Steven D. Phillips, Bruce R. Borchardt, Gregory W. Caskey, David E. Ward, Bryon S. Faust, Daniel S. Sawyer
NIST is currently developing equipment and techniques to rapidly access the performance of Coordinate Measuring machines (CMMs). This will allow the frequent testing of CMMs to insure that they measure parts accurately. A novel interim testing artifact, which can be described as a pseudo three-dimensional calibrated ball plate, has been developed. Unlike an actual 3D ball plate, this artifact is lightweight, relatively inexpensive, easy to calibrate, and adaptable to different sizes and stylus of CMMs. The artifact is composed of ball bars that are calibrated for ball roundness, ball diameters, and sphere center-to-center length. These ball bars are kinematically mounted on supporting arms and can rotate (in 45 degree increments) to sweep out most of the CMM work zone. The horizontal and inclined arms are interchangeable and are available in lengths from 300 mm to 1.5 m. Specific technical innovations include a design which separates the functions of dimensional calibration accuracy from structural rigidity, the ability to carry out the interim test entirely under computer control, and a complete CMM system evaluation. The project is a joint effort between NIST, DOD, DOE, and private industry. The program is expected to be completed during 1994, and the testing equipment will be available as a commercial product through domestic industry.