Dimension inspection of spatial cams by CNC coordinate measuring machines

The problem of spatial cam inspection is still predominantly approached from simple gauging by manufacturers in today’s industry, despite the fact that Coordinate Measuring Machines (CMM) is both available and one of the most reliable and accurate metrological tools. Therefore, a kinematic model is presented in this paper to aid in the determination of the required NC data equations in order to move the probe to the desired position to inspect spatial cams on CNC CMM. This study originated from the need for advanced algorithms for the profile inspection of high precision manufactured spatial cams. To achieve this, the 4×4 homogeneous transformation matrix is employed to determine spatial cam profiles. Then, the CMM’s ability function matrix and the measuringprobe location matrix are derived. The desired NC data equations are obtained by solving the CMM link variables by equating the ability function matrix with the probe location matrix. A technique to minimize the sum of squared errors is also addressed by searching a best fit coordinate frame. To verify the validity of the method, this approach was implemented in software which was then used in a CNC CMM to measure a known spatial cam, with excellent results. The methodology developed in this paper can make the cam inspection process more flexible, automatic, and controllable.