Performing three-dimensional measurements on micro-scale features using a flexible coordinate measuring machine fiber probe with ellipsoidal tip

Abstract

The tip of a traditional coordinate measuring machine (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), facilitate 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 probe's 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 µm radius) performed with the NIST fiber probe (Muralikrishnan et al 2006 Precis. Eng. 30 154–64).