50% Time Savings on CMM Evaluation with Kinematic Platform

The Bal-tec Kinematic Platform reduces the time required for Ball Bar evaluation of Coordinate Measuring Machines by 50%. It does this by creating a micro-inch accurate reference datum at one end of the Ball Bar. This fixed datum consists of a three ball kinematic coupling mounted on a rugged steel platform. One of the spherical ends of the Ball Bar is placed in the nest formed between the three high quality stainless steel balls.

A great deal of time is saved by using kinematic coupling because the position of the fixed datum ball is only measured one time, while a multitude of measurements are made of the opposite ball in various X,Y,Z positions. The three stainless steel balls used in the coupling are hardened to 58 HRC for wear-resistance and can be indexed to give many years of quality service.

The 4 inch (101.6 mm) diameter solid steel platform is 1½ inch (38.1 mm) thick and weighs over 5 pounds (2.36 Kg). There is a counter-bored hole through the platform which allows it to be clamped solidly to the C.M.M. table. A precision flat-lapped annular ring forms a positive coupling between the bottom of the platform and the top of the C.M.M. table.

The Ball Bar consists of two very accurate spheres of exactly the same diameter attached to the opposite ends of a rather long rigid bar. In the conventional approach, the center of the Ball Bar is clamped to a vertical post and the positions of both spheres must be measured every time the Ball Bar is moved. This new kinematic device is entirely compatible with the American National Standard for "Performance Evaluation of Coordinate Measuring Machines", ANSI/ASME-B89.4.1-1997 specification.