size and shape of the cutting edge at the preselected stage from the obtained image including means for obtaining an image of the cutting tool against a background so that the cutting tool and the background within the image possess contrasting light intensities, and wherein the image-obtaining means includes a light source and a camera having a lens so that by positioning the cutting tool between the lens of the camera and the light source, the cutting tool image received by the camera is a shadow of the cutting tool edge;
• and
• means for comparing the generated information relating to the actual size and shape of the cutting edge with the criteria relating to the assumed size and shape of the cutting edge and for altering the preprogrammed path of relative movement in accordance with variations detected between the actual size and shape of the cutting edge and the assumed size and shape of the cutting edge;
• the means for generating information includes means for scanning the obtained image along predetermined paths and identifying and collecting as data points along the cutting edge those points along each path at which sharp light intensity transitions occur;
• the means for scanning includes means for scanning the image in one direction thereacross along a set of parallel paths and in another direction thereacross along another set of parallel paths wherein said one direction and another direction are orthogonal to one another;
• and
• the means for generating information includes means for determining a center of the tool with the collected data points and means for removing from the collected data points those points which were collected from the image along paths oriented generally tangentially along the image of the cutting edge and includes means for redetermining a center of the cutting tool with the point data remaining after the removal of the tangentially-collected points.