Characteristics, Accuracy and Reverification of Robotised Articulated Arm CMMs

Abstract

The Nikon RCA is a robot CMM arm: a seven-axis articulated measuring arm mounted inside a robotised exoskeleton, with joints three, five and seven rotating without limit, aiming at total volumetric accuracy under 100 micrometres. It is neither a Cartesian CMM nor a conventional articulated arm, and that is the problem. Sanders and Thornby set out how the two machine types differ – motorised against manual, accuracy independent of the operator against accuracy tied to the operator's skill – then read VDI 2617 Part 9 and ASME B89.4.22 against a machine neither was written for, state the assumptions that interpretation requires, and report reverification tests and results, including what different measures of error do to the answer.