The tip of a traditional CMM probe used for measurements of macro-scale artifacts is generally a sphere of excellent geometry. Its known diameter (from a prior calibration) and form along with the known approach direction (which is normal to the surface) facilitates probe radius compensation in a straightforward manner. Neither of these conditions is valid for micro-scale measurements made with a flexible fiber probe on a CMM. This presents two challenges. The first involves the calibration of the probes true size and shape. The second involves developing a method for compensating probe radius and form on measurement data from test artifacts. We describe these issues here in the context of an application involving three-dimensional measurements on micro-scale features (a conical section of 20 half angle and a rounded tip of 38 m radius) performed with the NIST fiber probe.
Citation: Measurement Science & Technology
Pub Type: Journals
Coordinate metrology, Ellipsoid fit, Fiber probe